title: Oral tradition

text: In a study published in February 2020, new evidence showed that both Budj Bim and Tower Hill volcanoes erupted between 34,000 and 40,000 years ago. Significantly, this is a "minimum age constraint for human presence in Victoria", and also could be interpreted as evidence for the oral histories of the Gunditjmara people, an Aboriginal Australian people of south-western Victoria, which tell of volcanic eruptions being some of the oldest oral traditions in existence. A basalt stone axe found underneath volcanic ash in 1947 had already proven that humans inhabited the region before the eruption of Tower Hill.


title: Oral tradition

text: An Irish "seanchaí" (plural: "seanchaithe"), meaning bearer of "old lore""," was a traditional Irish language storyteller (the Scottish Gaelic equivalent being the "seanchaidh," anglicised as shanachie). The job of a "seanchaí" was to serve the head of a lineage by passing information orally from one generation to the next about Irish folklore and history, particularly in medieval times. Seán Ó hEinirí of Cill Ghallagáin, County Mayo was thought to be the last "seanachaí" and the last monolingual speaker of the Irish language.


title: Oral tradition

text: Writing systems are not known to exist among Native North Americans before contact with Europeans except among some Mesoamerican cultures, and possibly the South American quipu and North American wampum, although those two are debatable. Oral storytelling traditions flourished in a context without the use of writing to record and preserve history, scientific knowledge, and social practices. While some stories were told for amusement and leisure, most functioned as practical lessons from tribal experience applied to immediate moral, social, psychological, and environmental issues. Stories fuse fictional, supernatural, or otherwise exaggerated characters and circumstances with real emotions and morals as a means of teaching. Plots often reflect real life situations and may be aimed at particular people known by the story's audience. In this way, social pressure could be exerted without directly causing embarrassment or social exclusion. For example, rather than yelling, Inuit parents might deter their children from wandering too close to the water's edge by telling a story about a sea monster with a pouch for children within its reach. One single story could provide dozens of lessons. Stories were also used as a means to assess whether traditional cultural ideas and practices are effective in tackling contemporary circumstances or if they should be revised.


title: Oral tradition

text: Native American storytelling is a collaborative experience between storyteller and listeners. Native American tribes generally have not had professional tribal storytellers marked by social status. Stories could and can be told by anyone, with each storyteller using their own vocal inflections, word choice, content, or form. Storytellers not only draw upon their own memories, but also upon a collective or tribal memory extending beyond personal experience but nevertheless representing a shared reality. Native languages have in some cases up to twenty words to describe physical features like rain or snow and can describe the spectra of human emotion in very precise ways, allowing storytellers to offer their own personalized take on a story based on their own lived experiences. Fluidity in story deliverance allowed stories to be applied to different social circumstances according to the storyteller's objective at the time. One's rendition of a story was often considered a response to another's rendition, with plot alterations suggesting alternative ways of applying traditional ideas to present conditions. Listeners might have heard the story told many times, or even may have told the same story themselves. This does not take away from a story's meaning, as curiosity about what happens next was less of a priority than hearing fresh perspectives on well-known themes and plots. Elder storytellers generally were not concerned with discrepancies between their version of historical events and neighboring tribes' version of similar events, such as in origin stories. Tribal stories are considered valid within the tribe's own frame of reference and tribal experience. The 19th century Oglala Lakota tribal member Four Guns was known for his justification of the oral tradition and criticism of the written word.


title: Oral tradition

text: Stories are used to preserve and transmit both tribal history and environmental history, which are often closely linked. Native oral traditions in the Pacific Northwest, for example, describe natural disasters like earthquakes and tsunamis. Various cultures from Vancouver Island and Washington have stories describing a physical struggle between a Thunderbird and a Whale. One such story tells of the Thunderbird, which can create thunder by moving just a feather, piercing the Whale's flesh with its talons, causing the Whale to dive to the bottom of the ocean, bringing the Thunderbird with it. Another depicts the Thunderbird lifting the Whale from the Earth then dropping it back down. Regional similarities in themes and characters suggests that these stories mutually describe the lived experience of earthquakes and floods within tribal memory. According to one story from the Suquamish Tribe, Agate Pass was created when an earthquake expanded the channel as a result of an underwater battle between a serpent and bird. Other stories in the region depict the formation of glacial valleys and moraines and the occurrence of landslides, with stories being used in at least one case to identify and date earthquakes that occurred in CE 900 and 1700. Further examples include Arikara origin stories of emergence from an "underworld" of persistent darkness, which may represent the remembrance of life in the Arctic Circle during the last ice age, and stories involving a "deep crevice", which may refer to the Grand Canyon. Despite such examples of agreement between geological and archeological records on one hand and Native oral records on the other, some scholars have cautioned against the historical validity of oral traditions because of their susceptibility to detail alteration over time and lack of precise dates. The Native American Graves Protection and Repatriation Act considers oral traditions as a viable source of evidence for establishing the affiliation between cultural objects and Native Nations.


title: Oral tradition

text: Oral traditions face the challenge of accurate transmission and verifiability of the accurate version, particularly when the culture lacks written language or has limited access to writing tools. Oral cultures have employed various strategies that achieve this without writing. For example, a heavily rhythmic speech filled with mnemonic devices enhances memory and recall. A few useful mnemonic devices include alliteration, repetition, assonance, and proverbial sayings. In addition, the verse is often metrically composed with an exact number of syllables or morae – such as with Greek and Latin prosody and in Chandas found in Hindu and Buddhist texts. The verses of the epic or text are typically designed wherein the long and short syllables are repeated by certain rules, so that if an error or inadvertent change is made, an internal examination of the verse reveals the problem. Oral traditions can be passed on through plays and acting, as shown in modern-day Cameroon by the Graffis or Grasslanders who perform and deliver speeches to teach their history through oral tradition. Such strategies facilitate transmission of information without a written intermediate, and they can also be applied to oral governance.


title: Oral tradition

text: Rudyard Kipling's "The Jungle Book" provides an excellent demonstration of oral governance in the Law of the Jungle. Not only does grounding rules in oral proverbs allow for simple transmission and understanding, but it also legitimizes new rulings by allowing extrapolation. These stories, traditions, and proverbs are not static, but are often altered upon each transmission, barring any change to the overall meaning. In this way, the rules that govern the people are modified by the whole and not authored by a single entity.


title: Oral tradition

text: Ancient texts of Hinduism, Buddhism and Jainism were preserved and transmitted by an oral tradition. For example, the śrutis of Hinduism called the Vedas, the oldest of which trace back to the second millennium BCE. Michael Witzel explains this oral tradition as follows:


title: Oral tradition

text: Ancient Indians developed techniques for listening, memorization and recitation of their knowledge, in schools called Gurukul, while maintaining exceptional accuracy of their knowledge across the generations. Many forms of recitation or "paths" were designed to aid accuracy in recitation and the transmission of the "Vedas" and other knowledge texts from one generation to the next. All hymns in each Veda were recited in this way; for example, all 1,028 hymns with 10,600 verses of the Rigveda was preserved in this way; as were all other Vedas including the Principal Upanishads, as well as the Vedangas. Each text was recited in a number of ways, to ensure that the different methods of recitation acted as a cross check on the other. Pierre-Sylvain Filliozat summarizes this as:


title: Oral tradition

text: These extraordinary retention techniques guaranteed an accurate Śruti, fixed across the generations, not just in terms of unaltered word order but also in terms of sound. That these methods have been effective, is testified to by the preservation of the most ancient Indian religious text, the "" ( 1500 BCE).


title: Oral tradition

text: Research by Milman Parry and Albert Lord indicates that the verse of the Greek poet Homer has been passed down not by rote memorization but by "oral-formulaic composition". In this process, extempore composition is aided by use of stock phrases or "formulas" (expressions that are used regularly "under the same metrical conditions, to express a particular essential idea"). In the case of the work of Homer, formulas included "eos rhododaktylos" ("rosy fingered dawn") and "oinops pontos" ("winedark sea") which fit in a modular fashion into the poetic form (in this case six-colon Greek hexameter). Since the development of this theory, of oral-formulaic composition has been "found in many different time periods and many different cultures", and according to another source (John Miles Foley) "touch[ed] on" over 100 "ancient, medieval and modern traditions."


title: Oral tradition

text: The most recent of the world's great religions, Islam claims two major sources of divine revelation—the Quran and hadith—compiled in written form relatively shortly after being revealed:


title: Oral tradition

text: The oral milieu in which the sources were revealed, and their oral form in general are important. The Arab poetry that preceded the Quran and the hadith were orally transmitted. Few Arabs were literate at the time and paper was not available in the Middle East.


title: Oral tradition

text: The written Quran is said to have been created in part through memorization by Muhammad's companions, and the decision to create a standard written work is said to have come after the death in battle (Yamama) of a large number of Muslims who had memorized the work.


title: Oral tradition

text: For centuries, copies of the Qurans were transcribed by hand, not printed, and their scarcity and expense made reciting the Quran from memory, not reading, the predominant mode of teaching it to others. To this day the Quran is memorized by millions and its recitation can be heard throughout the Muslim world from recordings and mosque loudspeakers (during Ramadan). Muslims state that some who teach memorization/recitation of the Quran constitute the end of an "un-broken chain" whose original teacher was Muhammad himself. It has been argued that "the Qur'an's rhythmic style and eloquent expression make it easy to memorize," and was made so to facilitate the "preservation and remembrance" of the work.


title: Oral tradition

text: Islamic doctrine holds that from the time it was revealed to the present day, the Quran has not been altered, its continuity from divine revelation to its current written form insured by the large numbers of Muhammad's supporters who had reverently memorized the work, a careful compiling process and divine intervention. (Muslim scholars agree that although scholars have worked hard to separate the corrupt and uncorrupted hadith, this other source of revelation is not nearly so free of corruption because of the hadith's great political and theological influence.)


title: Oral tradition

text: At least two non-Muslim scholars (Alan Dundes and Andrew G. Bannister) have examined the possibility that the Quran was not just "recited orally, but actually composed orally". Bannister postulates that some parts of the Quran—such as the seven re-tellings of the story of the Iblis and Adam, and the repeated phrases "which of the favours of your Lord will you deny?" in sura 55—make more sense addressed to listeners than readers.


