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Cholesterol oxidase	Cholesterol oxidase	In enzymology, a cholesterol oxidase (EC 1.1.3.6) is an enzyme that catalyzes the chemical reaction cholesterol + O2 ⇌ cholest-4-en-3-one + H2O2Thus, the two substrates of this enzyme are cholesterol and O2, whereas its two products are cholest-4-en-3-one and H2O2. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with oxygen as acceptor. The systematic name of this enzyme class is cholesterol:oxygen oxidoreductase. Other names in common use include cholesterol- O2 oxidoreductase, 3beta-hydroxy steroid oxidoreductase, and 3beta-hydroxysteroid:oxygen oxidoreductase. This enzyme participates in bile acid biosynthesis. The substrate-binding domain found in some bacterial cholesterol oxidases is composed of an eight-stranded mixed beta-pleated sheet and six alpha-helices. This domain is positioned over the isoalloxazine ring system of the FAD cofactor bound by the FAD-binding domain and forms the roof of the active site cavity, allowing for catalysis of oxidation and isomerisation of cholesterol to cholest-4-en-3-one.
Cholesterol oxidase	Structural studies	As of late 2007, 14 structures have been solved for this class of enzymes, with PDB accession codes 1B4V, 1B8S, 1CBO, 1CC2, 1COY, 1I19, 1IJH, 1MXT, 1N1P, 1N4U, 1N4V, 1N4W, 2GEW, and 3COX.
Visual snow syndrome	Visual snow syndrome	Visual snow syndrome (VSS) is an uncommon neurological condition in which the primary symptom is that affected individuals see persistent flickering white, black, transparent, or coloured dots across the whole visual field. Other common symptoms are palinopsia, enhanced entoptic phenomena, photophobia, and tension headaches. The condition is typically always present and has no known cure, as viable treatments are still under research. Astigmatism, although not presumed connected to these visual disturbances, is a common comorbidity. As well, migraine and tinnitus are common comorbidities which are both associated with a more severe presentation of the syndrome. TMJ may also be a common comorbidity.The cause of the syndrome is unclear. The underlying mechanism is believed to involve excessive excitability of neurons in the right lingual gyrus and left anterior lobe of cerebellum. Another hypothesis proposes that visual snow syndrome could be a type of thalamocortical dysrhythmia and may involve the thalamic reticular nucleus (TRN). A failure of inhibitory action from the TRN to the thalamus may be the underlying cause for inability to suppress excitatory sensory information. Research has been limited due to issues of case identification and diagnosis, the latter now largely addressed, and the limited size of any studied cohort. Initial functional brain imaging research suggests visual snow is a brain disorder.
Visual snow syndrome	Visual snow syndrome	There is no established treatment for visual snow syndrome. Medications that may be used to treat the condition include lamotrigine, acetazolamide, or verapamil. However, in absence of a secondary pharmaceutical indication, these do not necessarily result in benefits, and the evidence for their use is limited.
Visual snow syndrome	Signs and symptoms	In addition to visual snow, many of those affected have other types of visual disturbances such as starbursts, increased afterimages, floaters, trails, and many others.Visual snow likely represents a clinical continuum, with different degrees of severity. The presence of comorbidities such as migraine and tinnitus is associated with a more severe presentation of the visual symptoms. Diagnosis Visual snow syndrome is usually diagnosed with the following proposed criteria: Visual snow: dynamic, continuous, tiny dots in the entire visual field lasting more than three months. The dots are usually black/gray on a white background and gray/white on a black background; however, they can also be transparent, white flashing, or colored. Presence of at least 2 additional visual symptoms of the 4 following categories: i. Palinopsia. At least 1 of the following: afterimages or trailing of moving objects. ii. Enhanced entoptic phenomena. At least 1 of the following: excessive floaters in both eyes, excessive blue field entoptic phenomenon, self-light of the eye (phosphenes), or spontaneous photopsia. iii. Photophobia. iv. Nyctalopia; impaired night vision. Symptoms are not consistent with typical migraine aura. Symptoms are not better explained by another disorder (ophthalmological, drug abuse). Normal ophthalmology tests (best-corrected visual acuity, dilated fundus examination, visual field, and electroretinogram); not caused by previous intake of psychotropic drugs.Additional and non visual symptoms like tinnitus, ear pressure or brain fog and more might be present. It can also be diagnosed by PET scan.
Visual snow syndrome	Signs and symptoms	Comorbidities Migraine and migraine with aura are common comorbidities. However, comorbid migraine worsens some of the additional visual symptoms and tinnitus seen in "visual snow" syndrome. This might bias research studies by patients with migraine being more likely to offer study participation than those without migraine due to having more severe symptoms. In contrast to migraine, comorbidity of typical migraine aura does not appear to worsen symptoms.Psychological side effects of visual snow can include depersonalization, derealization, depression, photophobia and heliophobia in the individual affected.Patients with visual "snow" have normal equivalent input noise levels and contrast sensitivity. In a 2010 study, Raghaven et al. hypothesize that what the patients see as "snow" is eigengrau. This would also explain why many report more visual snow in low light conditions: "The intrinsic dark noise of primate cones is equivalent to ~4000 absorbed photons per second at mean light levels; below this the cone signals are dominated by intrinsic noise".
Visual snow syndrome	Causes	The causes are unclear. The underlying mechanism is believed to involve excessive excitability of neurons within the cortex of the brain, specifically the right lingual gyrus and left cerebellar anterior lobe of the brain.Persisting visual snow can feature as a leading addition to a migraine complication called persistent aura without infarction, commonly referred to as persistent migraine aura (PMA). In other clinical sub-forms of migraine headache may be absent and the migraine aura may not take the typical form of the zigzagged fortification spectrum (scintillating scotoma), but manifests with a large variety of focal neurological symptoms.Visual snow does not depend on the effect of psychotropic substances on the brain. Hallucinogen persisting perception disorder (HPPD), a condition caused by hallucinogenic drug use, is sometimes linked to visual snow, but both the connection of visual snow to HPPD and the cause and prevalence of HPPD is disputed. Most of the evidence for both is generally anecdotal, and subject to spotlight fallacy.
Visual snow syndrome	Timeline	In May 2015, visual snow was described as a persisting positive visual phenomenon distinct from migraine aura in a study by Schankin and Goadsby. In December 2020, a study found local increases in regional cerebral perfusion in patients with visual snow syndrome. In September 2021, two studies found white matter alterations in parts of the visual cortex and outside the visual cortex in patients with visual snow syndrome.
Visual snow syndrome	Treatments	It is difficult to resolve visual snow with treatment, but it is possible to reduce symptoms and improve quality of life through treatment, both of the syndrome and its comorbidities. Medications that may be used include lamotrigine, acetazolamide, or verapamil, but these do not always result in benefits. As of 2021, there were two ongoing clinical trials using transcranial magnetic stimulation and neurofeedback for visual snow.A recent study in the British Journal of Ophthalmology has confirmed that common drug treatments are generally ineffective in visual snow syndrome (VSS). Vitamins and benzodiazepines, however, were shown to be beneficial in some patients and can be considered safe for this condition.Victoria Pelak, a Professor of Neurology and Ophthalmology in the Department of Neurology at the University of Colorado Anschutz Medical Campus has recently directed, published, and completed enrollment for a TMS study protocol. The study protocol aims to investigate the use of rTMS intervention to improve symptoms and visual dysfunction associated with visual snow (VS); the study protocol also describes the challenges during the COVID-19 pandemic.In addition, Pelak described during her practice that she lets patients know that current treatment options are only limited to alleviating symptoms. She recommends that her patients focus on pharmaceutical and non-pharmaceutical treatments to control migraine, headaches, anxiety, and depression. As for light sensitivity complications, Pelak advises patients to use FL-41 tinted lenses indoors. She also recommends visual occupational therapists who assist patients with color-tinted lenses to alleviate VSS symptoms. Furthermore, Pelak states that exercising, meditation, and a healthy balanced diet can improve overall daily functioning.
Cyclohexene oxide	Cyclohexene oxide	Cyclohexene oxide is a cycloaliphatic epoxide. It can react in cationic polymerization to poly(cyclohexene oxide). As cyclohexene is monovalent, poly(cyclohexene oxide) is a thermoplastic.
Cyclohexene oxide	Production	Cyclohexene oxide is produced in epoxidation reaction from cyclohexene. The epoxidation can take place either in a homogeneous reaction by peracids or heterogeneous catalysis (e.g. silver and molecular oxygen).
