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Equally important advances have occurred in non-invasive techniques for examining the body's interior structures. X-rays can be passed through the body and used in medical radiography and fluoroscopy to differentiate interior structures that have varying degrees of opaqueness. Magnetic resonance imaging, computed tomography, and ultrasound imaging have all enabled the examination of internal structures in unprecedented detail to a degree far beyond the imagination of earlier generations. | Anatomy | Wikipedia | 84 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Aardvarks ( ; Orycteropus afer) are medium-sized, burrowing, nocturnal mammals native to Africa. Aardvarks are the only living species of the family Orycteropodidae and the order Tubulidentata. They have a long snout, similar to that of a pig, which is used to sniff out food.
They are afrotheres, a clade that also includes elephants, manatees, and hyraxes.
They are found over much of the southern two-thirds of the African continent, avoiding areas that are mainly rocky. Nocturnal feeders, aardvarks subsist on ants and termites by using their sharp claws and powerful legs to dig the insects out of their hills. Aardvarks also dig to create burrows in which to live and rear their young.
Name and taxonomy
Name
The aardvark is sometimes colloquially called the "African ant bear", "anteater" (not to be confused with the South American anteaters), or the "Cape anteater" after the Cape of Good Hope.
The name "aardvark" is Afrikaans () and comes from earlier Afrikaans . It means "earth pig" or "ground pig" (: , : ), because of its burrowing habits.
The name Orycteropus means "burrowing foot", and the name afer refers to Africa. The name of the aardvark's order, Tubulidentata, comes from the tubule-style teeth.
Taxonomy
The aardvark is not closely related to the pig; rather, it is the sole extant representative of the obscure mammalian order Tubulidentata, in which it is usually considered to form one variable species of the genus Orycteropus, the sole surviving genus in the family Orycteropodidae. The aardvark is not closely related to the South American anteater, despite sharing some characteristics and a superficial resemblance. The similarities are the outcome of convergent evolution. The closest living relatives of the aardvark are the elephant shrews, Tenrecidae, and golden moles. Along with sirenians, hyraxes, elephants, and their extinct relatives, these animals form the superorder Afrotheria. Studies of the brain have shown the similarities with Condylarthra. | Aardvark | Wikipedia | 483 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
Evolutionary history
Based on his study of fossils, Bryan Patterson has concluded that early relatives of the aardvark appeared in Africa around the end of the Paleocene. The ptolemaiidans, a mysterious clade of mammals with uncertain affinities, may actually be stem-aardvarks, either as a sister clade to Tubulidentata or as a grade leading to true tubulidentates.
The first unambiguous tubulidentate was probably Myorycteropus africanus from Kenyan Miocene deposits. The earliest example from the genus Orycteropus was Orycteropus mauritanicus, found in Algeria in deposits from the middle Miocene, with an equally old version found in Kenya. Fossils from the aardvark have been dated to 5 million years, and have been located throughout Europe and the Near East.
The mysterious Pleistocene Plesiorycteropus from Madagascar was originally thought to be a tubulidentate that was descended from ancestors that entered the island during the Eocene. However, a number of subtle anatomical differences coupled with recent molecular evidence now lead researchers to believe that Plesiorycteropus is a relative of golden moles and tenrecs that achieved an aardvark-like appearance and ecological niche through convergent evolution.
Subspecies
The aardvark has seventeen poorly defined subspecies listed:
Orycteropus afer afer (Southern aardvark)
O. a. adametzi Grote, 1921 (Western aardvark)
O. a. aethiopicus Sundevall, 1843
O. a. angolensis Zukowsky & Haltenorth, 1957
O. a. erikssoni Lönnberg, 1906
O. a. faradjius Hatt, 1932
O. a. haussanus Matschie, 1900
O. a. kordofanicus Rothschild, 1927
O. a. lademanni Grote, 1911
O. a. leptodon Hirst, 1906
O. a. matschiei Grote, 1921
O. a. observandus Grote, 1921
O. a. ruvanensis Grote, 1921
O. a. senegalensis Lesson, 1840
O. a. somalicus Lydekker, 1908
O. a. wardi Lydekker, 1908
O. a. wertheri Matschie, 1898 (Eastern aardvark) | Aardvark | Wikipedia | 489 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
The 1911 Encyclopædia Britannica also mentions O. a. capensis or Cape ant-bear from South Africa.
Description
The aardvark is vaguely pig-like in appearance. Its body is stout with a prominently arched back and is sparsely covered with coarse hairs. The limbs are of moderate length, with the rear legs being longer than the forelegs. The front feet have lost the pollex (or 'thumb'), resulting in four toes, while the rear feet have all five toes. Each toe bears a large, robust nail which is somewhat flattened and shovel-like, and appears to be intermediate between a claw and a hoof. Whereas the aardvark is considered digitigrade, it appears at times to be plantigrade. This confusion happens because when it squats it stands on its soles. A contributing characteristic to the burrow digging capabilities of aardvarks is an endosteal tissue called compacted coarse cancellous bone (CCCB). The stress and strain resistance provided by CCCB allows aardvarks to create their burrows, ultimately leading to a favourable environment for plants and a variety of animals. Digging is also facilitated by its forearm's unusually stout ulna and radius.An aardvark's weight is typically between . An aardvark's length is usually between , and can reach lengths of when its tail (which can be up to ) is taken into account. It is tall at the shoulder, and has a girth of about . It does not exhibit sexual dimorphism.
It is the largest member of the proposed clade Afroinsectiphilia. The aardvark is pale yellowish-grey in colour and often stained reddish-brown by soil. The aardvark's coat is thin, and the animal's primary protection is its tough skin. Its hair is short on its head and tail; however its legs tend to have longer hair. The hair on the majority of its body is grouped in clusters of three to four hairs. The hair surrounding its nostrils is dense to help filter particulate matter out as it digs. Its tail is very thick at the base and gradually tapers. | Aardvark | Wikipedia | 453 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
Head
The greatly elongated head is set on a short, thick neck, and the end of the snout bears a disc, which houses the nostrils. It contains a thin but complete zygomatic arch. The head of the aardvark contains many unique and different features. One of the most distinctive characteristics of the Tubulidentata is their teeth. Instead of having a pulp cavity, each tooth has a cluster of thin, hexagonal, upright, parallel tubes of vasodentin (a modified form of dentine), with individual pulp canals, held together by cementum. The number of columns is dependent on the size of the tooth, with the largest having about 1,500. The teeth have no enamel coating and are worn away and regrow continuously. The aardvark is born with conventional incisors and canines at the front of the jaw, which fall out and are not replaced. Adult aardvarks have only cheek teeth at the back of the jaw, and have a dental formula of: These remaining teeth are peg-like and rootless and are of unique composition. The teeth consist of 14 upper and 12 lower jaw molars. The nasal area of the aardvark is another unique area, as it contains ten nasal conchae, more than any other placental mammal. | Aardvark | Wikipedia | 270 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
The sides of the nostrils are thick with hair. The tip of the snout is highly mobile and is moved by modified mimetic muscles. The fleshy dividing tissue between its nostrils probably has sensory functions, but it is uncertain whether they are olfactory or vibratory in nature. Its nose is made up of more turbinate bones than any other mammal, with between nine and 11, compared to dogs with four to five. With a large quantity of turbinate bones, the aardvark has more space for the moist epithelium, which is the location of the olfactory bulb. The nose contains nine olfactory bulbs, more than any other mammal. Its keen sense of smell is not just from the quantity of bulbs in the nose but also in the development of the brain, as its olfactory lobe is very developed. The snout resembles an elongated pig snout. The mouth is small and tubular, typical of species that feed on ants and termites. The aardvark has a long, thin, snakelike, protruding tongue (as much as long) and elaborate structures supporting a keen sense of smell. The ears, which are very effective, are disproportionately long, about long. The eyes are small for its head, and consist only of rods.
Digestive system
The aardvark's stomach has a muscular pyloric area that acts as a gizzard to grind swallowed food up, thereby rendering chewing unnecessary. Its cecum is large. Both sexes emit a strong smelling secretion from an anal gland. Its salivary glands are highly developed and almost completely ring the neck; their output is what causes the tongue to maintain its tackiness. The female has two pairs of teats in the inguinal region.
Genetically speaking, the aardvark is a living fossil, as its chromosomes are highly conserved, reflecting much of the early eutherian arrangement before the divergence of the major modern taxa. | Aardvark | Wikipedia | 400 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
Habitat and range
Aardvarks are found in sub-Saharan Africa, where suitable habitat (savannas, grasslands, woodlands and bushland) and food (i.e., ants and termites) is available. They spend the daylight hours in dark burrows to avoid the heat of the day. The only major habitat that they are not present in is swamp forest, as the high water table precludes digging to a sufficient depth. They also avoid terrain rocky enough to cause problems with digging. They have been documented as high as in Ethiopia. They can be found throughout sub-Saharan Africa from Ethiopia all the way to Cape of Good Hope in South Africa with few exceptions including the coastal areas of Namibia, Ivory Coast, and Ghana. They are not found in Madagascar.
Ecology and behaviour
Aardvarks live for up to 23 years in captivity. Its keen hearing warns it of predators: lions, leopards, cheetahs, African wild dogs, hyenas, and pythons. Some humans also hunt aardvarks for meat. Aardvarks can dig fast or run in zigzag fashion to elude enemies, but if all else fails, they will strike with their claws, tail and shoulders, sometimes flipping onto their backs lying motionless except to lash out with all four feet. They are capable of causing substantial damage to unprotected areas of an attacker. They will also dig to escape as they can. Sometimes, when pressed, aardvarks can dig extremely quickly.
Feeding
The aardvark is nocturnal and is a solitary creature that feeds almost exclusively on ants and termites (myrmecophagy); studies in the Nama Karoo revealed that ants, especially Anoplolepis custodiens, were the predominant prey year-round, followed by termites like Trinervitermes trinervoides. In winter, when ant numbers declined, aardvarks relied more on termites, often feeding on epigeal mounds coinciding with the presence of alates, possibly to meet their nutritional needs. They avoid eating the African driver ant and red ants. Due to their stringent diet requirements, they require a large range to survive. | Aardvark | Wikipedia | 452 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
The only fruit eaten by aardvarks is the aardvark cucumber. In fact, the cucumber and the aardvark have a symbiotic relationship as they eat the subterranean fruit, then defecate the seeds near their burrows, which then grow rapidly due to the loose soil and fertile nature of the area. The time spent in the intestine of the aardvark helps the fertility of the seed, and the fruit provides needed moisture for the aardvark.
An aardvark emerges from its burrow in the late afternoon or shortly after sunset, and forages over a considerable home range encompassing . While foraging for food, the aardvark will keep its nose to the ground and its ears pointed forward, which indicates that both smell and hearing are involved in the search for food. They zig-zag as they forage and will usually not repeat a route for five to eight days as they appear to allow time for the termite nests to recover before feeding on it again. | Aardvark | Wikipedia | 214 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
During a foraging period, they will stop to dig a V-shaped trench with their forefeet and then sniff it profusely as a means to explore their location. When a concentration of ants or termites is detected, the aardvark digs into it with its powerful front legs, keeping its long ears upright to listen for predators, and takes up an astonishing number of insects with its long, sticky tongue—as many as 50,000 in one night have been recorded. Its claws enable it to dig through the extremely hard crust of a termite or ant mound quickly. It avoids inhaling the dust by sealing the nostrils. When successful, the aardvark's long (up to ) tongue licks up the insects; the termites' biting, or the ants' stinging attacks are rendered futile by the tough skin. After an aardvark visit at a termite mound, other animals will visit to pick up all the leftovers. Termite mounds alone do not provide enough food for the aardvark, so they look for termites that are on the move. When these insects move, they can form columns long and these tend to provide easy pickings with little effort exerted by the aardvark. These columns are more common in areas of livestock or other hoofed animals. The trampled grass and dung attract termites from the Odontotermes, Microtermes, and Pseudacanthotermes genera.
On a nightly basis they tend to be more active during the first portion of night (roughly the four hours between 8:00p.m. and 12:00a.m.); however, they do not seem to prefer bright or dark nights over the other. During adverse weather or if disturbed they will retreat to their burrow systems. They cover between per night; however, some studies have shown that they may traverse as far as in a night.
Aardvarks shift their circadian rhythms to more diurnal activity patterns in response to a reduced food supply. This survival tactic may signify an increased risk of imminent mortality. | Aardvark | Wikipedia | 433 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
Vocalisation
The aardvark is a rather quiet animal. However, it does make soft grunting sounds as it forages and loud grunts as it makes for its tunnel entrance. It makes a bleating sound if frightened. When it is threatened it will make for one of its burrows. If one is not close it will dig a new one rapidly. This new one will be short and require the aardvark to back out when the coast is clear.
Movement
The aardvark is known to be a good swimmer and has been witnessed successfully swimming in strong currents. It can dig a yard of tunnel in about five minutes, but otherwise moves fairly slowly.
When leaving the burrow at night, they pause at the entrance for about ten minutes, sniffing and listening. After this period of watchfulness, it will bound out and within seconds it will be away. It will then pause, prick its ears, twisting its head to listen, then jump and move off to start foraging. | Aardvark | Wikipedia | 202 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
Aside from digging out ants and termites, the aardvark also excavates burrows in which to live, which generally fall into one of three categories: burrows made while foraging, refuge and resting location, and permanent homes. Temporary sites are scattered around the home range and are used as refuges, while the main burrow is also used for breeding. Main burrows can be deep and extensive, have several entrances and can be as long as . These burrows can be large enough for a person to enter. The aardvark changes the layout of its home burrow regularly, and periodically moves on and makes a new one. The old burrows are an important part of the African wildlife scene. As they are vacated, then they are inhabited by smaller animals like the African wild dog, ant-eating chat, Nycteris thebaica and warthogs. Other animals that use them are hares, mongooses, hyenas, owls, pythons, and lizards. Without these refuges many animals would die during wildfire season. Only mothers and young share burrows; however, the aardvark is known to live in small family groups or as a solitary creature. If attacked in the tunnel, it will escape by digging out of the tunnel thereby placing the fresh fill between it and its predator, or if it decides to fight it will roll onto its back, and attack with its claws. The aardvark has been known to sleep in a recently excavated ant nest, which also serves as protection from its predators.
Reproduction
It is believed to exhibit polygamous breeding behavior. During mating, the male secures himself to the female's back using his claws, which can occasionally result in noticeable scratches. Males play no role on parental care. | Aardvark | Wikipedia | 360 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
Aardvarks pair only during the breeding season; after a gestation period of seven months, one cub weighing around is born during May–July. When born, the young has flaccid ears and many wrinkles. When nursing, it will nurse off each teat in succession. After two weeks, the folds of skin disappear and after three, the ears can be held upright. After 5–6 weeks, body hair starts growing. It is able to leave the burrow to accompany its mother after only two weeks and eats termites at nine weeks, and is weaned between three months and 16 weeks. At six months of age, it is able to dig its own burrows, but it will often remain with the mother until the next mating season, and is sexually mature from approximately two years of age.
Conservation
Aardvarks were thought to have declining numbers, however, this is possibly because they are not readily seen. There are no definitive counts because of their nocturnal and secretive habits; however, their numbers seem to be stable overall. They are not considered common anywhere in Africa, but due to their large range, they maintain sufficient numbers. There may be a slight decrease in numbers in eastern, northern, and western Africa. Southern African numbers are not decreasing. It has received an official designation from the IUCN as least concern. However, they are a species in a precarious situation, as they are so dependent on such specific food; therefore if a problem arises with the abundance of termites, the species as a whole would be affected drastically.
Recent research suggests that aardvarks may be particularly vulnerable to alterations in temperature caused by climate change. Droughts negatively impact the availability of termites and ants, which comprise the bulk of an aardvark's diet. Nocturnal species faced with resource scarcity may increase their diurnal activity to spare the energy costs of staying warm at night, but this comes at the cost of withstanding high temperatures during the day. A study on aardvarks in the Kalahari Desert saw that five out of six aardvarks being studied perished following a drought. Aardvarks that survive droughts can take long periods of time to regain health and optimal thermoregulatory physiology, reducing the reproductive potential of the species.
Aardvarks handle captivity well. The first zoo to have one was London Zoo in 1869, which had an animal from South Africa.
Mythology and popular culture | Aardvark | Wikipedia | 499 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
In African folklore, the aardvark is much admired because of its diligent quest for food and its fearless response to soldier ants. Hausa magicians make a charm from the heart, skin, forehead, and nails of the aardvark, which they then proceed to pound together with the root of a certain tree. Wrapped in a piece of skin and worn on the chest, the charm is said to give the owner the ability to pass through walls or roofs at night. The charm is said to be used by burglars and those seeking to visit young girls without their parents' permission. Also, some tribes, such as the Margbetu, Ayanda, and Logo, will use aardvark teeth to make bracelets, which are regarded as good luck charms. The meat, which has a resemblance to pork, is eaten in certain cultures. In the mythology of the Dagbon people of Ghana, the aardvark is believed to possess superpowers. The Dagombas believe this animal can transfigure into and interact with humans.
The ancient Egyptian god Set is usually depicted with the head of an unidentified animal, whose similarity to an aardvark has been noted in scholarship.
The titular character and his families from Arthur, an animated television series for children based on a book series and produced by WGBH, shown in more than 180 countries, is an aardvark. In the first book of the series, Arthur's Nose (1976), he has a long, aardvark-like nose, but in later books, his face becomes more rounded.
Otis the Aardvark was a puppet character used on Children's BBC programming.
An aardvark features as the antagonist in the cartoon The Ant and the Aardvark as well as in the Canadian animated series The Raccoons.
The supersonic fighter-bomber F-111/FB-111 was nicknamed the Aardvark because of its long nose resembling the animal. It also had similarities with its nocturnal missions flown at a very low level employing ordnance that could penetrate deep into the ground. In the US Navy, the squadron VF-114 was nicknamed the Aardvarks, flying F-4s and then F-14s. The squadron mascot was adapted from the animal in the comic strip B.C., which the F-4 was said to resemble. | Aardvark | Wikipedia | 497 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
Cerebus the Aardvark is a 300-issue comic book series by Dave Sim. | Aardvark | Wikipedia | 20 | 680 | https://en.wikipedia.org/wiki/Aardvark | Biology and health sciences | Mammals | null |
The aardwolf (Proteles cristatus) is an insectivorous hyaenid species, native to East and Southern Africa. Its name means "earth-wolf" in Afrikaans and Dutch. It is also called the maanhaar-jackal (Afrikaans for "mane-jackal"), termite-eating hyena and civet hyena, based on its habit of secreting substances from its anal gland, a characteristic shared with the African civet.
Unlike many of its relatives in the order Carnivora, the aardwolf does not hunt large animals. It eats insects and their larvae, mainly termites; one aardwolf can lap up as many as 300,000 termites during a single night using its long, sticky tongue. The aardwolf's tongue has adapted to be tough enough to withstand the strong bite of termites.
The aardwolf lives in the shrublands of eastern and southern Africa – open lands covered with stunted trees and shrubs. It is nocturnal, resting in burrows during the day and emerging at night to seek food.
Taxonomy
The aardwolf is generally classified as part of the hyena family Hyaenidae. However, it was formerly placed in its own family Protelidae. Early on, scientists felt that it was merely mimicking the striped hyena, which subsequently led to the creation of Protelidae. Recent studies have suggested that the aardwolf probably diverged from other hyaenids early on; how early is still unclear, as the fossil record and genetic studies disagree by 10 million years.
The aardwolf is the only surviving species in the subfamily Protelinae. There is disagreement as to whether the species is monotypic, or can be divided into subspecies. A 2021 study found the genetic differences in eastern and southern aardwolves may be pronounced enough to categorize them as species.
A 2006 molecular analysis indicates it is phylogenetically the most basal of the four extant hyaenidae species.
Etymology
The generic name proteles comes from two words both of Greek origin, protos and teleos which combined means "complete in front" based on the fact that they have five toes on their front feet and four on the rear. The specific name, cristatus, comes from Latin and means "provided with a comb", relating to their mane.
Description | Aardwolf | Wikipedia | 497 | 681 | https://en.wikipedia.org/wiki/Aardwolf | Biology and health sciences | Other carnivora | Animals |
The aardwolf resembles a much smaller and thinner striped hyena, with a more slender muzzle, black vertical stripes on a coat of yellowish fur, and a long, distinct mane down the midline of the neck and back. It also has one or two diagonal stripes down the fore and hindquarters and several stripes on its legs. The mane is raised during confrontations to make the aardwolf appear larger. It is missing the throat spot that others in the family have. Its lower leg (from the knee down) is all black, and its tail is bushy with a black tip.
The aardwolf is about long, excluding its bushy tail, which is about long, and stands about tall at the shoulders. An adult aardwolf weighs approximately , sometimes reaching . The aardwolves in the south of the continent tend to be smaller (about ) than the eastern version (around ). This makes the aardwolf the smallest extant member of the Hyaenidae family. The front feet have five toes each, unlike the four-toed hyena. The skull is similar in shape to those of other hyenas, though much smaller, and its cheek teeth are specialised for eating insects. It still has canines, but unlike other hyenas, these teeth are used primarily for fighting and defense. Its ears, which are large, are very similar to those of the striped hyena.