title: Oral tradition

text: Banister, Dundes and other scholars (Shabbir Akhtar, Angelika Neuwirth, Islam Dayeh) have also noted the large amount of "formulaic" phraseology in the Quran consistent with "oral-formulaic composition" mentioned above. The most common formulas are the attributes of Allah—all-mighty, all-wise, all-knowing, all-high, etc.—often found as doublets at the end of a verse. Among the other repeated phrases are "Allah created the heavens and the earth" (found 19 times in the Quran).


title: Oral tradition

text: As much as one third of the Quran is made up of "oral formulas", according to Dundes' estimates. Bannister, using a computer database of (the original Arabic) words of the Quran and of their "grammatical role, root, number, person, gender and so forth", estimates that depending on the length of the phrase searched, somewhere between 52% (three word phrases) and 23% (five word phrases) are oral formulas. Dundes reckons his estimates confirm "that the Quran was orally transmitted from its very beginnings". Bannister believes his estimates "provide strong corroborative evidence that oral composition should be seriously considered as we reflect upon how the Qur'anic text was generated."


title: Oral tradition

text: Dundes argues oral-formulaic composition is consistent with "the cultural context of Arabic oral tradition", quoting researchers who have found poetry reciters in the Najd (the region next to where the Quran was revealed) using "a common store of themes, motives, stock images, phraseology and prosodical options", and "a discursive and loosely structured" style "with no fixed beginning or end" and "no established sequence in which the episodes must follow".


title: Gadolinium

text: Gadolinium is a chemical element with the symbol Gd and atomic number 64. Gadolinium is a silvery-white metal when oxidation is removed. It is only slightly malleable and is a ductile rare-earth element. Gadolinium reacts with atmospheric oxygen or moisture slowly to form a black coating. Gadolinium below its Curie point of is ferromagnetic, with an attraction to a magnetic field higher than that of nickel. Above this temperature it is the most paramagnetic element. It is found in nature only in an oxidized form. When separated, it usually has impurities of the other rare-earths because of their similar chemical properties.


title: Gadolinium

text: Gadolinium was discovered in 1880 by Jean Charles de Marignac, who detected its oxide by using spectroscopy. It is named after the mineral gadolinite, one of the minerals in which gadolinium is found, itself named for the Finnish chemist Johan Gadolin. Pure gadolinium was first isolated by the chemist Paul-Émile Lecoq de Boisbaudran around 1886.


title: Gadolinium

text: Gadolinium possesses unusual metallurgical properties, to the extent that as little as 1% of gadolinium can significantly improve the workability and resistance to oxidation at high temperatures of iron, chromium, and related metals. Gadolinium as a metal or a salt absorbs neutrons and is, therefore, used sometimes for shielding in neutron radiography and in nuclear reactors.


title: Gadolinium

text: Like most of the rare earths, gadolinium forms trivalent ions with fluorescent properties, and salts of gadolinium(III) are used as phosphors in various applications.


title: Gadolinium

text: Gadolinium(III) ions in water-soluble salts are highly toxic to mammals. However, chelated gadolinium(III) compounds prevent the gadolinium(III) from being exposed to the organism and the majority is excreted by healthy kidneys before it can deposit in tissues. Because of its paramagnetic properties, solutions of chelated organic gadolinium complexes are used as intravenously administered gadolinium-based MRI contrast agents in medical magnetic resonance imaging. Varying amounts deposit in tissues of the brain, cardiac muscle, kidney, other organs and the skin, mainly depending on kidney function, structure of the chelates (linear or macrocyclic) and the dose administered.


title: Gadolinium

text: Gadolinium is the eighth member of the lanthanide series. In the periodic table, it appears between the elements europium to its left and terbium to its right, and above the actinide curium. It is a silvery-white, malleable, ductile rare-earth element. Its 64 electrons are arranged in the configuration of [Xe]4f5d6s, of which the ten 4f, 5d, and 6s electrons are valence.


title: Gadolinium

text: Like most other metals in the lanthanide series, gadolinium usually uses three electrons as valence electrons, as afterward the remaining 4f electrons are too strongly bound: this is because the 4f orbitals penetrate the most through the inert xenon core of electrons to the nucleus, followed by 5d and 6s, and this increases with higher ionic charge. It crystallizes in the hexagonal close-packed α-form at room temperature, but, when heated to temperatures above , it transforms into its β-form, which has a body-centered cubic structure.


title: Gadolinium

text: The isotope gadolinium-157 has the highest thermal-neutron capture cross-section among any stable nuclide: about 259,000 barns. Only xenon-135 has a higher capture cross-section, about 2.0 million barns, but this isotope is radioactive.


title: Gadolinium

text: Gadolinium is believed to be ferromagnetic at temperatures below and is strongly paramagnetic above this temperature. There is evidence that gadolinium is a helical antiferromagnetic, rather than a ferromagnetic, below . Gadolinium demonstrates a magnetocaloric effect whereby its temperature increases when it enters a magnetic field and decreases when it leaves the magnetic field. The temperature is lowered to for the gadolinium alloy GdEr, and this effect is considerably stronger for the alloy Gd(SiGe), but at a much lower temperature (<). A significant magnetocaloric effect is observed at higher temperatures, up to about 300 kelvins, in the compounds Gd(SiGe).


title: Gadolinium

text: Individual gadolinium atoms can be isolated by encapsulating them into fullerene molecules, where they can be visualized with a transmission electron microscope. Individual Gd atoms and small Gd clusters can be incorporated into carbon nanotubes.


title: Gadolinium

text: Gadolinium combines with most elements to form Gd(III) derivatives. It also combines with nitrogen, carbon, sulfur, phosphorus, boron, selenium, silicon, and arsenic at elevated temperatures, forming binary compounds.


title: Gadolinium

text: Unlike the other rare-earth elements, metallic gadolinium is relatively stable in dry air. However, it tarnishes quickly in moist air, forming a loosely-adhering gadolinium(III) oxide (GdO):


title: Gadolinium

text: Gadolinium is a strong reducing agent, which reduces oxides of several metals into their elements. Gadolinium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form gadolinium hydroxide:


title: Gadolinium

text: Gadolinium metal is attacked readily by dilute sulfuric acid to form solutions containing the colorless Gd(III) ions, which exist as [Gd(HO)] complexes:


title: Gadolinium

text: In the great majority of its compounds, like many rare-earth metals, gadolinium adopts the oxidation state +3. However, gadolinium can be found on rare occasions in the 0, +1 and +2 oxidation states. All four trihalides are known. All are white, except for the iodide, which is yellow. Most commonly encountered of the halides is gadolinium(III) chloride (GdCl). The oxide dissolves in acids to give the salts, such as gadolinium(III) nitrate.


title: Gadolinium

text: Gadolinium(III), like most lanthanide ions, forms complexes with high coordination numbers. This tendency is illustrated by the use of the chelating agent DOTA, an octadentate ligand. Salts of [Gd(DOTA)] are useful in magnetic resonance imaging. A variety of related chelate complexes have been developed, including gadodiamide.


title: Gadolinium

text: Reduced gadolinium compounds are known, especially in the solid state. Gadolinium(II) halides are obtained by heating Gd(III) halides in presence of metallic Gd in tantalum containers. Gadolinium also form sesquichloride GdCl, which can be further reduced to GdCl by annealing at . This gadolinium(I) chloride forms platelets with layered graphite-like structure.


title: Gadolinium

text: Naturally occurring gadolinium is composed of six stable isotopes, Gd, Gd, Gd, Gd, Gd and Gd, and one radioisotope, Gd, with the isotope Gd being the most abundant (24.8% natural abundance). The predicted double beta decay of Gd has never been observed (an experimental lower limit on its half-life of more than 1.3×10 years has been measured).


title: Gadolinium

text: Thirty-three radioisotopes of gadolinium have been observed, with the most stable being Gd (naturally occurring), with a half-life of about 1.08×10 years, and Gd, with a half-life of 1.79×10 years. All of the remaining radioactive isotopes have half-lives of less than 75 years. The majority of these have half-lives of less than 25 seconds. Gadolinium isotopes have four metastable isomers, with the most stable being Gd ("t"= 110 seconds), Gd ("t"= 85 seconds) and Gd ("t"= 24.5 seconds).


title: Gadolinium

text: The isotopes with atomic masses lower than the most abundant stable isotope, Gd, primarily decay by electron capture to isotopes of europium. At higher atomic masses, the primary decay mode is beta decay, and the primary products are isotopes of terbium.


title: Gadolinium

text: Gadolinium is named after the mineral gadolinite, in turn named after Finnish chemist and geologist Johan Gadolin. In 1880, the Swiss chemist Jean Charles Galissard de Marignac observed the spectroscopic lines from gadolinium in samples of gadolinite (which actually contains relatively little gadolinium, but enough to show a spectrum) and in the separate mineral cerite. The latter mineral proved to contain far more of the element with the new spectral line. De Marignac eventually separated a mineral oxide from cerite, which he realized was the oxide of this new element. He named the oxide "gadolinia". Because he realized that "gadolinia" was the oxide of a new element, he is credited with the discovery of gadolinium. The French chemist Paul-Émile Lecoq de Boisbaudran carried out the separation of gadolinium metal from gadolinia in 1886.


title: Gadolinium

text: Gadolinium is a constituent in many minerals such as monazite and bastnäsite. The metal is too reactive to exist naturally. Paradoxically, as noted above, the mineral gadolinite actually contains only traces of this element. The abundance in the Earth's crust is about 6.2 mg/kg. The main mining areas are in China, the US, Brazil, Sri Lanka, India, and Australia with reserves expected to exceed one million tonnes. World production of pure gadolinium is about 400 tonnes per year. The only known mineral with essential gadolinium, lepersonnite-(Gd), is very rare.


title: Gadolinium

text: Gadolinium metal is obtained from its oxide or salts by heating it with calcium at in an argon atmosphere. Sponge gadolinium can be produced by reducing molten GdCl with an appropriate metal at temperatures below (the melting point of Gd) at reduced pressure.


title: Gadolinium

text: Because Gd has a high neutron cross-section, it is used to target tumors in neutron therapy. This element is effective for use with neutron radiography and in shielding of nuclear reactors. It is used as a secondary, emergency shut-down measure in some nuclear reactors, particularly of the CANDU reactor type. Gadolinium is also used in nuclear marine propulsion systems as a burnable poison.