Cyclohexene oxide	Production	In industrial production the heterogeneously catalyzed synthesis is preferred because of better atom economy, a simpler separation of the product and easier recycling of catalyst. A short overview and an investigation of the oxidation of cyclohexene by hydrogen peroxide is given in the literature. In recent times the catalytic oxidation of cyclohexene by (immobilized) metalloporphyrin complexes has been found to be an efficient way.In laboratory, cyclohexene oxide can also be prepared by reacting cyclohexene with magnesium monoperoxyphthalate (MMPP) in a mixture of isopropanol and water as solvent at room temperature.
Cyclohexene oxide	Production	With this method, good yields up to 85 % can be reached.
Cyclohexene oxide	Properties and reactions	Cyclohexene has been studied extensively by analytical methods. Cyclohexene oxide can be polymerized in solution, catalyzed by a solid acid catalyst.
Ferrocerium	Ferrocerium	Ferrocerium (also known in Europe as Auermetall) is a synthetic pyrophoric alloy of mischmetal (cerium, lanthanum, neodymium, other trace lanthanides and some iron – about 95% lanthanides and 5% iron) hardened by blending in oxides of iron and/or magnesium. When struck with a harder material, the mixture produces hot sparks that can reach temperatures of 3,315 °C (6,000 °F) when rapidly oxidized by the process of striking the rod. Striking both scrapes fragments off, exposing them to the oxygen in the air, and easily ignites them by friction heat due to cerium's remarkably low ignition temperature of between 150–180 °C (302–356 °F).
Ferrocerium	Ferrocerium	Its easy flammability gives ferrocerium many commercial applications, such as the ignition source for lighters, strikers for gas welding and cutting torches, deoxidization in metallurgy, and ferrocerium rods. Because of ferrocerium's ability to ignite in adverse conditions, rods of ferrocerium (also called ferro rods, spark rods, and flint-spark-lighters) are commonly used as an emergency fire lighting device in survival kits. The ferrocerium is referred to as a "flint" in this case despite being dissimilar to natural flint as both are used in conjunction for fire lighting, albeit with opposite mechanical operation.
Ferrocerium	Discovery	Ferrocerium alloy was invented in 1903 by the Austrian chemist Carl Auer von Welsbach. It takes its name from its two primary components: iron (from Latin: ferrum), and the rare-earth element cerium, which is the most prevalent of the lanthanides in the mixture. Except for the extra iron and magnesium oxides added to harden it, the mixture is approximately the combination found naturally in tailings from thorium mining, which Auer von Welsbach was investigating. The pyrophoric effect is dependent on the brittleness of the alloy and its low autoignition temperature.
Ferrocerium	Composition	In Auer von Welsbach's first alloy, 30% iron (ferrum) was added to purified cerium, hence the name "ferro-cerium". Two subsequent Auermetalls were developed: the second also included lanthanum to produce brighter sparks, and the third added other heavy metals. A modern ferrocerium firesteel product is composed of an alloy of rare-earth metals called mischmetal, containing approximately 20.8% iron, 41.8% cerium, about 4.4% each of praseodymium, neodymium, and magnesium, plus 24.2% lanthanum. A variety of other components are added to modify the spark and processing characteristics. Most contemporary flints are hardened with iron oxide and magnesium oxide.
Ferrocerium	Uses	Ferrocerium is used in fire lighting in conjunction with steel, similarly to natural flint-and-steel, though ferrocerium takes on the opposite role to the traditional system; instead of a natural flint rock striking tiny iron particles from a firesteel, a steel striker (which may be in the form of hardened steel wheel) strikes particles of ferrocerium off of the "flint". This manual rubbing action, done by squeezing the handle, creates a spark due to cerium's low ignition temperature between 150–180 °C (302–356 °F). Carbon steel works better than most other materials, in much the same way natural flint and firesteel are used.It is most commonly used for Bunsen burners and oxyacetylene welding torches.About 700 tons were produced in 2000.
Cinder track	Cinder track	A cinder track is a type of race track, generally purposed for track and field or horse racing, whose surface is composed of cinders. For running tracks, many cinder surfaces have been replaced by all-weather synthetic surfaces, which provide greater durability and more consistent results, and are less stressful on runners. The impact on performance as a result of differing track surfaces is a topic often raised when comparing athletes from different eras.Synthetic tracks emerged in the late 1960s; the 1964 Olympics were the last to use a cinder track.The Little 500 bicycle race at Indiana University is still run annually on a cinder track.
P-Dioxanone	P-Dioxanone	p-Dioxanone (1,4-dioxan-2-one) is the lactone of 2-(2-hydroxyethoxy)acetic acid. It is a monomer that can undergo ring-opening polymerization to give polydioxanone, a biodegradable implant material. It is isomeric to trimethylene carbonate (1,3-dioxan-2-one).
P-Dioxanone	Preparation	The common synthetic process for p-dioxanone is continuous gas-phase dehydrogenation of diethylene glycol on a copper or copper chromite catalyst at 280 °C. This gives yields of up to 86%. Removal of excess diethylene glycol is crucial to the stability of the product as a monomer. Further purification with recrystallization, vacuum distillation, or melt crystallization allows purities of >99.5% to be achieved.
P-Dioxanone	Properties	Pure p-dioxanone is a white crystalline solid with a melting point of 28 °C.
P-Dioxanone	Uses	The oxidation of p-dioxanone with nitric acid or dinitrogen tetroxide gives diglycolic acid at 75% yield.p-Dioxanone can undergo ring-opening polymerization catalyzed by organic compounds of tin, such as tin(II) octoate or dibutyltin dilaurate, or by basic alkoxides such as aluminium isopropoxide. This affords polydioxanone, a biodegradable, semicrystalline and thermally labile polymer with uses in industry and medicine. Depolymerization back to the monomer is triggered at 100 °C.
Mexrenoic acid	Mexrenoic acid	Mexrenoic acid, or mexrenoate, is a synthetic steroidal antimineralocorticoid which was never marketed.
Sulfur water	Sulfur water	Sulfur water (or sulphur water) is a condition where water is exposed to hydrogen sulfide gas, giving a distinct "rotten egg" smell. This condition has different purposes in culture varying to health and implications to plumbing.
Sulfur water	Chemical composition	Sulfur water is made out of dissolved minerals that contain sulfate. These include baryte (BaSO4), epsomite (MgSO4 7H2O) and gypsum (CaSO42H20). It is reported that a notable change in taste to the water is found differently to the type of sulfate affecting the water. For sodium sulfate, 250 to 500 mg/litre, with calcium sulfate at 250 to 1000 mg/litre and magnesium sulfate at 400 to 600 mg/litre. A study by Zoeteman found that having 270 mg of calcium sulfate and 90 mg of magnesium sulfate actually had improved the taste of the water.
Sulfur water	Health	Bathing in water high in sulfur or other minerals for its presumed health benefits is known as balneotherapy. These are said to give a person bathing in the waters "ageless beauty" and relief from aches and pains.While humans have been able to adapt to higher levels of concentrations with time, some effects of ingestion of sulfur water has found to have cathartic effects on people consuming water with sulfate concentrations of 600 mg/litre according to a study from the US Department of health in 1962. Some adverse effects that have been found include dehydration, with excess amounts of sodium or magnesium sulfate in a person's diet according to a study in 1980, with some populations, such as children and elderly people, being seen as higher risk.
Sulfur water	Health	A survey was done in North Dakota US to better derive whether there was direct causation of a laxative effect from having sulfur in drinking water. From this data, it was concluded that water containing more than 750 mg of sulfate per litre was due to a laxative effect, and below 600 was not. Concerns According to The Environmental Protection Agency (EPA) and the Centers for Disease Control and Prevention (CDC), drinking water with high levels of sulfate can cause diarrhea, especially in infants.
Sulfur water	Cultural implications	Farming At the University of Wyoming in America, sulfur water was studied to see the effects it can have upon the performance of steers that are on a forage-based diet. Due to sulfur being a requirement to living things, as it contains essential amino acids that are used to create proteins, sulfur water, which is commonly found in Western States of America, is a major contributor to sulfur in the herds diet. However, with a herd drinking high concentrate of sulfur water, ruminants may contract sulfur induced polioencephalomalacia (sPEM), which is a neurological disorder. Because of this finding, the study tries to reach the goal of finding a dietary supplement which can be used to counteract the negative health effects on the steers. To reduce the extra sulfur in the ruminant's diet, ruminal bacteria break the excess down, resulting in Hydrogen Sulfide, which is soluble in water, but as temperature increases, the solubility decreases, which leads to the hydrogen sulfide gas being reinhaled by the animal, causing sulfur induced polioencephalomalacia. The study attempted to resolve this issue by introducing clinoptilolite to the diet of the herd, but has found inconclusive evidence which requires more study of clinoptilolite effects on methanogenesis and biohydrogenation.
