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When penguins moult, they are unable to forage in the sea as their new feathers are not yet waterproof; therefore, they fast over the entire moulting period. African penguins typically take around three weeks to moult and lose about half of their body weight by burning up their fat reserves in the process.
African penguins spend most of their lives at sea until it comes time for them to lay their eggs. Females remain fertile for about 10 years. Due to high predation on the mainland, African penguins will seek protection on offshore islands, where they are safer from larger mammals and natural challenges. These penguins usually breed during the winter when temperatures are cooler. African penguins often will abandon their eggs if they become overheated in the hot sun and abandoned eggs never survive the heat. The eggs are three to four times bigger than chicken eggs. Ideally, the eggs are incubated in a burrow dug into the guano layer (which provides suitable temperature regulation), but the widespread human removal of guano deposits has rendered this type of nest unfeasible in many colonies. To compensate, penguins burrow holes in the sand, nest under rocks or bushes or make use of nest boxes if they are provided. The penguins spend three weeks on land caring for their offspring, after which chicks may be left alone during the day while the parents forage. The chicks are frequently killed by predators or succumb to the hot sun. Parents usually feed hatchlings during dusk or dawn.
In 2015, when foraging conditions were favourable, more male than female African penguin chicks were produced in the colony on Bird Island. Male chicks also had higher growth rates and fledging mass and therefore may have higher post-fledging survival than females. This, coupled with higher adult female mortality in this species, may result in a male-biased adult sex ratio and may indicate that conservation strategies focused on benefiting female African penguins may be necessary.
Predation
The average lifespan of an African penguin is 10 to around 25 years in the wild and up to 30 in captivity.
The primary predators of African penguins at sea include sharks and fur seals. While nesting: kelp gulls, Cape genets, mongooses, caracals and domestic cats and dogs may prey on the penguins and their chicks. Mortality from terrestrial predators is higher if penguins are forced to breed in the open in the absence of suitable burrows or nest boxes.
Threats and conservation | African penguin | Wikipedia | 488 | 318215 | https://en.wikipedia.org/wiki/African%20penguin | Biology and health sciences | Sphenisciformes | Animals |
Historical exploitation
African penguin eggs were considered a delicacy and were still being eaten and collected for sale as recently as the 1970s. In the 1950s, they were being collected from Dassen Island and sold in nearby towns. In 1953, 12,000 eggs were collected. In the late 1950s, some French chefs expressed interest in recipes including African penguin eggs collected from the islands off the west coast of South Africa and placed annual orders for small quantities. In the mid-1960s, eggs were collected in the thousands and sold by the dozen, with each customer limited to two dozen eggs in total.
The practice of collecting African penguin eggs involved smashing those found a few days before a collecting effort to ensure that only freshly laid eggs were sold. This added to the drastic decline of the African penguin population around the Cape coast, a decline which was hastened by the removal of guano from islands for use as fertiliser, eliminating the burrowing material used by penguins.
Oil spills
Penguins remain susceptible to pollution of their habitat by petrochemicals from spills, shipwrecks and cleaning of tankers while at sea. Accounts of African penguins impacted by oil date back to the 1930s. African penguins' exposure to oil spills is both chronic (higher frequency small discharges of oil at sea) and acute (rare maritime disasters where large volumes of oil are released in a single event). Penguins of many species have been impacted by oil spills across the southern hemisphere.
In 1948, the tanker Esso Wheeling sank, subsequently oiling and killing thousands of penguins of the Dyer Island colony. In 1953, dead penguins were among a range of dead birds, fish and other marine life that washed ashore after the tanker Sliedrecht was holed and spilled oil near Table Bay. In 1971, the SS Wafra oil spill impacted the African penguin colony of Dyer Island. In 1972, oil spilt following the Oswego-Guardian and Texanita collision oiled roughly 500 penguins. In 1975, newspapers reported that oil pollution from shipwrecks and the pumping of bilges at sea had killed tens of thousands of African penguins. At the time, the Dassen Island colony was being passed by 650 oil tankers each month because the Suez Canal had become blocked with wrecked vessels, thus increasing maritime traffic past the Cape of Good Hope. | African penguin | Wikipedia | 472 | 318215 | https://en.wikipedia.org/wiki/African%20penguin | Biology and health sciences | Sphenisciformes | Animals |
In 1979, an oil spill prompted the collection and treatment of 150 African penguins from St. Croix Island near Port Elizabeth. The animals were later released at Robben Island and four of them promptly swam back to St. Croix Island, surprising scientists.
In 1983, the exposure of penguins of Dassen Island to the oil slick from the Castillo de Bellver was also a topic of concern given the penguins' conservation status at the time, but owing to the prevailing wind and current, only gannets were oiled.
1994 MV Apollo Sea disaster
African penguin casualties were significant following the sinking of the MV Apollo Sea and a subsequent oil slick in 1994. 10,000 penguins were collected and cleaned, of which less than half survived.
2000 MV Treasure crisis
Disaster struck on 23 June 2000, when the iron ore tanker MV Treasure sank between Robben Island and Dassen Island, South Africa. It released of fuel oil, causing an unprecedented coastal bird crisis and oiling 19,000 adult penguins at the height of the best breeding season on record for this vulnerable species. The oiled birds were brought to an abandoned train repair warehouse in Cape Town to be cared for. An additional 19,500 un-oiled penguins were removed from Dassen Island and other areas before they became oiled and were released about 800 kilometres east of Cape Town. This gave workers enough time to clean up the oiled waters and shores before the birds could complete their long swim home (which took the penguins between one and three weeks). Some of the penguins were named and radio-tracked as they swam back to their breeding grounds. Tens of thousands of volunteers helped with the rescue and rehabilitation process, which was overseen by the International Fund for Animal Welfare (IFAW) and the South African Foundation for the Conservation of Coastal Birds (SANCCOB) and took more than three months to complete. This was the largest animal rescue event in history; more than 91% of the penguins were successfully rehabilitated and released – an amazing feat that could not have been accomplished without such a tremendous international response.
Due to the positive outcome of African penguins being raised in captivity after tragedies such as the Treasure oil spill, the species is considered a good "candidate for a captive-breeding programme which aims to release offspring into the wild"; however, worry about the spread of new strains of avian malaria is a major concern in the situation. | African penguin | Wikipedia | 480 | 318215 | https://en.wikipedia.org/wiki/African%20penguin | Biology and health sciences | Sphenisciformes | Animals |
Bringing the birds inland led to the exposure of penguins to parasites and disease vectors such as mosquitoes carrying avian malaria, which has caused 27% of the rehabilitated penguin deaths annually.
2016 & 2019 Port of Ngqura
Small-scale oil spills (of less than ) have occurred at the Port of Ngqura since bunkering activities started there in 2016. Bunkering is a ship refuelling process that can result in oil spills and oil slicks entering the water. Hundreds of African penguins have been harmed following these spills due to the port's close proximity to penguin rookeries on St. Croix Island and seabird habitat on neighbouring Jahleel and Brenton Islands.
Competition with fisheries
Commercial fisheries of sardines and anchovy, the two main prey species of the penguins, have forced these penguins to search for prey farther offshore, as well as having to switch to eating less nutritious prey. Restricting commercial fishing near colony sites such as Robben Island for short periods (3 years) was shown to markedly improve penguin breeding success. Longer closure periods and closures near other colonies are being evaluated.
Conservation status
The African penguin is one of the species to which the African-Eurasian Waterbird Agreement (AEWA) applies. In September 2010, it was listed as endangered under the US Endangered Species Act. As of 2024, the African penguin is listed as critically endangered on the IUCN Red List, with the remaining mature individuals around 19,800 birds in a declining population.
Mediation efforts
Many organisations such as SANCCOB, Dyer Island Conservation Trust, SAMREC, The National Aviary in Pittsburgh, and Raggy Charters with the Penguin Research Fund in Port Elizabeth are working to halt the decline of the African penguin. Measures include: monitoring population trends, hand-rearing and releasing abandoned chicks, establishing artificial nests and proclaiming marine reserves in which fishing is prohibited. Some colonies (such as on Dyer Island) are suspected to be under heavy pressure from predation by Cape fur seals and may benefit from the culling of individual problem animals, which has been found effective (although requiring a large amount of management effort) in trials. | African penguin | Wikipedia | 437 | 318215 | https://en.wikipedia.org/wiki/African%20penguin | Biology and health sciences | Sphenisciformes | Animals |
Established in 1968, SANCCOB is currently the only organisation mandated by the South African government to respond to crises involving seabirds along South Africa's coastline and is internationally recognised for the role it played during the MV Treasure oil spill. A modelling exercise conducted in 2003 by the University of Cape Town's FitzPatrick Institute of African Ornithology found that rehabilitating oiled African penguins has resulted in the current population being 19% larger than it would have been in the absence of SANCCOB's rehabilitation efforts.
In February 2015, the Dyer Island Conservation Trust opened the African Penguin and Seabird Sanctuary (APSS) in Gansbaai, South Africa. The centre was opened by then-Department of Tourism minister Derek Hanekom and will serve as a hub for seabird research carried out by the Dyer Island Conservation Trust. The centre will also run local education projects, host international marine volunteers and seek to improve seabird handling techniques and rehabilitation protocols.
Captivity
African penguins are a commonly seen species in zoos across the world. Because they do not require particularly low temperatures, they are often kept in outside enclosures. They adapt fairly well to this captive environment and are rather easy to breed compared to other species of the family. In Europe, the breeding programme EAZA is regulated by Artis Royal Zoo in the Netherlands, whilst in the United States the SSP programme is cooperatively managed by the AZA. The idea is to create a backup captive population, as well as to aid in the conservation of the population in its natural habitat. Between 2010 and 2013, American zoos spent $300,000 on in situ (wild population) conservation. | African penguin | Wikipedia | 335 | 318215 | https://en.wikipedia.org/wiki/African%20penguin | Biology and health sciences | Sphenisciformes | Animals |
The Pont Neuf (, "New Bridge") is the oldest standing bridge across the river Seine in Paris, France. It stands by the western (downstream) point of the Île de la Cité, the island in the middle of the river that was, between 250 and 225 BCE, the birthplace of Paris, then known as Lutetia and, during the medieval period, the heart of the city.
The bridge is composed of two separate spans, one of five arches joining the left bank to the Île de la Cité, another of seven joining the island to the right bank. Old engraved maps of Paris show that the newly built bridge just grazed the downstream tip of the Île de la Cité; since then, the natural sandbar building of a mid-river island, aided by stone-faced embankments called quais, has extended the island. Today the tip of the island is the location of the Square du Vert-Galant, a small public park named in honour of Henry IV, nicknamed the "Green Gallant".
The name Pont Neuf was given to distinguish it from older bridges that were lined on both sides with houses, and has remained after all of those were replaced. Its name notwithstanding, it has long been the oldest bridge in Paris crossing the Seine. It has been listed since 1889 as a monument historique by the French Ministry of Culture.
Construction
As early as 1550, Henry II considered building a new bridge at the Ile de la Cite because the existing Pont Notre-Dame was congested and needed repair. The idea was not advanced for lack of funds. By 1577, however, Henry III released funds from the national treasury for a new bridge and appointed a building commission for its designing and planning. Henry rejected the first design proposed by the committee, which included monumental arches, but no plan for buildings along the sides. The commission proceeded in 1578 with modifications to its initial plan, perhaps devised by the royal architect, Androuet de Cerceau. While Henry had already allowed for piers to be driven for the northern arm of bridge, the first construction under the 1579 design indicated a wider deck in preparation of buildings to be constructed on the side. The houses were never built, but the wide bridge deck was retained. | Pont Neuf | Wikipedia | 454 | 318262 | https://en.wikipedia.org/wiki/Pont%20Neuf | Technology | Bridges | null |
In February 1578, the decision to build the bridge was made by Henry III who laid its first stone in on 31 May 1578, the same year when the foundations of four piers and one abutment were completed. Pierre des Isles, one of the builders, convinced the supervisory commission that the bridge, which was originally planned straight, would be more resistant to the river currents if its two sections were built at a slight angle. The change was adopted in May 1578.
Further design changes were made during the summer of 1579. First, the number of arches was changed from eight and four to seven and five. This was not a problem on the north side, where nothing had been built, but on the south, where the four piles and the abutment on the Left Bank were already laid, the addition of the fifth arch necessitated reducing the length of the platform on the island, the terre-plein, from 28.5 toises to about 19. Second, it was decided to allow houses to be built on the bridge (though they never were). This required the widening of the bridge. The remaining piers were built over the next nine years. After a long delay beginning in 1588, due to political unrest and to the Wars of Religion, construction was resumed in 1599 under the reign of Henry IV. The bridge was opened to traffic in 1604 and completed in July 1606. It was inaugurated by Henry IV in 1607.