title: Gadolinium

text: Gadolinium possesses unusual metallurgic properties, with as little as 1% of gadolinium improving the workability and resistance of iron, chromium, and related alloys to high temperatures and oxidation.


title: Gadolinium

text: Gadolinium is paramagnetic at room temperature, with a ferromagnetic Curie point of . Paramagnetic ions, such as gadolinium, enhance nuclear relaxation rates, making gadolinium useful for magnetic resonance imaging (MRI). Solutions of organic gadolinium complexes and gadolinium compounds are used as intravenous MRI contrast agent to enhance images in medical magnetic resonance imaging and magnetic resonance angiography (MRA) procedures. Magnevist is the most widespread example. Nanotubes packed with gadolinium, called "gadonanotubes", are 40 times more effective than the usual gadolinium contrast agent. Traditional gadolinium-based contrast agents are un-targeted, generally distributing throughout the body after injection, but will not cross the intact blood–brain barrier. Brain tumors, and other disorders that degrade the blood-brain barrier, allow these agents to penetrate into the brain and facilitate their detection by contrast-enhanced MRI. Similarly, delayed gadolinium-enhanced magnetic resonance imaging of cartilage uses an ionic compound agent, originally Magnevist, that is excluded from healthy cartilage based on electrostatic repulsion but will enter proteoglycan-depleted cartilage in diseases such as osteoarthritis.


title: Gadolinium

text: Gadolinium as a phosphor is also used in other imaging. In X-ray systems gadolinium is contained in the phosphor layer, suspended in a polymer matrix at the detector. Terbium-doped gadolinium oxysulfide (GdOS:Tb) at the phosphor layer converts the X-rays released from the source into light. This material emits green light at 540 nm due to the presence of Tb, which is very useful for enhancing the imaging quality. The energy conversion of Gd is up to 20%, which means that 1/5 of the X-ray energy striking the phosphor layer can be converted into visible photons. Gadolinium oxyorthosilicate (GdSiO, GSO; usually doped by 0.1–1.0% of Ce) is a single crystal that is used as a scintillator in medical imaging such as positron emission tomography or for detecting neutrons.


title: Gadolinium

text: Gadolinium-153 is produced in a nuclear reactor from elemental europium or enriched gadolinium targets. It has a half-life of days and emits gamma radiation with strong peaks at 41 keV and 102 keV. It is used in many quality-assurance applications, such as line sources and calibration phantoms, to ensure that nuclear-medicine imaging systems operate correctly and produce useful images of radioisotope distribution inside the patient. It is also used as a gamma-ray source in X-ray absorption measurements or in bone density gauges for osteoporosis screening, as well as in the Lixiscope portable X-ray imaging system.


title: Gadolinium

text: Gadolinium is used for making gadolinium yttrium garnet (Gd:YAlO); it has microwave applications and is used in fabrication of various optical components and as substrate material for magneto-optical films.


title: Gadolinium

text: Gadolinium gallium garnet (GGG, GdGaO) was used for imitation diamonds and for computer bubble memory.


title: Gadolinium

text: Gadolinium can also serve as an electrolyte in solid oxide fuel cells (SOFCs). Using gadolinium as a dopant for materials like cerium oxide (in the form of gadolinium-doped ceria) creates an electrolyte with both high ionic conductivity and low operating temperatures, which are optimal for cost-effective production of fuel cells.


title: Gadolinium

text: Research is being conducted on magnetic refrigeration near room temperature, which could provide significant efficiency and environmental advantages over conventional refrigeration methods. Gadolinium-based materials, such as Gd(SiGe), are currently the most promising materials, owing to their high Curie temperature and giant magnetocaloric effect. Pure Gd itself exhibits a large magnetocaloric effect near its Curie temperature of , and this has sparked great interest into producing Gd alloys with a larger effect and tunable Curie temperature. In Gd(SiGe), Si and Ge compositions can be varied to adjust the Curie temperature. This technology is still very early in development, and significant material improvements still need to be made before it is commercially viable.


title: Gadolinium

text: Physicists Mark Vagins and John Beacom, of the Japanese Super Kamiokande, theorized that gadolinium may facilitate neutrino detection when it is added to very high-purity water in the tank.


title: Gadolinium

text: Gadolinium barium copper oxide (GdBCO) has been researched for its superconducting properties with applications in superconducting motors or generators - for example in a wind turbine. It can be manufactured in the same way as the most widely researched cuprate high temperature superconductor, Yttrium barium copper oxide (YBCO) and uses an analogous chemical composition (GdBaCuO ). Most notably, it was used by the Bulk Superconductivity Group from the University of Cambridge in 2014 to set a new world record for the highest trapped magnetic field in a bulk high temperature superconductor, with a field of 17.6T being trapped within two GdBCO bulks.


title: Gadolinium

text: As a free ion, gadolinium is reported often to be highly toxic, but MRI contrast agents are chelated compounds and are considered safe enough to be used in most persons. The toxicity of free gadolinium ions in animals is due to interference with a number of calcium-ion channel dependent processes. The 50% lethal dose is about 0.34 mmol/kg (IV, mouse) or 100–200 mg/kg. Toxicity studies in rodents show that chelation of gadolinium (which also improves its solubility) decreases its toxicity with regard to the free ion by a factor of 31 (i.e., the lethal dose for the Gd-chelate increases by 31 times). It is believed therefore that clinical toxicity of gadolinium-based contrast agents (GBCAs) in humans will depend on the strength of the chelating agent; however this research is still not complete. About a dozen different Gd-chelated agents have been approved as MRI contrast agents around the world.


title: Gadolinium

text: In patients with kidney failure, there is a risk of a rare but serious illness called nephrogenic systemic fibrosis (NSF) that is caused by the use of gadolinium based contrast agents. The disease resembles scleromyxedema and to some extent scleroderma. It may occur months after a contrast agent has been injected. Its association with gadolinium and not the carrier molecule is confirmed by its occurrence with various contrast materials in which gadolinium is carried by very different carrier molecules. Due to this, it is not recommended to use these agents for any individual with end-stage kidney failure as they will require emergent dialysis. Similar but not identical symptoms to NSF may occur in subjects with normal or near-normal renal function within hours to 2 months following the administration of GBCAs; the name "gadolinium deposition disease" (GDD) has been proposed for this condition, which occurs in the absence of pre-existent disease or subsequently developed disease of an alternate known process. A 2016 study reported numerous anecdotal cases of GDD. However, in that study, participants were recruited from online support groups for subjects self-identified as having gadolinium toxicity, and no relevant medical history or data were collected. There have yet to be definitive scientific studies proving the existence of the condition.


title: Gadolinium

text: Included in the current guidelines from the Canadian Association of Radiologists are that dialysis patients should only receive gadolinium agents where essential and that they should receive dialysis after the exam. If a contrast-enhanced MRI must be performed on a dialysis patient, it is recommended that certain high-risk contrast agents be avoided but not that a lower dose be considered. The American College of Radiology recommends that contrast-enhanced MRI examinations be performed as closely before dialysis as possible as a precautionary measure, although this has not been proven to reduce the likelihood of developing NSF. The FDA recommends that potential for gadolinium retention be considered when choosing the type of GBCA used in patients requiring multiple lifetime doses, pregnant women, children, and patients with inflammatory conditions.


title: Gadolinium

text: Long-term environmental impacts of gadolinium contamination due to human usage is a topic of ongoing research.


title: Gadolinium

text: Gadolinium has no known native biological role, but its compounds are used as research tools in biomedicine. Gd compounds are components of MRI contrast agents. It is used in various ion channel electrophysiology experiments to block sodium leak channels and stretch activated ion channels. Gadolinium has recently been used to measure the distance between two points in a protein via electron paramagnetic resonance, something that gadolinium is especially amenable to thanks to EPR sensitivity at w-band (95 GHz) frequencies.


title: Lebesgue integration

text: In mathematics, the integral of a non-negative function of a single variable can be regarded, in the simplest case, as the area between the graph of that function and the -axis. The Lebesgue integral, named after French mathematician Henri Lebesgue, extends the integral to a larger class of functions. It also extends the domains on which these functions can be defined.


title: Lebesgue integration

text: Long before the 20th century, mathematicians already understood that for non-negative functions with a smooth enough graph—such as continuous functions on closed bounded intervals—the "area under the curve" could be defined as the integral, and computed using approximation techniques on the region by polygons. However, as the need to consider more irregular functions arose—e.g., as a result of the limiting processes of mathematical analysis and the mathematical theory of probability—it became clear that more careful approximation techniques were needed to define a suitable integral. Also, one might wish to integrate on spaces more general than the real line. The Lebesgue integral provides the necessary abstractions for this.


title: Lebesgue integration

text: The Lebesgue integral plays an important role in probability theory, real analysis, and many other fields in mathematics. It is named after Henri Lebesgue (1875–1941), who introduced the integral . It is also a pivotal part of the axiomatic theory of probability.


title: Lebesgue integration

text: The term "Lebesgue integration" can mean either the general theory of integration of a function with respect to a general measure, as introduced by Lebesgue, or the specific case of integration of a function defined on a sub-domain of the real line with respect to the Lebesgue measure.


title: Lebesgue integration

text: The integral of a positive function between limits and can be interpreted as the area under the graph of . This is straightforward for functions such as polynomials, but what does it mean for more exotic functions? In general, for which class of functions does "area under the curve" make sense? The answer to this question has great theoretical and practical importance.


title: Lebesgue integration

text: As part of a general movement toward rigor in mathematics in the nineteenth century, mathematicians attempted to put integral calculus on a firm foundation. The Riemann integral—proposed by Bernhard Riemann (1826–1866)—is a broadly successful attempt to provide such a foundation. Riemann's definition starts with the construction of a sequence of easily calculated areas that converge to the integral of a given function. This definition is successful in the sense that it gives the expected answer for many already-solved problems, and gives useful results for many other problems.


title: Lebesgue integration

text: However, Riemann integration does not interact well with taking limits of sequences of functions, making such limiting processes difficult to analyze. This is important, for instance, in the study of Fourier series, Fourier transforms, and other topics. The Lebesgue integral is better able to describe how and when it is possible to take limits under the integral sign (via the monotone convergence theorem and dominated convergence theorem).