As an aardwolf ages, it will typically lose some of its teeth, though this has little impact on its feeding habits due to the softness of the insects that it eats.
Distribution and habitat
Aardwolves live in open, dry plains and bushland, avoiding mountainous areas. Due to their specific food requirements, they are found only in regions where termites of the family Hodotermitidae occur. Termites of this family depend on dead and withered grass and are most populous in heavily grazed grasslands and savannahs, including farmland. For most of the year, aardwolves spend time in shared territories consisting of up to a dozen dens, which are occupied for six weeks at a time.
There are two distinct populations: one in Southern Africa, and another in East and Northeast Africa. The species does not occur in the intermediary miombo forests.
An adult pair, along with their most-recent offspring, occupies a territory of .
Behavior and ecology | Aardwolf | Wikipedia | 496 | 681 | https://en.wikipedia.org/wiki/Aardwolf | Biology and health sciences | Other carnivora | Animals |
Aardwolves are shy and nocturnal, sleeping in burrows by day. They will, on occasion during the winter, become diurnal feeders. This happens during the coldest periods as they then stay in at night to conserve heat.
They are primarily solitary animals, though during mating season they form monogamous pairs which occupy a territory with their young. If their territory is infringed upon by another aardwolf, they will chase the intruder away for up to or to the border. If the intruder is caught, which rarely happens, a fight will occur, which is accompanied by soft clucking, hoarse barking, and a type of roar. The majority of incursions occur during mating season, when they can occur once or twice per week. When food is scarce, the stringent territorial system may be abandoned and as many as three pairs may occupy a single territory.
The territory is marked by both sexes, as they both have developed anal glands from which they extrude a black substance that is smeared on rocks or grass stalks in -long streaks. Aardwolves also have scent glands on the forefoot and penile pad. They often mark near termite mounds within their territory every 20 minutes or so. If they are patrolling their territorial boundaries, the marking frequency increases drastically, to once every . At this rate, an individual may mark 60 marks per hour, and upwards of 200 per night.
An aardwolf pair's territory may have up to 10 dens, and numerous middens where they dig small holes and bury their feces with sand. Their dens are usually abandoned aardvark, springhare, or porcupine dens, or on occasion they are crevices in rocks. They will also dig their own dens, or enlarge dens started by springhares. They typically will only use one or two dens at a time, rotating through all of their dens every six months. During the summer, they may rest outside their den during the night and sleep underground during the heat of the day.
Aardwolves are not fast runners nor are they particularly adept at fighting off predators. Therefore, when threatened, the aardwolf may attempt to mislead its foe by doubling back on its tracks. If confronted, it may raise its mane in an attempt to appear more menacing. It also emits a foul-smelling liquid from its anal glands. | Aardwolf | Wikipedia | 500 | 681 | https://en.wikipedia.org/wiki/Aardwolf | Biology and health sciences | Other carnivora | Animals |
Feeding
The aardwolf feeds primarily on termites and more specifically on Trinervitermes. This genus of termites has different species throughout the aardwolf's range. In East Africa, they eat Trinervitermes bettonianus, in central Africa, they eat Trinervitermes rhodesiensis, and in southern Africa, they eat T. trinervoides. Their technique consists of licking them off the ground as opposed to the aardvark, which digs into the mound. They locate their food by sound and also from the scent secreted by the soldier termites. An aardwolf may consume up to 250,000 termites per night using its long, broad, sticky tongue.
They do not destroy the termite mound or consume the entire colony, thus ensuring that the termites can rebuild and provide a continuous supply of food. They often memorize the location of such nests and return to them every few months. During certain seasonal events, such as the onset of the rainy season and the cold of midwinter, the primary termites become scarce, so the need for other foods becomes pronounced. During these times, the southern aardwolf will seek out Hodotermes mossambicus, a type of harvester termite active in the afternoon, which explains some of their diurnal behavior in the winter. The eastern aardwolf, during the rainy season, subsists on termites from the genera Odontotermes and Macrotermes. They are also known to feed on other insects and larvae, and, some sources mention, occasionally eggs, small mammals and birds, but these constitute a very small percentage of their total diet. They use their wide tongues to lap surface foraging termites off of the ground and consume large quantities of sand in the process, which aids in digestion in the absence of teeth to break down their food. | Aardwolf | Wikipedia | 393 | 681 | https://en.wikipedia.org/wiki/Aardwolf | Biology and health sciences | Other carnivora | Animals |
Unlike other hyenas, aardwolves do not scavenge or kill larger animals. Contrary to popular myths, aardwolves do not eat carrion, and if they are seen eating while hunched over a dead carcass, they are actually eating larvae and beetles. Also, contrary to some sources, they do not like meat, unless it is finely ground or cooked for them. The adult aardwolf was formerly assumed to forage in small groups, but more recent research has shown that they are primarily solitary foragers, necessary because of the scarcity of their insect prey. Their primary source, Trinervitermes, forages in small but dense patches of . While foraging, the aardwolf can cover about per hour, which translates to per summer night and per winter night.
Breeding
The breeding season varies depending on location, but normally takes place during autumn or spring. In South Africa, breeding occurs in early July. During the breeding season, unpaired male aardwolves search their own territory, as well as others, for a female to mate with. Dominant males also mate opportunistically with the females of less dominant neighboring aardwolves, which can result in conflict between rival males. Dominant males even go a step further and as the breeding season approaches, they make increasingly greater and greater incursions onto weaker males' territories. As the female comes into oestrus, they add pasting to their tricks inside of the other territories, sometimes doing so more in rivals' territories than their own. Females will also, when given the opportunity, mate with the dominant male, which increases the chances of the dominant male guarding "his" cubs with her. Copulation lasts between 1 and 4.5 hours. | Aardwolf | Wikipedia | 360 | 681 | https://en.wikipedia.org/wiki/Aardwolf | Biology and health sciences | Other carnivora | Animals |
Gestation lasts between 89 and 92 days, producing two to five cubs (most often two or three) during the rainy season (October–December), when termites are more active. They are born with their eyes open, but initially are helpless, and weigh around . The first six to eight weeks are spent in the den with their parents. The male may spend up to six hours a night watching over the cubs while the mother is out looking for food. After three months, they begin supervised foraging, and by four months are normally independent, though they often share a den with their mother until the next breeding season. By the time the next set of cubs is born, the older cubs have moved on. Aardwolves generally achieve sexual maturity at one and a half to two years of age.
Conservation
The aardwolf has not seen decreasing numbers and is relatively widespread throughout eastern Africa. They are not common throughout their range, as they maintain a density of no more than 1 per square kilometer, if food is abundant. Because of these factors, the IUCN has rated the aardwolf as least concern. In some areas, they are persecuted because of the mistaken belief that they prey on livestock; however, they are actually beneficial to the farmers because they eat termites that are detrimental. In other areas, the farmers have recognized this, but they are still killed, on occasion, for their fur. Dogs and insecticides are also common killers of the aardwolf.
In captivity
Frankfurt Zoo in Germany was home to the oldest recorded aardwolf in captivity at 18 years and 11 months. | Aardwolf | Wikipedia | 325 | 681 | https://en.wikipedia.org/wiki/Aardwolf | Biology and health sciences | Other carnivora | Animals |
Adobe ( ; ) is a building material made from earth and organic materials. is Spanish for mudbrick. In some English-speaking regions of Spanish heritage, such as the Southwestern United States, the term is used to refer to any kind of earthen construction, or various architectural styles like Pueblo Revival or Territorial Revival. Most adobe buildings are similar in appearance to cob and rammed earth buildings. Adobe is among the earliest building materials, and is used throughout the world.
Adobe architecture has been dated to before 5,100 BP.
Description
Adobe bricks are rectangular prisms small enough that they can quickly air dry individually without cracking. They can be subsequently assembled, with the application of adobe mud to bond the individual bricks into a structure. There is no standard size, with substantial variations over the years and in different regions. In some areas a popular size measured weighing about ; in other contexts the size is weighing about . The maximum sizes can reach up to ; above this weight it becomes difficult to move the pieces, and it is preferred to ram the mud in situ, resulting in a different typology known as rammed earth.
Strength
In dry climates, adobe structures are extremely durable, and account for some of the oldest existing buildings in the world. Adobe buildings offer significant advantages due to their greater thermal mass, but they are known to be particularly susceptible to earthquake damage if they are not reinforced. Cases where adobe structures were widely damaged during earthquakes include the 1976 Guatemala earthquake, the 2003 Bam earthquake, and the 2010 Chile earthquake.
Distribution
Buildings made of sun-dried earth are common throughout the world (Middle East, Western Asia, North Africa, West Africa, South America, Southwestern North America, Southwestern and Eastern Europe.). Adobe had been in use by indigenous peoples of the Americas in the Southwestern United States, Mesoamerica, and the Andes for several thousand years. Puebloan peoples built their adobe structures with handsful or basketsful of adobe, until the Spanish introduced them to making bricks. Adobe bricks were used in Spain from the Late Bronze and Iron Ages (eighth century BCE onwards). Its wide use can be attributed to its simplicity of design and manufacture, and economics.
Etymology | Adobe | Wikipedia | 435 | 682 | https://en.wikipedia.org/wiki/Adobe | Technology | Building materials | null |
The word adobe has existed for around 4,000 years with relatively little change in either pronunciation or meaning. The word can be traced from the Middle Egyptian () word ḏbt "mud brick" (with vowels unwritten). Middle Egyptian evolved into Late Egyptian and finally to Coptic (), where it appeared as ⲧⲱⲃⲉ tōbə. This was adopted into Arabic as aṭ-ṭawbu or aṭ-ṭūbu, with the definite article al- attached to the root tuba. This was assimilated into the Old Spanish language as adobe , probably via Mozarabic. English borrowed the word from Spanish in the early 18th century, still referring to mudbrick construction.
In more modern English usage, the term adobe has come to include a style of architecture popular in the desert climates of North America, especially in New Mexico, regardless of the construction method.
Composition
An adobe brick is a composite material made of earth mixed with water and an organic material such as straw or dung. The soil composition typically contains sand, silt and clay. Straw is useful in binding the brick together and allowing the brick to dry evenly, thereby preventing cracking due to uneven shrinkage rates through the brick. Dung offers the same advantage. The most desirable soil texture for producing the mud of adobe is 15% clay, 10–30% silt, and 55–75% fine sand. Another source quotes 15–25% clay and the remainder sand and coarser particles up to cobbles , with no deleterious effect. Modern adobe is stabilized with either emulsified asphalt or Portland cement up to 10% by weight.
No more than half the clay content should be expansive clays, with the remainder non-expansive illite or kaolinite. Too much expansive clay results in uneven drying through the brick, resulting in cracking, while too much kaolinite will make a weak brick. Typically the soils of the Southwest United States, where such construction has been widely used, are an adequate composition.
Material properties | Adobe | Wikipedia | 401 | 682 | https://en.wikipedia.org/wiki/Adobe | Technology | Building materials | null |
Adobe walls are load bearing, i.e. they carry their own weight into the foundation rather than by another structure, hence the adobe must have sufficient compressive strength. In the United States, most building codes call for a minimum compressive strength of for the adobe block. Adobe construction should be designed so as to avoid lateral structural loads that would cause bending loads. The building codes require the building sustain a lateral acceleration earthquake load. Such an acceleration will cause lateral loads on the walls, resulting in shear and bending and inducing tensile stresses. To withstand such loads, the codes typically call for a tensile modulus of rupture strength of at least for the finished block.
In addition to being an inexpensive material with a small resource cost, adobe can serve as a significant heat reservoir due to the thermal properties inherent in the massive walls typical in adobe construction. In climates typified by hot days and cool nights, the high thermal mass of adobe mediates the high and low temperatures of the day, moderating the temperature of the living space. The massive walls require a large and relatively long input of heat from the sun (radiation) and from the surrounding air (convection) before they warm through to the interior. After the sun sets and the temperature drops, the warm wall will continue to transfer heat to the interior for several hours due to the time-lag effect. Thus, a well-planned adobe wall of the appropriate thickness is very effective at controlling inside temperature through the wide daily fluctuations typical of desert climates, a factor which has contributed to its longevity as a building material. | Adobe | Wikipedia | 318 | 682 | https://en.wikipedia.org/wiki/Adobe | Technology | Building materials | null |
Thermodynamic material properties have significant variation in the literature. Some experiments suggest that the standard consideration of conductivity is not adequate for this material, as its main thermodynamic property is inertia, and conclude that experimental tests should be performed over a longer period of time than usual – preferably with changing thermal jumps. There is an effective R-value for a north facing wall of R0=10 hr ft2 °F/Btu, which corresponds to thermal conductivity k=10 in x 1 ft/12 in /R0=0.33 Btu/(hr ft °F) or 0.57 W/(m K) in agreement with the thermal conductivity reported from another source. To determine the total R-value of a wall, scale R0 by the thickness of the wall in inches. The thermal resistance of adobe is also stated as an R-value for a wall R0=4.1 hr ft2 °F/Btu. Another source provides the following properties: conductivity 0.30 Btu/(hr ft °F) or 0.52 W/(m K); specific heat capacity 0.24 Btu/(lb °F) or 1 kJ/(kg K) and density , giving heat capacity 25.4 Btu/(ft3 °F) or 1700 kJ/(m3 K). Using the average value of the thermal conductivity as k = 32 Btu/(hr ft °F) or 0.55 W/(m K), the thermal diffusivity is calculated to be .
Uses
Poured and puddled adobe walls
Poured and puddled adobe (puddled clay, piled earth), today called cob, is made by placing soft adobe in layers, rather than by making individual dried bricks or using a form. "Puddle" is a general term for a clay or clay and sand-based material worked into a dense, plastic state. These are the oldest methods of building with adobe in the Americas until holes in the ground were used as forms, and later wooden forms used to make individual bricks were introduced by the Spanish.
Adobe bricks
Bricks made from adobe are usually made by pressing the mud mixture into an open timber frame. In North America, the brick is typically about in size. The mixture is molded into the frame, which is removed after initial setting. After drying for a few hours, the bricks are turned on edge to finish drying. Slow drying in shade reduces cracking. | Adobe | Wikipedia | 503 | 682 | https://en.wikipedia.org/wiki/Adobe | Technology | Building materials | null |
The same mixture, without straw, is used to make mortar and often plaster on interior and exterior walls. Some cultures used lime-based cement for the plaster to protect against rain damage.
Depending on the form into which the mixture is pressed, adobe can encompass nearly any shape or size, provided drying is even and the mixture includes reinforcement for larger bricks. Reinforcement can include manure, straw, cement, rebar, or wooden posts. Straw, cement, or manure added to a standard adobe mixture can produce a stronger, more crack-resistant brick. A test is done on the soil content first. To do so, a sample of the soil is mixed into a clear container with some water, creating an almost completely saturated liquid. The container is shaken vigorously for one minute. It is then allowed to settle for a day until the soil has settled into layers. Heavier particles settle out first, sand above, silt above that, and very fine clay and organic matter will stay in suspension for days. After the water has cleared, percentages of the various particles can be determined. Fifty to 60 percent sand and 35 to 40 percent clay will yield strong bricks. The Cooperative State Research, Education, and Extension Service at New Mexico State University recommends a mix of not more than clay, not less than sand, and never more than silt.
During the Great Depression, designer and builder Hugh W. Comstock used cheaper materials and made a specialized adobe brick called "Bitudobe." His first adobe house was built in 1936. In 1948, he published the book Post-Adobe; Simplified Adobe Construction Combining A Rugged Timber Frame And Modern Stabilized Adobe, which described his method of construction, including how to make "Bitudobe." In 1938, he served as an adviser to the architects Franklin & Kump Associates, who built the Carmel High School, which used his Post-adobe system.
Adobe wall construction | Adobe | Wikipedia | 383 | 682 | https://en.wikipedia.org/wiki/Adobe | Technology | Building materials | null |
The ground supporting an adobe structure should be compressed, as the weight of adobe wall is significant and foundation settling may cause cracking of the wall. Footing depth is to be below the ground frost level. The footing and stem wall are commonly thick, respectively. Modern construction codes call for the use of reinforcing steel in the footing and stem wall. Adobe bricks are laid by course. Adobe walls usually never rise above two stories as they are load bearing and adobe has low structural strength. When creating window and door openings, a lintel is placed on top of the opening to support the bricks above. Atop the last courses of brick, bond beams made of heavy wood beams or modern reinforced concrete are laid to provide a horizontal bearing plate for the roof beams and to redistribute lateral earthquake loads to shear walls more able to carry the forces. To protect the interior and exterior adobe walls, finishes such as mud plaster, whitewash or stucco can be applied. These protect the adobe wall from water damage, but need to be reapplied periodically. Alternatively, the walls can be finished with other nontraditional plasters that provide longer protection. Bricks made with stabilized adobe generally do not need protection of plasters.
Adobe roof
The traditional adobe roof has been constructed using a mixture of soil/clay, water, sand and organic materials. The mixture was then formed and pressed into wood forms, producing rows of dried earth bricks that would then be laid across a support structure of wood and plastered into place with more adobe.
Depending on the materials available, a roof may be assembled using wood or metal beams to create a framework to begin layering adobe bricks. Depending on the thickness of the adobe bricks, the framework has been preformed using a steel framing and a layering of a metal fencing or wiring over the framework to allow an even load as masses of adobe are spread across the metal fencing like cob and allowed to air dry accordingly. This method was demonstrated with an adobe blend heavily impregnated with cement to allow even drying and prevent cracking.
The more traditional flat adobe roofs are functional only in dry climates that are not exposed to snow loads. The heaviest wooden beams, called vigas, lie atop the wall. Across the vigas lie smaller members called latillas and upon those brush is then laid. Finally, the adobe layer is applied. | Adobe | Wikipedia | 472 | 682 | https://en.wikipedia.org/wiki/Adobe | Technology | Building materials | null |
To construct a flat adobe roof, beams of wood were laid to span the building, the ends of which were attached to the tops of the walls. Once the vigas, latillas and brush are laid, adobe bricks are placed. An adobe roof is often laid with bricks slightly larger in width to ensure a greater expanse is covered when placing the bricks onto the roof. Following each individual brick should be a layer of adobe mortar, recommended to be at least thick to make certain there is ample strength between the brick's edges and also to provide a relative moisture barrier during rain.
Roof design evolved around 1850 in the American Southwest. of adobe mud was applied on top of the latillas, then of dry adobe dirt applied to the roof. The dirt was contoured into a low slope to a downspout aka a 'canal'. When moisture was applied to the roof the clay particles expanded to create a waterproof membrane. Once a year it was necessary to pull the weeds from the roof and re-slope the dirt as needed.
Depending on the materials, adobe roofs can be inherently fire-proof. The construction of a chimney can greatly influence the construction of the roof supports, creating an extra need for care in choosing the materials. The builders can make an adobe chimney by stacking simple adobe bricks in a similar fashion as the surrounding walls.
In 1927, the Uniform Building Code (UBC) was adopted in the United States. Local ordinances, referencing the UBC added requirements to building with adobe. These included: restriction of building height of adobe structures to 1-story, requirements for adobe mix (compressive and shear strength) and new requirements which stated that every building shall be designed to withstand seismic activity, specifically lateral forces. By the 1980s however, seismic related changes in the California Building Code effectively ended solid wall adobe construction in California; however Post-and-Beam adobe and veneers are still being used.
Adobe around the world
The largest structure ever made from adobe is the Arg-é Bam built by the Achaemenid Empire. Other large adobe structures are the Huaca del Sol in Peru, with 100 million signed bricks and the ciudellas of Chan Chan and Tambo Colorado, both in Peru. | Adobe | Wikipedia | 452 | 682 | https://en.wikipedia.org/wiki/Adobe | Technology | Building materials | null |
An android is a humanoid robot or other artificial being, often made from a flesh-like material. Historically, androids existed only in the domain of science fiction and were frequently seen in film and television, but advances in robot technology have allowed the design of functional and realistic humanoid robots.
Terminology
The Oxford English Dictionary traces the earliest use (as "Androides") to Ephraim Chambers' 1728 Cyclopaedia, in reference to an automaton that St. Albertus Magnus allegedly created. By the late 1700s, "androides", elaborate mechanical devices resembling humans performing human activities, were displayed in exhibit halls.
The term "android" appears in US patents as early as 1863 in reference to miniature human-like toy automatons. The term android was used in a more modern sense by the French author Auguste Villiers de l'Isle-Adam in his work Tomorrow's Eve (1886), featuring an artificial humanoid robot named Hadaly. The term made an impact into English pulp science fiction starting from Jack Williamson's The Cometeers (1936) and the distinction between mechanical robots and fleshy androids was popularized by Edmond Hamilton's Captain Future stories (1940–1944).
Although Karel Čapek's robots in R.U.R. (Rossum's Universal Robots) (1921)—the play that introduced the word robot to the world—were organic artificial humans, the word "robot" has come to primarily refer to mechanical humans, animals, and other beings. The term "android" can mean either one of these, while a cyborg ("cybernetic organism" or "bionic man") would be a creature that is a combination of organic and mechanical parts.