Like most bridges of its time, the Pont Neuf is constructed as a series of many short arch bridges, following Roman precedents. It was the first stone bridge in Paris not to support houses in addition to a thoroughfare, and was also fitted with pavements protecting pedestrians from mud and horses; pedestrians could also step aside into its bastions to let a bulky carriage pass. The decision not to include houses on the bridge can be traced back directly to Henry IV, who decided against their inclusion on the grounds that houses would impede a clear view of the Louvre, which the newly built galerie du bord de l'eau linked to the Tuileries Palace. | Pont Neuf | Wikipedia | 427 | 318262 | https://en.wikipedia.org/wiki/Pont%20Neuf | Technology | Bridges | null |
Pont Neuf was for a long time the widest bridge in Paris. It has undergone much repair and renovation work, including rebuilding of seven spans in the long arm and lowering of the roadway by changing the arches from an almost semi-circular to elliptical form (1848–1855), lowering of sidewalks and faces of the piers, spandrels, cornices and replacing crumbled corbels as closely to the originals as possible. In 1885, one of the piers of the short arm was undermined, removing the two adjacent arches, requiring them to be rebuilt and all the foundations strengthened.
A major restoration of the Pont Neuf was begun in 1994 and was completed in 2007, the year of its 400th anniversary.
Mascarons
The mascarons are the stone masks, 381 in number, each being different and which decorate the sides of the bridge. They represent the heads of forest and field divinities from ancient mythology, as well as satyrs and sylvains. They are copies of the originals attributed to the French Renaissance sculptor Germain Pilon (1525–1590), who also sculpted the tomb of King Henry II of France and Queen Catherine de'Medici in the Basilica of St Denis, five kilometers north of Paris. The mascarons remained in place until 1851–1854, when the bridge was completely rebuilt. At that time six of the original mascarons from the 16th century were placed in the Musée Carnavalet, along with eight molds of other originals. Eight other originals were first placed in the Musée de Cluny – Musée national du Moyen Âge, and are now in the French National Museum of the Renaissance in the Château d'Écouen. During their reconstruction, the Renaissance masks were replaced with copies made by noted 19th-century sculptors, including Hippolyte Maindron, Hubert Lavigne, Antoine-Louis Barye and Fontenelle. Fontenelle made 61 masks, which are found on the upstream side of the bridge between the right bank and the Île de la Cité.
Equestrian statue of Henry IV | Pont Neuf | Wikipedia | 419 | 318262 | https://en.wikipedia.org/wiki/Pont%20Neuf | Technology | Bridges | null |
At the point where the bridge crosses the Île de la Cité, there stands a bronze equestrian statue of king Henry IV, originally commissioned from Giambologna under the orders of Marie de Médicis, Henri's widow and Regent of France. After his death, Giambologna's assistant Pietro Tacca completed the statue, which was erected on its pedestal by Pietro Francavilla, in 1614. It was destroyed in 1792 during the French Revolution, but was rebuilt in 1818, following the restoration of the Bourbon monarchy. Commissioned from public donations, bronze for the new statue was obtained from a statue of Louis Charles Antoine Desaix and melted down. The new statue was cast from a mold made using a surviving cast of the original. Inside the statue, the new sculptor François-Frédéric Lemot put four boxes, containing a history of the life of Henry IV, a 17th-century parchment certifying the original statue, a document describing how the new statue was commissioned, and a list of people who contributed to a public subscription.
La Samaritaine
Between 1712 and 1719, replacing an earlier one, a large pump house was built on the bridge. It was decorated with an image of the Samaritan woman at the well. As a result, the structure (which included a carillon) was named La Samaritaine. Years after it was torn down (in 1813), Ernest Cognacq, a 19th-century merchant, set up a stand on the site and gradually grew his business to what became, in 1869, the department store La Samaritaine.
As the centre of Paris
Upon completion, Pont Neuf attracted throngs of visitors, many of whom used the bridge as a public square, conducting business, socializing, and taking in the view. One contemporary writer repeated a proverb about Pont Neuf to illustrate the variety of people who frequented the bridge, "one never crossed the Pont Neuf without meeting three things: a monk, a girl and a white horse."
All through the 18th century, the Pont Neuf was the center of Paris, lively with both crime and commerce: Czar Peter the Great, who came to study French civilization under the regency of the Duke d'Orleans, declared that he had found nothing more curious in Paris than the Pont Neuf; and, sixty years later, the philosopher Franklin wrote to his friends in America that he had not understood the Parisian character except in crossing the Pont Neuf. | Pont Neuf | Wikipedia | 503 | 318262 | https://en.wikipedia.org/wiki/Pont%20Neuf | Technology | Bridges | null |
In 1862, Édouard Fournier traced its history in his lively two-volume Histoire du Pont-Neuf. He describes how, even before it was completed (in 1607), gangs hid out in and around it, robbing and murdering people. It remained a dangerous place even as it became busier. For a long time, the bridge even had its own gallows.
This did not prevent people from congregating there, drawn by various stands and street performers (acrobats, fire-eaters, musicians, etc.). Charlatans and quacks of various sorts were also common, as well as the hustlers (shell game hucksters, etc.) and pickpockets often found in crowds – not to mention a lively trade in prostitution. Among the many businesses which, however, unofficially set up there, were several famous tooth pullers.
In 1701, Cotolendi quoted a letter supposedly written by a Sicilian tourist:
One finds on the Pont-Neuf an infinity of people who give tickets, some put fallen teeth back in, and others make crystal eyes; there are those who cure incurable illnesses; those who claim to have discovered the virtues of some powdered stones to white and to beautify the face. This one claims he makes old men young; there are those who remove wrinkles from the forehead and the eyes, who make wooden legs to repair the violence of bombs; finally everybody is so applied to work, so strongly and continually, that the devil can tempt no one but on Holidays and Sundays.
With its numerous sellers of pamphlets and satirical performers, it was also a center for social commentary:
In the 16th cent. the Pont-Neuf was the scene of the recitals of Tabarin, a famous satirist of the day, and it was long afterwards the favourite rendezvous of news-vendors, jugglers, showmen, loungers, and thieves. Any popular witticism in verse was long known as un Pont-Neuf. | Pont Neuf | Wikipedia | 411 | 318262 | https://en.wikipedia.org/wiki/Pont%20Neuf | Technology | Bridges | null |
In the seventeenth century, that bridge of memories, the old Pont Neuf of Paris, was the rendezvous of quacksalvers and mountebanks. Booths for the sale of various articles lined the sides of the bridge. People flocked there to see the sights, laugh, chat, make love and enjoy life as only Parisians can. Students and grisettes of the Quartier latin elbowed ladies and gentlemen of the court. Bourgeois families came to study the flippant manners of the aristocrats. Poodle clippers plied their trade; jugglers amused the quid nuncs with feats of dexterity; traveling dentists pulled teeth and sold balsams; clowns tumbled; and last, but not least, pickpockets lifted purses and silk handkerchiefs with impunity. Says Augustus J. C. Hare (Walks in Paris): "So central an artery is the Pont Neuf, that it used to be a saying with the Parisian police, that if, after watching three days, they did not see a man cross the bridge, he must have left Paris." One of the principal vendors of quack nostrums of the Pont Neuf was Montdor. He was aided by a buffoon named Tabarin, who made facetious replies to questions asked by his master, accompanied with laughable grimaces and grotesque gestures. The modern ringmaster and clown of the circus have similar scenes together, minus the selling of medicines.
Under Louis XV, thieves and entertainers were joined by recruiters, or "sellers of human flesh", who did their best to lure newcomers to Paris and others "with as much violence as the sale of Negros in the Congo". Silversmiths and other luxury businesses nearby (which gave their name to the Quai des Orfèvres) drew visitors as well.
One yearly event, held on the nearby Place Dauphine, prefigured the Salon des Refusés which would give rise to the Impressionists. During the celebration of the Corpus Christi (Fête-Dieu), the Place Dauphine hosted one of the most magnificent reposoirs (portable altars for the Host). | Pont Neuf | Wikipedia | 445 | 318262 | https://en.wikipedia.org/wiki/Pont%20Neuf | Technology | Bridges | null |
Along with all the rich silverwork and tapestries placed on it, some local silversmiths ordered paintings for these. This led to art dealers being asked to participate and, ultimately, to the newest talents being shown at the Petite Fête-Dieu (the Small Corpus Christi), a reduced version of the Corpus Christi holiday which took place eight days later. Though their canvases were only shown from six in the morning to noon, this became an important opportunity for unknown artists to draw attention. Among other things, this led to the painters there signing their work, as was not frequent in the Salon – which was not always an advantage when the work was publicly and loudly critiqued.
Showing works, which often had no pretense of a religious subject, they might then be noticed and find an entree into the official Academy. Chardin is one of the most famous painters to have started this way.
In 1720, a young man of about twenty-two, son of the man who maintained the king's billiards, displayed a canvas here showing an antique bas-relief. J.-B. Vanloo passed by, looked at the canvas for a long time, found great qualities there, and bought it. He wanted afterwards to know the young painter, encouraged him, gave him advice, of which the latter perhaps had no need, got him work, which was more useful, and eight years later, the unknown of the place Dauphine was his colleague at the Academy of Painting.... he was called Jean-Baptiste-Siméon Chardin.
The slow decline of the bridge's central role began in 1754: "Starting in 1754, the first year of the vogue, the madness of the boulevards, it was no longer the thing to talk about the Cours [the Champs-Elysées], and still less of this poor Pont-Neuf. To the Boulevard, at once, long live the Boulevard!". Still the bridge remained a lively place through the end of the century. With time, people became wary of its reputation and other changes subdued its atmosphere. In 1840, Lacroix wrote: "Once the pont Neuf was a perpetual fair; at present, it is just a bridge to be crossed without stopping."
Possible first photograph of human being | Pont Neuf | Wikipedia | 467 | 318262 | https://en.wikipedia.org/wiki/Pont%20Neuf | Technology | Bridges | null |
In 1838, Louis Daguerre produced his famous daguerreotype portrait of the View of the Boulevard du Temple, widely considered the first photograph where a human can be seen. However, between 1836 and 1837, Daguerre made several tests, in order to experiment with and perfect the new technique in an outdoor environment.
One surviving example is an image of the Pont Neuf and the equestrian statue of Henry IV, made possibly as early as 1836. On the lower-left side of the image, what appears to be a worker, or perhaps two, can be seen lying against the fence, in the shadow of the statue.
Christo's project
In 1985, after years of negotiation with the mayor of Paris, the art duo Christo and Jeanne-Claude wrapped the Pont Neuf.
Access | Pont Neuf | Wikipedia | 161 | 318262 | https://en.wikipedia.org/wiki/Pont%20Neuf | Technology | Bridges | null |
Moschidae is a family of pecoran even-toed ungulates, containing the musk deer (Moschus) and its extinct relatives. They are characterized by long "saber teeth" instead of horns, antlers or ossicones, modest size (Moschus only reaches ; other taxa were even smaller) and a lack of facial glands. While various Oligocene and Miocene pecorans were previously assigned to this family, recent studies find that most should be assigned to their own clades, although further research would need to confirm these traits. As a result, Micromeryx, Hispanomeryx, and Moschus are the only undisputed moschid members, making them known from at least 18 Ma. The group was abundant across Eurasia and North America during the Miocene, but afterwards declined to only the extant genus Moschus by the early Pleistocene.
Taxonomy and classification
Until the early 21st century, it was believed that the musk deer (family Moschidae) were an adjacent, sister-group to the "true deer" of the family Cervidae (caribou, moose, elk, and roughly 40–50 other species); however, a 2003 phylogenetic study by Alexandre Hassanin (of the National Museum of Natural History, France) and co., based on mitochondrial and nuclear analyses, revealed that Moschidae and Bovidae (antelope, cattle, goats, sheep), together, form a sister-clade to Cervidae. According to the study, the Cervidae diverged from the Bovidae-Moschidae clade roughly 27–28 million years ago. The following cladogram is based on this 2003 study:
After Prothero (2007)
Family Moschidae | Moschidae | Wikipedia | 364 | 318265 | https://en.wikipedia.org/wiki/Moschidae | Biology and health sciences | Other artiodactyla | Animals |
Musk deer can refer to any one, or all eight, of the species that make up Moschus, the only extant genus of the family Moschidae. Despite being commonly called deer, they are not true deer belonging to the family Cervidae, but rather their family is closely related to Bovidae, the group that contains antelopes, bovines, sheep, and goats. The musk deer family differs from cervids, or true deer, by lacking antlers and preorbital glands also, possessing only a single pair of teats, a gallbladder, a caudal gland, a pair of canine tusks and—of particular economic importance to humans—a musk gland.