title: Lebesgue integration

text: While the Riemann integral considers the area under a curve as made out of vertical rectangles, the Lebesgue definition considers horizontal slabs that are not necessarily just rectangles, and so it is more flexible. For this reason, the Lebesgue definition makes it possible to calculate integrals for a broader class of functions. For example, the Dirichlet function, which is 0 where its argument is irrational and 1 otherwise, has a Lebesgue integral, but does not have a Riemann integral. Furthermore, the Lebesgue integral of this function is zero, which agrees with the intuition that when picking a real number uniformly at random from the unit interval, the probability of picking a rational number should be zero.


title: Lebesgue integration

text: The insight is that one should be able to rearrange the values of a function freely, while preserving the value of the integral. This process of rearrangement can convert a very pathological function into one that is "nice" from the point of view of integration, and thus let such pathological functions be integrated.


title: Lebesgue integration

text: Folland (1984) summarizes the difference between the Riemann and Lebesgue approaches thus: "to compute the Riemann integral of , one partitions the domain into subintervals", while in the Lebesgue integral, "one is in effect partitioning the range of ."


title: Lebesgue integration

text: For the Riemann integral, the domain is partitioned into intervals, and bars are constructed to meet the height of the graph. The areas of these bars are added together, and this approximates the integral, in effect by summing areas of the form formula_1 where formula_2 is the height of a rectangle and formula_3 is its width.


title: Lebesgue integration

text: For the Lebesgue integral, the range is partitioned into intervals, and so the region under the graph is partitioned into horizontal "slabs" (which may not be connected sets). The area of a small horizontal "slab" under the graph of "f", of height "dy", is equal to the measure of the slab's width times "dy":


title: Lebesgue integration

text: An equivalent way to introduce the Lebesgue integral is to use so-called simple functions, which generalize the step functions of Riemann integration. Consider, for example, determining the cumulative COVID-19 case count from a graph of smoothed new daily cases (right).


title: Lebesgue integration

text: Measure theory was initially created to provide a useful abstraction of the notion of length of subsets of the real line—and, more generally, area and volume of subsets of Euclidean spaces. In particular, it provided a systematic answer to the question of which subsets of have a length. As later set theory developments showed (see non-measurable set), it is actually impossible to assign a length to all subsets of in a way that preserves some natural additivity and translation invariance properties. This suggests that picking out a suitable class of "measurable" subsets is an essential prerequisite.


title: Lebesgue integration

text: The Riemann integral uses the notion of length explicitly. Indeed, the element of calculation for the Riemann integral is the rectangle , whose area is calculated to be . The quantity is the length of the base of the rectangle and is the height of the rectangle. Riemann could only use planar rectangles to approximate the area under the curve, because there was no adequate theory for measuring more general sets.


title: Lebesgue integration

text: In the development of the theory in most modern textbooks (after 1950), the approach to measure and integration is "axiomatic". This means that a measure is any function μ defined on a certain class of subsets of a set , which satisfies a certain list of properties. These properties can be shown to hold in many different cases.


title: Lebesgue integration

text: We start with a measure space where is a set, is a σ-algebra of subsets of , and μ is a (non-negative) measure on defined on the sets of .


title: Lebesgue integration

text: For example, can be Euclidean -space or some Lebesgue measurable subset of it, is the σ-algebra of all Lebesgue measurable subsets of , and μ is the Lebesgue measure. In the mathematical theory of probability, we confine our study to a probability measure , which satisfies .


title: Lebesgue integration

text: Lebesgue's theory defines integrals for a class of functions called measurable functions. A real-valued function on is measurable if the pre-image of every interval of the form is in :


title: Lebesgue integration

text: We can show that this is equivalent to requiring that the pre-image of any Borel subset of R be in . The set of measurable functions is closed under algebraic operations, but more importantly it is closed under various kinds of point-wise sequential limits:


title: Lebesgue integration

text: The theory of the Lebesgue integral requires a theory of measurable sets and measures on these sets, as well as a theory of measurable functions and integrals on these functions.


title: Lebesgue integration

text: One approach to constructing the Lebesgue integral is to make use of so-called "simple functions": finite, real linear combinations of "indicator functions". Simple functions that lie directly underneath a given function can be constructed by partitioning the range of into a finite number of layers. The intersection of the graph of with a layer identifies a set of intervals in the domain of , which, taken together, is defined to be the preimage of the lower bound of that layer, under the simple function. In this way, the partitioning of the range of implies a partitioning of its domain. The integral of a simple function is found by summing, over these (not necessarily connected) subsets of the domain, the product of the measure of the subset and its image under the simple function (the lower bound of the corresponding layer); intuitively, this product is the sum of the areas of all bars of the same height. The integral of a non-negative general measurable function is then defined as an appropriate supremum of approximations by simple functions, and the integral of a (not necessarily positive) measurable function is the difference of two integrals of non-negative measurable functions.


title: Lebesgue integration

text: To assign a value to the integral of the indicator function of a measurable set consistent with the given measure μ, the only reasonable choice is to set:


title: Lebesgue integration

text: where the coefficients are real numbers and are disjoint measurable sets, is called a measurable simple function. We extend the integral by linearity to "non-negative" measurable simple functions. When the coefficients are positive, we set


title: Lebesgue integration

text: whether this sum is finite or +∞. A simple function can be written in different ways as a linear combination of indicator functions, but the integral will be the same by the additivity of measures.


title: Lebesgue integration

text: Some care is needed when defining the integral of a "real-valued" simple function, to avoid the undefined expression : one assumes that the representation


title: Lebesgue integration

text: is such that whenever . Then the above formula for the integral of "f" makes sense, and the result does not depend upon the particular representation of satisfying the assumptions.


title: Lebesgue integration

text: Let be a non-negative measurable function on , which we allow to attain the value , in other words, takes non-negative values in the extended real number line. We define


title: Lebesgue integration

text: We need to show this integral coincides with the preceding one, defined on the set of simple functions, when "E"  is a segment ["a", "b"]. There is also the question of whether this corresponds in any way to a Riemann notion of integration. It is possible to prove that the answer to both questions is yes.


title: Lebesgue integration

text: We have defined the integral of "f" for any non-negative extended real-valued measurable function on "E". For some functions, this integral  is infinite.


title: Lebesgue integration

text: It is often useful to have a particular sequence of simple functions that approximates the Lebesgue integral well (analogously to a Riemann sum). For a non-negative measurable function , let formula_14 be the simple function whose value is formula_15 whenever formula_16, for "k" a non-negative integer less than (say) formula_17. Then it can be proven directly that


title: Lebesgue integration

text: and that the limit on the right hand side exists as an extended real number. This bridges the connection between the approach to the Lebesgue integral using simple functions, and the motivation for the Lebesgue integral using a partition of the range.


title: Lebesgue integration

text: To handle signed functions, we need a few more definitions. If is a measurable function of the set to the reals (including ), then we can write


title: Lebesgue integration

text: We say that the Lebesgue integral of the measurable function "exists", or "is defined" if at least one of formula_23 and formula_24 is finite:


title: Lebesgue integration

text: is monotonically non-increasing. The Lebesgue integral may then be defined as the improper Riemann integral of formula_30:


title: Lebesgue integration

text: This integral is improper at formula_32 and (possibly) also at zero. It exists, with the allowance that it may be infinite.


title: Lebesgue integration

text: As above, the integral of a Lebesgue integrable (not necessarily non-negative) function is defined by subtracting the integral of its positive and negative parts.


title: Lebesgue integration

text: Complex-valued functions can be similarly integrated, by considering the real part and the imaginary part separately.


title: Lebesgue integration

text: If "h"="f"+"ig" for real-valued integrable functions "f", "g", then the integral of "h" is defined by


title: Lebesgue integration

text: The function is Lebesgue integrable if and only if its absolute value is Lebesgue integrable (see Absolutely integrable function).


title: Lebesgue integration

text: Consider the indicator function of the rational numbers, , also known as the Dirichlet function. This function is nowhere continuous.


title: Lebesgue integration

text: A technical issue in Lebesgue integration is that the domain of integration is defined as a "set" (a subset of a measure space), with no notion of orientation. In elementary calculus, one defines integration with respect to an orientation:


title: Lebesgue integration

text: Generalizing this to higher dimensions yields integration of differential forms. By contrast, Lebesgue integration provides an alternative generalization, integrating over subsets with respect to a measure; this can be notated as


title: Lebesgue integration

text: to indicate integration over a subset . For details on the relation between these generalizations, see .


title: Lebesgue integration

text: With the advent of Fourier series, many analytical problems involving integrals came up whose satisfactory solution required interchanging limit processes and integral signs. However, the conditions under which the integrals


title: Lebesgue integration

text: are equal proved quite elusive in the Riemann framework. There are some other technical difficulties with the Riemann integral. These are linked with the limit-taking difficulty discussed above.


title: Lebesgue integration

text: Failure of monotone convergence. As shown above, the indicator function on the rationals is not Riemann integrable. In particular, the Monotone convergence theorem fails. To see why, let be an enumeration of all the rational numbers in (they are countable so this can be done.) Then let


title: Lebesgue integration

text: The function is zero everywhere, except on a finite set of points. Hence its Riemann integral is zero. Each is non-negative, and this sequence of functions is monotonically increasing, but its limit as is , which is not Riemann integrable.


title: Lebesgue integration

text: Unsuitability for unbounded intervals. The Riemann integral can only integrate functions on a bounded interval. It can however be extended to unbounded intervals by taking limits, so long as this doesn't yield an answer such as .


title: Lebesgue integration

text: Integrating on structures other than Euclidean space. The Riemann integral is inextricably linked to the order structure of the real line.


title: Lebesgue integration

text: Two functions are said to be equal almost everywhere (formula_41 for short) if formula_42 is a subset of a null set.


title: Lebesgue integration

text: It is possible to develop the integral with respect to the Lebesgue measure without relying on the full machinery of measure theory. One such approach is provided by the Daniell integral.


title: Lebesgue integration

text: There is also an alternative approach to developing the theory of integration via methods of functional analysis. The Riemann integral exists for any continuous function of compact support defined on (or a fixed open subset). Integrals of more general functions can be built starting from these integrals.