The term "droid", popularized by George Lucas in the original Star Wars film and now used widely within science fiction, originated as an abridgment of "android", but has been used by Lucas and others to mean any robot, including distinctly non-human form machines like R2-D2. The word "android" was used in Star Trek: The Original Series episode "What Are Little Girls Made Of?" The abbreviation "andy", coined as a pejorative by writer Philip K. Dick in his novel Do Androids Dream of Electric Sheep?, has seen some further usage, such as within the TV series Total Recall 2070. | Android (robot) | Wikipedia | 485 | 713 | https://en.wikipedia.org/wiki/Android%20%28robot%29 | Technology | Machinery and tools: General | null |
While the term "android" is used in reference to human-looking robots in general (not necessarily male-looking humanoid robots), a robot with a female appearance can also be referred to as a gynoid. Besides one can refer to robots without alluding to their sexual appearance by calling them anthrobots (a portmanteau of anthrōpos and robot; see anthrobotics) or anthropoids (short for anthropoid robots; the term humanoids is not appropriate because it is already commonly used to refer to human-like organic species in the context of science fiction, futurism and speculative astrobiology).
Authors have used the term android in more diverse ways than robot or cyborg. In some fictional works, the difference between a robot and android is only superficial, with androids being made to look like humans on the outside but with robot-like internal mechanics. In other stories, authors have used the word "android" to mean a wholly organic, yet artificial, creation. Other fictional depictions of androids fall somewhere in between.
Eric G. Wilson, who defines an android as a "synthetic human being", distinguishes between three types of android, based on their body's composition:
the mummy type – made of "dead things" or "stiff, inanimate, natural material", such as mummies, puppets, dolls and statues
the golem type – made from flexible, possibly organic material, including golems and homunculi
the automaton type – made from a mix of dead and living parts, including automatons and robots
Although human morphology is not necessarily the ideal form for working robots, the fascination in developing robots that can mimic it can be found historically in the assimilation of two concepts: simulacra (devices that exhibit likeness) and automata (devices that have independence).
Projects
Several projects aiming to create androids that look, and, to a certain degree, speak or act like a human being have been launched or are underway.
Japan | Android (robot) | Wikipedia | 416 | 713 | https://en.wikipedia.org/wiki/Android%20%28robot%29 | Technology | Machinery and tools: General | null |
Japanese robotics have been leading the field since the 1970s. Waseda University initiated the WABOT project in 1967, and in 1972 completed the WABOT-1, the first android, a full-scale humanoid intelligent robot. Its limb control system allowed it to walk with the lower limbs, and to grip and transport objects with hands, using tactile sensors. Its vision system allowed it to measure distances and directions to objects using external receptors, artificial eyes and ears. And its conversation system allowed it to communicate with a person in Japanese, with an artificial mouth.
In 1984, WABOT-2 was revealed, and made a number of improvements. It was capable of playing the organ. Wabot-2 had ten fingers and two feet, and was able to read a score of music. It was also able to accompany a person. In 1986, Honda began its humanoid research and development program, to create humanoid robots capable of interacting successfully with humans.
The Intelligent Robotics Lab, directed by Hiroshi Ishiguro at Osaka University, and the Kokoro company demonstrated the Actroid at Expo 2005 in Aichi Prefecture, Japan and released the Telenoid R1 in 2010. In 2006, Kokoro developed a new DER 2 android. The height of the human body part of DER2 is 165 cm. There are 47 mobile points. DER2 can not only change its expression but also move its hands and feet and twist its body. The "air servosystem" which Kokoro developed originally is used for the actuator. As a result of having an actuator controlled precisely with air pressure via a servosystem, the movement is very fluid and there is very little noise. DER2 realized a slimmer body than that of the former version by using a smaller cylinder. Outwardly DER2 has a more beautiful proportion. Compared to the previous model, DER2 has thinner arms and a wider repertoire of expressions. Once programmed, it is able to choreograph its motions and gestures with its voice.
The Intelligent Mechatronics Lab, directed by Hiroshi Kobayashi at the Tokyo University of Science, has developed an android head called Saya, which was exhibited at Robodex 2002 in Yokohama, Japan. There are several other initiatives around the world involving humanoid research and development at this time, which will hopefully introduce a broader spectrum of realized technology in the near future. Now Saya is working at the Science University of Tokyo as a guide. | Android (robot) | Wikipedia | 498 | 713 | https://en.wikipedia.org/wiki/Android%20%28robot%29 | Technology | Machinery and tools: General | null |
The Waseda University (Japan) and NTT docomo's manufacturers have succeeded in creating a shape-shifting robot WD-2. It is capable of changing its face. At first, the creators decided the positions of the necessary points to express the outline, eyes, nose, and so on of a certain person. The robot expresses its face by moving all points to the decided positions, they say. The first version of the robot was first developed back in 2003. After that, a year later, they made a couple of major improvements to the design. The robot features an elastic mask made from the average head dummy. It uses a driving system with a 3DOF unit. The WD-2 robot can change its facial features by activating specific facial points on a mask, with each point possessing three degrees of freedom. This one has 17 facial points, for a total of 56 degrees of freedom. As for the materials they used, the WD-2's mask is fabricated with a highly elastic material called Septom, with bits of steel wool mixed in for added strength. Other technical features reveal a shaft driven behind the mask at the desired facial point, driven by a DC motor with a simple pulley and a slide screw. Apparently, the researchers can also modify the shape of the mask based on actual human faces. To "copy" a face, they need only a 3D scanner to determine the locations of an individual's 17 facial points. After that, they are then driven into position using a laptop and 56 motor control boards. In addition, the researchers also mention that the shifting robot can even display an individual's hair style and skin color if a photo of their face is projected onto the 3D Mask.
Singapore
Prof Nadia Thalmann, a Nanyang Technological University scientist, directed efforts of the Institute for Media Innovation along with the School of Computer Engineering in the development of a social robot, Nadine. Nadine is powered by software similar to Apple's Siri or Microsoft's Cortana. Nadine may become a personal assistant in offices and homes in future, or she may become a companion for the young and the elderly.
Assoc Prof Gerald Seet from the School of Mechanical & Aerospace Engineering and the BeingThere Centre led a three-year R&D development in tele-presence robotics, creating EDGAR. A remote user can control EDGAR with the user's face and expressions displayed on the robot's face in real time. The robot also mimics their upper body movements. | Android (robot) | Wikipedia | 512 | 713 | https://en.wikipedia.org/wiki/Android%20%28robot%29 | Technology | Machinery and tools: General | null |
South Korea
KITECH researched and developed EveR-1, an android interpersonal communications model capable of emulating human emotional expression via facial "musculature" and capable of rudimentary conversation, having a vocabulary of around 400 words. She is tall and weighs , matching the average figure of a Korean woman in her twenties. EveR-1's name derives from the Biblical Eve, plus the letter r for robot. EveR-1's advanced computing processing power enables speech recognition and vocal synthesis, at the same time processing lip synchronization and visual recognition by 90-degree micro-CCD cameras with face recognition technology. An independent microchip inside her artificial brain handles gesture expression, body coordination, and emotion expression. Her whole body is made of highly advanced synthetic jelly silicon and with 60 artificial joints in her face, neck, and lower body; she is able to demonstrate realistic facial expressions and sing while simultaneously dancing. In South Korea, the Ministry of Information and Communication had an ambitious plan to put a robot in every household by 2020. Several robot cities have been planned for the country: the first will be built in 2016 at a cost of 500 billion won (US$440 million), of which 50 billion is direct government investment. The new robot city will feature research and development centers for manufacturers and part suppliers, as well as exhibition halls and a stadium for robot competitions. The country's new Robotics Ethics Charter will establish ground rules and laws for human interaction with robots in the future, setting standards for robotics users and manufacturers, as well as guidelines on ethical standards to be programmed into robots to prevent human abuse of robots and vice versa.
United States
Walt Disney and a staff of Imagineers created Great Moments with Mr. Lincoln that debuted at the 1964 New York World's Fair.
Dr. William Barry, an Education Futurist and former visiting West Point Professor of Philosophy and Ethical Reasoning at the United States Military Academy, created an AI android character named "Maria Bot". This Interface AI android was named after the infamous fictional robot Maria in the 1927 film Metropolis, as a well-behaved distant relative. Maria Bot is the first AI Android Teaching Assistant at the university level. Maria Bot has appeared as a keynote speaker as a duo with Barry for a TEDx talk in Everett, Washington in February 2020. | Android (robot) | Wikipedia | 467 | 713 | https://en.wikipedia.org/wiki/Android%20%28robot%29 | Technology | Machinery and tools: General | null |
Resembling a human from the shoulders up, Maria Bot is a virtual being android that has complex facial expressions and head movement and engages in conversation about a variety of subjects. She uses AI to process and synthesize information to make her own decisions on how to talk and engage. She collects data through conversations, direct data inputs such as books or articles, and through internet sources.
Maria Bot was built by an international high-tech company for Barry to help improve education quality and eliminate education poverty. Maria Bot is designed to create new ways for students to engage and discuss ethical issues raised by the increasing presence of robots and artificial intelligence. Barry also uses Maria Bot to demonstrate that programming a robot with life-affirming, ethical framework makes them more likely to help humans to do the same.
Maria Bot is an ambassador robot for good and ethical AI technology.
Hanson Robotics, Inc., of Texas and KAIST produced an android portrait of Albert Einstein, using Hanson's facial android technology mounted on KAIST's life-size walking bipedal robot body. This Einstein android, also called "Albert Hubo", thus represents the first full-body walking android in history. Hanson Robotics, the FedEx Institute of Technology, and the University of Texas at Arlington also developed the android portrait of sci-fi author Philip K. Dick (creator of Do Androids Dream of Electric Sheep?, the basis for the film Blade Runner), with full conversational capabilities that incorporated thousands of pages of the author's works. In 2005, the PKD android won a first-place artificial intelligence award from AAAI.
Use in fiction
Androids are a staple of science fiction. Isaac Asimov pioneered the fictionalization of the science of robotics and artificial intelligence, notably in his 1950s series I, Robot. One thing common to most fictional androids is that the real-life technological challenges associated with creating thoroughly human-like robots — such as the creation of strong artificial intelligence—are assumed to have been solved. Fictional androids are often depicted as mentally and physically equal or superior to humans—moving, thinking and speaking as fluidly as them. | Android (robot) | Wikipedia | 430 | 713 | https://en.wikipedia.org/wiki/Android%20%28robot%29 | Technology | Machinery and tools: General | null |
The tension between the nonhuman substance and the human appearance—or even human ambitions—of androids is the dramatic impetus behind most of their fictional depictions. Some android heroes seek, like Pinocchio, to become human, as in the film Bicentennial Man, or Data in Star Trek: The Next Generation. Others, as in the film Westworld, rebel against abuse by careless humans. Android hunter Deckard in Do Androids Dream of Electric Sheep? and its film adaptation Blade Runner discovers that his targets appear to be, in some ways, more "human" than he is. The sequel Blade Runner 2049 involves android hunter K, himself an android, discovering the same thing. Android stories, therefore, are not essentially stories "about" androids; they are stories about the human condition and what it means to be human.
One aspect of writing about the meaning of humanity is to use discrimination against androids as a mechanism for exploring racism in society, as in Blade Runner. Perhaps the clearest example of this is John Brunner's 1968 novel Into the Slave Nebula, where the blue-skinned android slaves are explicitly shown to be fully human. More recently, the androids Bishop and Annalee Call in the films Aliens and Alien Resurrection are used as vehicles for exploring how humans deal with the presence of an "Other". The 2018 video game Detroit: Become Human also explores how androids are treated as second class citizens in a near future society.
Female androids, or "gynoids", are often seen in science fiction, and can be viewed as a continuation of the long tradition of men attempting to create the stereotypical "perfect woman". Examples include the Greek myth of Pygmalion and the female robot Maria in Fritz Lang's Metropolis. Some gynoids, like Pris in Blade Runner, are designed as sex-objects, with the intent of "pleasing men's violent sexual desires", or as submissive, servile companions, such as in The Stepford Wives. Fiction about gynoids has therefore been described as reinforcing "essentialist ideas of femininity", although others have suggested that the treatment of androids is a way of exploring racism and misogyny in society.
The 2015 Japanese film Sayonara, starring Geminoid F, was promoted as "the first movie to feature an android performing opposite a human actor". | Android (robot) | Wikipedia | 491 | 713 | https://en.wikipedia.org/wiki/Android%20%28robot%29 | Technology | Machinery and tools: General | null |
Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of skin supported by radially extended thin bony spines called lepidotrichia, as opposed to the bulkier, fleshy lobed fins of the sister class Sarcopterygii (lobe-finned fish). Resembling folding fans, the actinopterygian fins can easily change shape and wetted area, providing superior thrust-to-weight ratios per movement compared to sarcopterygian and chondrichthyian fins. The fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the articulation between these fins and the internal skeleton (e.g., pelvic and pectoral girdles).
The vast majority of actinopterygians are teleosts. By species count, they dominate the subphylum Vertebrata, and constitute nearly 99% of the over 30,000 extant species of fish. They are the most abundant nektonic aquatic animals and are ubiquitous throughout freshwater and marine environments from the deep sea to subterranean waters to the highest mountain streams. Extant species can range in size from Paedocypris, at ; to the massive ocean sunfish, at ; and to the giant oarfish, at . The largest ever known ray-finned fish, the extinct Leedsichthys from the Jurassic, has been estimated to have grown to .
Characteristics
Ray-finned fishes occur in many variant forms. The main features of typical ray-finned fish are shown in the adjacent diagram.
The swim bladder is a more derived structure and used for buoyancy. Except from the bichirs, which just like the lungs of lobe-finned fish have retained the ancestral condition of ventral budding from the foregut, the swim bladder in ray-finned fishes derives from a dorsal bud above the foregut. In early forms the swim bladder could still be used for breathing, a trait still present in Holostei (bowfins and gars). In some fish like the arapaima, the swim bladder has been modified for breathing air again, and in other lineages it have been completely lost. | Actinopterygii | Wikipedia | 501 | 734 | https://en.wikipedia.org/wiki/Actinopterygii | Biology and health sciences | Fishes | null |
The teleosts have urinary and reproductive tracts that are fully separated, while the Chondrostei have common urogenital ducts, and partially connected ducts are found in Cladistia and Holostei.
Ray-finned fishes have many different types of scales; but all teleosts have leptoid scales. The outer part of these scales fan out with bony ridges, while the inner part is crossed with fibrous connective tissue. Leptoid scales are thinner and more transparent than other types of scales, and lack the hardened enamel- or dentine-like layers found in the scales of many other fish. Unlike ganoid scales, which are found in non-teleost actinopterygians, new scales are added in concentric layers as the fish grows.
Teleosts and chondrosteans (sturgeons and paddlefish) also differ from the bichirs and holosteans (bowfin and gars) in having gone through a whole-genome duplication (paleopolyploidy). The WGD is estimated to have happened about 320 million years ago in the teleosts, which on average has retained about 17% of the gene duplicates, and around 180 (124–225) million years ago in the chondrosteans. It has since happened again in some teleost lineages, like Salmonidae (80–100 million years ago) and several times independently within the Cyprinidae (in goldfish and common carp as recently as 14 million years ago).
Body shapes and fin arrangements
Ray-finned fish vary in size and shape, in their feeding specializations, and in the number and arrangement of their ray-fins.
Reproduction
In nearly all ray-finned fish, the sexes are separate, and in most species the females spawn eggs that are fertilized externally, typically with the male inseminating the eggs after they are laid. Development then proceeds with a free-swimming larval stage. However other patterns of ontogeny exist, with one of the commonest being sequential hermaphroditism. In most cases this involves protogyny, fish starting life as females and converting to males at some stage, triggered by some internal or external factor. Protandry, where a fish converts from male to female, is much less common than protogyny. | Actinopterygii | Wikipedia | 491 | 734 | https://en.wikipedia.org/wiki/Actinopterygii | Biology and health sciences | Fishes | null |
Most families use external rather than internal fertilization. Of the oviparous teleosts, most (79%) do not provide parental care. Viviparity, ovoviviparity, or some form of parental care for eggs, whether by the male, the female, or both parents is seen in a significant fraction (21%) of the 422 teleost families; no care is likely the ancestral condition. The oldest case of viviparity in ray-finned fish is found in Middle Triassic species of Saurichthys. Viviparity is relatively rare and is found in about 6% of living teleost species; male care is far more common than female care. Male territoriality "preadapts" a species for evolving male parental care.
There are a few examples of fish that self-fertilise. The mangrove rivulus is an amphibious, simultaneous hermaphrodite, producing both eggs and spawn and having internal fertilisation. This mode of reproduction may be related to the fish's habit of spending long periods out of water in the mangrove forests it inhabits. Males are occasionally produced at temperatures below and can fertilise eggs that are then spawned by the female. This maintains genetic variability in a species that is otherwise highly inbred.
Classification and fossil record
Actinopterygii is divided into the subclasses Cladistia,Chondrostei and Neopterygii. The Neopterygii, in turn, is divided into the infraclasses Holostei and Teleostei. During the Mesozoic (Triassic, Jurassic, Cretaceous) and Cenozoic the teleosts in particular diversified widely. As a result, 96% of living fish species are teleosts (40% of all fish species belong to the teleost subgroup Acanthomorpha), while all other groups of actinopterygians represent depauperate lineages.
The classification of ray-finned fishes can be summarized as follows: | Actinopterygii | Wikipedia | 429 | 734 | https://en.wikipedia.org/wiki/Actinopterygii | Biology and health sciences | Fishes | null |
Cladistia, which include bichirs and reedfish
Actinopteri, which include:
Chondrostei, which include Acipenseriformes (paddlefishes and sturgeons)
Neopterygii, which include:
Teleostei (most living fishes)
Holostei, which include:
Lepisosteiformes (gars)
Amiiformes (bowfin)
The cladogram below shows the main clades of living actinopterygians and their evolutionary relationships to other extant groups of fishes and the four-limbed vertebrates (tetrapods). The latter include mostly terrestrial species but also groups that became secondarily aquatic (e.g. whales and dolphins). Tetrapods evolved from a group of bony fish during the Devonian period. Approximate divergence dates for the different actinopterygian clades (in millions of years, mya) are from Near et al., 2012.
The polypterids (bichirs and reedfish) are the sister lineage of all other actinopterygians, the Acipenseriformes (sturgeons and paddlefishes) are the sister lineage of Neopterygii, and Holostei (bowfin and gars) are the sister lineage of teleosts. The Elopomorpha (eels and tarpons) appear to be the most basal teleosts.
The earliest known fossil actinopterygian is Andreolepis hedei, dating back 420 million years (Late Silurian), remains of which have been found in Russia, Sweden, and Estonia. Crown group actinopterygians most likely originated near the Devonian-Carboniferous boundary. The earliest fossil relatives of modern teleosts are from the Triassic period (Prohalecites, Pholidophorus), although it is suspected that teleosts originated already during the Paleozoic Era.
Taxonomy
The listing below is a summary of all extinct (indicated by a dagger, †) and living groups of Actinopterygii with their respective taxonomic rank. The taxonomy follows Phylogenetic Classification of Bony Fishes with notes when this differs from Nelson, ITIS and FishBase and extinct groups from Van der Laan 2016 and Xu 2021. | Actinopterygii | Wikipedia | 477 | 734 | https://en.wikipedia.org/wiki/Actinopterygii | Biology and health sciences | Fishes | null |
Order †?Asarotiformes Schaeffer 1968
Order †?Discordichthyiformes Minikh 1998
Order †?Paphosisciformes Grogan & Lund 2015
Order †?Scanilepiformes Selezneya 1985
Order †Cheirolepidiformes Kazantseva-Selezneva 1977
Order †Paramblypteriformes Heyler 1969
Order †Rhadinichthyiformes
Order †Palaeonisciformes Hay 1902
Order †Tarrasiiformes sensu Lund & Poplin 2002
Order †Ptycholepiformes Andrews et al. 1967
Order †Haplolepidiformes Westoll 1944
Order †Aeduelliformes Heyler 1969
Order †Platysomiformes Aldinger 1937
Order †Dorypteriformes Cope 1871
Order †Eurynotiformes Sallan & Coates 2013
Subclass Cladistia Pander 1860
Order †Guildayichthyiformes Lund 2000
Order Polypteriformes Bleeker 1859 (bichirs and reedfishes)
Subclass Actinopteri Cope 1972 s.s.