Musk deer live mainly in forested and alpine scrub habitats in the mountains of South Asia, notably the Himalayas. Moschids, the proper term when referring to this type of deer rather than one/multiple species of musk deer, are entirely Asian in their present distribution, being extinct in Europe where the earliest musk deer are known to have existed from Oligocene deposits.
Characteristics
Musk deer resemble small deer, with a stocky build and hind legs longer than their front legs. They are about long, high at the shoulder, and weigh between . The feet of musk deer are adapted for climbing in rough terrain. Like the Chinese water deer, a cervid, they have no antlers, but the males do have enlarged upper canines, forming sabre-like tusks. The dental formula is similar to that of true deer:
The musk gland is found only in adult males. It lies in a sac located between the genitals and the umbilicus, and its secretions are most likely used to attract mates.
Musk deer are herbivores, living in hilly, forested environments, generally far from human habitation. Like true deer, they eat mainly leaves, flowers, and grasses, with some mosses and lichens. They are solitary animals and maintain well-defined territories, which they scent mark with their caudal glands. Musk deer are generally shy and either nocturnal or crepuscular. | Musk deer | Wikipedia | 446 | 318270 | https://en.wikipedia.org/wiki/Musk%20deer | Biology and health sciences | Other artiodactyla | Animals |
Males leave their territories during the rutting season and compete for mates, using their tusks as weapons. In order to indicate their area, musk deer build latrines. These locations can be used to identify the musk deer's existence, number, and preferred habitat in the wild. Female musk deer give birth to a single fawn after about 150–180 days. The newborn young are very small and essentially motionless for the first month of their lives, a feature that helps them remain hidden from predators.
Musk deer have been hunted for their scent glands, which are used in perfumes. The glands can fetch up to $45,000/kg on the black market. It is rumored that ancient royalty wore the scent of the musk deer, and that it is an aphrodisiac.
Population
Musk deer have a global population between 400,000 to 800,000 currently, however the exact count is undetermined. They are widely spread; however, their population density increases within China, Russia, and Mongolia. Musk deer are commonly found in China, and they are spread over 17 provinces. This population is mainly located around the Himalayas in southern Asia, southeast Asia, and eastern Asia. They are also found in a few spots in Russia. As of 2003, they became a protected species due to their declined overall population. Musk deer have many subspecies that have varying population sizes, within the overall total, and all are threatened. Over the past twenty years, the populations have been able to slightly recover due to the captive breeding of these animals, specifically in China. Musk deer populations are recovering due to the protocols and rules being set in place to protect the species. | Musk deer | Wikipedia | 346 | 318270 | https://en.wikipedia.org/wiki/Musk%20deer | Biology and health sciences | Other artiodactyla | Animals |
Habitat
The musk deer species is generally solitary and lives in the higher regions of mountain ranges, such as the Himalayas. The varying species' habitats include different atmospheres and necessary resources for their survival, while including similar universal resources. Musk deer population has been declining recently due to environmental and human factors. As a large-bodied mammal, they have great needs that are not able to be sustained due to habitat fragmentation. This species is largely protected due to the threat of extinction, due to the increase in illegal hunting. Illegal hunting has significantly decreased the population throughout many of the provinces musk deer occupy. Their habitats are being lost to colonization and deforestation and hunting for musk deer was on the rise. They were hunted for their distinct products that are very valuable in the market. Since then, the Chinese government has stepped in to regulate these issues. They have placed rules pertaining to the killing of musk deer and created havens for the deer to survive. To help with the declining numbers, the deforestation of their natural habitat should be stopped and new habitats should be invested in them. Global climate change has also driven the musk deer population down. The warmer climates result in the drive to higher elevations and latitudes. Global warming and habitat fragmentation are two causes for the population decrease.
Evolution
Musk deer are the only surviving members of the Moschidae, a family with a fossil record extending over 25 million years to the late Oligocene. The group was abundant across Eurasia and North America until the late Miocene, but underwent a substantial decline, with no Pliocene fossil record and Moschus the only genus since the Pleistocene. The oldest records of the genus Moschus are known from the Late Miocene (Turolian) of Lufeng, China.
Taxonomy
While they have been traditionally classified as members of the deer family (as the subfamily "Moschinae") and all the species were classified as one species (under Moschus moschiferus), recent studies have indicated that moschids are more closely related to bovids (antelope, goats, sheep and cattle). | Musk deer | Wikipedia | 428 | 318270 | https://en.wikipedia.org/wiki/Musk%20deer | Biology and health sciences | Other artiodactyla | Animals |
Chevrotains, or mouse-deer, are diminutive, even-toed ungulates that make up the family Tragulidae, and are the only living members of the infraorder Tragulina. The 10 extant species are placed in three genera, but several species also are known only from fossils. The extant species are found in forests in South and Southeast Asia; a single species, the water chevrotain, is found in the rainforests of Central and West Africa. In November 2019, conservation scientists announced that they had photographed silver-backed chevrotains (Tragulus versicolor) in a Vietnamese forest for the first time since the last confirmed sightings in 1990.
They are solitary, or live in loose groupings or pairs, and feed almost exclusively on plant material. Chevrotains are the smallest hoofed mammals in the world. The Asian species weigh between , while the African chevrotain is considerably larger, at . With an average length of and an average height of , the Java mouse-deer is the smallest surviving ungulate (hoofed) mammal, as well as the smallest artiodactyl (even-toed ungulate). Despite their common name of "mouse deer", they are not closely related to true deer.
Etymology
The word "chevrotain" comes from the Middle French word chevrot (kid or fawn), derived from chèvre (goat).
The single African species is consistently known as "chevrotain". The names "chevrotain" and "mouse-deer" have been used interchangeably among the Asian species, though recent authorities typically have preferred chevrotain for the species in the genus Moschiola and mouse-deer for the species in the genus Tragulus. Consequently, all species with pale-spotted or -striped upper parts are known as "chevrotain" and without are known as "mouse-deer". | Chevrotain | Wikipedia | 412 | 318319 | https://en.wikipedia.org/wiki/Chevrotain | Biology and health sciences | Other artiodactyla | Animals |
The Telugu name for the Indian spotted chevrotain is jarini pandi, which literally means "a deer and a pig". In Kannada, it is called barka (ಬರ್ಕ), in Malayalam, it is called kūramān, and the Konkani name for it is barinka. The Tamil term is sarukumāṉ "leaf-pile deer". The Sinhala name roughly translates to "mouse-like deer". This was used in the scientific name of the Sri Lankan spotted chevrotain, M. meminna.
Biology
The family was widespread and successful from the Oligocene (34 million years ago) through the Miocene (about 5 million years ago), but has remained almost unchanged over that time and remains as an example of an archaic ruminant type. They have four-chambered stomachs to ferment tough plant foods, but the third chamber is poorly developed. Unlike other artiodactyls, they lack an carotid rete, and so cannot heat exchange cool blood entering their brains, a thermoregulatory innovation that allows other artiodactyls to exploit hot arid habitats. Though most species feed exclusively on plant material, the water chevrotain occasionally takes insects and crabs or scavenges meat and fish. Like other ruminants, they lack upper incisors. They give birth to only a single young.
In other respects, however, they have primitive features, closer to nonruminants such as pigs. All species in the family lack antlers and horns, but both sexes have elongated canine teeth. These are especially prominent in males, where they project out on either side of the lower jaw, and are used in fights. Their legs are short and thin, which leave them lacking in agility, but also helps to maintain a smaller profile to aid in running through the dense foliage of their environments. Other pig-like features include the presence of four toes on each foot, the absence of facial scent glands, premolars with sharp crowns, and the form of their sexual behaviour and copulation. | Chevrotain | Wikipedia | 429 | 318319 | https://en.wikipedia.org/wiki/Chevrotain | Biology and health sciences | Other artiodactyla | Animals |
They are solitary or live in pairs. The young are weaned at three months of age, and reach sexual maturity between 5 and 10 months, depending on species. Parental care is relatively limited. Although they lack the types of scent glands found in most other ruminants, they do possess a chin gland for marking each other as mates or antagonists, and, in the case of the water chevrotain, anal and preputial glands for marking territory. Their territories are relatively small, on the order of , but neighbors generally ignore each other, rather than compete aggressively.
Some of the species show a remarkable affinity with water, often remaining submerged for prolonged periods to evade predators or other unwelcome intrusions. This has also lent support to the idea that whales evolved from water-loving creatures that looked like small deer.
Taxonomy
Tragulidae's placement within Artiodactyla can be represented in the following cladogram:
Traditionally, only four extant species were recognized in the family Tragulidae. In 2004, T. nigricans and T. versicolor were split from T. napu, and T. kanchil and T. williamsoni were split from T. javanicus. In 2005, M. indica and M. kathygre were split from M. meminna. With these changes, the 10 extant species are:
Family Tragulidae
Genus Hyemoschus
Water chevrotain, Hyemoschus aquaticus
Genus Moschiola
Indian spotted chevrotain, Moschiola indica
Sri Lankan spotted chevrotain, Moschiola meminna
Yellow-striped chevrotain, Moschiola kathygre
Genus Tragulus
Java mouse-deer, Tragulus javanicus
Lesser mouse-deer or kanchil, Tragulus kanchil
Greater mouse-deer, Tragulus napu
Philippine mouse-deer, Tragulus nigricans
Vietnam mouse-deer, Tragulus versicolor
Williamson's mouse-deer, Tragulus williamsoni
Ancient chevrotains
The Hypertragulidae were closely related to the Tragulidae.
The six extinct chevrotain genera include: | Chevrotain | Wikipedia | 459 | 318319 | https://en.wikipedia.org/wiki/Chevrotain | Biology and health sciences | Other artiodactyla | Animals |
Genus Dorcatherium
Dorcatherium minus from Pakistan
Dorcatherium majus from Pakistan
Dorcatherium naui, from Central Europe
Genus Dorcabune
Dorcabune anthracotherioides from Pakistan
Dorcabune nagrii from Pakistan
Genus Afrotragulus Sánchez, Quiralte, Morales and Pickford, 2010
Afrotragulus moruorotensis (previously "Dorcatherium" moruorotensis Pickford, 2001) (early Miocene) from Moruorot, Kenya
Afrotragulus parvus (previously "D." parvus Withworth 1958) (early Miocene) from Rusinga Island, Kenya
Genus Siamotragulus
Siamotragulus sanyathanai Thomas, Ginsburg, Hintong and Suteethorn, 1990 (middle Miocene) from Lampang, Thailand
Siamotragulus haripounchai Mein and Ginsburg, 1997 (Miocene) from Lamphun, Thailand
Genus Yunnanotherium
Genus Archaeotragulus
Archaeotragulus krabiensis Metais, Chaimanee, Jaeger and Ducrocq, 2001 (late Eocene) from Krabi, Thailand
The extinct chevrotains might also include
Genus Krabitherium
Krabitherium waileki Metais, Chaimanee, Jaeger and Ducrocq, 2007 (late Eocene) from Krabi, Thailand
Genus Nalameryx
Nalameryx savagei
Nalameryx sulaimani
Mythology
According to the Malay Annals, King Parameswara, seeking a place to found a new city, came to a place where he saw a mouse deer (kancil in Malay) kicking his hunting dog into the river. He thought this boded well, remarking, 'this place is excellent, even the mouse deer is formidable; it is best that we establish a kingdom here'. He then founded there the city of Malacca. In memory of this founding legend, the coat of arms of Malacca depicts two mouse deer.
The mouse deer or Sang Kancil is also a clever character from several Malay folktales. | Chevrotain | Wikipedia | 436 | 318319 | https://en.wikipedia.org/wiki/Chevrotain | Biology and health sciences | Other artiodactyla | Animals |
A crane is a machine used to move materials both vertically and horizontally, utilizing a system of a boom, hoist, wire ropes or chains, and sheaves for lifting and relocating heavy objects within the swing of its boom. The device uses one or more simple machines, such as the lever and pulley, to create mechanical advantage to do its work. Cranes are commonly employed in transportation for the loading and unloading of freight, in construction for the movement of materials, and in manufacturing for the assembling of heavy equipment.