Sulfur water	Cultural implications	Sulfur Springs There is also believed to be great health benefits within sulfur water, with sulfur water springs being a common thing within many cultures. Such springs can be found in many countries such as New Zealand, Japan and Greece. These sulfur springs are often created due to the local volcanic activity which contributes to heating up nearby water systems. This is due to volcanoes exhaling water vapour heavily encased in metals, with sulfur dioxide being one of them.
Sulfur water	Cultural implications	In New Zealand, the North Island was brought to fame in the 1800s, with its baths heated naturally from a volcano near the town of Rotorua. There are 28 spa hot pools which visitors can soak themselves, along with sulfur mud baths. Another famous spring is the spring in Greece, Thermopylae, which means "hot springs" derives its name from its springs, as it was believed to be the entrance to Hades.
Sulfur water	Cause and treatment	The condition indicates a high level of sulfate-reducing bacteria in the water supply. This may be due to the use of well water, poorly treated city water, or water heater contamination. Various methods exist to treat sulfur in water. These methods include Filtration of the water using a carbon filter (useful for very small amounts of hydrogen sulfide) Filtration of the water through a canister of manganese oxide coated greensand Aeration of the water Chlorination of water (can be used to treat large amounts of hydrogen sulfide)
Sulfur water	Levels of sulfur in water around the world	The Global Environment Monitoring System for Freshwater (GEMS/Water) has said that typical fresh water holds about 20 mg/litre of sulfur, and can range from 0 to 630 mg/litre in rivers, 2 to 250 mg/litre in lakes and 0 to 230 mg/litre in groundwater.Canada's rain has been found to have sulfate concentrations of 1.0 and 3.8 mg/L in 1980, found in a study by Franklin published in 1985. Western Canada in rivers ranged from 1 to 3040 mg/litre, with most concentrations below 580 mg/litre according to results from Environment Canada in 1984. Central Canada had levels that were also high in Saskatchewan, there were median levels of 368 mg/litre in drinking water from ground water supplies, and 97 mg/litre in surface water supplies, with a range of 32170 mg/litre.
Sulfur water	Levels of sulfur in water around the world	A study conducted in Canada found that a treatment to reduce sulfur in drinking water had actually increased it. This was conducted in Ontario, which had a mean sulfur level of 12.5 mg/litre when untreated, and 22.5 mg/litre after the treatment.
Sulfur water	Levels of sulfur in water around the world	The Netherlands has had below 150 mg/litre concentrations of sulfur water in their underground water supplies. 65% of water treatment plants reported that the sulfur level of drinking water was below 25 mg/litre, as found in a study by Dijk-Looijaard & Fonds in 1985.The US had the Public Health Service in 1970 to measure levels of sulfate in drinking water sources in nine different geographic areas. The results concluded that all of the 106 surface water supplies that were sampled had sulfate present, as well as 645 of 658 ground water deposits that were tested. The levels of sulfur that was found ranged from less than 1 mg/litre to 770.
Sulfur water	Environment	Due to sulfates being used in industrial products, they are often discharged into water supplies in the environment. This includes mines, textile mills and other industrial processes that involve using sulfates. Sulfates, such as magnesium, potassium and sodium are all highly soluble in water, which is what creates sulfur water, while other sulfates which are metal based, such as calcium and barium are less soluble. Atmospheric sulfur dioxide, also can infect surface water, and sulfur trioxide can combine with water vapour in the air, and create sulfur water rain, or what is colloquially known as acid rain.
NPR1	NPR1	Natriuretic peptide receptor A/guanylate cyclase A (atrionatriuretic peptide receptor A), also known as NPR1, is an atrial natriuretic peptide receptor. In humans it is encoded by the NPR1 gene.
NPR1	Function	NPR1 is a membrane-bound guanylate cyclase that serves as the receptor for both atrial and brain natriuretic peptides (ANP and BNP, respectively).It is localized in the kidney where it results in natriuresis upon binding to natriuretic peptides. However, it is found in even greater quantity in the lungs and adipocytes.
Hashtag	Hashtag	A hashtag is a metadata tag that is prefaced by the hash symbol, #. On social media, hashtags are used on microblogging and photo-sharing services such as Twitter or Tumblr as a form of user-generated tagging that enables cross-referencing of content by topic or theme. For example, a search within Instagram for the hashtag #bluesky returns all posts that have been tagged with that term. After the initial hash symbol, a hashtag may include letters, numerals, or underscores.The use of hashtags was first proposed by American blogger and product consultant Chris Messina in a 2007 tweet. Messina made no attempt to patent the use because he felt that "they were born of the internet, and owned by no one". Hashtags became entrenched in the culture of Twitter and soon emerged across Instagram, Facebook, and YouTube. In June 2014, hashtag was added to the Oxford English Dictionary as "a word or phrase with the symbol # in front of it, used on social media websites and apps so that you can search for all messages with the same subject".
Hashtag	Origin and acceptance	The number sign or hash symbol, #, has long been used in information technology to highlight specific pieces of text. In 1970, the number sign was used to denote immediate address mode in the assembly language of the PDP-11 when placed next to a symbol or a number, and around 1973, '#' was introduced in the C programming language to indicate special keywords that the C preprocessor had to process first. The pound sign was adopted for use within IRC (Internet Relay Chat) networks around 1988 to label groups and topics. Channels or topics that are available across an entire IRC network are prefixed with a hash symbol # (as opposed to those local to a server, which uses an ampersand '&').The use of the pound sign in IRC inspired Chris Messina to propose a similar system on Twitter to tag topics of interest on the microblogging network. He posted the first hashtag on Twitter: How do you feel about using # (pound) for groups. As in #barcamp [msg]? According to Messina, he suggested use of the hashtag to make it easy for lay users without specialized knowledge of search protocols to find specific relevant content. Therefore, the hashtag "was created organically by Twitter users as a way to categorize messages".The first published use of the term "hash tag" was in a blog post "Hash Tags = Twitter Groupings" by Stowe Boyd, on August 26, 2007, according to lexicographer Ben Zimmer, chair of the American Dialect Society's New Words Committee.
Hashtag	Origin and acceptance	Messina's suggestion to use the hashtag was not immediately adopted by Twitter, but the convention gained popular acceptance when hashtags were used in tweets relating to the 2007 San Diego forest fires in Southern California. The hashtag gained international acceptance during the 2009–2010 Iranian election protests; Twitter users used both English- and Persian-language hashtags in communications during the events.Hashtags have since played critical roles in recent social movements such as #jesuischarlie, #BLM, and #MeToo.Beginning July 2, 2009, Twitter began to hyperlink all hashtags in tweets to Twitter search results for the hashtagged word (and for the standard spelling of commonly misspelled words). In 2010, Twitter introduced "Trending Topics" on the Twitter front page, displaying hashtags that are rapidly becoming popular, and the significance of trending hashtags has become so great that the company makes significant efforts to foil attempts to spam the trending list. During the 2010 World Cup, Twitter explicitly encouraged the use of hashtags with the temporary deployment of "hashflags", which replaced hashtags of three-letter country codes with their respective national flags.Other platforms such as YouTube and Gawker Media followed in officially supporting hashtags, and real-time search aggregators such as Google Real-Time Search began supporting hashtags.
Hashtag	Format	A hashtag must begin with a hash (#) character followed by other characters, and is terminated by a space or the end of the line. Some platforms may require the # to be preceded with a space. Most or all platforms that support hashtags permit the inclusion of letters (without diacritics), numerals, and underscores. Other characters may be supported on a platform-by-platform basis. Some characters, such as & are generally not supported as they may already serve other search functions. Hashtags are not case sensitive (a search for "#hashtag" will match "#HashTag" as well), but the use of embedded capitals (i.e., CamelCase) increases legibility and improves accessibility.
Hashtag	Format	Languages that do not use word dividers handle hashtags differently. In China, microblogs Sina Weibo and Tencent Weibo use a double-hashtag-delimited #HashName# format, since the lack of spacing between Chinese characters necessitates a closing tag. Twitter uses a different syntax for Chinese characters and orthographies with similar spacing conventions: the hashtag contains unspaced characters, separated from preceding and following text by spaces (e.g., '我 #爱你' instead of '我#爱你') or by zero-width non-joiner characters before and after the hashtagged element, to retain a linguistically natural appearance (displaying as unspaced '我‌#爱‌你', but with invisible non-joiners delimiting the hashtag).