Order †Elonichthyiformes Kazantseva-Selezneva 1977
Order †Phanerorhynchiformes
Order †Bobasatraniiformes Berg 1940
Order †Saurichthyiformes Aldinger 1937
Subclass Chondrostei Müller, 1844
Order †Birgeriiformes Heyler 1969
Order †Chondrosteiformes Aldinger, 1937
Order Acipenseriformes Berg 1940 (includes sturgeons and paddlefishes)
Subclass Neopterygii Regan 1923 sensu Xu & Wu 2012
Order †Pholidopleuriformes Berg 1937
Order †Redfieldiiformes Berg 1940
Order †Platysiagiformes Brough 1939
Order †Polzbergiiformes Griffith 1977
Order †Perleidiformes Berg 1937
Order †Louwoichthyiformes Xu 2021
Order †Peltopleuriformes Lehman 1966
Order †Luganoiiformes Lehman 1958
Order †Pycnodontiformes Berg 1937
Infraclass Holostei Müller 1844
Division Halecomorphi Cope 1872 sensu Grande & Bemis 1998
Order †Parasemionotiformes Lehman 1966
Order †Ionoscopiformes Grande & Bemis 1998
Order Amiiformes Huxley 1861 sensu Grande & Bemis 1998 (bowfins)
Division Ginglymodi Cope 1871 | Actinopterygii | Wikipedia | 510 | 734 | https://en.wikipedia.org/wiki/Actinopterygii | Biology and health sciences | Fishes | null |
Order †Dapediiformes Thies & Waschkewitz 2015
Order †Semionotiformes Arambourg & Bertin 1958
Order Lepisosteiformes Hay 1929 (gars)
Clade Teleosteomorpha Arratia 2000 sensu Arratia 2013
Order †Prohaleciteiformes Arratia 2017
Division Aspidorhynchei Nelson, Grand & Wilson 2016
Order †Aspidorhynchiformes Bleeker 1859
Order †Pachycormiformes Berg 1937
Infraclass Teleostei Müller 1844 sensu Arratia 2013
Order †?Araripichthyiformes
Order †?Ligulelliiformes Taverne 2011
Order †?Tselfatiiformes Nelson 1994
Order †Pholidophoriformes Berg 1940
Order †Dorsetichthyiformes Nelson, Grand & Wilson 2016
Order †Leptolepidiformes
Order †Crossognathiformes Taverne 1989
Order †Ichthyodectiformes Bardeck & Sprinkle 1969
Teleocephala de Pinna 1996 s.s.
Megacohort Elopocephalai Patterson 1977 sensu Arratia 1999 (Elopomorpha Greenwood et al. 1966)
Order Elopiformes Gosline 1960 (ladyfishes and tarpon)
Order Albuliformes Greenwood et al. 1966 sensu Forey et al. 1996 (bonefishes)
Order Notacanthiformes Goodrich 1909 (halosaurs and spiny eels)
Order Anguilliformes Jarocki 1822 sensu Goodrich 1909 (true eels)
Megacohort Osteoglossocephalai sensu Arratia 1999
Supercohort Osteoglossocephala sensu Arratia 1999 (Osteoglossomorpha Greenwood et al. 1966)
Order †Lycopteriformes Chang & Chou 1977
Order Hiodontiformes McAllister 1968 sensu Taverne 1979 (mooneye and goldeye)
Order Osteoglossiformes Regan 1909 sensu Zhang 2004 (bony-tongued fishes)
Supercohort Clupeocephala Patterson & Rosen 1977 sensu Arratia 2010
Cohort Otomorpha Wiley & Johnson 2010 (Otocephala; Ostarioclupeomorpha)
Subcohort Clupei Wiley & Johnson 2010 (Clupeomorpha Greenwood et al. 1966) | Actinopterygii | Wikipedia | 503 | 734 | https://en.wikipedia.org/wiki/Actinopterygii | Biology and health sciences | Fishes | null |
Order †Ellimmichthyiformes Grande 1982
Order Clupeiformes Bleeker 1859 (herrings and anchovies)
Subcohort Alepocephali
Order Alepocephaliformes Marshall 1962
Subcohort Ostariophysi Sagemehl 1885
Section Anotophysa (Rosen & Greenwood 1970) Sagemehl 1885
Order †Sorbininardiformes Taverne 1999
Order Gonorynchiformes Regan 1909 (milkfishes)
Section Otophysa Garstang 1931
Order Cypriniformes Bleeker 1859 sensu Goodrich 1909 (barbs, carp, danios, goldfishes, loaches, minnows, rasboras)
Order Characiformes Goodrich 1909 (characins, pencilfishes, hatchetfishes, piranhas, tetras, dourado / golden (genus Salminus) and pacu)
Order Gymnotiformes Berg 1940 (electric eels and knifefishes)
Order Siluriformes Cuvier 1817 sensu Hay 1929 (catfishes)
Cohort Euteleosteomorpha (Greenwood et al. 1966) (Euteleostei Greenwood 1967 sensu Johnson & Patterson 1996)
Subcohort Lepidogalaxii
Order Lepidogalaxiiformes Betancur-Rodriguez et al. 2013 (salamanderfish)
Subcohort Protacanthopterygii Greenwood et al. 1966 sensu Johnson & Patterson 1996
Order Argentiniformes (barreleyes and slickheads) (formerly in Osmeriformes)
Order Galaxiiformes
Order Salmoniformes Bleeker 1859 sensu Nelson 1994 (salmon and trout)
Order Esociformes Bleeker 1859 (pike)
Subcohort Stomiati
Order Osmeriformes (smelts)
Order Stomiiformes Regan 1909 (bristlemouths and marine hatchetfishes)
Subcohort Neoteleostei Nelson 1969
Infracohort Ateleopodia
Order Ateleopodiformes (jellynose fish)
Infracohort Eurypterygia Rosen 1973
Section Aulopa [Cyclosquamata Rosen 1973]
Order Aulopiformes Rosen 1973 (Bombay duck and lancetfishes)
Section Ctenosquamata Rosen 1973
Subsection Myctophata [Scopelomorpha]
Order Myctophiformes Regan 1911 (lanternfishes) | Actinopterygii | Wikipedia | 508 | 734 | https://en.wikipedia.org/wiki/Actinopterygii | Biology and health sciences | Fishes | null |
Subsection Acanthomorpha Betancur-Rodriguez et al. 2013
Division Lampridacea Betancur-Rodriguez et al. 2013 [Lampridomorpha; Lampripterygii]
Order Lampriformes Regan 1909 (oarfish, opah and ribbonfishes)
Division Paracanthomorphacea sensu Grande et al. 2013 (Paracanthopterygii Greenwood 1937)
Order Percopsiformes Berg 1937 (cavefishes and trout-perches)
Order †Sphenocephaliformes Rosen & Patterson 1969
Order Zeiformes Regan 1909 (dories)
Order Stylephoriformes Miya et al. 2007
Order Gadiformes Goodrich 1909 (cods)
Division Polymixiacea Betancur-Rodriguez et al. 2013 (Polymyxiomorpha; Polymixiipterygii)
Order †Pattersonichthyiformes Gaudant 1976
Order †Ctenothrissiformes Berg 1937
Order Polymixiiformes Lowe 1838 (beardfishes)
Division Euacanthomorphacea Betancur-Rodriguez et al. 2013 (Euacanthomorpha sensu Johnson & Patterson 1993; Acanthopterygii Gouan 1770 sensu])
Subdivision Berycimorphaceae Betancur-Rodriguez et al. 2013
Order Beryciformes (fangtooths and pineconefishes) (incl. Stephanoberyciformes; Cetomimiformes)
Subdivision Holocentrimorphaceae Betancur-Rodriguez et al. 2013
Order Holocentriformes (Soldierfishes)
Subdivision Percomorphaceae Betancur-Rodriguez et al. 2013 (Percomorpha sensu Miya et al. 2003; Acanthopteri)
Series Ophidiimopharia Betancur-Rodriguez et al. 2013
Order Ophidiiformes (pearlfishes)
Series Batrachoidimopharia Betancur-Rodriguez et al. 2013
Order Batrachoidiformes (toadfishes)
Series Gobiomopharia Betancur-Rodriguez et al. 2013
Order Kurtiformes(Nurseryfishes and cardinalfishes)
Order Gobiiformes(Sleepers and gobies)
Series Scombrimopharia Betancur-Rodriguez et al. 2013 | Actinopterygii | Wikipedia | 489 | 734 | https://en.wikipedia.org/wiki/Actinopterygii | Biology and health sciences | Fishes | null |
Order Syngnathiformes (seahorses, pipefishes, sea moths, cornetfishes and flying gurnards)
Order Scombriformes (Tunas and (mackerels)
Series Carangimopharia Betancur-Rodriguez et al. 2013
Subseries Anabantaria Betancur-Rodriguez et al. 2014
Order Synbranchiformes (swamp eels)
Order Anabantiformes (Labyrinthici) (gouramies, snakeheads, )
Subseries Carangaria Betancur-Rodriguez et al. 2014
Carangaria incertae sedis
Order Istiophoriformes Betancur-Rodriguez 2013 (Marlins, swordfishes, billfishes)
Order Carangiformes (Jack mackerels, pompanos)
Order Pleuronectiformes Bleeker 1859 (flatfishes)
Subseries Ovalentaria Smith & Near 2012 (Stiassnyiformes sensu Li et al. 2009)
Ovalentaria incertae sedis
Order Cichliformes Betancur-Rodriguez et al. 2013 (Cichlids, Convict blenny, leaf fishes)
Order Atheriniformes Rosen 1964 (silversides and rainbowfishes)
Order Cyprinodontiformes Berg 1940 (livebearers, killifishes)
Order Beloniformes Berg 1940 (flyingfishes and ricefishes)
Order Mugiliformes Berg 1940 (mullets)
Order Blenniiformes Springer 1993 (Blennies)
Order Gobiesociformes Gill 1872 (Clingfishes)
Series Eupercaria Betancur-Rodriguez et al. 2014 (Percomorpharia Betancur-Rodriguez et al. 2013)
Eupercaria incertae sedis
Order Gerreiformes (Mojarras)
Order Labriformes (Wrasses and Parrotfishes)
Order Caproiformes (Boarfishes)
Order Lophiiformes Garman 1899 (Anglerfishes)
Order Tetraodontiformes Regan 1929 (Filefishes and pufferfish)
Order Centrarchiformes Bleeker 1859 (Sunfishes and mandarin fishes)
Order Gasterosteiformes (Sticklebacks and relatives)
Order Scorpaeniformes (Lionfishes and relatives)
Order Perciformes Bleeker 1859 | Actinopterygii | Wikipedia | 495 | 734 | https://en.wikipedia.org/wiki/Actinopterygii | Biology and health sciences | Fishes | null |
Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in the sky using the unaided eye, binoculars, or telescopes. Even though scientific research may not be their primary goal, some amateur astronomers make contributions in doing citizen science, such as by monitoring variable stars, double stars, sunspots, or occultations of stars by the Moon or asteroids, or by discovering transient astronomical events, such as comets, galactic novae or supernovae in other galaxies.
Amateur astronomers do not use the field of astronomy as their primary source of income or support, and usually have no professional degree in astrophysics or advanced academic training in the subject. Most amateurs are hobbyists, while others have a high degree of experience in astronomy and may often assist and work alongside professional astronomers. Many astronomers have studied the sky throughout history in an amateur framework; however, since the beginning of the twentieth century, professional astronomy has become an activity clearly distinguished from amateur astronomy and associated activities.
Amateur astronomers typically view the sky at night, when most celestial objects and astronomical events are visible, but others observe during the daytime by viewing the Sun and solar eclipses. Some just look at the sky using nothing more than their eyes or binoculars, but more dedicated amateurs often use portable telescopes or telescopes situated in their private or club observatories. Amateurs also join amateur astronomical societies, which can advise, educate or guide them towards ways of finding and observing celestial objects. They also promote the science of astronomy among the general public.
Objectives
Collectively, amateur astronomers observe a variety of celestial objects and phenomena. Common targets of amateur astronomers include the Sun, the Moon, planets, stars, comets, meteor showers, and a variety of deep sky objects such as star clusters, galaxies, and nebulae. Many amateurs like to specialise in observing particular objects, types of objects, or types of events which interest them. One branch of amateur astronomy, amateur astrophotography, involves the taking of photos of the night sky. Astrophotography has become more popular with the introduction of far easier to use equipment including, digital cameras, DSLR cameras and relatively sophisticated purpose built high quality CCD cameras and CMOS cameras. | Amateur astronomy | Wikipedia | 438 | 748 | https://en.wikipedia.org/wiki/Amateur%20astronomy | Physical sciences | Astronomy basics | Astronomy |
Most amateur astronomers work at visible wavelengths, but a small minority experiment with wavelengths outside the visible spectrum. An early pioneer of radio astronomy was Grote Reber, an amateur astronomer who constructed the first purpose-built radio telescope in the late 1930s to follow up on the discovery of radio wavelength emissions from space by Karl Jansky. Non-visual amateur astronomy includes the use of infrared filters on conventional telescopes, and also the use of radio telescopes. Some amateur astronomers use home-made radio telescopes, while others use radio telescopes that were originally built for astronomical research but have since been made available for use by amateurs. The One-Mile Telescope is one such example.
Common tools
Amateur astronomers use a range of instruments to study the sky, depending on a combination of their interests and resources. Methods include simply looking at the night sky with the naked eye, using binoculars, and using a variety of optical telescopes of varying power and quality, as well as additional sophisticated equipment, such as cameras, to study light from the sky in both the visual and non-visual parts of the spectrum. To further improve studying the visual and non-visual part of the spectrum, amateur astronomers go to rural areas to get away from light pollution. Commercial telescopes are available, new and used, but it is also common for amateur astronomers to build (or commission the building of) their own custom telescopes. Some people even focus on amateur telescope making as their primary interest within the hobby of amateur astronomy.
Although specialized and experienced amateur astronomers tend to acquire more specialized and more powerful equipment over time, relatively simple equipment is often preferred for certain tasks. Binoculars, for instance, although generally of lower power than the majority of telescopes, also tend to provide a wider field of view, which is preferable for looking at some objects in the night sky. Recent models of iPhones have introduced a "night mode" option when taking pictures as well, that allows you to increase exposure, which is a period of time the picture is being taken for. This optimizes focus on light in the frame which is why it is used primarily at night.
Amateur astronomers also use star charts that, depending on experience and intentions, may range from simple planispheres through to star atlases with detailed charts of the entire night sky. A range of astronomy software is also available and used by amateur astronomers, including software that generates maps of the sky, software to assist with astrophotography, observation scheduling software, and software to perform various calculations pertaining to astronomical phenomena. | Amateur astronomy | Wikipedia | 502 | 748 | https://en.wikipedia.org/wiki/Amateur%20astronomy | Physical sciences | Astronomy basics | Astronomy |
Amateur astronomers often like to keep records of their observations, which usually takes the form of an observing log. Observing logs typically record details about which objects were observed and when, as well as describing the details that were seen. Sketching is sometimes used within logs, and photographic records of observations have also been used in recent times. The information gathered is used to help studies and interactions between amateur astronomers in yearly gatherings. Although not professional information or credible, it is a way for the hobby lovers to share their new sightings and experiences.
The popularity of imaging among amateurs has led to large numbers of web sites being written by individuals about their images and equipment. Much of the social interaction of amateur astronomy occurs on mailing lists or discussion groups. Discussion group servers host numerous astronomy lists. A great deal of the commerce of amateur astronomy, the buying and selling of equipment, occurs online. Many amateurs use online tools to plan their nightly observing sessions, using tools such as the Clear Sky Chart.
Common techniques
While a number of interesting celestial objects are readily identified by the naked eye, sometimes with the aid of a star chart, many others are so faint or inconspicuous that technical means are necessary to locate them. Although many methods are used in amateur astronomy, most are variations of a few specific techniques.
Star hopping
Star hopping is a method often used by amateur astronomers with low-tech equipment such as binoculars or a manually driven telescope. It involves the use of maps (or memory) to locate known landmark stars, and "hopping" between them, often with the aid of a finderscope. Because of its simplicity, star hopping is a very common method for finding objects that are close to naked-eye stars.
More advanced methods of locating objects in the sky include telescope mounts with setting circles, which allow pointing to targets in the sky using celestial coordinates, and GOTO telescopes, which are fully automated telescopes that are capable of locating objects on demand (having first been calibrated). | Amateur astronomy | Wikipedia | 397 | 748 | https://en.wikipedia.org/wiki/Amateur%20astronomy | Physical sciences | Astronomy basics | Astronomy |
Mobile apps
The advent of mobile applications for use in smartphones has led to the creation of many dedicated apps. These apps allow any user to easily locate celestial objects of interest by simply pointing the smartphone device in that direction in the sky. These apps make use of the inbuilt hardware in the phone, such as GPS location and gyroscope. Useful information about the pointed object like celestial coordinates, the name of the object, its constellation, etc. are provided for a quick reference. Some paid versions give more information. These apps are gradually getting into regular use during observing, for the alignment process of telescopes.
Setting circles
Setting circles are angular measurement scales that can be placed on the two main rotation axes of some telescopes. Since the widespread adoption of digital setting circles, any classical engraved setting circle is now specifically identified as an "analog setting circle" (ASC). By knowing the coordinates of an object (usually given in equatorial coordinates), the telescope user can use the setting circle to align (i.e., point) the telescope in the appropriate direction before looking through its eyepiece. A computerized setting circle is called a "digital setting circle" (DSC). Although digital setting circles can be used to display a telescope's RA and Dec coordinates, they are not simply a digital read-out of what can be seen on the telescope's analog setting circles. As with go-to telescopes, digital setting circle computers (commercial names include Argo Navis, Sky Commander, and NGC Max) contain databases of tens of thousands of celestial objects and projections of planet positions.
To find a celestial object in a telescope equipped with a DSC computer, one does not need to look up the specific RA and Dec coordinates in a book or other resource, and then adjust the telescope to those numerical readings. Rather, the object is chosen from the electronic database, which causes distance values and arrow markers to appear in the display that indicate the distance and direction to move the telescope. The telescope is moved until the two angular distance values reach zero, indicating that the telescope is properly aligned. When both the RA and Dec axes are thus "zeroed out", the object should be in the eyepiece. Many DSCs, like go-to systems, can also work in conjunction with laptop sky programs. | Amateur astronomy | Wikipedia | 468 | 748 | https://en.wikipedia.org/wiki/Amateur%20astronomy | Physical sciences | Astronomy basics | Astronomy |
Computerized systems provide the further advantage of computing coordinate precession. Traditional printed sources are subtitled by the epoch year, which refers to the positions of celestial objects at a given time to the nearest year (e.g., J2005, J2007). Most such printed sources have been updated for intervals of only about every fifty years (e.g., J1900, J1950, J2000). Computerized sources, on the other hand, are able to calculate the right ascension and declination of the "epoch of date" to the exact instant of observation.
GoTo telescopes
GOTO telescopes have become more popular since the 1980s as technology has improved and prices have been reduced. With these computer-driven telescopes, the user typically enters the name of the item of interest and the mechanics of the telescope point the telescope towards that item automatically. They have several notable advantages for amateur astronomers intent on research. For example, GOTO telescopes tend to be faster for locating items of interest than star hopping, allowing more time for studying of the object. GOTO also allows manufacturers to add equatorial tracking to mechanically simpler alt-azimuth telescope mounts, allowing them to produce an overall less expensive product. GOTO telescopes usually have to be calibrated using alignment stars to provide accurate tracking and positioning. However, several telescope manufacturers have recently developed telescope systems that are calibrated with the use of built-in GPS, decreasing the time it takes to set up a telescope at the start of an observing session.
Remote-controlled telescopes
With the development of fast internet in the last part of the 20th century along with advances in computer controlled telescope mounts and CCD cameras, "remote telescope" astronomy is now a viable means for amateur astronomers not aligned with major telescope facilities to partake in research and deep sky imaging. This enables anyone to control a telescope a great distance away in a dark location. The observer can image through the telescope using CCD cameras. The digital data collected by the telescope is then transmitted and displayed to the user by means of the Internet. An example of a digital remote telescope operation for public use via the Internet is the Bareket observatory, and there are telescope farms in New Mexico, Australia and Atacama in Chile.
Imaging techniques | Amateur astronomy | Wikipedia | 460 | 748 | https://en.wikipedia.org/wiki/Amateur%20astronomy | Physical sciences | Astronomy basics | Astronomy |
Amateur astronomers engage in many imaging techniques including film, DSLR, LRGB, and CCD astrophotography. Because CCD imagers are linear, image processing may be used to subtract away the effects of light pollution, which has increased the popularity of astrophotography in urban areas. Narrowband filters may also be used to minimize light pollution.
Scientific research
Scientific research is most often not the main goal for many amateur astronomers, unlike professional astronomers. Work of scientific merit is possible, however, and many amateurs successfully contribute to the knowledge base of professional astronomers. Astronomy is sometimes promoted as one of the few remaining sciences for which amateurs can still contribute useful data. To recognize this, the Astronomical Society of the Pacific annually gives Amateur Achievement Awards for significant contributions to astronomy by amateurs.
The majority of scientific contributions by amateur astronomers are in the area of data collection. In particular, this applies where large numbers of amateur astronomers with small telescopes are more effective than the relatively small number of large telescopes that are available to professional astronomers. Several organizations, such as the American Association of Variable Star Observers and the British Astronomical Association, exist to help coordinate these contributions.
Amateur astronomers often contribute toward activities such as monitoring the changes in brightness of variable stars and supernovae, helping to track asteroids, and observing occultations to determine both the shape of asteroids and the shape of the terrain on the apparent edge of the Moon as seen from Earth. With more advanced equipment, but still cheap in comparison to professional setups, amateur astronomers can measure the light spectrum emitted from astronomical objects, which can yield high-quality scientific data if the measurements are performed with due care. A relatively recent role for amateur astronomers is searching for overlooked phenomena (e.g., Kreutz Sungrazers) in the vast libraries of digital images and other data captured by Earth and space based observatories, much of which is available over the Internet.