The first known crane machine was the shaduf, a water-lifting device that was invented in ancient Mesopotamia (modern Iraq) and then appeared in ancient Egyptian technology. Construction cranes later appeared in ancient Greece, where they were powered by men or animals (such as donkeys), and used for the construction of buildings. Larger cranes were later developed in the Roman Empire, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbour cranes were introduced to load and unload ships and assist with their construction—some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron, iron and steel took over with the coming of the Industrial Revolution.
For many centuries, power was supplied by the physical exertion of men or animals, although hoists in watermills and windmills could be driven by the harnessed natural power. The first mechanical power was provided by steam engines, the earliest steam crane being introduced in the 18th or 19th century, with many remaining in use well into the late 20th century. Modern cranes usually use internal combustion engines or electric motors and hydraulic systems to provide a much greater lifting capability than was previously possible, although manual cranes are still utilized where the provision of power would be uneconomic.
There are many different types of cranes, each tailored to a specific use. Sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes, used for constructing high buildings. Mini-cranes are also used for constructing high buildings, to facilitate constructions by reaching tight spaces. Large floating cranes are generally used to build oil rigs and salvage sunken ships.
Some lifting machines do not strictly fit the above definition of a crane, but are generally known as cranes, such as stacker cranes and loader cranes.
Etymology
Cranes were so called from the resemblance to the long neck of the bird, cf. , French grue.
History | Crane (machine) | Wikipedia | 501 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Ancient Near East
The first type of crane machine was the shadouf, which had a lever mechanism and was used to lift water for irrigation. It was invented in Mesopotamia (modern Iraq) circa 3000 BC. The shadouf subsequently appeared in ancient Egyptian technology circa 2000 BC.
Ancient Greece
A crane for lifting heavy loads was developed by the Ancient Greeks in the late 6th century BC. The archaeological record shows that no later than c. 515 BC distinctive cuttings for both lifting tongs and lewis irons begin to appear on stone blocks of Greek temples. Since these holes point at the use of a lifting device, and since they are to be found either above the center of gravity of the block, or in pairs equidistant from a point over the center of gravity, they are regarded by archaeologists as the positive evidence required for the existence of the crane.
The introduction of the winch and pulley hoist soon led to a widespread replacement of ramps as the main means of vertical motion. For the next 200 years, Greek building sites witnessed a sharp reduction in the weights handled, as the new lifting technique made the use of several smaller stones more practical than fewer larger ones. In contrast to the archaic period with its pattern of ever-increasing block sizes, Greek temples of the classical age like the Parthenon invariably featured stone blocks weighing less than 15–20 metric tons. Also, the practice of erecting large monolithic columns was practically abandoned in favour of using several column drums.
Although the exact circumstances of the shift from the ramp to the crane technology remain unclear, it has been argued that the volatile social and political conditions of Greece were more suitable to the employment of small, professional construction teams than of large bodies of unskilled labour, making the crane preferable to the Greek polis over the more labour-intensive ramp which had been the norm in the autocratic societies of Egypt or Assyria.
The first unequivocal literary evidence for the existence of the compound pulley system appears in the Mechanical Problems (Mech. 18, 853a32–853b13) attributed to Aristotle (384–322 BC), but perhaps composed at a slightly later date. Around the same time, block sizes at Greek temples began to match their archaic predecessors again, indicating that the more sophisticated compound pulley must have found its way to Greek construction sites by then.
Roman Empire | Crane (machine) | Wikipedia | 484 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
The heyday of the crane in ancient times came during the Roman Empire, when construction activity soared and buildings reached enormous dimensions. The Romans adopted the Greek crane and developed it further. There is much available information about their lifting techniques, thanks to rather lengthy accounts by the engineers Vitruvius (De Architectura 10.2, 1–10) and Heron of Alexandria (Mechanica 3.2–5). There are also two surviving reliefs of Roman treadwheel cranes, with the Haterii tombstone from the late first century AD being particularly detailed.
The simplest Roman crane, the trispastos, consisted of a single-beam jib, a winch, a rope, and a block containing three pulleys. Having thus a mechanical advantage of 3:1, it has been calculated that a single man working the winch could raise (3 pulleys x = 150), assuming that represent the maximum effort a man can exert over a longer time period. Heavier crane types featured five pulleys (pentaspastos) or, in case of the largest one, a set of three by five pulleys (Polyspastos) and came with two, three or four masts, depending on the maximum load. The polyspastos, when worked by four men at both sides of the winch, could readily lift (3 ropes x 5 pulleys x 4 men x = ). If the winch was replaced by a treadwheel, the maximum load could be doubled to at only half the crew, since the treadwheel possesses a much bigger mechanical advantage due to its larger diameter. This meant that, in comparison to the construction of the ancient Egyptian pyramids, where about 50 men were needed to move a 2.5 ton stone block up the ramp ( per person), the lifting capability of the Roman polyspastos proved to be 60 times higher ( per person). | Crane (machine) | Wikipedia | 391 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
However, numerous extant Roman buildings which feature much heavier stone blocks than those handled by the polyspastos indicate that the overall lifting capability of the Romans went far beyond that of any single crane. At the temple of Jupiter at Baalbek, for instance, the architrave blocks weigh up to 60 tons each, and one corner cornice block even over 100 tons, all of them raised to a height of about . In Rome, the capital block of Trajan's Column weighs 53.3 tons, which had to be lifted to a height of about (see construction of Trajan's Column).
It is assumed that Roman engineers lifted these extraordinary weights by two measures (see picture below for comparable Renaissance technique): First, as suggested by Heron, a lifting tower was set up, whose four masts were arranged in the shape of a quadrangle with parallel sides, not unlike a siege tower, but with the column in the middle of the structure (Mechanica 3.5). Second, a multitude of capstans were placed on the ground around the tower, for, although having a lower leverage ratio than treadwheels, capstans could be set up in higher numbers and run by more men (and, moreover, by draught animals). This use of multiple capstans is also described by Ammianus Marcellinus (17.4.15) in connection with the lifting of the Lateranense obelisk in the Circus Maximus (c. 357 AD). The maximum lifting capability of a single capstan can be established by the number of lewis iron holes bored into the monolith. In case of the Baalbek architrave blocks, which weigh between 55 and 60 tons, eight extant holes suggest an allowance of 7.5 ton per lewis iron, that is per capstan. Lifting such heavy weights in a concerted action required a great amount of coordination between the work groups applying the force to the capstans. | Crane (machine) | Wikipedia | 399 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Middle Ages
During the High Middle Ages, the treadwheel crane was reintroduced on a large scale after the technology had fallen into disuse in western Europe with the demise of the Western Roman Empire. The earliest reference to a treadwheel (magna rota) reappears in archival literature in France about 1225, followed by an illuminated depiction in a manuscript of probably also French origin dating to 1240. In navigation, the earliest uses of harbor cranes are documented for Utrecht in 1244, Antwerp in 1263, Bruges in 1288 and Hamburg in 1291, while in England the treadwheel is not recorded before 1331.
Generally, vertical transport could be done more safely and inexpensively by cranes than by customary methods. Typical areas of application were harbors, mines, and, in particular, building sites where the treadwheel crane played a pivotal role in the construction of the lofty Gothic cathedrals. Nevertheless, both archival and pictorial sources of the time suggest that newly introduced machines like treadwheels or wheelbarrows did not completely replace more labor-intensive methods like ladders, hods and handbarrows. Rather, old and new machinery continued to coexist on medieval construction sites and harbors.
Apart from treadwheels, medieval depictions also show cranes to be powered manually by windlasses with radiating spokes, cranks and by the 15th century also by windlasses shaped like a ship's wheel. To smooth out irregularities of impulse and get over 'dead-spots' in the lifting process flywheels are known to be in use as early as 1123.
The exact process by which the treadwheel crane was reintroduced is not recorded, although its return to construction sites has undoubtedly to be viewed in close connection with the simultaneous rise of Gothic architecture. The reappearance of the treadwheel crane may have resulted from a technological development of the windlass from which the treadwheel structurally and mechanically evolved. Alternatively, the medieval treadwheel may represent a deliberate reinvention of its Roman counterpart drawn from Vitruvius' De architectura which was available in many monastic libraries. Its reintroduction may have been inspired, as well, by the observation of the labor-saving qualities of the waterwheel with which early treadwheels shared many structural similarities. | Crane (machine) | Wikipedia | 464 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Structure and placement
The medieval treadwheel was a large wooden wheel turning around a central shaft with a treadway wide enough for two workers walking side by side. While the earlier 'compass-arm' wheel had spokes directly driven into the central shaft, the more advanced "clasp-arm" type featured arms arranged as chords to the wheel rim, giving the possibility of using a thinner shaft and providing thus a greater mechanical advantage.
Contrary to a popularly held belief, cranes on medieval building sites were neither placed on the extremely lightweight scaffolding used at the time nor on the thin walls of the Gothic churches which were incapable of supporting the weight of both hoisting machine and load. Rather, cranes were placed in the initial stages of construction on the ground, often within the building. When a new floor was completed, and massive tie beams of the roof connected the walls, the crane was dismantled and reassembled on the roof beams from where it was moved from bay to bay during construction of the vaults. Thus, the crane "grew" and "wandered" with the building with the result that today all extant construction cranes in England are found in church towers above the vaulting and below the roof, where they remained after building construction for bringing material for repairs aloft.
Less frequently, medieval illuminations also show cranes mounted on the outside of walls with the stand of the machine secured to putlogs.
Mechanics and operation
In contrast to modern cranes, medieval cranes and hoists — much like their counterparts in Greece and Rome — were primarily capable of a vertical lift, and not used to move loads for a considerable distance horizontally as well. Accordingly, lifting work was organized at the workplace in a different way than today. In building construction, for example, it is assumed that the crane lifted the stone blocks either from the bottom directly into place, or from a place opposite the centre of the wall from where it could deliver the blocks for two teams working at each end of the wall. Additionally, the crane master who usually gave orders at the treadwheel workers from outside the crane was able to manipulate the movement laterally by a small rope attached to the load. Slewing cranes which allowed a rotation of the load and were thus particularly suited for dockside work appeared as early as 1340. While ashlar blocks were directly lifted by sling, lewis or devil's clamp (German Teufelskralle), other objects were placed before in containers like pallets, baskets, wooden boxes or barrels. | Crane (machine) | Wikipedia | 502 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
It is noteworthy that medieval cranes rarely featured ratchets or brakes to forestall the load from running backward. This curious absence is explained by the high friction force exercised by medieval tread-wheels which normally prevented the wheel from accelerating beyond control.
Harbour usage
According to the "present state of knowledge" unknown in antiquity, stationary harbor cranes are considered a new development of the Middle Ages. The typical harbor crane was a pivoting structure equipped with double treadwheels. These cranes were placed docksides for the loading and unloading of cargo where they replaced or complemented older lifting methods like see-saws, winches and yards.
Two different types of harbor cranes can be identified with a varying geographical distribution: While gantry cranes, which pivoted on a central vertical axle, were commonly found at the Flemish and Dutch coastside, German sea and inland harbors typically featured tower cranes where the windlass and treadwheels were situated in a solid tower with only jib arm and roof rotating. Dockside cranes were not adopted in the Mediterranean region and the highly developed Italian ports where authorities continued to rely on the more labor-intensive method of unloading goods by ramps beyond the Middle Ages.
Unlike construction cranes where the work speed was determined by the relatively slow progress of the masons, harbor cranes usually featured double treadwheels to speed up loading. The two treadwheels whose diameter is estimated to be 4 m or larger were attached to each side of the axle and rotated together. Their capacity was 2–3 tons, which apparently corresponded to the customary size of marine cargo. Today, according to one survey, fifteen treadwheel harbor cranes from pre-industrial times are still extant throughout Europe. Some harbour cranes were specialised at mounting masts to newly built sailing ships, such as in Gdańsk, Cologne and Bremen. Beside these stationary cranes, floating cranes, which could be flexibly deployed in the whole port basin came into use by the 14th century. | Crane (machine) | Wikipedia | 392 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
A sheer hulk (or shear hulk) was used in shipbuilding and repair as a floating crane in the days of sailing ships, primarily to place the lower masts of a ship under construction or repair. Booms known as sheers were attached to the base of a hulk's lower masts or beam, supported from the top of those masts. Blocks and tackle were then used in such tasks as placing or removing the lower masts of the vessel under construction or repair. These lower masts were the largest and most massive single timbers aboard a ship, and erecting them without the assistance of either a sheer hulk or land-based masting sheer was extremely difficult.