title: Lebesgue integration

text: Let be the space of all real-valued compactly supported continuous functions of R. Define a norm on by


title: Lebesgue integration

text: Then is a normed vector space (and in particular, it is a metric space.) All metric spaces have Hausdorff completions, so let be its completion. This space is isomorphic to the space of Lebesgue integrable functions modulo the subspace of functions with integral zero. Furthermore, the Riemann integral is a uniformly continuous functional with respect to the norm on , which is dense in . Hence has a unique extension to all of . This integral is precisely the Lebesgue integral.


title: Lebesgue integration

text: More generally, when the measure space on which the functions are defined is also a locally compact topological space (as is the case with the real numbers R), measures compatible with the topology in a suitable sense (Radon measures, of which the Lebesgue measure is an example) an integral with respect to them can be defined in the same manner, starting from the integrals of continuous functions with compact support. More precisely, the compactly supported functions form a vector space that carries a natural topology, and a (Radon) measure is defined as a continuous linear functional on this space. The value of a measure at a compactly supported function is then also by definition the integral of the function. One then proceeds to expand the measure (the integral) to more general functions by continuity, and defines the measure of a set as the integral of its indicator function. This is the approach taken by and a certain number of other authors. For details see Radon measures.


title: Lebesgue integration

text: The main purpose of the Lebesgue integral is to provide an integral notion where limits of integrals hold under mild assumptions. There is no guarantee that every function is Lebesgue integrable. But it may happen that improper integrals exist for functions that are not Lebesgue integrable. One example would be the sinc function:


title: Lebesgue integration

text: On the other hand, formula_67 exists as an improper integral and can be computed to be finite; it is twice the Dirichlet integral and equal to formula_68.


title: Step Up 2: The Streets

text: Step Up 2: The Streets is a 2008 American dance drama film directed by Jon M. Chu (in his feature film directorial debut) and written by Toni Ann Johnson and Karen Barna. It serves as a sequel to 2006's "Step Up" and the second installment in the "Step Up" film series. The film stars Briana Evigan, Robert Hoffman, Will Kemp, and Cassie Ventura.


title: Step Up 2: The Streets

text: Set at the fictional Maryland School of the Arts, the story revolves around rebellious street dancer Andie West (Evigan) who lands at the elite school and finds herself fighting to fit in while also trying to hold onto her old life. She eventually joins forces with the school's hottest dancer Chase Collins (Hoffman) to form a crew of classmate outcasts to compete in Baltimore's underground dance battle The Streets, finding a way to live her dream while building a bridge between her two separate worlds.


title: Step Up 2: The Streets

text: "Step Up 2: The Streets" was released in the United States on February 14, 2008, by Walt Disney Studios Motion Pictures. Although the film received better reviews than its predecessor, it received mostly negative reviews from critics, but became a box office success, grossing $150.8 million worldwide against a budget of $17.5 million.


title: Step Up 2: The Streets

text: In Baltimore, Maryland, Andie West pursues her dream of becoming a street dancer, but feels like she does not belong anywhere. Her mother recently died of cancer, so she now lives with a guardian, her mother's best friend Sarah. She is doing poorly at school, but her passion for dancing brings something good into her life. She rehearses regularly with her "crew", the 410, to retain top ranking in the illegal competition "The Streets".


title: Step Up 2: The Streets

text: Andie's friend and older brother figure Tyler Gage persuades her to audition for the Maryland School of the Arts, hoping it will help turn her life around the same way it did him in the first film. Andie auditions and Chase Collins convinces his older brother Blake, the school's director, to let her join. When the 410 find out about Andie's studies, they angrily kick her out. Andie and Chase form a new crew with help from many people Chase knows at the school who are not accepted as who they are. Chase has a copied key to the studio and the crew secretly practices their routine late at night when the school is empty. Missy, Andie's friend, joins the crew after dropping out of the 410 following Andie's removal. Missy tells the crew that the only way to enter the streets is to first do a prank and post it on the internet to show that the crew is entering the competition. Wanting revenge from being humiliated before, Chase decides to make a fool out of Tuck, leader of the 410, by leaving a dead fish in the vent of Tuck's home.


title: Step Up 2: The Streets

text: But the 410 doesn't like the fact that they had a new crew to compete with so they warn Andie's new crew to stay out of the Streets or there will be consequences. When Tuck finds Chase, he assaults him because of his prank. Chase comes into school the next day badly bruised and hurt. On top of that the dance studio has been trashed by the 410 late at night. Director Collins forbids the school from being involved in these types of competitions and expels Andie from MSA because of her involvement with the Streets competition; Andie proclaims herself the sole participant to protect her teammates. Chase attempts to defend her, but Director Collins is too busy with an upcoming MSA fundraiser to let her back in.


title: Step Up 2: The Streets

text: When Andie's guardian hears the news of Andie's expulsion, she becomes fed up with Andie's behavior and decides to send her to live with her aunt in Texas. Later that night, Andie receives a text message that the Streets is on that night, the same night as the MSA fundraiser. Along with Andie, her whole crew gets the text message. They decide to ditch the MSA fundraiser, and instead compete at the Streets. Andie's guardian hears about what Andie did to protect her crew and is proud of her; she reconsiders sending Andie to Texas and allows her to compete at the Streets with her crew.


title: Step Up 2: The Streets

text: When Director Collins goes in search of his students, he ends up at the Streets as well. He sees them compete and realizes that the street dancing he has been opposing is in fact a legitimate form of artistic expression. He accepts Andie back into MSA. With Andie's crew as a group of friends supporting her and her education now being secured, the film finds its optimistic ending.


title: Step Up 2: The Streets

text: At the U.S. Box office, the film opened at #3 and earned $18,908,826 in its opening weekend. As of August 4, 2008, "Step Up 2: The Streets" have grossed $58,017,783 in domestic box office and $92,798,917 in other parts of the world, bringing a worldwide total of $150,816,700, outperforming its predecessor.


title: Step Up 2: The Streets

text: The film was met with negative reviews from critics. On Rotten Tomatoes, it has an approval rating of 28% based on reviews from 65 critics, with an average rating of 4.90/10. The website's consensus states "There's a kinetic appeal to the handsome cast and their smooth moves, but everything else about "Step Up 2: The Streets" is been there, danced that." On Metacritic it has a weighted average score of 50 out of 100 based on reviews from 20 critics, indicating "mixed or average reviews". Audiences polled by CinemaScore gave the film a grade A−.


title: Leukonychia

text: Leukonychia (or leuconychia) is a medical term for white discoloration appearing on nails. It is derived from the Greek words "leuko" 'white' and "onyx" 'nail'. The most common cause is injury to the base of the nail (the matrix) where the nail is formed.


title: Leukonychia

text: This condition consists of a whitening of the entire nail and mostly likely occurs on all nails. Whitening of one, and only one, entire nail is not recognized as a symptom of Leukonychia totalis but as a likely result of mechanical trauma. Leukonychia totalis may be a clinical sign of hypoalbuminaemia (low albumin), which can be seen in nephrotic syndrome (a form of kidney failure), liver failure, protein malabsorption and protein-losing enteropathies. A genetic condition or a side effect from taking sulphonamides (a family of antibiotics) can also cause this appearance. By 2011, only 6 cases of non-hereditary Leukonychia totalis were published.


title: Leukonychia

text: In familial cases of leukonychia totalis, this condition is caused by mutations in the PLCD1 gene, in chromosome 3p22.2, this mutation shows an autosomal dominant pattern of inheritance, but in some cases, this condition may be autosomal recessive.


title: Leukonychia

text: This condition consists of a whitening of parts of the nail plate in the form of small white dots. There are three different variations of partial leukonychia; punctate, transverse and longitudinal leukonychia. Some of the more serious variations of leukonychia partialis may lead to leukonychia totalis.


title: Leukonychia

text: Leukonychia striata, transverse leukonychia, or Mees' lines are a whitening or discoloration of the nail in bands or "stria" that run parallel to the lunula (nail base). This is commonly caused by physical injury or disruption of the nail matrix. Common examples include excessive biting or tapping of the nails, trauma or injury from accidents involving doors or windows, and extensive use of manicure. It may also occur in great toenails as a result of trauma from footwear. Alternatively, the condition can be caused by heavy metal poisoning, most commonly by lead. Finally, it can be caused by cirrhosis of the liver or chemotherapy.


title: Leukonychia

text: The tendency toward leukonychia striata is sometimes inherited in an autosomal dominant fashion. In other cases, it can be attributed to vigorous manicuring and trauma aforementioned, or to a wide variety of systemic illnesses. Serious infections known for high fevers, measles, malaria, herpes, and leprosy may also cause this condition. In many patients, there is no obvious cause, and the streaks resolve spontaneously.


title: Leukonychia

text: There is a similar condition called Muehrcke's lines (apparent leukonychia) which differs from leukonychia in that the lines fade with digital compression and do not migrate with the growth of the nail.


title: Leukonychia

text: Also known as "true" leukonychia, this is the most common form of leukonychia, in which small white spots appear on the nails. Picking and biting of the nails are a prominent cause in young children and nail biters. Besides parakeratosis, air that is trapped between the cells may also cause this appearance. It is also caused by trauma. In most cases, when white spots appear on a single or a couple of fingernails or toenails, the most common cause is injury to the base (matrix) of the nail. When this is the case, white spots disappear after around eight months, which is the amount of time the nails take to regrow completely. The pattern and number of spots may change as the nail grows.


title: Leukonychia

text: Longitudinal leukonychia is far less common and features smaller 1mm white longitudinal lines visible under the nail plate and perpendicular to the nail bed. It may be associated with Darier's disease.


title: Leukonychia

text: It is harmless and most commonly caused by minor injuries, such as nail biting, which occur while the nail is growing. Leukonychia occurs most commonly in healthy individuals, and is unrelated to any known nutritional or physiological deficiency. When caused by injury the marks will disappear as the nail grows outwards. While there are various sources that link dietary needs or vitamin deficiency with recurrent leukonychia, this notion has been challenged by some medical researchers.


title: Leukonychia

text: A doctor will take a thorough medical history, and may take blood tests as well as examining liver and kidney function. Intracellular (red blood cell) assays are more sensitive than tests for plasma levels.


title: Leukonychia

text: Improvements have been reported from treating malnutrition associated with zinc deficiency and other minerals.