In the past and present, amateur astronomers have played a major role in discovering new comets. Recently however, funding of projects such as the Lincoln Near-Earth Asteroid Research and Near Earth Asteroid Tracking projects has meant that most comets are now discovered by automated systems long before it is possible for amateurs to see them.
Societies | Amateur astronomy | Wikipedia | 449 | 748 | https://en.wikipedia.org/wiki/Amateur%20astronomy | Physical sciences | Astronomy basics | Astronomy |
There are a large number of amateur astronomical societies around the world, that serve as a meeting point for those interested in amateur astronomy. Members range from active observers with their own equipment to "armchair astronomers" who are simply interested in the topic. Societies range widely in their goals and activities, which may depend on a variety of factors such as geographic spread, local circumstances, size, and membership. For example, a small local society located in dark countryside may focus on practical observing and star parties, whereas a large one based in a major city might have numerous members but be limited by light pollution and thus hold regular indoor meetings with guest speakers instead. Major national or international societies generally publish their own academic journal or newsletter, and some hold large multi-day meetings akin to a scientific conference or convention. They may also have sections devoted to particular topics, such as lunar observation or amateur telescope making.
Notable contributions by amateur astronomers
There have been many significant scientific, technological, and cultural contributions made by amateur astronomers: | Amateur astronomy | Wikipedia | 199 | 748 | https://en.wikipedia.org/wiki/Amateur%20astronomy | Physical sciences | Astronomy basics | Astronomy |
George Alcock, one of the most successful visual discoverers comets and novae.
John E. Bortle, authored '"Comet Digest" in Sky and Telescope magazine and the monthly AAVSO circular for the American Association of Variable Star Observers. Created the Bortle scale to quantify the darkness of the night sky.
Robert Burnham Jr. (1931–1993), author of the Celestial Handbook.
Andrew Ainslie Common (1841–1903), built his own very large reflecting telescopes and demonstrated that photography could record astronomical features invisible to the human eye.
Robert E. Cox (1917–1989) who conducted the "Gleanings for ATMs" column in Sky & Telescope magazine for 21 years.
John Dobson (1915–2014), promoter of astronomy whose name is associated with the Dobsonian telescope.
Robert Owen Evans (1937–2022) was an amateur astronomer who currently holds the all-time record for visual discoveries of supernovae.
Giuseppe Donatiello, discovered eleven nearby dwarf galaxies in the Local Volume including the first galaxy to be named after its non-professional discoverer. .
Will Hay, the famous comedian and actor, who discovered a white spot on Saturn.
Walter Scott Houston (1912–1993) who wrote the "Deep-Sky Wonders" column in Sky & Telescope magazine for almost 50 years.
Albert G. Ingalls (1888–1958), editor of Amateur Telescope Making, Vols. 1–3 and "The Amateur Scientist".
David H. Levy discovered or co-discovered 22 comets including Comet Shoemaker-Levy 9, the most for any individual.
Sir Patrick Moore (1923–2012), presenter of the BBC's long-running The Sky at Night and author of many books on astronomy.
Russell W. Porter (1871–1949) founded Stellafane and has been referred to as a "founder" of amateur telescope making.
Grote Reber (1911–2002), pioneer of radio astronomy constructing the first purpose-built radio telescope and conducted the first sky survey in the radio frequency.
Citizen science projects
Amateur astronomers and other non-professionals make contributions through ongoing citizen science projects:
XO Project, an international team of amateur and professional astronomers tasked with identifying extrasolar planets.
Many amateur astronomers contribute to scientific discoveries as part of the citizen science Zooniverse project.
Prizes recognizing amateur astronomers
Amateur Achievement Award of Astronomical Society of the Pacific
Chambliss Amateur Achievement Award | Amateur astronomy | Wikipedia | 491 | 748 | https://en.wikipedia.org/wiki/Amateur%20astronomy | Physical sciences | Astronomy basics | Astronomy |
Abortion is the termination of a pregnancy by removal or expulsion of an embryo or fetus. An abortion that occurs without intervention is known as a miscarriage or "spontaneous abortion"; these occur in approximately 30% to 40% of all pregnancies. When deliberate steps are taken to end a pregnancy, it is called an induced abortion, or less frequently "induced miscarriage". The unmodified word abortion generally refers to an induced abortion. The most common reasons given for having an abortion are for birth-timing and limiting family size. Other reasons reported include maternal health, an inability to afford a child, domestic violence, lack of support, feeling they are too young, wishing to complete education or advance a career, and not being able or willing to raise a child conceived as a result of rape or incest.
When done legally in industrialized societies, induced abortion is one of the safest procedures in medicine. Unsafe abortions—those performed by people lacking the necessary skills, or in inadequately resourced settings—are responsible for between 5–13% of maternal deaths, especially in the developing world. However, medication abortions that are self-managed are highly effective and safe throughout the first trimester. Public health data show that making safe abortion legal and accessible reduces maternal deaths.
Modern methods use medication or surgery for abortions. The drug mifepristone (aka RU-486) in combination with prostaglandin appears to be as safe and effective as surgery during the first and second trimesters of pregnancy. The most common surgical technique involves dilating the cervix and using a suction device. Birth control, such as the pill or intrauterine devices, can be used immediately following abortion. When performed legally and safely on a woman who desires it, an induced abortion does not increase the risk of long-term mental or physical problems. In contrast, unsafe abortions performed by unskilled individuals, with hazardous equipment, or in unsanitary facilities cause between 22,000 and 44,000 deaths and 6.9 million hospital admissions each year. The World Health Organization states that "access to legal, safe and comprehensive abortion care, including post-abortion care, is essential for the attainment of the highest possible level of sexual and reproductive health". Historically, abortions have been attempted using herbal medicines, sharp tools, forceful massage, or other traditional methods. | Abortion | Wikipedia | 489 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Around 73 million abortions are performed each year in the world, with about 45% done unsafely. Abortion rates changed little between 2003 and 2008, before which they decreased for at least two decades as access to family planning and birth control increased. , 37% of the world's women had access to legal abortions without limits as to reason. Countries that permit abortions have different limits on how late in pregnancy abortion is allowed. Abortion rates are similar between countries that restrict abortion and countries that broadly allow it, though this is partly because countries which restrict abortion tend to have higher unintended pregnancy rates.
Globally, there has been a widespread trend towards greater legal access to abortion since 1973, but there remains debate with regard to moral, religious, ethical, and legal issues. Those who oppose abortion often argue that an embryo or fetus is a person with a right to life, and thus equate abortion with murder. Those who support abortion's legality often argue that it is a woman's reproductive right. Others favor legal and accessible abortion as a public health measure. Abortion laws and views of the procedure are different around the world. In some countries abortion is legal and women have the right to make the choice about abortion. In some areas, abortion is legal only in specific cases such as rape, incest, fetal defects, poverty, and risk to a woman's health.
Types
Induced
An induced abortion is a medical procedure to end a pregnancy. In present-day English, the term abortion, when used without further qualification, generally refers to induced abortion.
A pregnancy can be intentionally aborted in several ways. The abortion method depends upon the gestational age of the embryo or fetus, which gains mass as the pregnancy progresses. Abortion laws, regional availability, and the personal preference of the women and her doctor may inform the women's choice of a specific abortion procedure. | Abortion | Wikipedia | 382 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Abortions can be characterized as either therapeutic or elective. When an abortion is performed for medical reasons, the procedure is referred to as a therapeutic abortion. Medical reasons for therapeutic abortion include saving the life of the pregnant woman, preventing harm to the woman's physical or mental health, preventing the birth of a child who will have a significantly increased chance of mortality or morbidity, and reducing the number of fetuses to lessen health risks associated with multiple pregnancy. An abortion is referred to as elective or voluntary when it is performed at the request of the woman for non-medical reasons. Confusion sometimes arises over the term elective because "elective surgery" generally refers to all scheduled surgery, whether medically necessary or not.
About one in five pregnancies worldwide ends with an induced abortion. Most abortions result from unintended pregnancies. In the United Kingdom, 1 to 2% of abortions are done because of genetic problems in the fetus.
Spontaneous
Miscarriage, also known as spontaneous abortion, is the unintentional expulsion of an embryo or fetus before the 24th week of gestation. A pregnancy that ends before 37 weeks of gestation resulting in a live-born infant is a "premature birth" or a "preterm birth". When a fetus dies in utero after viability, or during delivery, it is usually termed "stillborn". Premature births and stillbirths are generally not considered to be miscarriages, although usage of these terms can sometimes overlap.
Studies of pregnant women in the US and China have shown that between 40% and 60% of embryos do not progress to birth. The vast majority of miscarriages occur before the woman is aware that she is pregnant, and many pregnancies spontaneously abort before medical practitioners can detect an embryo. Between 15% and 30% of known pregnancies end in clinically apparent miscarriage, depending upon the age and health of the pregnant woman. 80% of these spontaneous abortions happen in the first trimester. | Abortion | Wikipedia | 416 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
The most common cause of spontaneous abortion during the first trimester is chromosomal abnormalities of the embryo or fetus, accounting for at least 50% of sampled early pregnancy losses. Other causes include vascular disease (such as lupus), diabetes, other hormonal problems, infection, and abnormalities of the uterus. Advancing maternal age and a woman's history of previous spontaneous abortions are the two leading factors associated with a greater risk of spontaneous abortion. A spontaneous abortion can also be caused by accidental trauma; intentional trauma or stress to cause miscarriage is considered induced abortion or feticide.
Methods
Medical
Medical abortions are those induced by abortifacient pharmaceuticals. Medical abortion became an alternative method of abortion with the availability of prostaglandin analogs in the 1970s and the antiprogestogen mifepristone (also known as RU-486) in the 1980s.
The most common early first trimester medical abortion regimens use mifepristone in combination with misoprostol (or sometimes another prostaglandin analog, gemeprost) up to 10 weeks (70 days) gestational age, methotrexate in combination with a prostaglandin analog up to 7 weeks gestation, or a prostaglandin analog alone. Mifepristone–misoprostol combination regimens work faster and are more effective at later gestational ages than methotrexate–misoprostol combination regimens, and combination regimens are more effective than misoprostol alone, particularly in the second trimester. Medical abortion regimens involving mifepristone followed by misoprostol in the cheek between 24 and 48 hours later are effective when performed before 70 days' gestation.
In very early abortions, up to 7 weeks gestation, medical abortion using a mifepristone–misoprostol combination regimen is considered to be more effective than surgical abortion (vacuum aspiration), especially when clinical practice does not include detailed inspection of aspirated tissue. Early medical abortion regimens using mifepristone, followed 24–48 hours later by buccal or vaginal misoprostol are 98% effective up to 9 weeks gestational age; from 9 to 10 weeks efficacy decreases modestly to 94%. If medical abortion fails, surgical abortion must be used to complete the procedure. | Abortion | Wikipedia | 503 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Early medical abortions account for the majority of abortions before 9 weeks gestation in Britain, France, Switzerland, United States, and the Nordic countries.
Medical abortion regimens using mifepristone in combination with a prostaglandin analog are the most common methods used for second trimester abortions in Canada, most of Europe, China and India, in contrast to the United States where 96% of second trimester abortions are performed surgically by dilation and evacuation.
A 2020 Cochrane Systematic Review concluded that providing women with medications to take home to complete the second stage of the procedure for an early medical abortion results in an effective abortion. Further research is required to determine if self-administered medical abortion is as safe as provider-administered medical abortion, where a health care professional is present to help manage the medical abortion. Safely permitting women to self-administer abortion medication has the potential to improve access to abortion. The review also noted a research gap concerning methods to support women who take medication at home for a self-administered abortion.
Surgical
Up to 15 weeks' gestation, suction-aspiration or vacuum aspiration are the most common surgical methods of induced abortion. Manual vacuum aspiration (MVA) consists of removing the fetus or embryo, placenta, and membranes by suction using a manual syringe, while electric vacuum aspiration (EVA) uses an electric pump. Both techniques can be used very early in pregnancy. MVA can be used up to 14 weeks but is more often used earlier in the U.S. EVA can be used later.
MVA, also known as "mini-suction" and "menstrual extraction", or EVA can be used in very early pregnancy when cervical dilation may not be required. Dilation and curettage (D&C) refers to opening the cervix (dilation) and removing tissue (curettage) via suction or sharp instruments. D&C is a standard gynecological procedure performed for a variety of reasons, including examination of the uterine lining for possible malignancy, investigation of abnormal bleeding, and abortion. The World Health Organization recommends sharp curettage only when suction aspiration is unavailable. | Abortion | Wikipedia | 454 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Dilation and evacuation (D&E), used after 12 to 16 weeks, consists of opening the cervix and emptying the uterus using surgical instruments and suction. D&E is performed vaginally and does not require an incision. Intact dilation and extraction (D&X) refers to a variant of D&E sometimes used after 18 to 20 weeks when removal of an intact fetus improves surgical safety or for other reasons.
Abortion may also be performed surgically by hysterotomy or gravid hysterectomy. Hysterotomy abortion is a procedure similar to a caesarean section and is performed under general anesthesia. It requires a smaller incision than a caesarean section and can be used during later stages of pregnancy. Gravid hysterectomy refers to removal of the whole uterus while still containing the pregnancy. Hysterotomy and hysterectomy are associated with much higher rates of maternal morbidity and mortality than D&E or induction abortion.
First trimester procedures can generally be performed using local anesthesia, while second trimester methods may require deep sedation or general anesthesia.
Labor induction abortion
In places lacking the necessary medical skill for dilation and extraction, or when preferred by practitioners, an abortion can be induced by first inducing labor and then inducing fetal demise if necessary. This is sometimes called "induced miscarriage". This procedure may be performed from 13 weeks gestation to the third trimester. Although it is very uncommon in the United States, more than 80% of induced abortions throughout the second trimester are labor-induced abortions in Sweden and other nearby countries.
Only limited data are available comparing labor-induced abortion with the dilation and extraction method. Unlike D&E, labor-induced abortions after 18 weeks may be complicated by the occurrence of brief fetal survival, which may be legally characterized as live birth. For this reason, labor-induced abortion is legally risky in the United States.
Other methods
Historically, a number of herbs reputed to possess abortifacient properties have been used in folk medicine. Such herbs include tansy, pennyroyal, black cohosh, and the now-extinct silphium. | Abortion | Wikipedia | 459 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
In 1978, one woman in Colorado died and another developed organ damage when they attempted to terminate their pregnancies by taking pennyroyal oil.
Because the indiscriminant use of herbs as abortifacients can cause serious—even lethal—side effects, such as multiple organ failure, such use is not recommended by physicians.
Abortion is sometimes attempted by causing trauma to the abdomen. The degree of force, if severe, can cause serious internal injuries without necessarily succeeding in inducing miscarriage. In Southeast Asia, there is an ancient tradition of attempting abortion through forceful abdominal massage. One of the bas reliefs decorating the temple of Angkor Wat in Cambodia depicts a demon performing such an abortion upon a woman who has been sent to the underworld.
Reported methods of unsafe, self-induced abortion include misuse of misoprostol and insertion of non-surgical implements such as knitting needles and clothes hangers into the uterus. These and other methods to terminate pregnancy may be called "induced miscarriage". Such methods are rarely used in countries where surgical abortion is legal and available.
Safety
The health risks of abortion depend principally on how, and under what conditions, the procedure is performed. The World Health Organization (WHO) defines unsafe abortions as those performed by unskilled individuals, with hazardous equipment, or in unsanitary facilities. Legal abortions performed in the developed world are among the safest procedures in medicine. According to a 2012 study in Obstetrics & Gynecology, in the United States the risk of maternal mortality is 14 times lower after induced abortion than after childbirth. The CDC estimated in 2019 that US pregnancy-related mortality was 17.2 maternal deaths per 100,000 live births, while the US abortion mortality rate was 0.43 maternal deaths per 100,000 procedures. In the UK, guidelines of the Royal College of Obstetricians and Gynaecologists state that "Women should be advised that abortion is generally safer than continuing a pregnancy to term." Worldwide, on average, abortion is safer than carrying a pregnancy to term. A 2007 study reported that "26% of all pregnancies worldwide are terminated by induced abortion," whereas "deaths from improperly performed [abortion] procedures constitute 13% of maternal mortality globally." In Indonesia in 2000 it was estimated that 2 million pregnancies ended in abortion, 4.5 million pregnancies were carried to term, and 14–16 percent of maternal deaths resulted from abortion. | Abortion | Wikipedia | 503 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
In the US from 2000 to 2009, abortion had a mortality rate lower than plastic surgery, lower or similar to running a marathon, and about equivalent to traveling in a passenger car. Five years after seeking abortion services, women who gave birth after being denied an abortion reported worse health than women who had either first or second trimester abortions. The risk of abortion-related mortality increases with gestational age, but remains lower than that of childbirth. Outpatient abortion is as safe from 64 to 70 days' gestation as it before 63 days.
Safety of abortion methods
There is little difference in terms of safety and efficacy between medical abortion using a combined regimen of mifepristone and misoprostol and surgical abortion (vacuum aspiration) in early first trimester abortions up to 10 weeks gestation. Medical abortion using the prostaglandin analog misoprostol alone is less effective and more painful than medical abortion using a combined regimen of mifepristone and misoprostol or surgical abortion.
Safety and gestational age
Vacuum aspiration in the first trimester is the safest method of surgical abortion, and can be performed in a primary care office, abortion clinic, or hospital. Complications, which are rare, can include uterine perforation, pelvic infection, and retained products of conception requiring a second procedure to evacuate. Infections account for one-third of abortion-related deaths in the United States. The rate of complications of vacuum aspiration abortion in the first trimester is similar regardless of whether the procedure is performed in a hospital, surgical center, or office. Preventive antibiotics (such as doxycycline or metronidazole) are typically given before abortion procedures, as they are believed to substantially reduce the risk of postoperative uterine infection; however, antibiotics are not routinely given with abortion pills. The rate of failed procedures does not appear to vary significantly depending on whether the abortion is performed by a doctor or a mid-level practitioner. | Abortion | Wikipedia | 412 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Complications after second trimester abortion are similar to those after first trimester abortion, and depend somewhat on the method chosen. The risk of death from abortion approaches roughly half the risk of death from childbirth the farther along a woman is in pregnancy; from one in a million before 9 weeks gestation to nearly one in ten thousand at 21 weeks or more (as measured from the last menstrual period). It appears that having had a prior surgical uterine evacuation (whether because of induced abortion or treatment of miscarriage) correlates with a small increase in the risk of preterm birth in future pregnancies. The studies supporting this did not control for factors not related to abortion or miscarriage, and hence the causes of this correlation have not been determined, although multiple possibilities have been suggested.
Mental health
Current evidence finds no relationship between most induced abortions and mental health problems other than those expected for any unwanted pregnancy. A report by the American Psychological Association concluded that a woman's first abortion is not a threat to mental health when carried out in the first trimester, with such women no more likely to have mental-health problems than those carrying an unwanted pregnancy to term; the mental-health outcome of a woman's second or greater abortion is less certain. Some older reviews concluded that abortion was associated with an increased risk of psychological problems; however, later reviews of the medical literature found that previous reviews did not use an appropriate control group. When a control group is utilized, receiving abortion is not associated with adverse psychological outcomes. However, women seeking abortion who are denied access to abortion have an increase in anxiety after the denial.
Although some studies show negative mental-health outcomes in women who choose abortions after the first trimester because of fetal abnormalities, more rigorous research would be needed to show this conclusively. Some proposed negative psychological effects of abortion have been referred to by anti-abortion advocates as a separate condition called "post-abortion syndrome", but this is not recognized by medical or psychological professionals in the United States.
A 2020 long term-study among US women found that about 99% of women felt that they made the right decision five years after they had an abortion. Relief was the primary emotion with few women feeling sadness or guilt. Social stigma was a main factor predicting negative emotions and regret years later. The researchers also stated: "These results add to the scientific evidence that emotions about an abortion are associated with personal and social context, and are not a product of the abortion procedure itself." | Abortion | Wikipedia | 507 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Safety in the abortion debate
Some purported risks of abortion are promoted primarily by anti-abortion groups,
but lack scientific support. For example, the question of a link between induced abortion and breast cancer has been investigated extensively. Major medical and scientific bodies (including the WHO, National Cancer Institute, American Cancer Society, Royal College of OBGYN and American Congress of OBGYN) have concluded that abortion does not cause breast cancer.
In the past even illegality has not automatically meant that the abortions were unsafe. Referring to the U.S., historian Linda Gordon states: "In fact, illegal abortions in this country have an impressive safety record."
According to Rickie Solinger,
A 1940s American physician spoke of his pride in having performed 13,844 illegal abortions without any fatalities.