The concept of sheer hulks originated with the Royal Navy in the 1690s, and persisted in Britain until the early nineteenth century. Most sheer hulks were decommissioned warships; Chatham, built in 1694, was the first of only three purpose-built vessels. There were at least six sheer hulks in service in Britain at any time throughout the 1700s. The concept spread to France in the 1740s with the commissioning of a sheer hulk at the port of Rochefort.
Early modern age
A lifting tower similar to that of the ancient Romans was used to great effect by the Renaissance architect Domenico Fontana in 1586 to relocate the 361 t heavy Vatican obelisk in Rome. From his report, it becomes obvious that the coordination of the lift between the various pulling teams required a considerable amount of concentration and discipline, since, if the force was not applied evenly, the excessive stress on the ropes would make them rupture.
Cranes were also used domestically during this period. The chimney or fireplace crane was used to swing pots and kettles over the fire and the height was adjusted by a trammel.
Industrial revolution
With the onset of the Industrial Revolution the first modern cranes were installed at harbours for loading cargo. In 1838, the industrialist and businessman William Armstrong designed a water-powered hydraulic crane. His design used a ram in a closed cylinder that was forced down by a pressurized fluid entering the cylinder and a valve regulated the amount of fluid intake relative to the load on the crane. This mechanism, the hydraulic jigger, then pulled on a chain to lift the load. | Crane (machine) | Wikipedia | 451 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
In 1845 a scheme was set in motion to provide piped water from distant reservoirs to the households of Newcastle. Armstrong was involved in this scheme and he proposed to Newcastle Corporation that the excess water pressure in the lower part of town could be used to power one of his hydraulic cranes for the loading of coal onto barges at the Quayside. He claimed that his invention would do the job faster and more cheaply than conventional cranes. The corporation agreed to his suggestion, and the experiment proved so successful that three more hydraulic cranes were installed on the Quayside.
The success of his hydraulic crane led Armstrong to establish the Elswick works at Newcastle, to produce his hydraulic machinery for cranes and bridges in 1847. His company soon received orders for hydraulic cranes from Edinburgh and Northern Railways and from Liverpool Docks, as well as for hydraulic machinery for dock gates in Grimsby. The company expanded from a workforce of 300 and an annual production of 45 cranes in 1850, to almost 4,000 workers producing over 100 cranes per year by the early 1860s.
Armstrong spent the next few decades constantly improving his crane design; his most significant innovation was the hydraulic accumulator. Where water pressure was not available on site for the use of hydraulic cranes, Armstrong often built high water towers to provide a supply of water at pressure. However, when supplying cranes for use at New Holland on the Humber Estuary, he was unable to do this, because the foundations consisted of sand. He eventually produced the hydraulic accumulator, a cast-iron cylinder fitted with a plunger supporting a very heavy weight. The plunger would slowly be raised, drawing in water, until the downward force of the weight was sufficient to force the water below it into pipes at great pressure. This invention allowed much larger quantities of water to be forced through pipes at a constant pressure, thus increasing the crane's load capacity considerably.
One of his cranes, commissioned by the Italian Navy in 1883 and in use until the mid-1950s, is still standing in Venice, where it is now in a state of disrepair.
Mechanical principles
There are three major considerations in the design of cranes. First, the crane must be able to lift the weight of the load; second, the crane must not topple; third, the crane must not fail structurally. | Crane (machine) | Wikipedia | 456 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Stability
For stability, the sum of all moments about the base of the crane must be close to zero so that the crane does not overturn. In practice, the magnitude of load that is permitted to be lifted (called the "rated load" in the US) is some value less than the load that will cause the crane to tip, thus providing a safety margin.
Under United States standards for mobile cranes, the stability-limited rated load for a crawler crane is 75% of the tipping load. The stability-limited rated load for a mobile crane supported on outriggers is 85% of the tipping load. These requirements, along with additional safety-related aspects of crane design, are established by the American Society of Mechanical Engineers in the volume ASME B30.5-2018 Mobile and Locomotive Cranes.
Standards for cranes mounted on ships or offshore platforms are somewhat stricter because of the dynamic load on the crane due to vessel motion. Additionally, the stability of the vessel or platform must be considered.
For stationary pedestal or kingpost mounted cranes, the moment produced by the boom, jib, and load is resisted by the pedestal base or kingpost. Stress within the base must be less than the yield stress of the material or the crane will fail.
Dynamic Lift Factor
Overview
The dynamic lift factor (DLF), also known as the design dynamic factor, is a critical parameter in the crane design and operation. It accounts for the dynamic effects that can increase the load on a crane's structure and components during lifting operations. These effects include:
Hoisting acceleration and deceleration of the load, which is a significant factor;
Crane movement such as slewing or luffing;
Load swinging;
Wind forces acting on the crane, the load and the rigging; and
Operator error or other unexpected events.
The DLF for a new crane design can be determined with analytical calculations and mathematical models following the relevant design specifications. If available, data from previous tests of similar crane types can be used to estimate the DLF. More sophisticated methods, such as finite element analysis or other simulation techniques, may also be used to model the crane's behavior under various loading conditions, as deemed appropriate by the designer or certifying authority.To verify the actual DLF, control load tests can be conducted on the completed crane using instrumentation such as load cells, accelerometers, and strain gauges. This process is usually part of the crane's type approval. | Crane (machine) | Wikipedia | 501 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
In offshore lifting, where the crane and/or lifted object are on a floating vessel, the DLF is higher compared to onshore lifts because of the additional movement caused by wave action. This motion introduces additional acceleration forces and necessitates increased hoisting and lowering speeds to minimize the risk of repeated collisions when the load is near the deck. Additionally, the DLF increases further when lifting objects that are underwater or going through the splash zone. The wind speeds tend to be higher than onshore as well.
Though actual DLF values are determined through crane tests under representative operational conditions, design specifications can be used for guidance. The values vary according to the specification, which reflects the type of crane and its usage. Here are some example typical values:
Jib cranes typically have a lower DLF () compared to traveling gantry cranes () because they are stiffer;
For grab cranes, the DLF can increase by 20% to 30% reflecting the shock loads caused by the release of the lifted material; and
The DLF generally decreases as the mass of the lifted object increases, as cranes tend to operate at lower velocities with heavier loads to ensure safety and stability. For offshore lifts, the DLF typically decreases from 1.3 at 100 tonnes to 1.1 at 2500 tonnes.
Formulas
The methods for determining the DLF vary in the different crane specifications. The following formulas are examples from one specification.
The working load (suspended load) is the total weight that a crane is designed to safely lift under normal operating conditions. It is
where
is the working load,
is the acceleration of gravity,
is the maximum lifted mass, which is also called the crane working load limit (WLL) or safe working load (SWL), and
is the mass of lifting appliances or parts of the crane that move with the lifted mass.
The DLF is then used as a multiplier to determine the force applied to the crane structure and componentswhere
is the design force, and
is the DLF.
The DLF can then be calculated usingwhere
is relative velocity between lifted object and hook at the time of pick-up, and
is the stiffness of the crane system at the hook.
The relative velocity is dependent on the crane's operational requirements and the system stiffness at the hook can be determined by calculation or load deflection tests.
Types
The crane types outlined in this section are categorized based on their primary area of application: | Crane (machine) | Wikipedia | 499 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Construction
Truck-mounted
Loader
Telescopic
Rough terrain
All terrain
Crawler
Pick and carry
Carry deck
Telescopic handler
Block setting
Tower
Climbing crane
Cargo Handling
Reach stacker
Sidelifter
Straddle carrier
Industrial
Ring
Hammerhead
Level luffing
Overhead
Gantry
Jib
Bulk handling
Stacker
Wind turbine installation vessel
Marine
Floating
Deck
Other Types
Railroad
Aerial
Construction
Truck-mounted
The most basic truck-mounted crane configuration is a "boom truck" or "lorry loader", which features a rear-mounted rotating telescopic-boom crane mounted on a commercial truck chassis.
Larger, heavier duty, purpose-built "truck-mounted" cranes are constructed in two parts: the carrier, often called the lower, and the lifting component, which includes the boom, called the upper. These are mated together through a turntable, allowing the upper to swing from side to side. These modern hydraulic truck cranes are usually single-engine machines, with the same engine powering the undercarriage and the crane. The upper is usually powered via hydraulics run through the turntable from the pump mounted on the lower. In older model designs of hydraulic truck cranes, there were two engines. One in the lower pulled the crane down the road and ran a hydraulic pump for the outriggers and jacks. The one in the upper ran the upper through a hydraulic pump of its own. Many older operators favor the two-engine system due to leaking seals in the turntable of aging newer design cranes. Hiab invented the world's first hydraulic truck mounted crane in 1947. The name, Hiab, comes from the commonly used abbreviation of Hydrauliska Industri AB, a company founded in Hudiksvall, Sweden 1944 by Eric Sundin, a ski manufacturer who saw a way to utilize a truck's engine to power loader cranes through the use of hydraulics. | Crane (machine) | Wikipedia | 378 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Generally, these cranes are able to travel on highways, eliminating the need for special equipment to transport the crane unless weight or other size constrictions are in place such as local laws. If this is the case, most larger cranes are equipped with either special trailers to help spread the load over more axles or are able to disassemble to meet requirements. An example is counterweights. Often a crane will be followed by another truck hauling the counterweights that are removed for travel. In addition some cranes are able to remove the entire upper. However, this is usually only an issue in a large crane and mostly done with a conventional crane such as a Link-Belt HC-238. When working on the job site, outriggers are extended horizontally from the chassis then vertically to level and stabilize the crane while stationary and hoisting. Many truck cranes have slow-travelling capability (a few miles per hour) while suspending a load. Great care must be taken not to swing the load sideways from the direction of travel, as most anti-tipping stability then lies in the stiffness of the chassis suspension. Most cranes of this type also have moving counterweights for stabilization beyond that provided by the outriggers. Loads suspended directly aft are the most stable, since most of the weight of the crane acts as a counterweight. Factory-calculated charts (or electronic safeguards) are used by crane operators to determine the maximum safe loads for stationary (outriggered) work as well as (on-rubber) loads and travelling speeds.
Truck cranes range in lifting capacity from about to about . Although most only rotate about 180 degrees, the more expensive truck mounted cranes can turn a full 360 degrees.
Loader
A loader crane (also called a knuckle-boom crane or articulating crane) is an hydraulically powered articulated arm fitted to a truck or trailer, and is used for loading/unloading the vehicle cargo. The numerous jointed sections can be folded into a small space when the crane is not in use. One or more of the sections may be telescopic. Often the crane will have a degree of automation and be able to unload or stow itself without an operator's instruction.
Unlike most cranes, the operator must move around the vehicle to be able to view his load; hence modern cranes may be fitted with a portable cabled or radio-linked control system to supplement the crane-mounted hydraulic control levers. | Crane (machine) | Wikipedia | 503 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
In the United Kingdom and Canada, this type of crane is often known colloquially as a "Hiab", partly because this manufacturer invented the loader crane and was first into the UK market, and partly because the distinctive name was displayed prominently on the boom arm.
A rolloader crane is a loader crane mounted on a chassis with wheels. This chassis can ride on the trailer. Because the crane can move on the trailer, it can be a light crane, so the trailer is allowed to transport more goods.
Telescopic
A telescopic crane has a boom that consists of a number of tubes fitted one inside the other. A hydraulic cylinder or other powered mechanism extends or retracts the tubes to increase or decrease the total length of the boom. These types of booms are often used for short term construction projects, rescue jobs, lifting boats in and out of the water, etc. The relative compactness of telescopic booms makes them adaptable for many mobile applications.
Though not all telescopic cranes are mobile cranes, many of them are truck-mounted.
A telescopic tower crane has a telescopic mast and often a superstructure (jib) on top so that it functions as a tower crane. Some telescopic tower cranes also have a telescopic jib.
Rough terrain
A rough terrain crane has a boom mounted on an undercarriage atop four rubber tires that is designed for off-road pick-and-carry operations. Outriggers are used to level and stabilize the crane for hoisting.
These telescopic cranes are single-engine machines, with the same engine powering the undercarriage and the crane, similar to a crawler crane. The engine is usually mounted in the undercarriage rather than in the upper, as with crawler crane. Most have 4 wheel drive and 4 wheel steering for traversing tighter and slicker terrain than a standard truck crane, with less site prep.