title: One by One (Foo Fighters album)

text: One by One is the fourth studio album by American rock band Foo Fighters, released on October 22, 2002, through Roswell and RCA Records. Production on the album was troubled, with initial recording sessions considered unsatisfying and raising tensions between the band members. They eventually decided to redo the album from scratch during a two-week period at frontman Dave Grohl's home studio in Alexandria, Virginia. The album, which includes the successful singles "All My Life" and "Times Like These", has been noted for its introspective lyrics and a heavier, more aggressive sound compared to the band's earlier work, which Grohl said was intended to translate the energy of the Foo Fighters' live performances into a recording. This was the first album recorded with Chris Shiflett as part of the band, and the first in which Grohl did not play drums, as drum duties were permanently assigned to Taylor Hawkins.


title: One by One (Foo Fighters album)

text: The album was a commercial success, topping the charts in Australia, Ireland, and the United Kingdom, and sold over one million copies in the United States. "One by One" was positively received by critics, who praised its sound and production, and won a Grammy Award for Best Rock Album in 2004, the second for the band.


title: One by One (Foo Fighters album)

text: Frontman Dave Grohl began working on new material for the band's next album as early as 2000 during the band's tour promoting "There Is Nothing Left to Lose". Following the tour, the band started to compose songs for their next album in early 2001. After demo work in drummer Taylor Hawkins' home studio in Topanga, the band used the second quarter of 2001 to perform in European festivals. In August, after performing in Chelmsford's V Festival, Hawkins suffered a heroin overdose that left him in a coma for two weeks. After taking time off to recover, during which Grohl accepted an offer to play drums for the Queens of the Stone Age on their album "Songs for the Deaf", the band got together in October 2001 to continue composition. During November and December, they had been recording at Grohl's Studio 606 in Alexandria, Virginia, working with both the producer for their previous album, Adam Kasper, and recording engineer Nick Raskulinecz, whom they met after he had engineered "A320" for "". Raskulinecz had just left his job at Sound City Studios, and speculated that Grohl, having found difficulty in 'finding a guy who would commit to sitting in his basement for four months', picked him for his energetic and enthusiastic nature.


title: One by One (Foo Fighters album)

text: The progress of the Virginia sessions started to become stale, so with six tracks finished, in January 2002 the band moved to Los Angeles' Conway Studios for a "change of scenery". 29 songs were recorded, including "The One"—featured in the film "Orange County" and released as a standalone single— and ten finished tracks that were considered for the upcoming album. The sessions took four months and were at the cost of over US$1,000,000. It was the first Foo Fighters album produced with Pro Tools and on which the band members have recorded separately.


title: One by One (Foo Fighters album)

text: The recording sessions were considered unsatisfying; Hawkins said that "nobody had their studio chops together", and Grohl considered that the band was lacking enthusiasm and were too focused on production, adding that he felt the rough mixes "sucked a lot of the life out of the songs" and "sound[e]d like another band playing our songs." Tensions were escalating, as arguments broke out at the studio, and Hawkins said he "didn't feel we were much of a band" as there was much animosity among the bandmembers. Bassist Nate Mendel said that he was in a bad attitude during the sessions due to disagreements with Grohl, and guitarist Chris Shiflett added that he felt he would at times spend whole days in the studio without playing anything.


title: One by One (Foo Fighters album)

text: The band also showed disappointment with the ten songs that emerged from the sessions, as Hawkins described the finished tracks as "million-dollar demos", and Grohl considered the recordings "far too clean, too tame and boring". The band only liked five of the ten songs, and thought that listeners would enjoy the other five anyway. Grohl was afraid to promote the album because of his lack of confidence in it. After manager John Silva listened to the recordings, he agreed that it was not a work that represented the band well, and that "we can release it now, but I don't know if anyone would want to buy it".


title: One by One (Foo Fighters album)

text: In April 2002, the band discarded the recordings and took a break. The members then each started individual projects: Grohl became the full-time Queens of the Stone Age drummer for a tour, Shiflett started the Viva Death and Jackson projects with his brother Scott and rejoined his former band Me First and the Gimme Gimmes, Hawkins played with Jane's Addiction bassist Eric Avery, and Mendel both played with Juno and reunited with his former bandmate William Goldsmith in The Fire Theft. Later on April, they reunited for the Foo Fighters' scheduled concert at the 2002 Coachella Valley Music and Arts Festival, which Grohl felt could be the last the band would perform. During the rehearsals, the tensions broke out in huge fights, especially between Grohl and Hawkins. The musicians decided to at least perform in Coachella before deciding whether to continue playing together or end the band. After enjoying their performance, the bandmembers decided to remain united and returned to re-recording the album.


title: One by One (Foo Fighters album)

text: Grohl decided to take a two-week period before the QOTSA went on tour to work on the Foo Fighters record, and after consulting Raskulinecz decided to promote him to producer. First, Grohl visited Hawkins in Topanga to rework the songs that had already been done and show new compositions, such as "Times Like These", "Low", and "Disenchanted Lullaby". Then Grohl and Hawkins went to Virginia to redo the drum, vocal and guitar tracks across a twelve-day period, and Mendel and Shiflett were later called to record their parts in Los Angeles' The Hook Studios, which were mostly done with the supervision of Raskulinecz, as Grohl had to go back to QOTSA. The only remaining track from the original sessions was "Tired of You", which features a guest appearance by Queen guitarist Brian May. Two of the demos would leak online in 2012, with the other five unreleased demos being leaked on Reddit in 2015.


title: One by One (Foo Fighters album)

text: The title "One by One"—taken from a lyric on "All My Life", and for which the spelling "1 X 1" was also considered—was chosen according to Grohl because "it somehow made sense", and even worked as a reference to relationships—"one person by another person, or one after another". The singer added that the word "one" is frequently used in the album's lyrics, meaning either loneliness or continuation.


title: One by One (Foo Fighters album)

text: Upon its release, "One by One" was considered the band's heaviest album, as Grohl described the sound as a darker and more aggressive approach as opposed to the band's usual work. Grohl said that the album mainly focused on the energy of live performances, which he attributed to both the extensive touring preceding the compositions, and the short period during which the re-recordings were done. The frontman added that although the previous albums had songs which were never played live, the track listing on "One by One" was compared to a set list where he would play all songs every night. The early recording sessions had manager John Silva complimenting the songs that did not sound like the band's previous work, and suggesting that Grohl "stop trying to write hit singles and go back to being weird", the band decided to be more experimental in addition to writing music meant to be played in full arenas. The variety included moody songs such as "Have It All" and "Tired of You", the seven-minute "epic opus" album closer "Come Back", and the alternating dynamics of "Halo", which drew inspiration from Tom Petty, Cheap Trick and Guided by Voices. Grohl added that the sonority tried to blend dissonance and melody: "We figured we're gonna get mean, we're gonna get ugly. And then I end up putting this four-part harmony on it, and all of sudden it's beautiful. Like 'wait a second, it was supposed to be gross, and now it's gorgeous'."


title: One by One (Foo Fighters album)

text: While in previous records Grohl tried to not get introspective in his lyrics, for "One by One" he found himself writing lyrics that matched the "emotional level we were hinting with the music", such as "Come Back", with words "revealing all these dark, shitty sides of myself". The lyrics to a song were usually done after finishing the vocal track for another. Grohl described the track listing as "11 tortured love songs", with a major theme of "surrendering to yourself", and a sequencing that described the difficult beginnings of falling in love, and then the relief of feeling comfortable in love. A major inspiration was Grohl's new girlfriend Jordyn Blum, as well as the troubled times with the band, demonstrated in "Times Like These", which laments the absence of the Foo Fighters and ponders about their future. Grohl also described "All My Life", released as a single, as representative of the album's sound for being "much more aggressive" as well as "a little darker, more romantic, creepier than anything we have done".


title: One by One (Foo Fighters album)

text: The album artwork was done by Raymond Pettibon, who has worked with punk bands such as Black Flag and Minutemen. Grohl was introduced to Pettibon by ex-Minutemen bassist Mike Watt and, after visiting his house, decided to hire him for the artwork because "we had to somehow pay tribute to Pettibon as a hero, because his stuff, those images just stuck with me my whole life." Grohl came up with the heart theme used in the booklet and related singles. The album was issued with two different covers, black and white. The first 575,000 units comprised a limited edition with a bonus DVD.


title: One by One (Foo Fighters album)

text: A limited international edition features seven bonus tracks: the outtake "Walking a Line", three live songs, and three covers, The Psychedelic Furs' "Sister Europe", the Ramones' "Danny Says"—with Shiflett on the vocals—and Joe Walsh's "Life of Illusion"—sung by Hawkins. A Norwegian version had an extra album with tracks recorded at the Oslo Spektrum on December 4, 2002. "One by One" was also issued as a double vinyl LP record, and a DVD-Audio with 5.1 surround sound mixes.


title: One by One (Foo Fighters album)

text: An Enhanced CD edition was released with weblinks to their official website and where to download free music.


title: One by One (Foo Fighters album)

text: "One by One" received generally positive reviews from contemporary music critics. At Metacritic, a website that assigns a normalized rating out of 100 to reviews from mainstream critics, the album received an average score of 75, based on 19 reviews. Reviewer Jon Pareles of "Rolling Stone" praised the "potent guitar riffs" and the introspective themes, which he called "stronger and broader than autobiography". "NME"s April Long felt that "even the quieter moments bristle" and considered the album an affirmation of the band's quality. Michael Paoletta of "Billboard" considered the album "among the band's best work" and that the themes gave the record "an emotional intimacy that makes it all more satisfying". "Entertainment Weekly"s Ken Tucker rated the album A−, calling it full of "unexpected exhilaration" and liking the "exploration of various relationships" on the lyrics. "The Austin Chronicle" reviewer praised the heavy sound of the album, saying it drifted from the light-hearted tone of songs such as "Big Me" while "retaining their melodic instincts".