In 1870s New York City, the abortionist/midwife Madame Restell (Anna Trow Lohman) is said to have lost very few women among her more than 100,000 patients—a lower mortality rate than the childbirth mortality rate at the time. In 1936, obstetrics and gynecology professor Frederick J. Taussig wrote that a cause of increasing mortality during the years of illegality in the U.S. was that
Unsafe abortion
Women seeking an abortion may use unsafe methods, especially when abortion is legally restricted. They may attempt self-induced abortion or seek the help of a person without proper medical training or facilities. This can lead to severe complications, such as incomplete abortion, sepsis, hemorrhage, and damage to internal organs.
Unsafe abortions are a major cause of injury and death among women worldwide. Although data are imprecise, it is estimated that approximately 20 million unsafe abortions are performed annually, with 97% taking place in developing countries. Unsafe abortions are believed to result in millions of injuries. Estimates of deaths vary according to methodology, and have ranged from 37,000 to 70,000 in the past decade; deaths from unsafe abortion account for around 13% of all maternal deaths. The World Health Organization believes that mortality has fallen since the 1990s. To reduce the number of unsafe abortions, public health organizations have generally advocated emphasizing the legalization of abortion, training of medical personnel, and ensuring access to reproductive-health services. | Abortion | Wikipedia | 460 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
A major factor in whether abortions are performed safely or not is the legal standing of abortion. Countries with restrictive abortion laws have higher rates of unsafe abortion and similar overall abortion rates compared to countries where abortion is legal and available. For example, the 1996 legalization of abortion in South Africa led to an immediate reduction in abortion-related complications, with abortion-related deaths dropping by more than 90%. Similar reductions in maternal mortality have been observed after other countries have liberalized their abortion laws, such as Romania and Nepal. A 2011 study concluded that in the United States, some state-level anti-abortion laws are correlated with lower rates of abortion in that state. The analysis, however, did not take into account travel to other states without such laws to obtain an abortion. In addition, a lack of access to effective contraception contributes to unsafe abortion. It has been estimated that the incidence of unsafe abortion could be reduced by up to 75% (from 20 million to 5 million annually) if modern family planning and maternal health services were readily available globally. Rates of such abortions may be difficult to measure because they can be reported variously as miscarriage, "induced miscarriage", "menstrual regulation", "mini-abortion", and "regulation of a delayed/suspended menstruation".
Forty percent of the world's women are able to access therapeutic and elective abortions within gestational limits, while an additional 35 percent have access to legal abortion if they meet certain physical, mental, or socioeconomic criteria. While maternal mortality seldom results from safe abortions, unsafe abortions result in 70,000 deaths and 5 million disabilities per year. Complications of unsafe abortion account for approximately an eighth of maternal mortalities worldwide, though this varies by region. Secondary infertility caused by an unsafe abortion affects an estimated 24 million women. The rate of unsafe abortions has increased from 44% to 49% between 1995 and 2008. Health education, access to family planning, and improvements in health care during and after abortion have been proposed to address consequences of unsafe abortion.
Incidence
There are two commonly used methods of measuring the incidence of abortion:
Abortion rate – number of abortions annually per 1,000 women between 15 and 44 years of age; some sources use a range of 15–49.
Abortion percentage – number of abortions out of 100 known pregnancies; pregnancies include live births, abortions, and miscarriages. | Abortion | Wikipedia | 496 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
In many places, where abortion is illegal or carries a heavy social stigma, medical reporting of abortion is not reliable. For this reason, estimates of the incidence of abortion must be made without determining certainty related to standard error. The number of abortions performed worldwide was characterized as stable in the early 2000s, with 41.6 million having been performed in 2003 and 43.8 million having been performed in 2008. The abortion rate worldwide was 28 per 1000 women per year, though it was 24 per 1000 women per year for developed countries and 29 per 1000 women per year for developing countries. The same 2012 study indicated that in 2008, the estimated abortion percentage of known pregnancies was at 21% worldwide, with 26% in developed countries and 20% in developing countries.
On average, the incidence of abortion is similar in countries with restrictive abortion laws and those with more liberal access to abortion. Restrictive abortion laws are associated with increases in the percentage of abortions performed unsafely. The unsafe abortion rate in developing countries is partly attributable to lack of access to modern contraceptives; according to the Guttmacher Institute, providing access to contraceptives would result in about 14.5 million fewer unsafe abortions and 38,000 fewer deaths from unsafe abortion annually worldwide.
The rate of legal, induced abortion varies extensively worldwide. According to the report of employees of Guttmacher Institute it ranged from 7 per 1000 women per year (Germany and Switzerland) to 30 per 1000 women per year (Estonia) in countries with complete statistics in 2008. The proportion of pregnancies that ended in induced abortion ranged from about 10% (Israel, the Netherlands and Switzerland) to 30% (Estonia) in the same group, though it might be as high as 36% in Hungary and Romania, whose statistics were deemed incomplete. | Abortion | Wikipedia | 364 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
An American study in 2002 concluded that about half of women having abortions were using a form of contraception at the time of becoming pregnant. Inconsistent use was reported by half of those using condoms and three-quarters of those using the birth control pill; 42% of those using condoms reported failure through slipping or breakage. Of the other half of women, who were not using contraception at the time of becoming pregnant, the vast majority had used contraception at some point in the past, indicating some level of dissatisfaction with the contraceptive options available to them. Indeed, 32% of these contraceptive nonusers cited concerns about contraceptive methods as their reason for nonuse, and a more recent study found similar results. Taken together, these statistics suggest that new contraceptive methods, such as non-hormonal contraceptives or male contraceptives, could reduce unintended pregnancy and abortion rates.
The Guttmacher Institute has found that "most abortions in the United States are obtained by minority women" because minority women "have much higher rates of unintended pregnancy". In a 2022 analysis by the Kaiser Family Foundation, while people of color comprise 44% of the population in Mississippi, 59% of the population in Texas, 42% of the population in Louisiana, and 35% of the population in Alabama, they comprise 80%, 74%, 72%, and 70%, respectively, of those receiving abortions.
Gestational age and method | Abortion | Wikipedia | 298 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Abortion rates vary depending on the stage of pregnancy and the method practiced. In 2003, the Centers for Disease Control and Prevention (CDC) reported that 26% of reported legal induced abortions in the United States were known to have been obtained at the end of 6 weeks of gestation or less, 18% at 7 weeks, 15% at 8 weeks, 18% at 9 through 10 weeks, 10% at 11 through 12 weeks, 6% at 13 through 15 weeks, 4% at 16 through 20 weeks and 1% at more than 21 weeks. 91% of these were classified as having been done by "curettage" (suction-aspiration, dilation and curettage, dilation and evacuation), 8% by "medical" means (mifepristone), >1% by "intrauterine instillation" (saline or prostaglandin), and 1% by "other" (including hysterotomy and hysterectomy). According to the CDC, due to data collection difficulties the data must be viewed as tentative and some fetal deaths reported beyond 20 weeks may be natural deaths erroneously classified as abortions if the removal of the dead fetus is accomplished by the same procedure as an induced abortion.
The Guttmacher Institute estimated there were 2,200 intact dilation and extraction procedures in the US during 2000; this accounts for <0.2% of the total number of abortions performed that year. Similarly, in England and Wales in 2006, 89% of terminations occurred at or under 12 weeks, 9% between 13 and 19 weeks, and 2% at or over 20 weeks. 64% of those reported were by vacuum aspiration, 6% by D&E, and 30% were medical. There are more second trimester abortions in developing countries such as China, India and Vietnam than in developed countries.
There are both medical and non-medical reasons to have an abortion later in pregnancy (after 20 weeks). A study was conducted from 2008 to 2010 at the University of California San Francisco where more than 440 women were asked about why they experienced delays in obtaining abortion care, if there were any. This study found that almost half of individuals who obtained an abortion after 20 weeks did not suspect that they were pregnant until later in their pregnancy. Other barriers to abortion care found in the study included lack of information about where to access an abortion, difficulties with transportation, lack of insurance coverage, and inability to pay for the abortion procedure. | Abortion | Wikipedia | 511 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Medical reasons for seeking an abortion later in pregnancy include fetal anomalies and health risk to the pregnant person. There are prenatal tests that can diagnose Down Syndrome or cystic fibrosis as early as 10 weeks into gestation, but structural fetal anomalies are often detected much later in pregnancy. A proportion of structural fetal anomalies are lethal, which means that the fetus will almost certainly die before or shortly after birth. Life-threatening conditions may also develop later in pregnancy, such as early severe preeclampsia, newly diagnosed cancer in need of urgent treatment, and intrauterine infection (chorioamnionitis), which often occurs along with premature rupture of the amniotic sac (PPROM). If serious medical conditions such as these arise before the fetus is viable, the person carrying the pregnancy may pursue an abortion to preserve their own health.
Motivation
Personal
The reasons why women have abortions are diverse and vary across the world. Some of the reasons may include an inability to afford a child, domestic violence, lack of support, feeling they are too young, and the wish to complete education or advance a career. Additional reasons include not being able or willing to raise a child conceived as a result of rape or incest.
Societal
Some abortions are undergone as the result of societal pressures. These might include the preference for children of a specific sex or race, disapproval of single or early motherhood, stigmatization of people with disabilities, insufficient economic support for families, lack of access to or rejection of contraceptive methods, or efforts toward population control (such as China's one-child policy). These factors can sometimes result in compulsory abortion or sex-selective abortion. In cultures where there is a preference for male children, some women have sex selective abortions, which have partially replaced the earlier practice of female infanticide.
Maternal health
Some abortions are performed due to concerns over maternal health. In 1990s, women cited maternal health as their main motivating factor in about a third of abortions in three of 27 countries analyzed. In seven additional countries, about 7% of abortions were maternal health related. | Abortion | Wikipedia | 441 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
In the U.S., the Supreme Court decisions in Roe v. Wade and Doe v. Bolton: "ruled that the state's interest in the life of the fetus became compelling only at the point of viability, defined as the point at which the fetus can survive independently of its mother. Even after the point of viability, the state cannot favor the life of the fetus over the life or health of the pregnant woman. Under the right of privacy, physicians must be free to use their "medical judgment for the preservation of the life or health of the mother." On the same day that the Court decided Roe, it also decided Doe v. Bolton, in which the Court defined health very broadly: "The medical judgment may be exercised in the light of all factors—physical, emotional, psychological, familial, and the woman's age—relevant to the well-being of the patient. All these factors may relate to health. This allows the attending physician the room he needs to make his best medical judgment."
Cancer
The rate of cancer during pregnancy is 0.02–1%, and in many cases, cancer of the mother leads to consideration of abortion to protect the life of the mother, or in response to the potential damage that may occur to the fetus during treatment. This is particularly true for cervical cancer, the most common type of which occurs in 1 of every 2,000–13,000 pregnancies, for which initiation of treatment "cannot co-exist with preservation of fetal life (unless neoadjuvant chemotherapy is chosen)". Very early stage cervical cancers (I and IIa) may be treated by radical hysterectomy and pelvic lymph node dissection, radiation therapy, or both, while later stages are treated by radiotherapy. Chemotherapy may be used simultaneously. Treatment of breast cancer during pregnancy also involves fetal considerations, because lumpectomy is discouraged in favor of modified radical mastectomy unless late-term pregnancy allows follow-up radiation therapy to be administered after the birth. | Abortion | Wikipedia | 422 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Exposure to a single chemotherapy drug is estimated to cause a 7.5–17% risk of teratogenic effects on the fetus, with higher risks for multiple drug treatments. Treatment with more than 40 Gy of radiation usually causes spontaneous abortion. Exposure to much lower doses during the first trimester, especially 8 to 15 weeks of development, can cause intellectual disability or microcephaly, and exposure at this or subsequent stages can cause reduced intrauterine growth and birth weight. Exposures above 0.005–0.025 Gy cause a dose-dependent reduction in IQ. It is possible to greatly reduce exposure to radiation with abdominal shielding, depending on how far the area to be irradiated is from the fetus.
The process of birth itself may also put the mother at risk. According to Li et al., "[v]aginal delivery may result in dissemination of neoplastic cells into lymphovascular channels, haemorrhage, cervical laceration and implantation of malignant cells in the episiotomy site, while abdominal delivery may delay the initiation of non-surgical treatment."
Fetal health
Congenital disorders, revealed by prenatal screening, motivate some women to seek abortions. Health outcomes of preterm births include a significant probability of long-term neurodevelopmental impairment before gestational age of 29 weeks, with a higher probability with decreasing gestational age.
In the United States, public opinion shifted after television personality Sherri Finkbine's was exposed to thalidomide, a teratogen, in her fifth month of pregnancy. Unable to obtain a legal abortion in the United States, Finkbine traveled to Sweden. From 1962 to 1965, an outbreak of German measles left 15,000 babies with severe birth defects. In 1967, the American Medical Association publicly supported liberalization of abortion laws. A National Opinion Research Center poll in 1965 showed 73% supported abortion when the mother's life was at risk, 57% when birth defects were present and 59% for pregnancies resulting from rape or incest.
History and religion | Abortion | Wikipedia | 437 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Since ancient times, abortions have been done using a number of methods, including herbal medicines acting as abortifacients, sharp tools through the use of force, or through other traditional medicine methods. Induced abortion has a long history and can be traced back to civilizations as varied as ancient China (abortifacient knowledge is often attributed to the mythological ruler Shennong), ancient India since its Vedic age, ancient Egypt with its Ebers Papyrus (), and the Roman Empire in the time of Juvenal (). One of the earliest known artistic representations of abortion is in a bas relief at Angkor Wat (). Found in a series of friezes that represent judgment after death in Hindu and Buddhist culture, it depicts the technique of abdominal abortion.
In Judaism (Genesis 2:7), the fetus is not considered to have a human soul until it is safely outside of the woman, is viable, and has taken its first breath. The fetus is considered valuable property of the woman and not a human life while in the womb (Exodus 21:22-23). While Judaism encourages people to be fruitful and multiply by having children, abortion is allowed and is deemed necessary when a pregnant woman's life is in danger. Several religions, including Judaism, which disagree that human life begins at conception, support the legality of abortion on religious freedom grounds. In Islam, abortion is traditionally permitted until a point in time when Muslims believe the soul enters the fetus, considered by various theologians to be at conception, 40 days after conception, 120 days after conception, or at quickening. Abortion is largely heavily restricted or forbidden in areas of high Islamic faith such as the Middle East and North Africa. | Abortion | Wikipedia | 352 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Some medical scholars and abortion opponents have suggested that the Hippocratic Oath forbade physicians in Ancient Greece from performing abortions; other scholars disagree with this interpretation, and state that the medical texts of Hippocratic Corpus contain descriptions of abortive techniques right alongside the Oath. The physician Scribonius Largus wrote in 43 CE that the Hippocratic Oath prohibits abortion, as did Soranus of Ephesus, although apparently not all doctors adhered to it strictly at the time. According to Soranus' 1st or 2nd century CE work Gynaecology, one party of medical practitioners banished all abortives as required by the Hippocratic Oath; the other party to which he belonged was willing to prescribe abortions only for the sake of the mother's health. In Politics (350 BCE), Aristotle condemned infanticide as a means of population control. He preferred abortion in such cases, with the restriction that it "must be practised on it before it has developed sensation and life; for the line between lawful and unlawful abortion will be marked by the fact of having sensation and being alive."
In the Catholic Church, opinion was divided on how serious abortion was in comparison with such acts as contraception and oral or anal sex. The Catholic Church did not begin vigorously opposing abortion until the 19th century. As early as ~100 CE, the Didache taught that abortion was sinful. Several historians argue that prior to the 19th century most Catholic authors did not regard termination of pregnancy before quickening or ensoulment as an abortion. Among these authors were the Doctors of the Church, such as St. Augustine, St. Thomas Aquinas, and St. Alphonsus Liguori. In 1588, Pope Sixtus V ( 1585–1590) was the only Pope before Pope Pius IX (in his 1869 bull, Apostolicae Sedis) to institute a Church policy labeling all abortion as homicide and condemning abortion regardless of the stage of pregnancy. Sixtus V's pronouncement was reversed in 1591 by Pope Gregory XIV. In the recodification of 1917 Code of Canon Law, Apostolicae Sedis was strengthened, in part to remove a possible reading that excluded excommunication of the mother. Statements made in the Catechism of the Catholic Church, the codified summary of the Church's teachings, considers abortion from the moment of conception as homicide and called for the end of legal abortion. | Abortion | Wikipedia | 498 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Denominations that support abortion rights with some limits include the United Methodist Church, Episcopal Church, Evangelical Lutheran Church in America and Presbyterian Church USA. A 2014 Guttmacher survey of abortion patients in the United States found that many reported a religious affiliation: 24% were Catholic while 30% were Protestant. A 1995 survey reported that Catholic women are as likely as the general population to terminate a pregnancy, Protestants are less likely to do so, and evangelical Christians are the least likely to do so. A 2019 Pew Research Center study found that most Christian denominations were against overturning Roe v. Wade, which in the United States legalized abortion, at around 70%, except White Evangelicals at 35%.
Abortion has been a fairly common practice, and was not always illegal or controversial until the 19th century. Under common law, including early English common law dating back to Edward Coke in 1648, abortion was generally permitted before quickening (14–26 weeks after conception, or between the fourth and sixth month), and at women's discretion; it was whether abortion was performed after quickening that determined if it was a crime. In Europe and North America, abortion techniques advanced starting in the 17th century; the conservatism of most in the medical profession with regards to sexual matters prevented the wide expansion of abortion techniques. Other medical practitioners in addition to some physicians advertised their services, and they were not widely regulated until the 19th century when the practice, sometimes called restellism, was banned in both the United States and the United Kingdom.
Some 19th-century physicians, one of the most famous and consequential being the American Horatio Storer, argued for anti-abortion laws on racist and misogynist as well as moral grounds. Church groups were also highly influential in anti-abortion movements, and religious groups more so since the 20th century. Some of the early anti-abortion laws punished only the doctor or abortionist, and while women could be criminally tried for a self-induced abortion, they were rarely prosecuted in general. In the United States, some argued that abortion was more dangerous than childbirth until about 1930 when incremental improvements in abortion procedures relative to childbirth made abortion safer. Others maintain that in the 19th century early abortions under the hygienic conditions in which midwives usually worked were relatively safe. Several scholars argue that, despite improved medical procedures, the period from the 1930s until the 1970s saw more zealous enforcement of anti-abortion laws, alongside an increasing control of abortion providers by organized crime. | Abortion | Wikipedia | 508 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
In 1920, Soviet Russia became the first country to legalize abortion after Lenin insisted that no woman be forced to give birth. Iceland (1935) and Sweden (1938) would follow suit to legalize certain or all forms of abortion. In Nazi Germany (1935), a law permitted abortions for those deemed "hereditarily ill", while women considered of German stock were specifically prohibited from having abortions. Beginning in the second half of the 20th century, abortion was legalized in a greater number of countries. In Japan, abortion was first legalized by the 1948 "Eugenics Protection Law" meant to prevent the births of "inferior" humans. , due to Japan's continuing strongly patriarchal culture and traditional views on women's societal roles, women who want an abortion must normally get written permission from their partner.
Society and culture
Abortion debate
Induced abortion has long been the source of considerable debate. Ethical, moral, philosophical, biological, religious and legal issues surrounding abortion are related to value systems. Opinions of abortion may be about fetal rights, governmental authority, and women's rights.
In both public and private debate, arguments presented in favor of or against abortion access focus on either the moral permissibility of an induced abortion, or the justification of laws permitting or restricting abortion. The World Medical Association Declaration on Therapeutic Abortion notes, "circumstances bringing the interests of a mother into conflict with the interests of her unborn child create a dilemma and raise the question as to whether or not the pregnancy should be deliberately terminated." Abortion debates, especially pertaining to abortion laws, are often spearheaded by groups advocating one of these two positions. Groups who favor greater legal restrictions on abortion, including complete prohibition, most often describe themselves as "pro-life" while groups who are against such legal restrictions describe themselves as "pro-choice".
Modern abortion law
Current laws pertaining to abortion are diverse. Religious, moral, and cultural factors continue to influence abortion laws throughout the world. The right to life, the right to liberty, the right to security of person, and the right to reproductive health are major issues of human rights that sometimes constitute the basis for the existence or absence of abortion laws. | Abortion | Wikipedia | 440 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
In jurisdictions where abortion is legal, certain requirements must often be met before a woman may obtain a legal abortion (an abortion performed without the woman's consent is considered feticide and is generally illegal). These requirements usually depend on the age of the fetus, often using a trimester-based system to regulate the window of legality, or as in the U.S., on a doctor's evaluation of the fetus' viability. Some jurisdictions require a waiting period before the procedure, prescribe the distribution of information on fetal development, or require that parents be contacted if their minor daughter requests an abortion. Other jurisdictions may require that a woman obtain the consent of the fetus' father before aborting the fetus, that abortion providers inform women of health risks of the procedure—sometimes including "risks" not supported by the medical literature—and that multiple medical authorities certify that the abortion is either medically or socially necessary. Many restrictions are waived in emergency situations. China, which has ended their one-child policy, and now has a three-child policy, has at times incorporated mandatory abortions as part of their population control strategy.