All-terrain
An all-terrain crane is a hybrid combining the roadability of a truck-mounted and on-site maneuverability of a rough-terrain crane. It can both travel at speed on public roads and maneuver on rough terrain at the job site using all-wheel and crab steering.
AT's have 2–12 axles and are designed for lifting loads up to . | Crane (machine) | Wikipedia | 471 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Crawler
Main article: Lattice boom crawler crane
A crawler crane has its boom mounted on an undercarriage fitted with a set of crawler tracks that provide both stability and mobility. Crawler cranes range in lifting capacity from about as seen from the XGC88000 crawler crane.
The main advantage of a crawler crane is its ready mobility and use, since the crane is able to operate on sites with minimal improvement and stable on its tracks without outriggers. Wide tracks spread the weight out over a great area and are far better than wheels at traversing soft ground without sinking in. A crawler crane is also capable of traveling with a load. Its main disadvantage is its weight, making it difficult and expensive to transport. Typically a large crawler must be disassembled at least into boom and cab and moved by trucks, rail cars or ships to its next location.
Pick and carry
A pick and carry crane is similar to a mobile crane in that is designed to travel on public roads; however, pick and carry cranes have no stabiliser legs or outriggers and are designed to lift the load and carry it to its destination, within a small radius, then be able to drive to the next job. Pick and carry cranes are popular in Australia, where large distances are encountered between job sites. One popular manufacturer in Australia was Franna, who have since been bought by Terex, and now all pick and carry cranes are commonly called "Frannas", even though they may be made by other manufacturers. Nearly every medium- and large-sized crane company in Australia has at least one and many companies have fleets of these cranes. The capacity range is between as a maximum lift, although this is much less as the load gets further from the front of the crane. Pick and carry cranes have displaced the work usually completed by smaller truck cranes, as the set-up time is much quicker. Many steel fabrication yards also use pick and carry cranes, as they can "walk" with fabricated steel sections and place these where required with relative ease.
Smaller pick and carry cranes may be based on an articulated tractor chassis, with the boom mounted over the front wheels. In Australia these are popularly known as "wobbly cranes". | Crane (machine) | Wikipedia | 455 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Carry deck
A carry deck crane is a small 4 wheel crane with a 360-degree rotating boom placed right in the centre and an operators cab located at one end under this boom. The rear section houses the engine and the area above the wheels is a flat deck. Very much an American invention the Carry deck can hoist a load in a confined space and then load it on the deck space around the cab or engine and subsequently move to another site. The Carry Deck principle is the American version of the pick and carry crane and both allow the load to be moved by the crane over short distances.
Telescopic handler
Telescopic handlers are forklift-like trucks that have a set of forks mounted on a telescoping extendable boom like a crane. Early telescopic handlers only lifted in one direction and did not rotate; however, several of the manufacturers have designed telescopic handlers that rotate 360 degrees through a turntable and these machines look almost identical to the Rough Terrain Crane. These new 360-degree telescopic handler/crane models have outriggers or stabiliser legs that must be lowered before lifting; however, their design has been simplified so that they can be more quickly deployed. These machines are often used to handle pallets of bricks and install frame trusses on many new building sites and they have eroded much of the work for small telescopic truck cranes. Many of the world's armed forces have purchased telescopic handlers and some of these are the much more expensive fully rotating types. Their off-road capability and their on site versatility to unload pallets using forks, or lift like a crane make them a valuable piece of machinery.
Block-setting crane
A block-setting crane is a form of crane. They were used for installing the large stone blocks used to build breakwaters, moles and stone piers. | Crane (machine) | Wikipedia | 382 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Tower
Tower cranes are a modern form of balance crane that consist of the same basic parts. Fixed to the ground on a concrete slab (and sometimes attached to the sides of structures), tower cranes often give the best combination of height and lifting capacity and are used in the construction of tall buildings. The base is then attached to the mast which gives the crane its height. Further, the mast is attached to the slewing unit (gear and motor) that allows the crane to rotate. On top of the slewing unit there are three main parts which are: the long horizontal jib (working arm), shorter counter-jib, and the operator's cab.
Optimization of tower crane location in the construction sites has an important effect on material transportation costs of a project, but site operators need to ensure they assess where the jib will oversail the property of other landowners and tenants as it rotates over the site. Under English law a landowner also owns the airspace above their property and developers will need to agree terms with adjacent property owners before oversailing their land.
The long horizontal jib is the part of the crane that carries the load. The counter-jib carries a counterweight, usually of concrete blocks, while the jib suspends the load to and from the center of the crane. The crane operator either sits in a cab at the top of the tower or controls the crane by radio remote control from the ground. In the first case the operator's cab is most usually located at the top of the tower attached to the turntable, but can be mounted on the jib, or partway down the tower. The lifting hook is operated by the crane operator using electric motors to manipulate wire rope cables through a system of sheaves. The hook is located on the long horizontal arm to lift the load which also contains its motor.
In order to hook and unhook the loads, the operator usually works in conjunction with a signaller (known as a "dogger", "rigger" or "swamper"). They are most often in radio contact, and always use hand signals. The rigger or dogger directs the schedule of lifts for the crane, and is responsible for the safety of the rigging and loads.
Tower cranes can achieve a height under hook of over 100 metres. | Crane (machine) | Wikipedia | 471 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Components
Tower cranes are used extensively in construction and other industry to hoist and move materials. There are many types of tower cranes. Although they are different in type, the main parts are the same, as follows:
Mast: the main supporting tower of the crane. It is made of steel trussed sections that are connected together during installation.
Slewing unit: the slewing unit sits at the top of the mast. This is the engine that enables the crane to rotate.
Operating cabin: on most tower cranes the operating cabin sits just above the slewing unit. It contains the operating controls, load-movement indicator system (LMI), scale, anemometer, etc.
Jib: the jib, or operating arm, extends horizontally from the crane. A "luffing" jib is able to move up and down; a fixed jib has a rolling trolley car that runs along the underside to move loads horizontally.
Counter jib: holds counterweights, hoist motor, hoist drum and the electronics.
Hoist winch: the hoist winch assembly consists of the hoist winch (motor, gearbox, hoist drum, hoist rope, and brakes), the hoist motor controller, and supporting components, such as the platform. Many tower cranes have transmissions with two or more speeds.
Hook: the hook is used to connect the material to the crane, suspended from the hoist rope either at the tip (on luffing jib cranes) or routed through the trolley (on hammerhead cranes).
Weights: Large, moveable concrete counterweights are mounted toward the rear of the counterdeck, to compensate for the weight of the goods lifted and keep the center of gravity over the supporting tower.
Assembly
A tower crane is usually assembled by a telescopic jib (mobile) crane of greater reach (also see "self-erecting crane" below) and in the case of tower cranes that have risen while constructing very tall skyscrapers, a smaller crane (or derrick) will often be lifted to the roof of the completed tower to dismantle the tower crane afterwards, which may be more difficult than the installation.
Tower cranes can be operated by remote control, removing the need for the crane operator to sit in a cab atop the crane. | Crane (machine) | Wikipedia | 469 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Operation
Each model and distinctive style of tower crane has a predetermined lifting chart that can be applied to any radii available, depending on its configuration. Similar to a mobile crane, a tower crane may lift an object of far greater mass closer to its center of rotation than at its maximum radius. An operator manipulates several levers and pedals to control each function of the crane.
Safety
When a tower crane is used in proximity to buildings, roads, power lines, or other tower cranes, a tower crane anti-collision system is used. This operator support system reduces the risk of a dangerous interaction occurring between a tower crane and another structure.
In some countries, such as France, tower crane anti-collision systems are mandatory.
Self-erecting tower cranes
Generally a type of pedestrian operated tower crane, self-erecting tower cranes are transported as a single unit and can be assembled by a qualified technician without the assistance of a larger mobile crane. They are bottom slewing cranes that stand on outriggers, have no counter jib, have their counterweights and ballast at the base of the mast, cannot climb themselves, have a reduced capacity compared to standard tower cranes, and seldom have an operator's cabin.
In some cases, smaller self-erecting tower cranes may have axles permanently fitted to the tower section to make maneuvering the crane onsite easier.
Tower cranes can also use a hydraulic-powered jack frame to raise themselves to add new tower sections without any additional other cranes assisting beyond the initial assembly stage. This is how it can grow to nearly any height needed to build the tallest skyscrapers when tied to a building as the building rises. The maximum unsupported height of a tower crane is around 265 ft. For a video of a crane getting taller, see "Crane Building Itself" on YouTube.
For another animation of such a crane in use, see "SAS Tower Construction Simulation" on YouTube. Here, the crane is used to erect a scaffold, which, in turn, contains a gantry to lift sections of a bridge spire.
Climbing crane
Many tower cranes are designed to "jump" in stages, effectively lifting themselves to the next level. A specialty example of a climbing crane was introduced by Lagerwey Wind and Enercon to construct a wind turbine tower, where instead of erecting a large crane a smaller climbing crane can raise itself with the structure's construction, lift the generator housing to its top, add the rotor blades, then climb down. | Crane (machine) | Wikipedia | 512 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Cargo Handling
Rubber tyred gantry crane
Reach stacker
A reach stacker is a vehicle used for handling intermodal cargo containers in small terminals or medium-sized ports. Reach stackers are able to transport a container short distances very quickly and pile them in various rows depending on its access.
Sidelifter
A sidelifter crane is a road-going truck or semi-trailer, able to hoist and transport ISO standard containers. Container lift is done with parallel crane-like hoists, which can lift a container from the ground or from a railway vehicle.
Travel lift
A travel lift (also called a boat gantry crane, or boat crane) is a crane with two rectangular side panels joined by a single spanning beam at the top of one end. The crane is mobile with four groups of steerable wheels, one on each corner. These cranes allow boats with masts or tall super structures to be removed from the water and transported around docks or marinas. Not to be confused mechanical device used for transferring a vessel between two levels of water, which is also called a boat lift.
Straddle carrier
A Straddle carrier moves and stacks intermodal containers.
Industrial
Ring
Ring cranes are some of the largest and heaviest land-based cranes ever designed. A ring-shaped track support the main superstructure allowing for extremely heavy loads (up to thousands of tonnes).
Hammerhead
The "hammerhead", or giant cantilever, crane is a fixed-jib crane consisting of a steel-braced tower on which revolves a large, horizontal, double cantilever; the forward part of this cantilever or jib carries the lifting trolley, the jib is extended backwards in order to form a support for the machinery and counterbalancing weight. In addition to the motions of lifting and revolving, there is provided a so-called "racking" motion, by which the lifting trolley, with the load suspended, can be moved in and out along the jib without altering the level of the load. Such horizontal movement of the load is a marked feature of later crane design. These cranes are generally constructed in large sizes and can lift up to 350 tons. | Crane (machine) | Wikipedia | 440 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
The design of Hammerkran evolved first in Germany around the turn of the 19th century and was adopted and developed for use in British shipyards to support the battleship construction program from 1904 to 1914. The ability of the hammerhead crane to lift heavy weights was useful for installing large pieces of battleships such as armour plate and gun barrels. Giant cantilever cranes were also installed in naval shipyards in Japan and in the United States. The British government also installed a giant cantilever crane at the Singapore Naval Base (1938) and later a copy of the crane was installed at Garden Island Naval Dockyard in Sydney (1951). These cranes provided repair support for the battle fleet operating far from Great Britain.
In the British Empire, the engineering firm Sir William Arrol & Co. was the principal manufacturer of giant cantilever cranes; the company built a total of fourteen. Among the sixty built in the world, few remain; seven in England and Scotland of about fifteen worldwide.
The Titan Clydebank is one of the four Scottish cranes on the River Clyde and preserved as a tourist attraction.
Level luffing
Normally a crane with a hinged jib will tend to have its hook also move up and down as the jib moves (or luffs). A level luffing crane is a crane of this common design, but with an extra mechanism to keep the hook at the same level when the jib is pivoted in or out.