title: One by One (Foo Fighters album)

text: However, many reviewers felt that the album was not up to the standards of the Foo Fighters' previous work. AllMusic's Stephen Thomas Erlewine said that although "One by One" was well-produced and played, it was too polished to "hit at a gut-level" and that the songs were "not as immediate or memorable" as the band's earlier compositions. Writing for PopMatters, Margaret Schwartz considered the album "ultimately unsatisfying" despite its quality writing and production, particularly for not drifting much from the band's typical style. Stephen Thompson of "The A.V. Club" described "One by One" as "mostly middling, sticking to slick, pounding, functional rock that doesn't dig much deeper than the usual spleen-venting and loud-quiet brooding-to-bluster formula". BBC's Nick Reynolds found the record inconsistent, praising the first four tracks but saying the following songs did not maintain the same quality, and concluding that although "One By One" is a good record, it may frustrate a listener. Eric Carr of "Pitchfork" was very critical of the album, saying it was overproduced and the songs are "weightless, antiseptic cuts" with "skillful composition" but "lacking strength and character".


title: One by One (Foo Fighters album)

text: In 2004, "One by One" won the Grammy Award for Best Rock Album, while one year earlier at the 45th Grammy Awards "All My Life" was chosen as Best Hard Rock Performance. While the band had a positive opinion about the record following release, as Grohl said the songs were "the best we've ever written", he and the rest of the Foo Fighters eventually grew distasteful about the results. Grohl stated that he was frustrated at himself for rushing on the album: "four of the songs were good, and the other seven I've never played again in my life." Hawkins said that "if you think about things too much, they kinda get sterile, as we found out there", and Shiflett declared that "there are great songs [in "One by One"], and then there are... "parts" of great songs".


title: One by One (Foo Fighters album)

text: "One by One" was released on October 22, 2002. That same day, the band began the One by One Tour with a concert at the Los Angeles Wiltern Theatre. The lead single "All My Life" had been released on September 7, and the band issued three more songs as singles in 2003: "Times Like These", "Low", and "Have It All". BMG became partners with telecom firm O2 and music provider Musiwave to promote the album in Europe with a special campaign focused on cellphones.


title: One by One (Foo Fighters album)

text: The album debuted at third place on the "Billboard" 200, with 122,000 copies sold in its first week, and spent 50 overall weeks on the chart. By 2011, "One by One" had sold 1.333 million units in North America, being certified Platinum by the RIAA. The international release was also successful, with RCA announcing "One by One" had surpassed 2 million copies worldwide in January 2003. The album debuted at number one in the United Kingdom, Ireland, and Australia, and outsold predecessor "There Is Nothing Left to Lose" in Australia, Japan and various Asian markets.


title: Act of Valor

text: Act of Valor is a 2012 American action film produced and directed by Mike McCoy and Scott Waugh, and written by Kurt Johnstad. Starring Alex Veadov, Roselyn Sánchez, Nestor Serrano and Emilio Rivera, as well as active duty U.S. Navy SEALs and U.S. Navy Special Warfare Combatant-craft Crewmen, the film was released by Relativity Media on February 24, 2012.


title: Act of Valor

text: The film opened to negative reviews from critics, but was well-received by audiences, grossing $81 million worldwide and being nominated at the 70th Golden Globe Awards for Best Original Song.


title: Act of Valor

text: In Manila a terrorist assassinates the United States Ambassador to the Philippines, and also kills his son and dozens of children at an international primary school, using an ice cream truck to lure the children then detonating. The mastermind, a Chechen terrorist, Abu Shabal, escapes to a training camp in Indonesia. Elsewhere in Costa Rica, two CIA officers, Walter Ross and Lisa Morales, meet to consolidate intelligence about their target, a drug smuggler named Mikhail "Christo" Troykovich. Christo's men kill Ross and capture Morales, who is imprisoned in a jungle compound and tortured.


title: Act of Valor

text: At Coronado, the members of Bandito Platoon, SEAL Team 7 are at home. Lieutenant Rorke confides to Chief Dave that his wife is pregnant and has the entire team spend time together with their families until their next deployment. A squad from the platoon consisting of Rorke, Dave, Wiemy, Mikey, Ray, Sonny, and Ajay, is then deployed to Costa Rica to exfiltrate Morales.


title: Act of Valor

text: The seven Navy SEALs insert into the jungle via HALO and hold position outside the compound all night. At dawn, they approach the compound and engage several enemy guards. Mikey is shot in the head, blinding him in one eye, and knocking him unconscious, though he survives. The SEALs extract Morales, escaping with her and recovering a cellphone full of the information she had gathered. However, the gunfight alerts the enemy quick reaction force. The SEALs commandeer an enemy truck and exfiltrate. The hot pursuit forces them to revert to a tertiary extraction point where two SWCC boats extract the team and neutralize the enemy pursuit with miniguns.


title: Act of Valor

text: Christo and Shabal, who are revealed to have been childhood friends, meet in Kyiv. Christo knows the CIA is watching him and informs Shabal that subordinates will complete their project, which is to equip suicide bombers with specialized undetectable explosive vests.


title: Act of Valor

text: On the amphibious assault ship USS "Bonhomme Richard", Rorke is informed that the intelligence recovered confirms Shabal and Christo were working together. Shabal, an old-school Islamic terrorist, seeks to bring jihad to the U.S., while Christo provides the routes for smuggling drugs and people into the U.S. Ajay and Ray are sent to Somalia, where an arms transfer involving Shabal is taking place. The remaining SEALs, comprising Rorke, Dave, Sonny and Weimy, stay in the U.S. in case the terrorists make it in. Miller himself has been reassigned to SEAL Team Four, hunting for Christo somewhere on the oceans. Lieutenant Rorke gives Dave a letter to give to his family in case he is killed.


title: Act of Valor

text: Shabal and sixteen terrorists are found to be on an island off Baja California, where the SEALs act to secure the island, killing eight terrorists. Shabal and eight others escape. Elsewhere, in the South Pacific, SEAL Team Four captures Christo and interrogate him, learning that Shabal's plot is to create panic and economic disruption to outdo the September 11 attacks.


title: Act of Valor

text: The SEALs are informed that Shabal is en route to the U.S. via tunnels underneath a milk factory, and are ordered to link up with Mexican Special Forces and neutralize the remaining targets. Arriving at the factory, the SEALs and Mexican forces launch an assault there, engaging numerous Mexican cartel and Shabal's terrorists in the process. During the gunfight, a combatant throws a grenade, and Rorke sacrifices himself by diving on it to save his team before it detonates, killing him. Dave pursues the terrorists and shoots them as they try to escape through the tunnels. He is then shot several times and gravely wounded by Shabal, who is intercepted and killed by Sonny before he could execute Dave.


title: Act of Valor

text: At home, Rorke is given a military funeral with full honors, where the SEALs pay their respects. It is then revealed that Dave's narration throughout the movie was a written letter meant for Rorke's son. The film ends with a dedication to 60 U.S. Navy SEAL and Special Warfare Combatant-craft Crewmen (SWCC) killed in action since 9/11 along with a listing of their names as well as a photo montage of fallen public servants.


title: Act of Valor

text: In 2007, Mike McCoy and Scott Waugh of Bandito Brothers Production filmed a promotional ad video for the Special Boat Teams which led the U.S. Navy to allow them to use actual active duty SEALs and Special Boat Team members. After spending so much time working closely with the SEALs and SWCC, McCoy and Waugh conceived the idea for a modern-day action movie about this covert and elite fighting force. As "Act of Valor" developed with the SEALs on board as advisors, the filmmakers realized that no actors could realistically portray or physically fill the roles they had written and the actual SEALs and SWCC were drafted to star in the film. The SEALs and Special Boat Team members would remain anonymous, as none of their names appear in the film's credits. Legendary Pictures' founder and then-chairman/CEO Thomas Tull serves as executive producer.


title: Act of Valor

text: For the Navy, the film is an initiative to recruit SEALs and SWCC. According to "The Huffington Post", the Navy required the active-duty SEALs to participate.


title: Act of Valor

text: Following a bidding war with Dark Castle Entertainment, Alcon Entertainment (both companies had their own respective distribution deals with Legendary's then-partner Warner Bros.), Lionsgate, and FilmDistrict, Relativity Media acquired the rights to the project on June 12, 2011 for $13 million and a $30 million in prints and advertising commitment. "Deadline Hollywood" called it "the biggest money paid for a finished film with an unknown cast". The production budget was estimated to be between $15 million and $18 million.


title: Act of Valor

text: Filming took place in Cambodia where an explosion was shot in Phnom Penh with 300 children as extras. Scenes were shot in San Diego at Blue Foot Bar and in a house in the North Park area. Other locations included Mexico, Puerto Rico, Ukraine, Florida, and at the John C. Stennis Space Center in Mississippi.


title: Act of Valor

text: The crew filmed at Navy training sites to provide realistic settings, such as a drug cartel base, a terrorist camp on an isolated island, and a smuggler's yacht.


title: Act of Valor

text: Cinematographer Shane Hurlbut used Canon EOS 5D Mark II cameras with Zeiss ZE and Panavision Primo lenses. The cameras followed the SEALs' planned out missions in the film. Hurlbut used an 18mm Zeiss ZE mounted on the SEALs' helmets to capture their point of view. The 25mm Zeiss ZE was used to capture natural light coming through windows. The 21mm Zeiss ZE was used as a stake cam so a truck could drive over it. The Navy held final cut privileges in order to remove any frames to address security concerns and kept raw footage to use for real-life training and other purposes.


title: Act of Valor

text: "Act of Valor" was scheduled to be released on February 17, 2012 in the U.S. to coincide with Presidents' Day, but was pushed back to February 24, 2012. The film was released in the UK and Ireland on March 23 as "Act of Valour" by Momentum Pictures.


title: Act of Valor

text: The film received a polarized review between critics and audiences. On Rotten Tomatoes the film has an approval rating of 28% based on 144 reviews with an average rating of 4.54/10, but an audience rating of 72% based on 50,000 reviews. The site's critical consensus reads, "It's undeniably reverent of the real-life heroes in its cast, but "Act of Valor" lets them down with a clichéd script, stilted acting, and a jingoistic attitude that ignores the complexities of war." Metacritic assigned the film an average score of 40 out of 100, based on 34 critics, indicating "mixed or average reviews".


title: Act of Valor

text: The film opened at #1 at the box office, earning $24.5 million in its opening weekend from 3,039 theaters for an average of $8,054 per theater.