Other jurisdictions ban abortion almost entirely. Many, but not all, of these allow legal abortions in a variety of circumstances. These circumstances vary based on jurisdiction, but may include whether the pregnancy is a result of rape or incest, the fetus' development is impaired, the woman's physical or mental well-being is endangered, or socioeconomic considerations make childbirth a hardship. In countries where abortion is banned entirely, such as Nicaragua, medical authorities have recorded rises in maternal death directly and indirectly due to pregnancy as well as deaths due to doctors' fears of prosecution if they treat other gynecological emergencies. Some countries, such as Bangladesh, that nominally ban abortion, may also support clinics that perform abortions under the guise of menstrual hygiene. This is also a terminology in traditional medicine. In places where abortion is illegal or carries heavy social stigma, pregnant women may engage in medical tourism and travel to countries where they can terminate their pregnancies. Women without the means to travel can resort to providers of illegal abortions or attempt to perform an abortion by themselves. | Abortion | Wikipedia | 455 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
The organization Women on Waves has been providing education about medical abortions since 1999. The NGO created a mobile medical clinic inside a shipping container, which then travels on rented ships to countries with restrictive abortion laws. Because the ships are registered in the Netherlands, Dutch law prevails when the ship is in international waters. While in port, the organization provides free workshops and education; while in international waters, medical personnel are legally able to prescribe medical abortion drugs and counseling.
Sex-selective abortion
Sonography and amniocentesis allow parents to determine sex before childbirth. The development of this technology has led to sex-selective abortion, or the termination of a fetus based on its sex. The selective termination of a female fetus is most common.
Sex-selective abortion is partially responsible for the noticeable disparities between the birth rates of male and female children in some countries. The preference for male children is reported in many areas of Asia, and abortion used to limit female births has been reported in Taiwan, South Korea, India, and China. This deviation from the standard birth rates of males and females occurs despite the fact that the country in question may have officially banned sex-selective abortion or even sex-screening. In China, a historical preference for a male child has been exacerbated by the one-child policy, which was enacted in 1979.
Many countries have taken legislative steps to reduce the incidence of sex-selective abortion. At the International Conference on Population and Development in 1994 over 180 states agreed to eliminate "all forms of discrimination against the girl child and the root causes of son preference", conditions also condemned by a PACE resolution in 2011. The World Health Organization and UNICEF, along with other United Nations agencies, have found that measures to restrict access to abortion in an effort to reduce sex-selective abortions have unintended negative consequences, largely stemming from the fact that women may seek or be coerced into seeking unsafe, extralegal abortions. On the other hand, measures to reduce gender inequality can reduce the prevalence of such abortions without attendant negative consequences.
Anti-abortion violence | Abortion | Wikipedia | 424 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Abortion providers and facilities have been subjected to violence, including murder, assault, arson, and bombing. Some scholars consider anti-abortion violence to be within the definition of terrorism, a view shared by some governments. In the U.S. and Canada, over 8,000 incidents of violence, trespassing, and death threats have been recorded by providers since 1977, including over 200 bombings/arsons and hundreds of assaults. Abortion clinics have also been targeted by acid attacks, invasions, and vandalism The majority of abortion opponents have not been involved in violent acts.
Physicians and other abortion clinic staff have been murdered by abortion opponents. In the United States, at least four physicians have been murdered in connection with their work at abortion clinics, including David Gunn (1993), John Britton (1994), Barnett Slepian (1998), and George Tiller (2009). In Canada, gynecologist Garson Romalis survived murder attempts in both 1994 and 2000. Besides physicians, killings have targeted other clinic staff, such as John Salvi's 1994 murder of two receptionists in Massachusetts clinic and Peter Knight's 2001 murder of a security guard in a Melbourne clinic. Notable perpetrators of anti-abortion violence include Eric Rudolph, Scott Roeder, Shelley Shannon, and Paul Hill, the first person to be executed in the United States for murdering an abortion provider.
Some countries have laws to protecting access to abortion.
Such laws prevent abortion opponents from interfering with access to legal abortion services. For example, the American Freedom of Access to Clinic Entrances Act bars the use of threats or violence to interfere with abortion access. Abortion access laws may also establish safe access zones around abortion clinics, with limits on protests and enhanced penalties for anti-abortion violence.
Psychological pressure may also be used to limit abortion access. In 2003, Chris Danze organized anti-abortion organizations throughout Texas to prevent the construction of a Planned Parenthood facility in Austin. The organizations released the personal information online of those involved with construction, sent them up to 1200 phone calls a day and contacted their churches. Some protestors record women entering clinics on camera.
Non-human examples | Abortion | Wikipedia | 432 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
Spontaneous abortion occurs in various animals. For example, in sheep it may be caused by stress or physical exertion, such as crowding through doors or being chased by dogs. In cows, abortion may be caused by contagious disease, such as brucellosis or Campylobacter, but can often be controlled by vaccination. Eating pine needles can also induce abortions in cows. Several plants, including broomweed, skunk cabbage, poison hemlock, and tree tobacco, are known to cause fetal deformities and abortion in cattle and in sheep and goats. In horses, a fetus may be aborted or reabsorbed if it has lethal white syndrome. Foal embryos that are homozygous for the dominant white gene (WW) are theorized to also be aborted or resorbed before birth. In many species of sharks and rays, stress-induced abortions occur frequently on capture.
Viral infection can cause abortion in dogs. Cats can experience spontaneous abortion for many reasons, including hormonal imbalance. A combined abortion and spaying is performed on pregnant cats, especially in trap–neuter–return programs, to prevent unwanted kittens from being born. Female rodents may terminate a pregnancy when exposed to the smell of a male not responsible for the pregnancy, known as the Bruce effect.
Abortion may also be induced in animals, in the context of animal husbandry. For example, abortion may be induced in mares that have been mated improperly, or that have been purchased by owners who did not realize the mares were pregnant, or that are pregnant with twin foals. Feticide can occur in horses and zebras due to male harassment of pregnant mares or forced copulation, although the frequency in the wild has been questioned. Male gray langur monkeys may attack females following male takeover, causing miscarriage. | Abortion | Wikipedia | 385 | 765 | https://en.wikipedia.org/wiki/Abortion | Biology and health sciences | Health, fitness, and medicine | null |
The ampere ( , ; symbol: A), often shortened to amp, is the unit of electric current in the International System of Units (SI). One ampere is equal to 1 coulomb (C) moving past a point per second. It is named after French mathematician and physicist André-Marie Ampère (1775–1836), considered the father of electromagnetism along with Danish physicist Hans Christian Ørsted.
As of the 2019 revision of the SI, the ampere is defined by fixing the elementary charge to be exactly , which means an ampere is an electric current equivalent to elementary charges moving every seconds or elementary charges moving in a second. Prior to the redefinition the ampere was defined as the current passing through two parallel wires 1 metre apart that produces a magnetic force of newtons per metre.
The earlier CGS system has two units of current, one structured similarly to the SI's and the other using Coulomb's law as a fundamental relationship, with the CGS unit of charge defined by measuring the force between two charged metal plates. The CGS unit of current is then defined as one unit of charge per second.
History
The ampere is named for French physicist and mathematician André-Marie Ampère (1775–1836), who studied electromagnetism and laid the foundation of electrodynamics. In recognition of Ampère's contributions to the creation of modern electrical science, an international convention, signed at the 1881 International Exposition of Electricity, established the ampere as a standard unit of electrical measurement for electric current.
The ampere was originally defined as one tenth of the unit of electric current in the centimetre–gram–second system of units. That unit, now known as the abampere, was defined as the amount of current that generates a force of two dynes per centimetre of length between two wires one centimetre apart. The size of the unit was chosen so that the units derived from it in the MKSA system would be conveniently sized.
The "international ampere" was an early realization of the ampere, defined as the current that would deposit of silver per second from a silver nitrate solution. Later, more accurate measurements revealed that this current is . | Ampere | Wikipedia | 459 | 772 | https://en.wikipedia.org/wiki/Ampere | Physical sciences | Electromagnetism | null |
Since power is defined as the product of current and voltage, the ampere can alternatively be expressed in terms of the other units using the relationship , and thus 1 A = 1 W/V. Current can be measured by a multimeter, a device that can measure electrical voltage, current, and resistance.
Former definition in the SI
Until 2019, the SI defined the ampere as follows:
The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed one metre apart in vacuum, would produce between these conductors a force equal to newtons per metre of length.
Ampère's force law states that there is an attractive or repulsive force between two parallel wires carrying an electric current. This force is used in the formal definition of the ampere.
The SI unit of charge, the coulomb, was then defined as "the quantity of electricity carried in 1 second by a current of 1 ampere". Conversely, a current of one ampere is one coulomb of charge going past a given point per second:
In general, charge was determined by steady current flowing for a time as .
This definition of the ampere was most accurately realised using a Kibble balance, but in practice the unit was maintained via Ohm's law from the units of electromotive force and resistance, the volt and the ohm, since the latter two could be tied to physical phenomena that are relatively easy to reproduce, the Josephson effect and the quantum Hall effect, respectively.
Techniques to establish the realisation of an ampere had a relative uncertainty of approximately a few parts in 10, and involved realisations of the watt, the ohm and the volt.
Present definition
The 2019 revision of the SI defined the ampere by taking the fixed numerical value of the elementary charge to be when expressed in the unit C, which is equal to A⋅s, where the second is defined in terms of , the unperturbed ground state hyperfine transition frequency of the caesium-133 atom.
The SI unit of charge, the coulomb, "is the quantity of electricity carried in 1 second by a current of 1 ampere". Conversely, a current of one ampere is one coulomb of charge going past a given point per second:
In general, charge is determined by steady current flowing for a time as . | Ampere | Wikipedia | 492 | 772 | https://en.wikipedia.org/wiki/Ampere | Physical sciences | Electromagnetism | null |
Constant, instantaneous and average current are expressed in amperes (as in "the charging current is 1.2 A") and the charge accumulated (or passed through a circuit) over a period of time is expressed in coulombs (as in "the battery charge is "). The relation of the ampere (C/s) to the coulomb is the same as that of the watt (J/s) to the joule.
Units derived from the ampere
The international system of units (SI) is based on seven SI base units the second, metre, kilogram, kelvin, ampere, mole, and candela representing seven fundamental types of physical quantity, or "dimensions", (time, length, mass, temperature, electric current, amount of substance, and luminous intensity respectively) with all other SI units being defined using these. These SI derived units can either be given special names e.g. watt, volt, lux, etc. or defined in terms of others, e.g. metre per second. The units with special names derived from the ampere are:
There are also some SI units that are frequently used in the context of electrical engineering and electrical appliances, but are defined independently of the ampere, notably the hertz, joule, watt, candela, lumen, and lux.
SI prefixes
Like other SI units, the ampere can be modified by adding a prefix that multiplies it by a power of 10. | Ampere | Wikipedia | 305 | 772 | https://en.wikipedia.org/wiki/Ampere | Physical sciences | Electromagnetism | null |
In mathematics and computer science, an algorithm () is a finite sequence of mathematically rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing calculations and data processing. More advanced algorithms can use conditionals to divert the code execution through various routes (referred to as automated decision-making) and deduce valid inferences (referred to as automated reasoning).
In contrast, a heuristic is an approach to solving problems that do not have well-defined correct or optimal results. For example, although social media recommender systems are commonly called "algorithms", they actually rely on heuristics as there is no truly "correct" recommendation.
As an effective method, an algorithm can be expressed within a finite amount of space and time and in a well-defined formal language for calculating a function. Starting from an initial state and initial input (perhaps empty), the instructions describe a computation that, when executed, proceeds through a finite number of well-defined successive states, eventually producing "output" and terminating at a final ending state. The transition from one state to the next is not necessarily deterministic; some algorithms, known as randomized algorithms, incorporate random input. | Algorithm | Wikipedia | 252 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
Etymology
Around 825 AD, Persian scientist and polymath Muḥammad ibn Mūsā al-Khwārizmī wrote kitāb al-ḥisāb al-hindī ("Book of Indian computation") and kitab al-jam' wa'l-tafriq al-ḥisāb al-hindī ("Addition and subtraction in Indian arithmetic"). In the early 12th century, Latin translations of said al-Khwarizmi texts involving the Hindu–Arabic numeral system and arithmetic appeared, for example Liber Alghoarismi de practica arismetrice, attributed to John of Seville, and Liber Algorismi de numero Indorum, attributed to Adelard of Bath. Hereby, alghoarismi or algorismi is the Latinization of Al-Khwarizmi's name; the text starts with the phrase Dixit Algorismi, or "Thus spoke Al-Khwarizmi". Around 1230, the English word algorism is attested and then by Chaucer in 1391, English adopted the French term. In the 15th century, under the influence of the Greek word ἀριθμός (arithmos, "number"; cf. "arithmetic"), the Latin word was altered to algorithmus.
Definition
One informal definition is "a set of rules that precisely defines a sequence of operations", which would include all computer programs (including programs that do not perform numeric calculations), and any prescribed bureaucratic procedure
or cook-book recipe. In general, a program is an algorithm only if it stops eventually—even though infinite loops may sometimes prove desirable. define an algorithm to be an explicit set of instructions for determining an output, that can be followed by a computing machine or a human who could only carry out specific elementary operations on symbols.
Most algorithms are intended to be implemented as computer programs. However, algorithms are also implemented by other means, such as in a biological neural network (for example, the human brain performing arithmetic or an insect looking for food), in an electrical circuit, or a mechanical device.
History | Algorithm | Wikipedia | 438 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
Ancient algorithms
Step-by-step procedures for solving mathematical problems have been recorded since antiquity. This includes in Babylonian mathematics (around 2500 BC), Egyptian mathematics (around 1550 BC), Indian mathematics (around 800 BC and later), the Ifa Oracle (around 500 BC), Greek mathematics (around 240 BC), Chinese mathematics (around 200 BC and later), and Arabic mathematics (around 800 AD).
The earliest evidence of algorithms is found in ancient Mesopotamian mathematics. A Sumerian clay tablet found in Shuruppak near Baghdad and dated to describes the earliest division algorithm. During the Hammurabi dynasty , Babylonian clay tablets described algorithms for computing formulas. Algorithms were also used in Babylonian astronomy. Babylonian clay tablets describe and employ algorithmic procedures to compute the time and place of significant astronomical events.
Algorithms for arithmetic are also found in ancient Egyptian mathematics, dating back to the Rhind Mathematical Papyrus . Algorithms were later used in ancient Hellenistic mathematics. Two examples are the Sieve of Eratosthenes, which was described in the Introduction to Arithmetic by Nicomachus, and the Euclidean algorithm, which was first described in Euclid's Elements ().Examples of ancient Indian mathematics included the Shulba Sutras, the Kerala School, and the Brāhmasphuṭasiddhānta.
The first cryptographic algorithm for deciphering encrypted code was developed by Al-Kindi, a 9th-century Arab mathematician, in A Manuscript On Deciphering Cryptographic Messages. He gave the first description of cryptanalysis by frequency analysis, the earliest codebreaking algorithm.
Computers
Weight-driven clocks
Bolter credits the invention of the weight-driven clock as "the key invention [of Europe in the Middle Ages]," specifically the verge escapement mechanism producing the tick and tock of a mechanical clock. "The accurate automatic machine" led immediately to "mechanical automata" in the 13th century and "computational machines"—the difference and analytical engines of Charles Babbage and Ada Lovelace in the mid-19th century. Lovelace designed the first algorithm intended for processing on a computer, Babbage's analytical engine, which is the first device considered a real Turing-complete computer instead of just a calculator. Although a full implementation of Babbage's second device was not realized for decades after her lifetime, Lovelace has been called "history's first programmer". | Algorithm | Wikipedia | 492 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
Electromechanical relay
Bell and Newell (1971) write that the Jacquard loom, a precursor to Hollerith cards (punch cards), and "telephone switching technologies" led to the development of the first computers. By the mid-19th century, the telegraph, the precursor of the telephone, was in use throughout the world. By the late 19th century, the ticker tape () was in use, as were Hollerith cards (c. 1890). Then came the teleprinter () with its punched-paper use of Baudot code on tape.
Telephone-switching networks of electromechanical relays were invented in 1835. These led to the invention of the digital adding device by George Stibitz in 1937. While working in Bell Laboratories, he observed the "burdensome" use of mechanical calculators with gears. "He went home one evening in 1937 intending to test his idea... When the tinkering was over, Stibitz had constructed a binary adding device".
Formalization
In 1928, a partial formalization of the modern concept of algorithms began with attempts to solve the Entscheidungsproblem (decision problem) posed by David Hilbert. Later formalizations were framed as attempts to define "effective calculability" or "effective method". Those formalizations included the Gödel–Herbrand–Kleene recursive functions of 1930, 1934 and 1935, Alonzo Church's lambda calculus of 1936, Emil Post's Formulation 1 of 1936, and Alan Turing's Turing machines of 1936–37 and 1939.
Representations
Algorithms can be expressed in many kinds of notation, including natural languages, pseudocode, flowcharts, drakon-charts, programming languages or control tables (processed by interpreters). Natural language expressions of algorithms tend to be verbose and ambiguous and are rarely used for complex or technical algorithms. Pseudocode, flowcharts, drakon-charts, and control tables are structured expressions of algorithms that avoid common ambiguities of natural language. Programming languages are primarily for expressing algorithms in a computer-executable form, but are also used to define or document algorithms. | Algorithm | Wikipedia | 451 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
Turing machines
There are many possible representations and Turing machine programs can be expressed as a sequence of machine tables (see finite-state machine, state-transition table, and control table for more), as flowcharts and drakon-charts (see state diagram for more), as a form of rudimentary machine code or assembly code called "sets of quadruples", and more. Algorithm representations can also be classified into three accepted levels of Turing machine description: high-level description, implementation description, and formal description. A high-level description describes qualities of the algorithm itself, ignoring how it is implemented on the Turing machine. An implementation description describes the general manner in which the machine moves its head and stores data in order to carry out the algorithm, but does not give exact states. In the most detail, a formal description gives the exact state table and list of transitions of the Turing machine.
Flowchart representation
The graphical aid called a flowchart offers a way to describe and document an algorithm (and a computer program corresponding to it). It has four primary symbols: arrows showing program flow, rectangles (SEQUENCE, GOTO), diamonds (IF-THEN-ELSE), and dots (OR-tie). Sub-structures can "nest" in rectangles, but only if a single exit occurs from the superstructure.
Algorithmic analysis
It is often important to know how much time, storage, or other cost an algorithm may require. Methods have been developed for the analysis of algorithms to obtain such quantitative answers (estimates); for example, an algorithm that adds up the elements of a list of n numbers would have a time requirement of , using big O notation. The algorithm only needs to remember two values: the sum of all the elements so far, and its current position in the input list. If the space required to store the input numbers is not counted, it has a space requirement of , otherwise is required.
Different algorithms may complete the same task with a different set of instructions in less or more time, space, or 'effort' than others. For example, a binary search algorithm (with cost ) outperforms a sequential search (cost ) when used for table lookups on sorted lists or arrays.
Formal versus empirical | Algorithm | Wikipedia | 459 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
The analysis, and study of algorithms is a discipline of computer science. Algorithms are often studied abstractly, without referencing any specific programming language or implementation. Algorithm analysis resembles other mathematical disciplines as it focuses on the algorithm's properties, not implementation. Pseudocode is typical for analysis as it is a simple and general representation. Most algorithms are implemented on particular hardware/software platforms and their algorithmic efficiency is tested using real code. The efficiency of a particular algorithm may be insignificant for many "one-off" problems but it may be critical for algorithms designed for fast interactive, commercial or long life scientific usage. Scaling from small n to large n frequently exposes inefficient algorithms that are otherwise benign.
Empirical testing is useful for uncovering unexpected interactions that affect performance. Benchmarks may be used to compare before/after potential improvements to an algorithm after program optimization.
Empirical tests cannot replace formal analysis, though, and are non-trivial to perform fairly.
Execution efficiency
To illustrate the potential improvements possible even in well-established algorithms, a recent significant innovation, relating to FFT algorithms (used heavily in the field of image processing), can decrease processing time up to 1,000 times for applications like medical imaging. In general, speed improvements depend on special properties of the problem, which are very common in practical applications. Speedups of this magnitude enable computing devices that make extensive use of image processing (like digital cameras and medical equipment) to consume less power.
Design
Algorithm design is a method or mathematical process for problem-solving and engineering algorithms. The design of algorithms is part of many solution theories, such as divide-and-conquer or dynamic programming within operation research. Techniques for designing and implementing algorithm designs are also called algorithm design patterns, with examples including the template method pattern and the decorator pattern. One of the most important aspects of algorithm design is resource (run-time, memory usage) efficiency; the big O notation is used to describe e.g., an algorithm's run-time growth as the size of its input increases. | Algorithm | Wikipedia | 412 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
Structured programming
Per the Church–Turing thesis, any algorithm can be computed by any Turing complete model. Turing completeness only requires four instruction types—conditional GOTO, unconditional GOTO, assignment, HALT. However, Kemeny and Kurtz observe that, while "undisciplined" use of unconditional GOTOs and conditional IF-THEN GOTOs can result in "spaghetti code", a programmer can write structured programs using only these instructions; on the other hand "it is also possible, and not too hard, to write badly structured programs in a structured language". Tausworthe augments the three Böhm-Jacopini canonical structures: SEQUENCE, IF-THEN-ELSE, and WHILE-DO, with two more: DO-WHILE and CASE. An additional benefit of a structured program is that it lends itself to proofs of correctness using mathematical induction.