Overhead
An overhead crane, also known as a bridge crane, is a type of crane where the hook-and-line mechanism runs along a horizontal beam that itself runs along two widely separated rails. Often it is in a long factory building and runs along rails along the building's two long walls. It is similar to a gantry crane. Overhead cranes typically consist of either a single beam or a double beam construction. These can be built using typical steel beams or a more complex box girder type. Pictured on the right is a single bridge box girder crane with the hoist and system operated with a control pendant. Double girder bridge are more typical when needing heavier capacity systems from 10 tons and above. The advantage of the box girder type configuration results in a system that has a lower deadweight yet a stronger overall system integrity. Also included would be a hoist to lift the items, the bridge, which spans the area covered by the crane, and a trolley to move along the bridge. | Crane (machine) | Wikipedia | 493 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
The most common overhead crane use is in the steel industry. At every step of the manufacturing process, until it leaves a factory as a finished product, steel is handled by an overhead crane. Raw materials are poured into a furnace by crane, hot steel is stored for cooling by an overhead crane, the finished coils are lifted and loaded onto trucks and trains by overhead crane, and the fabricator or stamper uses an overhead crane to handle the steel in his factory. The automobile industry uses overhead cranes for handling of raw materials. Smaller workstation cranes handle lighter loads in a work-area, such as CNC mill or saw.
Almost all paper mills use bridge cranes for regular maintenance requiring removal of heavy press rolls and other equipment. The bridge cranes are used in the initial construction of paper machines because they facilitate installation of the heavy cast iron paper drying drums and other massive equipment, some weighing as much as 70 tons.
In many instances the cost of a bridge crane can be largely offset with savings from not renting mobile cranes in the construction of a facility that uses a lot of heavy process equipment.
This electric overhead traveling crane is most common type of overhead crane, found in many factories. These cranes are electrically operated by a control pendant, radio/IR remote pendant, or from an operator cabin attached to the crane.
Gantry
A gantry crane has a hoist in a fixed machinery house or on a trolley that runs horizontally along rails, usually fitted on a single beam (mono-girder) or two beams (twin-girder). The crane frame is supported on a gantry system with equalized beams and wheels that run on the gantry rail, usually perpendicular to the trolley travel direction. These cranes come in all sizes, and some can move very heavy loads, particularly the extremely large examples used in shipyards or industrial installations. A special version is the container crane (or "Portainer" crane, named by the first manufacturer), designed for loading and unloading ship-borne containers at a port.
Most container cranes are of this type.
Jib | Crane (machine) | Wikipedia | 418 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
A jib crane is a type of crane - not to be confused with a crane rigged with a jib to extend its main boom - where a horizontal member (jib or boom), supporting a moveable hoist, is fixed to a wall or to a floor-mounted pillar. Jib cranes are used in industrial premises and on military vehicles. The jib may swing through an arc, to give additional lateral movement, or be fixed. Similar cranes, often known simply as hoists, were fitted on the top floor of warehouse buildings to enable goods to be lifted to all floors.
Bulk-handling
Bulk-handling cranes are designed from the outset to carry a shell grab or bucket, rather than using a hook and a sling. They are used for bulk cargoes, such as coal, minerals, scrap metal etc.
Stacker
A crane with a forklift type mechanism used in automated (computer-controlled) warehouses (known as an automated storage and retrieval system (AS/RS)). The crane moves on a track in an aisle of the warehouse. The fork can be raised or lowered to any of the levels of a storage rack and can be extended into the rack to store and retrieve the product. The product can in some cases be as large as an automobile. Stacker cranes are often used in the large freezer warehouses of frozen food manufacturers. This automation avoids requiring forklift drivers to work in below-freezing temperatures every day.
Marine
Floating
Floating cranes are used mainly in bridge building and port construction, but they are also used for occasional loading and unloading of especially heavy or awkward loads on and off ships. Some floating cranes are mounted on pontoons, others are specialized crane barges with a lifting capacity exceeding and have been used to transport entire bridge sections. Floating cranes have also been used to salvage sunken ships.
Crane vessels are often used in offshore construction.
The largest revolving cranes can be found on SSCV Sleipnir, which has two cranes with a capacity of each. For 50 years, the largest such crane was "Herman the German" at the Long Beach Naval Shipyard, one of three constructed by Nazi Germany and captured in the war. The crane was sold to the Panama Canal in 1996 where it is now known as Titan.
Deck | Crane (machine) | Wikipedia | 456 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Deck cranes, also known as shipboard or cargo cranes, are located on ships and boats, used for cargo operations where no shore unloading facilities are available, raising and lowering loads (such as shellfish dredges and fish nets) into the water, and small boat unloading and retrieval. Most are diesel-hydraulic or electric-hydraulic, supporting an increasingly automated control interface.
Other Types
Railroad
A railroad crane has flanged wheels for use on railroads.
The simplest form is a crane mounted on a flatcar. More capable devices are purpose-built. Different types of crane are used for maintenance work, recovery operations and freight loading in goods yards and scrap handling facilities.
Aerial
Aerial cranes or "sky cranes" usually are helicopters designed to lift large loads. Helicopters are able to travel to and lift in areas that are difficult to reach by conventional cranes. Helicopter cranes are most commonly used to lift loads onto shopping centers and high-rise buildings. They can lift anything within their lifting capacity, such as air conditioning units, cars, boats, swimming pools, etc. They also perform disaster relief after natural disasters for clean-up, and during wild-fires they are able to carry huge buckets of water to extinguish fires.
Some aerial cranes, mostly concepts, have also used lighter-than air aircraft, such as airships.
Efficiency increase of cranes
Lifetime of existing cranes made of welded metal structures can often be extended for many years by after treatment of welds. During development of cranes, load level (lifting load) can be significantly increased by taking into account the IIW recommendations, leading in most cases to an increase of the permissible lifting load and thus to an efficiency increase.
Similar machines
The generally accepted definition of a crane is a machine for lifting and moving heavy objects by means of ropes or cables suspended from a movable arm. As such, a lifting machine that does not use cables, or else provides only vertical and not horizontal movement, cannot strictly be called a 'crane'.
Types of crane-like lifting machine include:
gin pole
Block and tackle
Capstan (nautical)
Hoist (device)
Winch
Windlass
Cherry picker
More technically advanced types of such lifting machines are often known as "cranes", regardless of the official definition of the term. | Crane (machine) | Wikipedia | 460 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
Special examples
Finnieston Crane, a.k.a. the Stobcross Crane
Category A-listed example of a "hammerhead" (cantilever) crane in Glasgow's former docks, built by the William Arrol company.
tall, capacity, built 1926
Taisun
double bridge crane at Yantai, China.
capacity, World Record Holder
tall, span, lift-height
Kockums Crane
shipyard crane formerly at Kockums, Sweden.
tall, capacity, since moved to Ulsan, South Korea
Samson and Goliath (cranes)
two gantry cranes at the Harland & Wolff shipyard in Belfast built by Krupp
Goliath is tall, Samson is
span , lift-height , capacity each, combined
Breakwater Crane Railway
self-propelled steam crane that formerly ran the length of the breakwater at Douglas.
ran on gauge track, the broadest in the British Isles
Liebherr TCC 78000
Heavy-duty gantry crane used for heavy lifting operated in Rostock, Germany.
capacity, lift-height
Crane operators
Crane operators are skilled workers and heavy equipment operators.
Key skills that are needed for a crane operator include:
An understanding of how to use and maintain machines and tools
Good team working skills
Attention to details
Good spatial awareness.
Patience and the ability to stay calm in stressful situations
Terminology
The ISO 4306 series of specifications establish the vocabulary for cranes:
Part 1: General
Part 2: Mobile cranes
Part 3: Tower cranes
Part 4: Jib cranes
Part 5: Bridge and gantry cranes
Luffing
Slewing
Hoisting | Crane (machine) | Wikipedia | 319 | 318378 | https://en.wikipedia.org/wiki/Crane%20%28machine%29 | Technology | Basics_8 | null |
A foxhound is a type of large hunting hound bred for strong hunting instincts, a keen sense of smell, and their barking, energy, drive, and speed. In fox hunting, the foxhound's namesake, packs of foxhounds track quarry, followed—usually on horseback—by the hunters, sometimes for several miles at a stretch; moreover, foxhounds also sometimes guard sheep and houses.
There are different breeds of foxhound, each having slightly different characteristics and appearances, and each often called simply Foxhound in their native countries:
American Foxhound
Dumfriesshire Black and Tan Foxhound (extinct)
English Foxhound
Welsh Foxhound
The American Masters of Foxhounds Association recognizes these breeds of foxhounds:
American, Penn-Marydel, English, and crossbred foxhounds.
The International Foxhound Association was created in 2012 for the international promotion of the Foxhound as a breed.
Characteristics
Foxhounds are medium-large dogs and males typically weigh 29-32 kg (65-70 lb) and females 27-29 kg (60-65 lb). Height for males measures 55-63 cm (22-25 in) and females 53-60 cm (21-24 in). Foxhounds have a short coat, and long, strong legs, as well as deep chests for lots of lung space.
Disposition
Foxhounds generally display a gentle and affectionate temperament. Foxhounds are highly active and energetic, and therefore require activity and exercise. Foxhounds are sociable and these dogs have great stamina, sense of smell, and enjoy being in a pack, as they are bred for hunting in packs.
Fox hunting
In fox hunting, the foxhound's namesake, packs of foxhounds track and chase fox while hunters follow along on horseback. Fox hunting has shifted over the years and may differ depending on the country. Some changes over time include focusing on chasing rather than killing, and chasing other creatures, such as the coyote, instead of only the fox.
Most common causes of death
Most common causes of death among Foxhound puppies are respiratory disease, anorexia and dehydration, skin disorders, and gastrointestinal disease. | Foxhound | Wikipedia | 459 | 318563 | https://en.wikipedia.org/wiki/Foxhound | Biology and health sciences | Dogs | Animals |
Respiratory disease in foxhounds
A kennel of working, hunting English Foxhounds in the south of England, had an outbreak of tuberculosis (TB) that impacted 180 dogs in late 2016 and early 2017. The kennel housed Foxhound puppies to adults, up to 8 years old. The Foxhounds work among six counties and some of the six counties are in the "Edge Area" that is impacted by bovine tuberculosis.
An investigation occurred which consisted of testing the dogs and looking deeper into the regional area, diet of the dogs, and even more factors while conducting tests and gathering information. The dogs eat raw meat and there was speculation about the diet containing the M. bovis that causes TB as the meat comes from areas impacted by M. bovis.
Registrations
In 2005, the American Kennel Club reported that the English and American Foxhounds were their least and fourth least registered breeds in North America with 22 and 44 registrations, respectively; the top registered breed, the Labrador Retriever, had 137,867 registrations during the same year.
Notable foxhounds
Sweet Lips and the Virginia Hounds - George Washington bred foxhounds and enjoyed fox hunting. He called his pack of dogs the Virginia Hounds. Sweet Lips was a female foxhound, a product of his vision to breed his pack to produce a "superior dog" who is fast and intelligent.
The state of Virginia's "state dog" is the American Foxhound.
Old Drum - said to have been the inspiration for the phrase "Man's Best Friend", which arose from an 1870 court case regarding him.
Mountain and Muse - In 1814 the Duke of Leeds gave two Irish foxhounds, Mountain and Muse, to a visiting guest, Bolton Jackson. This famous pair of hounds changed hands several times before going to Charles Carroll at his Homewood estate. Descendants of Mountain and Muse still hunt territories in Maryland that were once hunted by George Washington, Thomas Jefferson, Charles Carroll, and the Marquis de Lafayette.
Colonel - In 2011, Baron von Pfetten's Colonel was Champion of the World Dog Show in Paris and was the first ever English Foxhound invited to compete in the final Champion of Champions competition in Bruxelles that same year. | Foxhound | Wikipedia | 455 | 318563 | https://en.wikipedia.org/wiki/Foxhound | Biology and health sciences | Dogs | Animals |
The Cavendish experiment, performed in 1797–1798 by English scientist Henry Cavendish, was the first experiment to measure the force of gravity between masses in the laboratory and the first to yield accurate values for the gravitational constant. Because of the unit conventions then in use, the gravitational constant does not appear explicitly in Cavendish's work. Instead, the result was originally expressed as the relative density of Earth, or equivalently the mass of Earth. His experiment gave the first accurate values for these geophysical constants.
The experiment was devised sometime before 1783 by geologist John Michell, who constructed a torsion balance apparatus for it. However, Michell died in 1793 without completing the work. After his death the apparatus passed to Francis John Hyde Wollaston and then to Cavendish, who rebuilt the apparatus but kept close to Michell's original plan. Cavendish then carried out a series of measurements with the equipment and reported his results in the Philosophical Transactions of the Royal Society in 1798.