Hashtag	Format	Etiquette and regulation Some communities may limit, officially or unofficially, the number of hashtags permitted on a single post.Misuse of hashtags can lead to account suspensions. Twitter warns that adding hashtags to unrelated tweets, or repeated use of the same hashtag without adding to a conversation can filter an account from search results, or suspend the account.Individual platforms may deactivate certain hashtags either for being too generic to be useful, such as #photography on Instagram, or due to their use to facilitate illegal activities.
Hashtag	Format	Alternate formats In 2009, StockTwits began using ticker symbols preceded by the dollar sign (e.g., $XRX). In July 2012, Twitter began supporting the tag convention and dubbed it the "cashtag". The convention has extended to national currencies, and Cash App has implemented the cashtag to mark usernames.
Hashtag	Function	Hashtags are particularly useful in unmoderated forums that lack a formal ontological organization. Hashtags help users find content similar interest. Hashtags are neither registered nor controlled by any one user or group of users. They do not contain any set definitions, meaning that a single hashtag can be used for any number of purposes, and that the accepted meaning of a hashtag can change with time.
Hashtag	Function	Hashtags intended for discussion of a particular event tend to use an obscure wording to avoid being caught up with generic conversations on similar subjects, such as a cake festival using #cakefestival rather than simply #cake. However, this can also make it difficult for topics to become "trending topics" because people often use different spelling or words to refer to the same topic. For topics to trend, there must be a consensus, whether silent or stated, that the hashtag refers to that specific topic.
Hashtag	Function	Hashtags may be used informally to express context around a given message, with no intent to categorize the message for later searching, sharing, or other reasons. Hashtags may thus serve as a reflexive meta-commentary.This can help express contextual cues or offer more depth to the information or message that appears with the hashtag. "My arms are getting darker by the minute. #toomuchfaketan". Another function of the hashtag can be used to express personal feelings and emotions. For example, with "It's Monday!! #excited #sarcasm" in which the adjectives are directly indicating the emotions of the speaker.Verbal use of the word hashtag is sometimes used in informal conversations. Use may be humorous, such as "I'm hashtag confused!" By August 2012, use of a hand gesture, sometimes called the "finger hashtag", in which the index and middle finger both hands are extended and arranged perpendicularly to form the hash, was documented.
Hashtag	Function	Co-optation by other industries Companies, businesses, and advocacy organizations have taken advantage of hashtag-based discussions for promotion of their products, services or campaigns.
Hashtag	Function	In the early 2010s, some television broadcasters began to employ hashtags related to programs in digital on-screen graphics, to encourage viewers to participate in a backchannel of discussion via social media prior to, during, or after the program. Television commercials have sometimes contained hashtags for similar purposes.The increased usage of hashtags as brand promotion devices has been compared to the promotion of branded "keywords" by AOL in the late 1990s and early 2000s, as such keywords were also promoted at the end of television commercials and series episodes.Organized real-world events have used hashtags and ad hoc lists for discussion and promotion among participants. Hashtags are used as beacons by event participants to find each other, both on Twitter and, in many cases, during actual physical events.
Hashtag	Function	Since the 2012–13 season, the NBA has allowed fans to vote players in as All-Star Game starters on Twitter and Facebook using #NBAVOTE.Hashtag-centered biomedical Twitter campaigns have shown to increase the reach, promotion, and visibility of healthcare-related open innovation platforms.
Hashtag	Function	Non-commercial use Political protests and campaigns in the early 2010s, such as #OccupyWallStreet and #LibyaFeb17, have been organized around hashtags or have made extensive usage of hashtags for the promotion of discussion. Hashtags have also been used to promote official events; the Finnish Ministry of Foreign Affairs officially titled the 2018 Russia–United States summit as the "#HELSINKI2018 Meeting".Hashtags have been used to gather customer criticism of large companies. In January 2012, McDonald's created the #McDStories hashtag so that customers could share positive experiences about the restaurant chain, but the marketing effort was cancelled after two hours when critical tweets outnumbered praising ones.
Hashtag	Function	In 2017, the #MeToo hashtag became viral in response to the sexual harassment accusations against Harvey Weinstein. The use of this hashtag can be considered part of hashtag activism, spreading awareness across eighty-five different countries with more than seventeen million Tweets using the hashtag #MeToo. This hashtag was not only used to spread awareness of accusations regarding Harvey Weinstein but allowed different women to share their experiences of sexual violence. Using this hashtag birthed multiple different hashtags in connection to #MeToo to encourage more women to share their stories, resulting in further spread of the phenomenon of hashtag activism. The use of hashtags, especially, in this case, allowed for better and easier access to search for content related to this social media movement.
Hashtag	Function	Sentiment analysis The use of hashtags also reveals what feelings or sentiment an author attaches to a statement. This can range from the obvious, where a hashtag directly describes the state of mind, to the less obvious. For example, words in hashtags are the strongest predictor of whether or not a statement is sarcastic—a difficult AI problem.
Hashtag	Function	Professional development and education Hashtags play an important role for employees and students in professional fields and education. In industry, individuals' engagement with a hashtags can provide opportunities for them develop and gain some professional knowledge in their fields.In education, research on language teachers who engaged in the #MFLtwitterati hashtag demonstrates the uses of hashtags for creating community and sharing teaching resources. The majority of participants reported positive impact on their teaching strategies as inspired by many ideas shared by different individuals in the Hashtag. Emerging research in communication and learning demonstrates how hashtag practices influence the teaching and development of students. An analysis of eight studies examined the use of hashtags in K–12 classrooms and found significant results. These results indicated that hashtags assisted students in voicing their opinions. In addition, hashtags also helped students understand self-organisation and the concept of space beyond place. Related research demonstrated how high school students engagement with hashtag communication practices allowed them to develop story telling skills and cultural awareness. For young people at risk of poverty and social exclusion during the COVID-19 pandemic, Instagram hashtags were shown in a 2022 article to foster scientific education and promote remote learning.
Hashtag	In popular culture	During the April 2011 Canadian party leader debate, Jack Layton, then-leader of the New Democratic Party, referred to Conservative Prime Minister Stephen Harper's crime policies as "a [sic] hashtag fail" (presumably #fail).In 2010 Kanye West used the term "hashtag rap" to describe a style of rapping that, according to Rizoh of the Houston Press, uses "a metaphor, a pause, and a one-word punch line, often placed at the end of a rhyme". Rappers Nicki Minaj, Big Sean, Drake, and Lil Wayne are credited with the popularization of hashtag rap, while the style has been criticized by Ludacris, The Lonely Island, and various music writers.On September 13, 2013, a hashtag, #TwitterIPO, appeared in the headline of a New York Times front-page article regarding Twitter's initial public offering.In 2014 Bird's Eye foods released "Mashtags", a mashed potato product with pieces shaped either like @ or #.In 2019, the British Ornithological Union included as hash character in the design of its new Janet Kear Union Medal, to represent "science communication and social media".
Duhem–Margules equation	Duhem–Margules equation	The Duhem–Margules equation, named for Pierre Duhem and Max Margules, is a thermodynamic statement of the relationship between the two components of a single liquid where the vapour mixture is regarded as an ideal gas: ln ln ln ln ⁡xB)T,P where PA and PB are the partial vapour pressures of the two constituents and xA and xB are the mole fractions of the liquid. The equation gives the relation between changes in mole fraction and partial pressure of the components.
Duhem–Margules equation	Derivation	Let us consider a binary liquid mixture of two component in equilibrium with their vapor at constant temperature and pressure. Then from the Gibbs–Duhem equation, we have Where nA and nB are number of moles of the component A and B while μA and μB are their chemical potentials. Dividing equation (1) by nA + nB, then nAnA+nBdμA+nBnA+nBdμB=0 Or Now the chemical potential of any component in mixture is dependent upon temperature, pressure and the composition of the mixture. Hence if temperature and pressure are taken to be constant, the chemical potentials must satisfy Putting these values in equation (2), then Because the sum of mole fractions of all components in the mixture is unity, i.e., x1+x2=1 we have dx1+dx2=0 so equation (5) can be re-written: Now the chemical potential of any component in mixture is such that ln ⁡P where P is the partial pressure of that component. By differentiating this equation with respect to the mole fraction of a component: ln ⁡Pdx we have for components A and B Substituting these value in equation (6), then ln ln ⁡PBdxB or ln ln ln ln ⁡xB)T,P This final equation is the Duhem–Margules equation.