Legal status
By themselves, algorithms are not usually patentable. In the United States, a claim consisting solely of simple manipulations of abstract concepts, numbers, or signals does not constitute "processes" (USPTO 2006), so algorithms are not patentable (as in Gottschalk v. Benson). However practical applications of algorithms are sometimes patentable. For example, in Diamond v. Diehr, the application of a simple feedback algorithm to aid in the curing of synthetic rubber was deemed patentable. The patenting of software is controversial, and there are criticized patents involving algorithms, especially data compression algorithms, such as Unisys's LZW patent. Additionally, some cryptographic algorithms have export restrictions (see export of cryptography).
Classification | Algorithm | Wikipedia | 340 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
By implementation
Recursion
A recursive algorithm invokes itself repeatedly until meeting a termination condition, and is a common functional programming method. Iterative algorithms use repetitions such as loops or data structures like stacks to solve problems. Problems may be suited for one implementation or the other. The Tower of Hanoi is a puzzle commonly solved using recursive implementation. Every recursive version has an equivalent (but possibly more or less complex) iterative version, and vice versa.
Serial, parallel or distributed
Algorithms are usually discussed with the assumption that computers execute one instruction of an algorithm at a time on serial computers. Serial algorithms are designed for these environments, unlike parallel or distributed algorithms. Parallel algorithms take advantage of computer architectures where multiple processors can work on a problem at the same time. Distributed algorithms use multiple machines connected via a computer network. Parallel and distributed algorithms divide the problem into subproblems and collect the results back together. Resource consumption in these algorithms is not only processor cycles on each processor but also the communication overhead between the processors. Some sorting algorithms can be parallelized efficiently, but their communication overhead is expensive. Iterative algorithms are generally parallelizable, but some problems have no parallel algorithms and are called inherently serial problems.
Deterministic or non-deterministic
Deterministic algorithms solve the problem with exact decision at every step; whereas non-deterministic algorithms solve problems via guessing. Guesses are typically made more accurate through the use of heuristics.
Exact or approximate
While many algorithms reach an exact solution, approximation algorithms seek an approximation that is close to the true solution. Such algorithms have practical value for many hard problems. For example, the Knapsack problem, where there is a set of items and the goal is to pack the knapsack to get the maximum total value. Each item has some weight and some value. The total weight that can be carried is no more than some fixed number X. So, the solution must consider weights of items as well as their value.
Quantum algorithm
Quantum algorithms run on a realistic model of quantum computation. The term is usually used for those algorithms which seem inherently quantum or use some essential feature of Quantum computing such as quantum superposition or quantum entanglement.
By design paradigm
Another way of classifying algorithms is by their design methodology or paradigm. Some common paradigms are: | Algorithm | Wikipedia | 475 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
Brute-force or exhaustive search
Brute force is a problem-solving method of systematically trying every possible option until the optimal solution is found. This approach can be very time-consuming, testing every possible combination of variables. It is often used when other methods are unavailable or too complex. Brute force can solve a variety of problems, including finding the shortest path between two points and cracking passwords.
Divide and conquer
A divide-and-conquer algorithm repeatedly reduces a problem to one or more smaller instances of itself (usually recursively) until the instances are small enough to solve easily. Merge sorting is an example of divide and conquer, where an unordered list can be divided into segments containing one item and sorting of entire list can be obtained by merging the segments. A simpler variant of divide and conquer is called a decrease-and-conquer algorithm, which solves one smaller instance of itself, and uses the solution to solve the bigger problem. Divide and conquer divides the problem into multiple subproblems and so the conquer stage is more complex than decrease and conquer algorithms. An example of a decrease and conquer algorithm is the binary search algorithm.
Search and enumeration
Many problems (such as playing chess) can be modelled as problems on graphs. A graph exploration algorithm specifies rules for moving around a graph and is useful for such problems. This category also includes search algorithms, branch and bound enumeration, and backtracking.
Randomized algorithm
Such algorithms make some choices randomly (or pseudo-randomly). They find approximate solutions when finding exact solutions may be impractical (see heuristic method below). For some problems the fastest approximations must involve some randomness. Whether randomized algorithms with polynomial time complexity can be the fastest algorithm for some problems is an open question known as the P versus NP problem. There are two large classes of such algorithms:
Monte Carlo algorithms return a correct answer with high probability. E.g. RP is the subclass of these that run in polynomial time.
Las Vegas algorithms always return the correct answer, but their running time is only probabilistically bound, e.g. ZPP.
Reduction of complexity | Algorithm | Wikipedia | 436 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
This technique transforms difficult problems into better-known problems solvable with (hopefully) asymptotically optimal algorithms. The goal is to find a reducing algorithm whose complexity is not dominated by the resulting reduced algorithms. For example, one selection algorithm finds the median of an unsorted list by first sorting the list (the expensive portion), then pulling out the middle element in the sorted list (the cheap portion). This technique is also known as transform and conquer.
Back tracking
In this approach, multiple solutions are built incrementally and abandoned when it is determined that they cannot lead to a valid full solution. | Algorithm | Wikipedia | 125 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
Optimization problems
For optimization problems there is a more specific classification of algorithms; an algorithm for such problems may fall into one or more of the general categories described above as well as into one of the following: | Algorithm | Wikipedia | 40 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
Linear programming
When searching for optimal solutions to a linear function bound by linear equality and inequality constraints, the constraints can be used directly to produce optimal solutions. There are algorithms that can solve any problem in this category, such as the popular simplex algorithm. Problems that can be solved with linear programming include the maximum flow problem for directed graphs. If a problem also requires that any of the unknowns be integers, then it is classified in integer programming. A linear programming algorithm can solve such a problem if it can be proved that all restrictions for integer values are superficial, i.e., the solutions satisfy these restrictions anyway. In the general case, a specialized algorithm or an algorithm that finds approximate solutions is used, depending on the difficulty of the problem.
Dynamic programming
When a problem shows optimal substructures—meaning the optimal solution can be constructed from optimal solutions to subproblems—and overlapping subproblems, meaning the same subproblems are used to solve many different problem instances, a quicker approach called dynamic programming avoids recomputing solutions. For example, Floyd–Warshall algorithm, the shortest path between a start and goal vertex in a weighted graph can be found using the shortest path to the goal from all adjacent vertices. Dynamic programming and memoization go together. Unlike divide and conquer, dynamic programming subproblems often overlap. The difference between dynamic programming and simple recursion is the caching or memoization of recursive calls. When subproblems are independent and do not repeat, memoization does not help; hence dynamic programming is not applicable to all complex problems. Using memoization dynamic programming reduces the complexity of many problems from exponential to polynomial.
The greedy method
Greedy algorithms, similarly to a dynamic programming, work by examining substructures, in this case not of the problem but of a given solution. Such algorithms start with some solution and improve it by making small modifications. For some problems they always find the optimal solution but for others they may stop at local optima. The most popular use of greedy algorithms is finding minimal spanning trees of graphs without negative cycles. Huffman Tree, Kruskal, Prim, Sollin are greedy algorithms that can solve this optimization problem.
The heuristic method | Algorithm | Wikipedia | 455 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
In optimization problems, heuristic algorithms find solutions close to the optimal solution when finding the optimal solution is impractical. These algorithms get closer and closer to the optimal solution as they progress. In principle, if run for an infinite amount of time, they will find the optimal solution. They can ideally find a solution very close to the optimal solution in a relatively short time. These algorithms include local search, tabu search, simulated annealing, and genetic algorithms. Some, like simulated annealing, are non-deterministic algorithms while others, like tabu search, are deterministic. When a bound on the error of the non-optimal solution is known, the algorithm is further categorized as an approximation algorithm. | Algorithm | Wikipedia | 146 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
Examples
One of the simplest algorithms finds the largest number in a list of numbers of random order. Finding the solution requires looking at every number in the list. From this follows a simple algorithm, which can be described in plain English as:
High-level description:
If a set of numbers is empty, then there is no highest number.
Assume the first number in the set is the largest.
For each remaining number in the set: if this number is greater than the current largest, it becomes the new largest.
When there are no unchecked numbers left in the set, consider the current largest number to be the largest in the set.
(Quasi-)formal description:
Written in prose but much closer to the high-level language of a computer program, the following is the more formal coding of the algorithm in pseudocode or pidgin code:
Input: A list of numbers L.
Output: The largest number in the list L.
if L.size = 0 return null
largest ← L[0]
for each item in L, do
if item > largest, then
largest ← item
return largest | Algorithm | Wikipedia | 221 | 775 | https://en.wikipedia.org/wiki/Algorithm | Mathematics | Mathematics: General | null |
Mouthwash, mouth rinse, oral rinse, or mouth bath is a liquid which is held in the mouth passively or swirled around the mouth by contraction of the perioral muscles and/or movement of the head, and may be gargled, where the head is tilted back and the liquid bubbled at the back of the mouth.
Usually mouthwashes are antiseptic solutions intended to reduce the microbial load in the mouth, although other mouthwashes might be given for other reasons such as for their analgesic, anti-inflammatory or anti-fungal action. Additionally, some rinses act as saliva substitutes to neutralize acid and keep the mouth moist in xerostomia (dry mouth). Cosmetic mouthrinses temporarily control or reduce bad breath and leave the mouth with a pleasant taste.
Rinsing with water or mouthwash after brushing with a fluoride toothpaste can reduce the availability of salivary fluoride. This can lower the anti-cavity re-mineralization and antibacterial effects of fluoride. Fluoridated mouthwash may mitigate this effect or in high concentrations increase available fluoride, but is not as cost-effective as leaving the fluoride toothpaste on the teeth after brushing. A group of experts discussing post brushing rinsing in 2012 found that although there was clear guidance given in many public health advice publications to "spit, avoid rinsing with water/excessive rinsing with water" they believed there was a limited evidence base for best practice.
Use
Common use involves rinsing the mouth with about of mouthwash. The wash is typically swished or gargled for about half a minute and then spat out. Most companies suggest not drinking water immediately after using mouthwash. In some brands, the expectorate is stained, so that one can see the bacteria and debris.
Mouthwash should not be used immediately after brushing the teeth so as not to wash away the beneficial fluoride residue left from the toothpaste. Similarly, the mouth should not be rinsed out with water after brushing. Patients were told to "spit don't rinse" after toothbrushing as part of a National Health Service campaign in the UK. A fluoride mouthrinse can be used at a different time of the day to brushing. | Mouthwash | Wikipedia | 478 | 782 | https://en.wikipedia.org/wiki/Mouthwash | Biology and health sciences | Hygiene products | Health |
Gargling is where the head is tilted back, allowing the mouthwash to sit in the back of the mouth while exhaling, causing the liquid to bubble. Gargling is practiced in Japan for perceived prevention of viral infection. One commonly used way is with infusions or tea. In some cultures, gargling is usually done in private, typically in a bathroom at a sink so the liquid can be rinsed away.
Dangerous misuse
Serious harm and even death can quickly result from ingestion due to the high alcohol content and other substances harmful to ingestion present in some brands of mouthwash. Zero percent alcohol mouthwashes do exist, as well as many other formulations for different needs (covered in the above sections).
These risks may be higher in toddlers and young children if they are allowed to use toothpaste and/or mouthwash unsupervised, where they may swallow it. Misuse in this way can be avoided with parental admission or supervision and by using child-safe forms or a children's brand of mouthwash.
Surrogate alcohol use such as ingestion of mouthwash is a common cause of death among homeless people during winter months, because a person can feel warmer after drinking it.
Effects
The most-commonly-used mouthwashes are commercial antiseptics, which are used at home as part of an oral hygiene routine. Mouthwashes combine ingredients to treat a variety of oral conditions. Variations are common, and mouthwash has no standard formulation, so its use and recommendation involves concerns about patient safety. Some manufacturers of mouthwash state that their antiseptic and antiplaque mouthwashes kill the bacterial plaque that causes cavities, gingivitis, and bad breath. It is, however, generally agreed that the use of mouthwash does not eliminate the need for both brushing and flossing. The American Dental Association asserts that regular brushing and proper flossing are enough in most cases, in addition to regular dental check-ups, although they approve many mouthwashes.
For many patients, however, the mechanical methods could be tedious and time-consuming, and, additionally, some local conditions may render them especially difficult. Chemotherapeutic agents, including mouthwashes, could have a key role as adjuncts to daily home care, preventing and controlling supragingival plaque, gingivitis and oral malodor. | Mouthwash | Wikipedia | 497 | 782 | https://en.wikipedia.org/wiki/Mouthwash | Biology and health sciences | Hygiene products | Health |
Minor and transient side effects of mouthwashes are very common, such as taste disturbance, tooth staining, sensation of a dry mouth, etc. Alcohol-containing mouthwashes may make dry mouth and halitosis worse, as they dry out the mouth. Soreness, ulceration and redness may sometimes occur (e.g., aphthous stomatitis or allergic contact stomatitis) if the person is allergic or sensitive to mouthwash ingredients, such as preservatives, coloring, flavors and fragrances. Such effects might be reduced or eliminated by diluting the mouthwash with water, using a different mouthwash (e.g. saltwater), or foregoing mouthwash entirely.
Prescription mouthwashes are used prior to and after oral surgery procedures, such as tooth extraction, or to treat the pain associated with mucositis caused by radiation therapy or chemotherapy. They are also prescribed for aphthous ulcers, other oral ulcers, and other mouth pain. "Magic mouthwashes" are prescription mouthwashes compounded in a pharmacy from a list of ingredients specified by a doctor. Despite a lack of evidence that prescription mouthwashes are more effective in decreasing the pain of oral lesions, many patients and prescribers continue to use them. There has been only one controlled study to evaluate the efficacy of magic mouthwash; it shows no difference in efficacy between the most common magic-mouthwash formulation, on the one hand, and commercial mouthwashes (such as chlorhexidine) or a saline/baking soda solution, on the other. Current guidelines suggest that saline solution is just as effective as magic mouthwash in pain relief and in shortening the healing time of oral mucositis from cancer therapies.
History
The first known references to mouth rinsing is in Ayurveda for treatment of gingivitis. Later, in the Greek and Roman periods, mouth rinsing following mechanical cleansing became common among the upper classes, and Hippocrates recommended a mixture of salt, alum, and vinegar. The Jewish Talmud, dating back about 1,800 years, suggests a cure for gum ailments containing "dough water" and olive oil. The ancient Chinese had also gargled salt water, tea and wine as a form of mouthwash after meals, due to the antiseptic properties of those liquids. | Mouthwash | Wikipedia | 493 | 782 | https://en.wikipedia.org/wiki/Mouthwash | Biology and health sciences | Hygiene products | Health |
Before Europeans came to the Americas, Native North American and Mesoamerican cultures used mouthwashes, often made from plants such as Coptis trifolia. Peoples of the Americas used salt water mouthwashes for sore throats, and other mouthwashes for problems such as teething and mouth ulcers.
Anton van Leeuwenhoek, the famous 17th century microscopist, discovered living organisms (living, because they were mobile) in deposits on the teeth (what we now call dental plaque). He also found organisms in water from the canal next to his home in Delft. He experimented with samples by adding vinegar or brandy and found that this resulted in the immediate immobilization or killing of the organisms suspended in water. Next he tried rinsing the mouth of himself and somebody else with a mouthwash containing vinegar or brandy and found that living organisms remained in the dental plaque. He concluded—correctly—that the mouthwash either did not reach, or was not present long enough, to kill the plaque organisms.
In 1892, German Richard Seifert invented mouthwash product Odol, which was produced by company founder Karl August Lingner (1861–1916) in Dresden.
That remained the state of affairs until the late 1960s when Harald Loe (at the time a professor at the Royal Dental College in Aarhus, Denmark) demonstrated that a chlorhexidine compound could prevent the build-up of dental plaque. The reason for chlorhexidine's effectiveness is that it strongly adheres to surfaces in the mouth and thus remains present in effective concentrations for many hours.
Since then commercial interest in mouthwashes has been intense and several newer products claim effectiveness in reducing the build-up in dental plaque and the associated severity of gingivitis, in addition to fighting bad breath. Many of these solutions aim to control the volatile sulfur compound–creating anaerobic bacteria that live in the mouth and excrete substances that lead to bad breath and unpleasant mouth taste. For example, the number of mouthwash variants in the United States of America has grown from 15 (1970) to 66 (1998) to 113 (2012). | Mouthwash | Wikipedia | 442 | 782 | https://en.wikipedia.org/wiki/Mouthwash | Biology and health sciences | Hygiene products | Health |
Research
Research in the field of microbiotas shows that only a limited set of microbes cause tooth decay, with most of the bacteria in the human mouth being harmless. Focused attention on cavity-causing bacteria such as Streptococcus mutans has led research into new mouthwash treatments that prevent these bacteria from initially growing. While current mouthwash treatments must be used with a degree of frequency to prevent this bacteria from regrowing, future treatments could provide a viable long-term solution.
A clinical trial and laboratory studies have shown that alcohol-containing mouthwash could reduce the growth of Neisseria gonorrhoeae in the pharynx. However, subsequent trials have found that there was no difference in gonorrhoea cases among men using daily mouthwash compared to those who did not use mouthwash for 12 weeks.
Ingredients
Alcohol
Alcohol is added to mouthwash not to destroy bacteria but to act as a carrier agent for essential active ingredients such as menthol, eucalyptol and thymol, which help to penetrate plaque. Sometimes a significant amount of alcohol (up to 27% vol) is added, as a carrier for the flavor, to provide "bite". Because of the alcohol content, it is possible to fail a breathalyzer test after rinsing, although breath alcohol levels return to normal after 10 minutes. In addition, alcohol is a drying agent, which encourages bacterial activity in the mouth, releasing more malodorous volatile sulfur compounds. Therefore, alcohol-containing mouthwash may temporarily worsen halitosis in those who already have it, or, indeed, be the sole cause of halitosis in other individuals. Alcohol in mouthwashes may act as a carcinogen (cancer-inducing agent) in some cases . Many newer brands of mouthwash are alcohol-free, not just in response to consumer concerns about oral cancer, but also to cater for religious groups who abstain from alcohol consumption.
Benzydamine (analgesic)
In painful oral conditions such as aphthous stomatitis, analgesic mouthrinses (e.g. benzydamine mouthwash, or "Difflam") are sometimes used to ease pain, commonly used before meals to reduce discomfort while eating.
Benzoic acid
Benzoic acid acts as a buffer. | Mouthwash | Wikipedia | 472 | 782 | https://en.wikipedia.org/wiki/Mouthwash | Biology and health sciences | Hygiene products | Health |
Betamethasone
Betamethasone is sometimes used as an anti-inflammatory, corticosteroid mouthwash. It may be used for severe inflammatory conditions of the oral mucosa such as the severe forms of aphthous stomatitis.
Cetylpyridinium chloride (antiseptic, antimalodor)
Cetylpyridinium chloride containing mouthwash (e.g. 0.05%) is used in some specialized mouthwashes for halitosis. Cetylpyridinium chloride mouthwash has less anti-plaque effect than chlorhexidine and may cause staining of teeth, or sometimes an oral burning sensation or ulceration.
Chlorhexidine digluconate and hexetidine (antiseptic)
Chlorhexidine digluconate is a chemical antiseptic and is used in a 0.05–0.2% solution as a mouthwash. There is no evidence to support that higher concentrations are more effective in controlling dental plaque and gingivitis. A randomized clinical trial conducted in Rabat University in Morocco found better results in plaque inhibition when chlorohexidine with alcohol base 0.12% was used, when compared to an alcohol-free 0.1% chlorhexidine mouthrinse. | Mouthwash | Wikipedia | 274 | 782 | https://en.wikipedia.org/wiki/Mouthwash | Biology and health sciences | Hygiene products | Health |
Chlorhexidine has good substantivity (the ability of a mouthwash to bind to hard and soft tissues in the mouth). It has anti-plaque action, and also some anti-fungal action. It is especially effective against Gram-negative rods. The proportion of Gram-negative rods increase as gingivitis develops, so it is also used to reduce gingivitis. It is sometimes used as an adjunct to prevent dental caries and to treat periodontal disease, although it does not penetrate into periodontal pockets well. Chlorhexidine mouthwash alone is unable to prevent plaque, so it is not a substitute for regular toothbrushing and flossing. Instead, chlorhexidine mouthwash is more effective when used as an adjunctive treatment with toothbrushing and flossing. In the short term, if toothbrushing is impossible due to pain, as may occur in primary herpetic gingivostomatitis, chlorhexidine mouthwash is used as a temporary substitute for other oral hygiene measures. It is not suited for use in acute necrotizing ulcerative gingivitis, however. Rinsing with chlorhexidine mouthwash before and after a tooth extraction may reduce the risk of a dry socket. Other uses of chlorhexidine mouthwash include prevention of oral candidiasis in immunocompromised persons, treatment of denture-related stomatitis, mucosal ulceration/erosions and oral mucosal lesions, general burning sensation and many other uses. | Mouthwash | Wikipedia | 329 | 782 | https://en.wikipedia.org/wiki/Mouthwash | Biology and health sciences | Hygiene products | Health |
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