title: Act of Valor

text: Many reviews, both positive and negative, expressed praise for the action sequences while criticizing the plot and acting. Claudia Puig from "USA Today", for example, said the action in the film is "breathtaking," but gave the film an overall negative review, in which she wrote that "the soldiers' awkward line readings are glaring enough to distract from the potency of the story." Similarly, Amy Biancolli from the "San Francisco Chronicle" wrote, ""Act of Valor" is intended to wow audiences with high-test action while planting a giant wet kiss on the smacker of the U.S. military – and it scores at both tasks," but that, ultimately, "the film gets snagged by its own narrative convention." Michael Rechtshaffen from "The Hollywood Reporter" had a similar opinion, stating, "Although the film has its undeniably immersive, convincing moments, the merging of dramatic re-creations and on-camera 'performances' proves less seamlessly executed than those masterfully coordinated land, sea and air missions."


title: Act of Valor

text: Roger Ebert of the "Chicago Sun-Times" gave the film two and a half out of four stars, and complained that "we don't get to know the characters as individuals, they don't have personality traits, they have no back stories, they don't speak in colorful dialogue, and after the movie you'd find yourself describing events but not people." The film was accused of having an antisemitic subtext by bloggers Debbie Schlussel and Pamela Geller as well as other Jewish sources.


title: Act of Valor

text: Relativity Media released the film's soundtrack on February 21, 2012. It includes 10 songs by country music artists. The first cut on the soundtrack, Keith Urban's "For You", was released as a single. The song was nominated for a Golden Globe Award for Best Original Song.


title: Om Birla

text: Om Birla (born 23 November 1962) is an Indian politician, agriculturist and social worker who is the 17th and current Speaker of the Lok Sabha. He serves as a Member of Parliament from Kota-Bundi constituency in Rajasthan. Prior to parliament, he was elected thrice to the assembly of Rajasthan. He belongs to the Bharatiya Janata Party.


title: Om Birla

text: Om Birla was born on 23 November 1962, to Shrikrishna Birla and Shakuntala Devi in a Marwari Hindu Maheshwari family. He completed his master's degree in commerce from Govt. Commerce College, Kota and Maharshi Dayanand Saraswati University, Ajmer. He married Amita Birla in 1991 and has two daughters Akansha and Anjali.


title: Om Birla

text: Om Birla won his first assembly elections contesting from Kota South in 2003. He defeated Shanti Dhariwal from Congress by a margin of 10,101 votes. In the next assembly elections, he defended his seat with a comfortable margin of 24,300 votes to his nearest candidate Ram Kishan Verma from Congress in 2008. Before becoming a Member of Parliament, he won his third assembly election against Pankaj Mehta (Congress) by close to 50,000 votes in 2013. During his tenure in 2003–08, he was the Parliamentary Secretary (MoS rank) in Rajasthan Government.


title: Om Birla

text: In the 16th Lok Sabha, he was a member of the Standing Committee on Energy and Consultative Committee for the Ministry of Social Justice and Empowerment.


title: Om Birla

text: Selection of the Kota-Bundi MP, Om Birla for the post of the Lok Sabha speaker surprised many including MPs from the treasury bench.


title: Om Birla

text: On the 19 June 2019 Om Birla was elected Speaker of the 17th Lok Sabha, following a motion for election moved by Prime Minister Modi of the Bharatiya Janata Party. The Congress and the Dravida Munnetra Kazhagam parties also moved notices for Birla and urged him to be impartial as presiding officer of the Lower House. The parliamentary convention for the Republic of India is for the Deputy Speaker of the Lok Sabha to come from the Opposition benches. As of March 2021, uniquely in the history of the Republic, the Lok Sabha approaches two years of a vacant Deputy Speaker seat.


title: Black hair

text: Black hair is the darkest and most common of all human hair colors globally, due to larger populations with this dominant trait. It is a dominant genetic trait, and it is found in people of all backgrounds and ethnicities. Black hair contains a large amount of eumelanin pigmentation, a type of melanin. This hair type contains a much more dense quantity of eumelanin in comparison to other hair colors, such as brown, blonde and red. In English, various types of black hair are sometimes described as soft-black, raven black, or jet-black. The range of skin colors associated with black hair is vast, ranging from the palest of light skin tones to dark skin. Black-haired humans can have dark or light eyes.


title: Black hair

text: Black hair is known to be the most common in the countries of Asia and Africa. Though this characteristic can also be seen in people of Southern Europe and France, it is less common. People of Celtic heritage in Ireland with such traits are sometimes known as the "Black Irish". Black hair can come in a variety of textures, just as any hair color. Generally, the Asian population has straight, black hair with a very thick cuticle layer while the general hair type seen in black African hair is thick, curly and dense with more hair growing from the head. The curly quality comes from the shape of the hair follicle, as straight hair grows from more circular hair follicles, and curly hair grows from more oval-like follicles.


title: Black hair

text: Hair is naturally reflective, so black hair is not completely dark in bright light. However, the darkest shade will not have a warm, neutral tone but a sheen which can seem almost blue, like the iridescence of a raven's wing; hence, sometimes referred to as raven-black.


title: Black hair

text: Native Americans, East Asian, Southeast Asian, Southwest Asian, Middle Eastern, Far East Russian, South Asian and Himalayan black-haired people


title: Black hair

text: have thicker and straighter hair due to the derived EDAR gene allele that is linked to thicker and straighter hair and shovel-shaped incisors. The derived EDAR gene arose approximately 30,000 years ago in China. One study shows that Paleo-Indians had both variants of the EDAR gene, the derived G-allele and the ancestral A-allele. When they tested ancient DNA remains found in the Americas of the individuals named USR1, Anzick-1 and Laranjal-6700 the results showed that they carried the ancestral A-allele.


title: Black hair

text: 11,000-year-old remains of Cuncaicha and Lauricocha individuals from South America share alleles at the highest rate with present-day Amerindians, indicating that the derived G-allele increased in frequency in parallel with the ancestral A-allele.


title: Black hair

text: One of the most studied genes that produce brown hair is MC1R, which helps the body to produce the melanocortin protein. This protein in turn helps the body’s hair follicles to produce the type of melanin called eumelanin. To have black hair, one must have genetically inherited this gene from both of their parents, and brown hair is achieved when it is inherited from one parent. This gene is demographically common, as 90% of the total world population carries this gene. Black hair, along with grown hair, comes to turn grey in old age as the hair follicles can no longer produce the pigmentation, but the cause of this inability has yet to be determined.


title: Virgin Atlantic fleet

text: Virgin Atlantic operates a fleet consisting of widebody twinjet aircraft from both Airbus and Boeing.


title: Virgin Atlantic fleet

text: Over the course of the airline's history, Virgin Atlantic has operated a mix of widebody aircraft from Airbus and Boeing, as well as a limited number of narrowbody Airbus aircraft. Initially launching with a fleet of Boeing 747-200 aircraft in 1984, the airline's fleet continued to be composed entirely of four-engined widebody aircraft with the incorporation of a single Boeing 747-100 in 1990, the Airbus A340-300 in 1993, and the larger Boeing 747-400 in 1994. Between 1995 and 2000, the airline began operating the twin-engined Airbus A320 family and Boeing 767. In August 2002, Virgin Atlantic became the first airline to operate the larger Airbus A340-600 variant of the A340. By 2005, the airline retired its Boeing 747-100 and 747-200 aircraft, retaining the 747-400s.


title: Virgin Atlantic fleet

text: On 27 September 2006, Richard Branson announced plans to reduce greenhouse gas emissions by cutting aircraft weight and fuel consumption. There was also an experiment in 2007 in partnership with Boeing to have aircraft towed to the runway to save fuel, as a potential change to future operational procedures. Virgin Atlantic also volunteered a Boeing 747 for a test of biofuels in February 2008. The aircraft flew without passengers from Heathrow to Amsterdam Airport Schiphol, with 20% of the power for one engine provided by plant-based biofuel. Virgin Atlantic said that it expected to use algae-based biofuels in the future.


title: Virgin Atlantic fleet

text: On 24 April 2007, Virgin Atlantic announced it had ordered the Boeing 787 Dreamliner, for a total of 15 Boeing 787-9s, with options on eight more. The exercised options, later making for a total fleet of 17 Boeing 787-9s, were planned replace the Heathrow-based 747 fleet during 2015 and 2016. The 787s were due to be delivered in 2011, but by 2008 were expected to be delayed to at least 2013. The following year on 22 June 2009, the airline announced an order for ten Airbus A330-300s, which would enter service initially in 2011, ahead of its delayed Boeing 787s. The announcement of the orders and subsequent induction of the two aircraft types notably ended the airline's four-engined aircraft fleet composition, as the airline previously marketed itself with the "4 engines 4 long haul" slogan. While its first two Airbus A330-300s would operate on leisure-oriented routes following delivery in 2011, Virgin Atlantic would begin operating A330s on its premium routes from Heathrow in April 2012. Virgin Atlantic had also ordered six Airbus A380-800 aircraft, with options on a further six, delivery initially due in 2006, but the deliveries repeatedly deferred. The A380 order was officially cancelled in March 2018, with deposits transferred to A330 and A350 aircraft orders.


title: Virgin Atlantic fleet

text: In March 2013, Virgin Atlantic resumed operations of narrowbody Airbus A320 family aircraft, with four Airbus A320-200s wet-leased from Aer Lingus to operate short-haul, domestic services from its Heathrow hub. The services were operated by Virgin Atlantic Little Red, a new subsidiary airline founded for the operation of the services. Due to low passenger numbers and significant financial losses, Virgin Atlantic Little Red's services were discontinued by September 2015, and Virgin Atlantic had returned to wholly widebody aircraft operations.


title: Virgin Atlantic fleet

text: Virgin Atlantic took delivery of its first Boeing 787-9 in October 2014, becoming the first European airline to fly the variant. The older Airbus A340-300 aircraft were withdrawn from service in April 2015, as rising costs had made it less economical to run the type. Virgin Atlantic had begun to replace the A340-300 on routes with the two-engine A330-300 and 787-9. The final Virgin Atlantic A340-300 flight was made on 9 April, landing at Heathrow early on 10 April. Eight of the larger Airbus A340-600s remained in service.


title: Virgin Atlantic fleet

text: Branson announced in March 2016 that The Spaceship Company would partner with Boom Technology to develop supersonic jets capable of travelling between London and New York in three and a half hours. He confirmed that Virgin Atlantic had options on 10 of the aircraft.