Duhem–Margules equation	Sources	Atkins, Peter and Julio de Paula. 2002. Physical Chemistry, 7th ed. New York: W. H. Freeman and Co. Carter, Ashley H. 2001. Classical and Statistical Thermodynamics. Upper Saddle River: Prentice Hall.
Curium	Curium	Curium is a transuranic, radioactive chemical element with the symbol Cm and atomic number 96. This actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first intentionally made by the team of Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso in 1944, using the cyclotron at Berkeley. They bombarded the newly discovered element plutonium (the isotope 239Pu) with alpha particles. This was then sent to the Metallurgical Laboratory at University of Chicago where a tiny sample of curium was eventually separated and identified. The discovery was kept secret until after the end of World War II. The news was released to the public in November 1947. Most curium is produced by bombarding uranium or plutonium with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains ~20 grams of curium.
Curium	Curium	Curium is a hard, dense, silvery metal with a high melting and boiling point for an actinide. It is paramagnetic at ambient conditions, but becomes antiferromagnetic upon cooling, and other magnetic transitions are also seen in many curium compounds. In compounds, curium usually has valence +3 and sometimes +4; the +3 valence is predominant in solutions. Curium readily oxidizes, and its oxides are a dominant form of this element. It forms strongly fluorescent complexes with various organic compounds, but there is no evidence of its incorporation into bacteria and archaea. If it gets into the human body, curium accumulates in bones, lungs, and liver, where it promotes cancer.
Curium	Curium	All known isotopes of curium are radioactive and have small critical mass for a nuclear chain reaction. They mostly emit α-particles; radioisotope thermoelectric generators can use the heat from this process, but this is hindered by the rarity and high cost of curium. Curium is used in making heavier actinides and the 238Pu radionuclide for power sources in artificial cardiac pacemakers and RTGs for spacecraft. It served as the α-source in the alpha particle X-ray spectrometers of several space probes, including the Sojourner, Spirit, Opportunity, and Curiosity Mars rovers and the Philae lander on comet 67P/Churyumov–Gerasimenko, to analyze the composition and structure of the surface.
Curium	History	Though curium had likely been produced in previous nuclear experiments as well as the natural nuclear fission reactor at Oklo, Gabon, it was first intentionally synthesized, isolated and identified in 1944, at University of California, Berkeley, by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso. In their experiments, they used a 60-inch (150 cm) cyclotron.Curium was chemically identified at the Metallurgical Laboratory (now Argonne National Laboratory), University of Chicago. It was the third transuranium element to be discovered even though it is the fourth in the series – the lighter element americium was still unknown.The sample was prepared as follows: first plutonium nitrate solution was coated on a platinum foil of ~0.5 cm2 area, the solution was evaporated and the residue was converted into plutonium(IV) oxide (PuO2) by annealing. Following cyclotron irradiation of the oxide, the coating was dissolved with nitric acid and then precipitated as the hydroxide using concentrated aqueous ammonia solution. The residue was dissolved in perchloric acid, and further separation was done by ion exchange to yield a certain isotope of curium. The separation of curium and americium was so painstaking that the Berkeley group initially called those elements pandemonium (from Greek for all demons or hell) and delirium (from Latin for madness).Curium-242 was made in July–August 1944 by bombarding 239Pu with α-particles to produce curium with the release of a neutron: Pu 94 239 He Cm 96 242 +n01 Curium-242 was unambiguously identified by the characteristic energy of the α-particles emitted during the decay: Cm 96 242 Pu 94 238 He 24 The half-life of this alpha decay was first measured as 150 days and then corrected to 162.8 days.Another isotope 240Cm was produced in a similar reaction in March 1945: Pu 94 239 He Cm 96 240 +301n The α-decay half-life of 240Cm was correctly determined as 26.7 days.The discovery of curium and americium in 1944 was closely related to the Manhattan Project, so the results were confidential and declassified only in 1945. Seaborg leaked the synthesis of the elements 95 and 96 on the U.S. radio show for children, the Quiz Kids, five days before the official presentation at an American Chemical Society meeting on November 11, 1945, when one listener asked if any new transuranic element beside plutonium and neptunium had been discovered during the war. The discovery of curium (242Cm and 240Cm), its production, and its compounds was later patented listing only Seaborg as the inventor.
Curium	History	The element was named after Marie Curie and her husband Pierre Curie, who are known for discovering radium and for their work in radioactivity. It followed the example of gadolinium, a lanthanide element above curium in the periodic table, which was named after the explorer of rare-earth elements Johan Gadolin: "As the name for the element of atomic number 96 we should like to propose "curium", with symbol Cm. The evidence indicates that element 96 contains seven 5f electrons and is thus analogous to the element gadolinium, with its seven 4f electrons in the regular rare earth series. On this basis element 96 is named after the Curies in a manner analogous to the naming of gadolinium, in which the chemist Gadolin was honored."The first curium samples were barely visible, and were identified by their radioactivity. Louis Werner and Isadore Perlman made the first substantial sample of 30 µg curium-242 hydroxide at University of California, Berkeley in 1947 by bombarding americium-241 with neutrons. Macroscopic amounts of curium(III) fluoride were obtained in 1950 by W. W. T. Crane, J. C. Wallmann and B. B. Cunningham. Its magnetic susceptibility was very close to that of GdF3 providing the first experimental evidence for the +3 valence of curium in its compounds. Curium metal was produced only in 1951 by reduction of CmF3 with barium.
Curium	Characteristics	Physical A synthetic, radioactive element, curium is a hard, dense metal with a silvery-white appearance and physical and chemical properties resembling gadolinium. Its melting point of 1344 °C is significantly higher than that of the previous elements neptunium (637 °C), plutonium (639 °C) and americium (1176 °C). In comparison, gadolinium melts at 1312 °C. Curium boils at 3556 °C. With a density of 13.52 g/cm3, curium is lighter than neptunium (20.45 g/cm3) and plutonium (19.8 g/cm3), but heavier than most other metals. Of two crystalline forms of curium, α-Cm is more stable at ambient conditions. It has a hexagonal symmetry, space group P63/mmc, lattice parameters a = 365 pm and c = 1182 pm, and four formula units per unit cell. The crystal consists of double-hexagonal close packing with the layer sequence ABAC and so is isotypic with α-lanthanum. At pressure >23 GPa, at room temperature, α-Cm becomes β-Cm, which has face-centered cubic symmetry, space group Fm3m and lattice constant a = 493 pm. On further compression to 43 GPa, curium becomes an orthorhombic γ-Cm structure similar to α-uranium, with no further transitions observed up to 52 GPa. These three curium phases are also called Cm I, II and III.Curium has peculiar magnetic properties. Its neighbor element americium shows no deviation from Curie-Weiss paramagnetism in the entire temperature range, but α-Cm transforms to an antiferromagnetic state upon cooling to 65–52 K, and β-Cm exhibits a ferrimagnetic transition at ~205 K. Curium pnictides show ferromagnetic transitions upon cooling: 244CmN and 244CmAs at 109 K, 248CmP at 73 K and 248CmSb at 162 K. The lanthanide analog of curium, gadolinium, and its pnictides, also show magnetic transitions upon cooling, but the transition character is somewhat different: Gd and GdN become ferromagnetic, and GdP, GdAs and GdSb show antiferromagnetic ordering.In accordance with magnetic data, electrical resistivity of curium increases with temperature – about twice between 4 and 60 K – and then is nearly constant up to room temperature. There is a significant increase in resistivity over time (~10 µΩ·cm/h) due to self-damage of the crystal lattice by alpha decay. This makes uncertain the true resistivity of curium (~125 µΩ·cm). Curium's resistivity is similar to that of gadolinium, and the actinides plutonium and neptunium, but significantly higher than that of americium, uranium, polonium and thorium.Under ultraviolet illumination, curium(III) ions show strong and stable yellow-orange fluorescence with a maximum in the range of 590–640 nm depending on their environment. The fluorescence originates from the transitions from the first excited state 6D7/2 and the ground state 8S7/2. Analysis of this fluorescence allows monitoring interactions between Cm(III) ions in organic and inorganic complexes.
Curium	Characteristics	Chemical Curium ion in solution almost always has a +3 oxidation state, the most stable oxidation state for curium. A +4 oxidation state is seen mainly in a few solid phases, such as CmO2 and CmF4. Aqueous curium(IV) is only known in the presence of strong oxidizers such as potassium persulfate, and is easily reduced to curium(III) by radiolysis and even by water itself. Chemical behavior of curium is different from the actinides thorium and uranium, and is similar to americium and many lanthanides. In aqueous solution, the Cm3+ ion is colorless to pale green; Cm4+ ion is pale yellow. The optical absorption of Cm3+ ion contains three sharp peaks at 375.4, 381.2 and 396.5 nm and their strength can be directly converted into the concentration of the ions. The +6 oxidation state has only been reported once in solution in 1978, as the curyl ion (CmO2+2): this was prepared from beta decay of americium-242 in the americium(V) ion 242AmO+2. Failure to get Cm(VI) from oxidation of Cm(III) and Cm(IV) may be due to the high Cm4+/Cm3+ ionization potential and the instability of Cm(V).Curium ions are hard Lewis acids and thus form most stable complexes with hard bases. The bonding is mostly ionic, with a small covalent component. Curium in its complexes commonly exhibits a 9-fold coordination environment, with a tricapped trigonal prismatic molecular geometry.
Curium	Characteristics	Isotopes About 19 radioisotopes and 7 nuclear isomers, 233Cm to 251Cm, are known; none are stable. The longest half-lives are 15.6 million years (247Cm) and 348,000 years (248Cm). Other long-lived ones are 245Cm (8500 years), 250Cm (8300 years) and 246Cm (4760 years). Curium-250 is unusual: it mostly (~86%) decays by spontaneous fission. The most commonly used isotopes are 242Cm and 244Cm with the half-lives 162.8 days and 18.1 years, respectively.
Curium	Characteristics	All isotopes 242Cm-248Cm, and 250Cm, undergo a self-sustaining nuclear chain reaction and thus in principle can be a nuclear fuel in a reactor. As in most transuranic elements, nuclear fission cross section is especially high for the odd-mass curium isotopes 243Cm, 245Cm and 247Cm. These can be used in thermal-neutron reactors, whereas a mixture of curium isotopes is only suitable for fast breeder reactors since the even-mass isotopes are not fissile in a thermal reactor and accumulate as burn-up increases. The mixed-oxide (MOX) fuel, which is to be used in power reactors, should contain little or no curium because neutron activation of 248Cm will create californium. Californium is a strong neutron emitter, and would pollute the back end of the fuel cycle and increase the dose to reactor personnel. Hence, if minor actinides are to be used as fuel in a thermal neutron reactor, the curium should be excluded from the fuel or placed in special fuel rods where it is the only actinide present.
Curium	Characteristics	The adjacent table lists the critical masses for curium isotopes for a sphere, without moderator or reflector. With a metal reflector (30 cm of steel), the critical masses of the odd isotopes are about 3–4 kg. When using water (thickness ~20–30 cm) as the reflector, the critical mass can be as small as 59 gram for 245Cm, 155 gram for 243Cm and 1550 gram for 247Cm. There is significant uncertainty in these critical mass values. While it is usually on the order of 20%, the values for 242Cm and 246Cm were listed as large as 371 kg and 70.1 kg, respectively, by some research groups.Curium is not currently used as nuclear fuel due to its low availability and high price. 245Cm and 247Cm have very small critical mass and so could be used in tactical nuclear weapons, but none are known to have been made. Curium-243 is not suitable for such, due to its short half-life and strong α emission, which would cause excessive heat. Curium-247 would be highly suitable due to its long half-life, which is 647 times longer than plutonium-239 (used in many existing nuclear weapons).
Curium	Characteristics	Occurrence The longest-lived isotope, 247Cm, has half-life 15.6 million years; so any primordial curium, that is, present on Earth when it formed, should have decayed by now. Its past presence as an extinct radionuclide is detectable as an excess of its primordial, long-lived daughter 235U. Traces of curium may occur naturally in uranium minerals due to neutron capture and beta decay, though this has not been confirmed. Traces of 247Cm are also probably brought to Earth in cosmic rays, but again this has not been confirmed.Curium is made artificially in small amounts for research purposes. It also occurs as one of the waste products in spent nuclear fuel. Curium is present in nature in some areas used for nuclear weapons testing. Analysis of the debris at the test site of the United States' first thermonuclear weapon, Ivy Mike, (1 November 1952, Enewetak Atoll), besides einsteinium, fermium, plutonium and americium also revealed isotopes of berkelium, californium and curium, in particular 245Cm, 246Cm and smaller quantities of 247Cm, 248Cm and 249Cm.Atmospheric curium compounds are poorly soluble in common solvents and mostly adhere to soil particles. Soil analysis revealed about 4,000 times higher concentration of curium at the sandy soil particles than in water present in the soil pores. An even higher ratio of about 18,000 was measured in loam soils.The transuranium elements from americium to fermium, including curium, occurred naturally in the natural nuclear fission reactor at Oklo, but no longer do so.Curium, and other non-primordial actinides, have also been suspected to exist in the spectrum of Przybylski's Star.
Curium	Synthesis	Isotope preparation Curium is made in small amounts in nuclear reactors, and by now only kilograms of 242Cm and 244Cm have been accumulated, and grams or even milligrams for heavier isotopes. Hence the high price of curium, which has been quoted at 160–185 USD per milligram, with a more recent estimate at US$2,000/g for 242Cm and US$170/g for 244Cm. In nuclear reactors, curium is formed from 238U in a series of nuclear reactions. In the first chain, 238U captures a neutron and converts into 239U, which via β− decay transforms into 239Np and 239Pu.
Curium	Synthesis	Further neutron capture followed by β−-decay gives americium (241Am) which further becomes 242Cm: For research purposes, curium is obtained by irradiating not uranium but plutonium, which is available in large amounts from spent nuclear fuel. A much higher neutron flux is used for the irradiation that results in a different reaction chain and formation of 244Cm: Curium-244 alpha decays to 240Pu, but it also absorbs neutrons, hence a small amount of heavier curium isotopes. Of those, 247Cm and 248Cm are popular in scientific research due to their long half-lives. But the production rate of 247Cm in thermal neutron reactors is low because it is prone to fission due to thermal neutrons. Synthesis of 250Cm by neutron capture is unlikely due to the short half-life of the intermediate 249Cm (64 min), which β− decays to the berkelium isotope 249Bk.
Curium	Synthesis	The above cascade of (n,γ) reactions gives a mix of different curium isotopes. Their post-synthesis separation is cumbersome, so a selective synthesis is desired. Curium-248 is favored for research purposes due to its long half-life. The most efficient way to prepare this isotope is by α-decay of the californium isotope 252Cf, which is available in relatively large amounts due to its long half-life (2.65 years). About 35–50 mg of 248Cm is produced thus, per year. The associated reaction produces 248Cm with isotopic purity of 97%.
Curium	Synthesis	Another isotope, 245Cm, can be obtained for research, from α-decay of 249Cf; the latter isotope is produced in small amounts from β−-decay of 249Bk.
Curium	Synthesis	Metal preparation Most synthesis routines yield a mix of actinide isotopes as oxides, from which a given isotope of curium needs to be separated. An example procedure could be to dissolve spent reactor fuel (e.g. MOX fuel) in nitric acid, and remove the bulk of the uranium and plutonium using a PUREX (Plutonium – URanium EXtraction) type extraction with tributyl phosphate in a hydrocarbon. The lanthanides and the remaining actinides are then separated from the aqueous residue (raffinate) by a diamide-based extraction to give, after stripping, a mixture of trivalent actinides and lanthanides. A curium compound is then selectively extracted using multi-step chromatographic and centrifugation techniques with an appropriate reagent. Bis-triazinyl bipyridine complex has been recently proposed as such reagent which is highly selective to curium. Separation of curium from the very chemically similar americium can also be done by treating a slurry of their hydroxides in aqueous sodium bicarbonate with ozone at elevated temperature. Both americium and curium are present in solutions mostly in the +3 valence state; americium oxidizes to soluble Am(IV) complexes, but curium stays unchanged and so can be isolated by repeated centrifugation.Metallic curium is obtained by reduction of its compounds. Initially, curium(III) fluoride was used for this purpose. The reaction was done in an environment free of water and oxygen, in an apparatus made of tantalum and tungsten, using elemental barium or lithium as reducing agents.
Curium	Synthesis	CmF3+3Li⟶Cm+3LiF Another possibility is reduction of curium(IV) oxide using a magnesium-zinc alloy in a melt of magnesium chloride and magnesium fluoride.
Curium	Compounds and reactions	Oxides Curium readily reacts with oxygen forming mostly Cm2O3 and CmO2 oxides, but the divalent oxide CmO is also known. Black CmO2 can be obtained by burning curium oxalate (Cm2(C2O4)3), nitrate (Cm(NO3)3), or hydroxide in pure oxygen. Upon heating to 600–650 °C in vacuum (about 0.01 Pa), it transforms into the whitish Cm2O3: CmO Cm 2O3+O2 .Or, Cm2O3 can be obtained by reducing CmO2 with molecular hydrogen: CmO Cm 2O3+H2O Also, a number of ternary oxides of the type M(II)CmO3 are known, where M stands for a divalent metal, such as barium.Thermal oxidation of trace quantities of curium hydride (CmH2–3) has been reported to give a volatile form of CmO2 and the volatile trioxide CmO3, one of two known examples of the very rare +6 state for curium. Another observed species was reported to behave similar to a supposed plutonium tetroxide and was tentatively characterized as CmO4, with curium in the extremely rare +8 state; but new experiments seem to indicate that CmO4 does not exist, and have cast doubt on the existence of PuO4 as well.
Curium	Compounds and reactions	Halides The colorless curium(III) fluoride (CmF3) can be made by adding fluoride ions into curium(III)-containing solutions. The brown tetravalent curium(IV) fluoride (CmF4) on the other hand is only obtained by reacting curium(III) fluoride with molecular fluorine: 2CmF3+F2⟶2CmF4 A series of ternary fluorides are known of the form A7Cm6F31 (A = alkali metal).The colorless curium(III) chloride (CmCl3) is made by reacting curium hydroxide (Cm(OH)3) with anhydrous hydrogen chloride gas. It can be further turned into other halides such as curium(III) bromide (colorless to light green) and curium(III) iodide (colorless), by reacting it with the ammonia salt of the corresponding halide at temperatures of ~400–450°C: CmCl3+3NH4I⟶CmI3+3NH4Cl Or, one can heat curium oxide to ~600°C with the corresponding acid (such as hydrobromic for curium bromide). Vapor phase hydrolysis of curium(III) chloride gives curium oxychloride: CmCl3+H2O⟶CmOCl+2HCl Chalcogenides and pnictides Sulfides, selenides and tellurides of curium have been obtained by treating curium with gaseous sulfur, selenium or tellurium in vacuum at elevated temperature. Curium pnictides of the type CmX are known for nitrogen, phosphorus, arsenic and antimony. They can be prepared by reacting either curium(III) hydride (CmH3) or metallic curium with these elements at elevated temperature.
Curium	Compounds and reactions	Organocurium compounds and biological aspects Organometallic complexes analogous to uranocene are known also for other actinides, such as thorium, protactinium, neptunium, plutonium and americium. Molecular orbital theory predicts a stable "curocene" complex (η8-C8H8)2Cm, but it has not been reported experimentally yet.Formation of the complexes of the type Cm(n-C3H7-BTP)3 (BTP = 2,6-di(1,2,4-triazin-3-yl)pyridine), in solutions containing n-C3H7-BTP and Cm3+ ions has been confirmed by EXAFS. Some of these BTP-type complexes selectively interact with curium and thus are useful for separating it from lanthanides and another actinides. Dissolved Cm3+ ions bind with many organic compounds, such as hydroxamic acid, urea, fluorescein and adenosine triphosphate. Many of these compounds are related to biological activity of various microorganisms. The resulting complexes show strong yellow-orange emission under UV light excitation, which is convenient not only for their detection, but also for studying interactions between the Cm3+ ion and the ligands via changes in the half-life (of the order ~0.1 ms) and spectrum of the fluorescence.Curium has no biological significance. There are a few reports on biosorption of Cm3+ by bacteria and archaea, but no evidence for incorporation of curium into them.
Curium	Applications	Radionuclides Curium is one of the most radioactive isolable elements. Its two most common isotopes 242Cm and 244Cm are strong alpha emitters (energy 6 MeV); they have fairly short half-lives, 162.8 days and 18.1 years, and give as much as 120 W/g and 3 W/g of heat, respectively. Therefore, curium can be used in its common oxide form in radioisotope thermoelectric generators like those in spacecraft. This application has been studied for the 244Cm isotope, while 242Cm was abandoned due to its prohibitive price, around 2000 USD/g. 243Cm with a ~30-year half-life and good energy yield of ~1.6 W/g could be a suitable fuel, but it gives significant amounts of harmful gamma and beta rays from radioactive decay products. As an α-emitter, 244Cm needs much less radiation shielding, but it has a high spontaneous fission rate, and thus a lot of neutron and gamma radiation. Compared to a competing thermoelectric generator isotope such as 238Pu, 244Cm emits 500 times more neutrons, and its higher gamma emission requires a shield that is 20 times thicker—2 inches (51 mm) of lead for a 1 kW source, compared to 0.1 inches (2.5 mm) for 238Pu. Therefore, this use of curium is currently considered impractical.A more promising use of 242Cm is for making 238Pu, a better radioisotope for thermoelectric generators such as in heart pacemakers. The alternate routes to 238Pu use the (n,γ) reaction of 237Np, or deuteron bombardment of uranium, though both reactions always produce 236Pu as an undesired by-product since the latter decays to 232U with strong gamma emission. Curium is a common starting material for making higher transuranic and superheavy elements. Thus, bombarding 248Cm with neon (22Ne), magnesium (26Mg), or calcium (48Ca) yields isotopes of seaborgium (265Sg), hassium (269Hs and 270Hs), and livermorium (292Lv, 293Lv, and possibly 294Lv). Californium was discovered when a microgram-sized target of curium-242 was irradiated with 35 MeV alpha particles using the 60-inch (150 cm) cyclotron at Berkeley: 24296Cm + 42He → 24598Cf + 10nOnly about 5,000 atoms of californium were produced in this experiment.The odd-mass curium isotopes 243Cm, 245Cm, and 247Cm are all highly fissile and can release additional energy in a thermal spectrum nuclear reactor. All curium isotopes are fissionable in fast-neutron reactors. This is one of the motives for minor actinide separation and transmutation in the nuclear fuel cycle, helping to reduce the long-term radiotoxicity of used, or spent nuclear fuel.
Curium	Applications	X-ray spectrometer The most practical application of 244Cm—though rather limited in total volume—is as α-particle source in alpha particle X-ray spectrometers (APXS). These instruments were installed on the Sojourner, Mars, Mars 96, Mars Exploration Rovers and Philae comet lander, as well as the Mars Science Laboratory to analyze the composition and structure of the rocks on the surface of planet Mars. APXS was also used in the Surveyor 5–7 moon probes but with a 242Cm source.An elaborate APXS setup has a sensor head containing six curium sources with a total decay rate of several tens of millicuries (roughly one gigabecquerel). The sources are collimated on a sample, and the energy spectra of the alpha particles and protons scattered from the sample are analyzed (proton analysis is done only in some spectrometers). These spectra contain quantitative information on all major elements in the sample except for hydrogen, helium and lithium.
Curium	Safety	Due to its radioactivity, curium and its compounds must be handled in appropriate labs under special arrangements. While curium itself mostly emits α-particles which are absorbed by thin layers of common materials, some of its decay products emit significant fractions of beta and gamma rays, which require a more elaborate protection. If consumed, curium is excreted within a few days and only 0.05% is absorbed in the blood. From there, ~45% goes to the liver, 45% to the bones, and the remaining 10% is excreted. In bone, curium accumulates on the inside of the interfaces to the bone marrow and does not significantly redistribute with time; its radiation destroys bone marrow and thus stops red blood cell creation. The biological half-life of curium is about 20 years in the liver and 50 years in the bones. Curium is absorbed in the body much more strongly via inhalation, and the allowed total dose of 244Cm in soluble form is 0.3 μCi. Intravenous injection of 242Cm- and 244Cm-containing solutions to rats increased the incidence of bone tumor, and inhalation promoted lung and liver cancer.Curium isotopes are inevitably present in spent nuclear fuel (about 20 g/tonne). The isotopes 245Cm–248Cm have decay times of thousands of years and must be removed to neutralize the fuel for disposal. Such a procedure involves several steps, where curium is first separated and then converted by neutron bombardment in special reactors to short-lived nuclides. This procedure, nuclear transmutation, while well documented for other elements, is still being developed for curium.
Primordial cyst	Primordial cyst	A primordial cyst is a developmental odontogenic cyst. It is found in an area where a tooth should have formed but is missing. Primordial cysts most commonly arise in the area of mandibular third molars. Under microscopes, the cyst looks like an odontogenic keratocyst (also called a Keratocyst odontogenic tumor) whereby the lesions displays a parakeratinized epithelium with palisading basal epithelial cells.
Primordial cyst	Primordial cyst	The term "Primordial cyst" is considered an outdated term and should be avoided. Most "primordial cysts" are actually Keratocyst odontogenic tumors (KOT's).
Cornhole	Cornhole	Bags (also known regionally as sack toss, or Cornhole) is a lawn game popular in North America in which players or teams take turns throwing fabric bean bags at a raised, angled board with a hole in its far end. The goal of the game is to score points by either landing a bag on the board (one point) or putting a bag through the hole (three points).
Cornhole	History	The game was first described in Heyliger de Windt's 1883 patent for "Parlor Quoits", which displays most of the features of modern cornhole, but uses a square hole. Quoits is a game similar to horseshoes, played by throwing steel discs at a metal spike. Several earlier "parlor quoits" patents had sought to recreate quoit gameplay in an indoor environment, but De Windt's was the first to use bean bags and a slanted board with a hole as the target.
Cornhole	History	He sold the rights to the game to a Massachusetts toy manufacturer which marketed a version of it under the name "Faba Baga". Unlike modern cornhole, which has one hole and one size of bags, a Faba Baga board had two different-sized holes, worth different point values, and provided each player with one extra-large bag per round, which could score double points.
Cornhole	History	In September 1974, Popular Mechanics magazine published an article written by Carolyn Farrell about a similar game called "bean-bag bull's-eye." Bean-bag bull's-eye was played on a board the same width of modern cornhole boards (24"), but only 36" long as opposed to the 48" length used in cornhole. The hole was the same diameter (6") but was centered 8" (rather than 9") from the back of the board. Each player threw two bags, weighing eight ounces each, "in succession". The boards in bean-bag bull's-eye were placed "about 30 ft. apart for adults, 10 ft. for kids." Scoring was essentially the same as that used in cornhole (three points for a bag in the hole, one point for a bag remaining on the board) and also used cancellation scoring.
Cornhole	History	In the Chicago area, a similar game is referred to as "bags", but uses rectangular bags. The game spread in Chicago, Illinois, and the Northwest region of Indiana in the late 1970s and early 1980s, perhaps due to the Popular Mechanics article mentioned above. Cornhole as it is now known originated and gained popularity on Cincinnati's west side (near Ferguson Avenue) in the 1980s and spread to surrounding areas in Kentucky and Southeast Indiana.
Cornhole	History	Tournaments The American Cornhole League (ACL) was founded in 2015 by Stacey Moore. According to the ACL's website, it promotes and develops cornhole as a sport on every level, and created software and apps to manage cornhole leagues, tournaments, special events, and player development.The American Cornhole Organization (ACO) was established in 2005 by Frank Geers and is headquartered in Milford, Ohio. As of August 1, 2019, the ACO claimed on its website to be the "governing body for the sport of cornhole".The American Cornhole Association (ACA) is an organization whose sole mission is to help cornhole players enjoy the game of cornhole. According to its website, "[o]ne of the most important ways to achieve this goal is for people to have high-quality equipment to play on." Accordingly, the ACA is largely focused on selling cornhole-related products and equipment rather than acting as a sanctioning body of the sport; however, it does have its own rules and does sponsor events.
Cornhole	Rules and format	Equipment and court layout Cornhole matches are played with two sets of four bags (eight total), two boards and two, four, or eight players.There are four bags to a set. Each set of bags should be distinguishable from the other, usually by using different colors. The American Cornhole League's rules call for double-seamed fabric bags measuring 6 by 6 inches (150 by 150 mm) and weighing 15.5 to 16.5 ounces (440 to 470 g). Although bags used to be filled with preserved corn kernels (hence "cornhole") or dried beans, bags are now usually filled with plastic resin or other materials that will maintain a consistent weight and shape over many throws without deforming. Bags are usually dual-sided, with each side of the bag being a different material that can affect grip and react faster or slower on the board's surface. Faster bags are often preferred in humid conditions when bags will not slide as readily. Additionally, professional players may opt for different materials depending on their personal throwing styles. Players with a lower, faster throw may use more rotation and prefer a slower bag material, whereas players with higher, slower throws may use less rotation and prefer a more reactive bag.
Cornhole	Rules and format	Each board is 2 by 4 feet (0.61 by 1.22 m), with a 6-inch (150 mm) diameter hole. The hole's center is positioned 9 inches (230 mm) down from the center of the top edge of the board. Each board is angled with the top edge of the playing surface 12 inches (300 mm) above the ground, and the bottom edge 3–4 inches (76–102 mm) above the ground. A standard court places the two boards 33 feet (10 m) or 27 feet (8.2 m) apart, measuring from the bottom edge of the boards. Different (usually shorter) distances may be used if space is limited or if younger players are participating. Some smaller versions of the game, with scaled-down boards, bags, and holes are available specifically for children.
Cornhole	Rules and format	The areas immediately to the left and right of the boards are the pitcher's boxes. The line (either drawn or imaginary) extending from the bottom edge of the board in both the left and right direction is the foul line. When throwing the bags, players cannot step past the foul line or else the throw does not count. Gameplay A cornhole match is separated into innings (or frames). During each inning, each player or team will throw their designated four bags. The manner in which the bags are thrown depends on which format of cornhole is being played: singles (1 vs. 1), doubles (2 vs. 2), or crew (4 vs. 4).
Cornhole	Rules and format	In singles (1 vs. 1), both players throw their four bags while standing on opposite sides of the same board (left vs. right pitcher's box), alternating throws between the two players. After all eight bags are thrown, both players walk to the opposite board, while remaining in their lane, to tally the score. To begin the next inning, both players turn around to throw at the other board in the same manner. The effect of this is that by always staying in their respective lane, the two players will alternate each inning throwing from the left vs. right pitcher's box.In doubles (2 vs. 2), one partner from each team stands in the left pitcher's box of one board while the other partner stands in the right pitcher's box of the opposite board. Thus, each team's partners are on opposite ends, facing each other, both in the same lane. From here, gameplay is similar to singles: the two opponents at one board alternate throwing their four bags at the other board, after which a mid-inning score is tallied; then their partners at that board alternate throwing their team's four bags back at the other board, after which the final inning score can be tallied. In doubles, players may not change sides, i.e. one partner will throw from the left pitcher's box of one board and the other from the right pitcher's box of the other board for the entire game.
Cornhole	Rules and format	In the crew format (4 vs. 4), play is identical to doubles, but with two teammates at each of the two boards, one pair in the left pitcher's box of one board and the other pair in the right pitcher's box of the opposite board, each pair facing each other, in the same lane. Instead of each partner pitching four bags per inning (as in doubles), in crew each teammate pitches two bags per inning, again alternating throws both with the opposing team (as in singles and doubles) and with the player's teammate who is standing with them at the same board.
Cornhole	Rules and format	Note that in doubles and crew, the score for any inning is based on eight throws per team, as opposed to four throws per player in singles.
Cornhole	Rules and format	In all formats, the pitcher must throw the bag within 20 seconds. The time begins when the pitcher is inside the pitcher's box with an intent to throw. The first pitch of an inning goes to whichever player or team scored in the previous inning. If neither player or team scored in the previous inning, then whichever pitched first in the previous inning will again pitch first in the next inning. The first pitch of the first inning can be decided by a coin toss.
Cornhole	Rules and format	A legal pitch must be tossed while the pitcher's feet are within the pitcher's box. If the pitcher begins the throw with a foot beyond the foul line or otherwise steps beyond the foul line before releasing the bag, the pitch is a foul and does not count. A foul throw cannot be re-taken and the bag is removed from play before continuing. If a foul bag moves other bags in the field of play, those bags are returned to their prior position before continuing, including if a bag was moved into the hole. If a bag lands only partially on the board and is also touching the ground, it does not count and is removed before continuing.
Cornhole	Rules and format	Scoring To score points, bags must be on the surface of the board or fall through the hole. To score three points, a bag may fall directly into the hole, slide into the hole after hitting the board, or be knocked into the hole by another bag. A bag remaining on the board scores one point. A bag partially on the board and partially on the ground ("dirt bag") does not count and should be removed before the next throw.

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