The experiment
The apparatus consisted of a torsion balance made of a wooden rod horizontally suspended from a wire, with two , lead spheres, one attached to each end. Two massive , lead balls, suspended separately, could be positioned away from or to either side of the smaller balls, away. The experiment measured the faint gravitational attraction between the small and large balls, which deflected the torsion balance rod by about 0.16" (or only 0.03" with a stiffer suspending wire).
The two large balls could be positioned either away from or to either side of the torsion balance rod. Their mutual attraction to the small balls caused the arm to rotate, twisting the suspension wire. The arm rotated until it reached an angle where the twisting force of the wire balanced the combined gravitational force of attraction between the large and small lead spheres. By measuring the angle of the rod and knowing the twisting force (torque) of the wire for a given angle, Cavendish was able to determine the force between the pairs of masses. Since the gravitational force of the Earth on the small ball could be measured directly by weighing it, the ratio of the two forces allowed the relative density of the Earth to be calculated, using Newton's law of gravitation.
Cavendish found that the Earth's density was times that of water (although due to a simple arithmetic error, found in 1821 by Francis Baily, the erroneous value appears in his paper). The current accepted value is 5.514 g/cm3. | Cavendish experiment | Wikipedia | 503 | 318577 | https://en.wikipedia.org/wiki/Cavendish%20experiment | Physical sciences | Classical mechanics | Physics |
To find the wire's torsion coefficient, the torque exerted by the wire for a given angle of twist, Cavendish timed the natural oscillation period of the balance rod as it rotated slowly clockwise and counterclockwise against the twisting of the wire. For the first 3 experiments the period was about 15 minutes and for the next 14 experiments the period was half of that, about 7.5 minutes. The period changed because after the third experiment Cavendish put in a stiffer wire. The torsion coefficient could be calculated from this and the mass and dimensions of the balance. Actually, the rod was never at rest; Cavendish had to measure the deflection angle of the rod while it was oscillating.
Cavendish's equipment was remarkably sensitive for its time. The force involved in twisting the torsion balance was very small, , (the weight of only 0.0177 milligrams) or about of the weight of the small balls. To prevent air currents and temperature changes from interfering with the measurements, Cavendish placed the entire apparatus in a mahogany box about 1.98 meters wide, 1.27 meters tall, and 14 cm thick, all in a closed shed on his estate. Through two holes in the walls of the shed, Cavendish used telescopes to observe the movement of the torsion balance's horizontal rod. The key observable was of course the deflection of the torsion balance rod, which Cavendish measured to be about 0.16" (or only 0.03" for the stiffer wire used mostly). Cavendish was able to measure this small deflection to an accuracy of better than using vernier scales on the ends of the rod.
The accuracy of Cavendish's result was not exceeded until C. V. Boys' experiment in 1895. In time, Michell's torsion balance became the dominant technique for measuring the gravitational constant (G) and most contemporary measurements still use variations of it.
Cavendish's result provided additional evidence for a planetary core made of metal, an idea first proposed by Charles Hutton based on his analysis of the 1774 Schiehallion experiment. Cavendish's result of 5.4 g·cm−3, 23% bigger than Hutton's, is close to 80% of the density of liquid iron, and 80% higher than the density of the Earth's outer crust, suggesting the existence of a dense iron core. | Cavendish experiment | Wikipedia | 491 | 318577 | https://en.wikipedia.org/wiki/Cavendish%20experiment | Physical sciences | Classical mechanics | Physics |
Reformulation of Cavendish's result to G
The formulation of Newtonian gravity in terms of a gravitational constant did not become standard until long after Cavendish's time. Indeed, one of the first references to G is in 1873, 75 years after Cavendish's work.
Cavendish expressed his result in terms of the density of the Earth. He referred to his experiment in correspondence as 'weighing the world'. Later authors reformulated his results in modern terms.
After converting to SI units, Cavendish's value for the Earth's density, 5.448 g cm−3, gives
G = ,
which differs by only 1% from the 2014 CODATA value of .
Today, physicists often use units where the gravitational constant takes a different form. The Gaussian gravitational constant used in space dynamics is a defined constant and the Cavendish experiment can be considered as a measurement of this constant.
In Cavendish's time, physicists used the same units for mass and weight, in effect taking g as a standard acceleration. Then, since R was known, ρ played the role of an inverse gravitational constant. The density of the Earth was hence a much sought-after quantity at the time, and there had been earlier attempts to measure it, such as the Schiehallion experiment in 1774.
Derivation of G and the Earth's mass
The following is not the method Cavendish used, but describes how modern physicists would calculate the results from his experiment. From Hooke's law, the torque on the torsion wire is proportional to the deflection angle of the balance. The torque is where is the torsion coefficient of the wire. However, a torque in the opposite direction is also generated by the gravitational pull of the masses. It can be written as a product of the attractive force of a large ball on a small ball and the distance L/2 to the suspension wire. Since there are two balls, each experiencing force F at a distance from the axis of the balance, the torque due to gravitational force is LF. At equilibrium (when the balance has been stabilized at an angle ), the total amount of torque must be zero as these two sources of torque balance out. Thus, we can equate their magnitudes given by the formulas above, which gives the following:
For F, Newton's law of universal gravitation is used to express the attractive force between a large and small ball:
Substituting F into the first equation above gives | Cavendish experiment | Wikipedia | 498 | 318577 | https://en.wikipedia.org/wiki/Cavendish%20experiment | Physical sciences | Classical mechanics | Physics |
To find the torsion coefficient () of the wire, Cavendish measured the natural resonant oscillation period T of the torsion balance:
Assuming the mass of the torsion beam itself is negligible, the moment of inertia of the balance is just due to the small balls. Treating them as point masses, each at L/2 from the axis, gives:
,
and so:
Solving this for , substituting into (1), and rearranging for G, the result is:
.
Once G has been found, the attraction of an object at the Earth's surface to the Earth itself can be used to calculate the Earth's mass and density:
Definitions of terms | Cavendish experiment | Wikipedia | 142 | 318577 | https://en.wikipedia.org/wiki/Cavendish%20experiment | Physical sciences | Classical mechanics | Physics |
Schizosaccharomyces pombe, also called "fission yeast", is a species of yeast used in traditional brewing and as a model organism in molecular and cell biology. It is a unicellular eukaryote, whose cells are rod-shaped. Cells typically measure 3 to 4 micrometres in diameter and 7 to 14 micrometres in length. Its genome, which is approximately 14.1 million base pairs, is estimated to contain 4,970 protein-coding genes and at least 450 non-coding RNAs.
These cells maintain their shape by growing exclusively through the cell tips and divide by medial fission to produce two daughter cells of equal size, which makes them a powerful tool in cell cycle research.
Fission yeast was isolated in 1893 by Paul Lindner from East African millet beer. The species name pombe is the Swahili word for beer. It was first developed as an experimental model in the 1950s: by Urs Leupold for studying genetics, and by Murdoch Mitchison for studying the cell cycle.
Paul Nurse, a fission yeast researcher, successfully merged the independent schools of fission yeast genetics and cell cycle research. Together with Lee Hartwell and Tim Hunt, Nurse won the 2001 Nobel Prize in Physiology or Medicine for work on cell cycle regulation.
The sequence of the S. pombe genome was published in 2002, by a consortium led by the Sanger Institute, becoming the sixth model eukaryotic organism whose genome has been fully sequenced. S. pombe researchers are supported by the PomBase MOD (model organism database). This has fully unlocked the power of this organism, with many genes orthologous to human genes identified — 70% to date, including many genes involved in human disease. In 2006, sub-cellular localization of almost all the proteins in S. pombe was published using green fluorescent protein as a molecular tag.
Schizosaccharomyces pombe has also become an important organism in studying the cellular responses to DNA damage and the process of DNA replication. | Schizosaccharomyces pombe | Wikipedia | 418 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
Approximately 160 natural strains of S. pombe have been isolated. These have been collected from a variety of locations including Europe, North and South America, and Asia. The majority of these strains have been collected from cultivated fruits such as apples and grapes, or from the various alcoholic beverages, such as Brazilian Cachaça. S. pombe is also known to be present in fermented tea, kombucha. It is not clear at present whether S. pombe is the major fermenter or a contaminant in such brews. The natural ecology of Schizosaccharomyces yeasts is not well-studied.
History
Schizosaccharomyces pombe was first discovered in 1893 when a group working in a Brewery Association Laboratory in Germany was looking at sediment found in millet beer imported from East Africa that gave it an acidic taste. The term schizo, meaning "split" or "fission", had previously been used to describe other Schizosaccharomycetes. The addition of the word pombe was due to its isolation from East African beer, as pombe means "beer" in Swahili. The standard S. pombe strains were isolated by Urs Leupold in 1946 and 1947 from a culture that he obtained from the yeast collection in Delft, The Netherlands. It was deposited there by A. Osterwalder under the name S. pombe var. liquefaciens, after he isolated it in 1924 from French wine (most probably rancid) at the Federal Experimental Station of Vini- and Horticulture in Wädenswil, Switzerland. The culture used by Urs Leupold contained (besides others) cells with the mating types h90 (strain 968), h- (strain 972), and h+ (strain 975). Subsequent to this, there have been two large efforts to isolate S. pombe from fruit, nectar, or fermentations: one by Florenzano et al. in the vineyards of western Sicily, and the other by Gomes et al. (2002) in four regions of southeast Brazil. | Schizosaccharomyces pombe | Wikipedia | 444 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
Ecology
The fission yeast S. pombe belongs to the division Ascomycota, which represents the largest and most diverse group of fungi. Free-living ascomycetes are commonly found in tree exudates, on plant roots and in surrounding soil, on ripe and rotting fruits, and in association with insect vectors that transport them between substrates. Many of these associations are symbiotic or saprophytic, although numerous ascomycetes (and their basidiomycete cousins) represent important plant pathogens that target myriad plant species, including commercial crops. Among the ascomycetous yeast genera, the fission yeast Schizosaccharomyces is unique because of the deposition of α-(1,3)-glucan or pseudonigeran in the cell wall in addition to the better known β-glucans and the virtual lack of chitin. Species of this genus also differ in mannan composition, which shows terminal d-galactose sugars in the side-chains of their mannans. S. pombe undergo aerobic fermentation in the presence of excess sugar. S. pombe can degrade L-malic acid, one of the dominant organic acids in wine, which makes them diverse among other Saccharomyces strains.
Comparison with budding yeast (Saccharomyces cerevisiae)
The yeast species Schizosaccharomyces pombe and Saccharomyces cerevisiae are both extensively studied; these two species diverged approximately 300 to 600 million years before present, and are significant tools in molecular and cellular biology. Some of the technical discriminants between these two species are: | Schizosaccharomyces pombe | Wikipedia | 348 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
S. cerevisiae has approximately 5,600 open reading frames; S. pombe has approximately 5,070 open reading frames.
Despite similar gene numbers, S. cerevisiae has only about 250 introns, while S. pombe has nearly 5,000.
S. cerevisiae has 16 chromosomes, S. pombe has 3.
S. cerevisiae is often diploid while S. pombe is usually haploid.
S. pombe has a shelterin-like telomere complex while S. cerevisiae does not.
S. cerevisiae is in the G1 phase of the cell cycle for an extended period (as a consequence, G1-S transition is tightly controlled), while S. pombe remains in the G2 phase of the cell cycle for an extended period (as a consequence, G2-M transition is under tight control).
Both species share genes with higher eukaryotes that they do not share with each other. S. pombe has RNAi machinery genes like those in vertebrates, while this is missing from S. cerevisiae. S. cerevisiae also has greatly simplified heterochromatin compared to S. pombe. Conversely, S. cerevisiae has well-developed peroxisomes, while S. pombe does not.
S. cerevisiae has small point centromere of 125 bp, and sequence-defined replication origins of about the same size. On the converse, S. pombe has large, repetitive centromeres (40–100 kb) more similar to mammalian centromeres, and degenerate replication origins of at least 1kb.
S. pombe pathways and cellular processes
S. pombe gene products (proteins and RNAs) participate in many cellular processes common across all life. The fission yeast GO slim provides a categorical high level overview of the biological role of all S. pombe gene products.
Life cycle
The fission yeast is a single-celled fungus with simple, fully characterized genome and a rapid growth rate. It has long been used in brewing, baking, and molecular genetics. S. pombe is a rod-shaped cell, approximately 3 μm in diameter, that grows entirely by elongation at the ends. After mitosis, division occurs by the formation of a septum, or cell plate, that cleaves the cell at its midpoint. | Schizosaccharomyces pombe | Wikipedia | 504 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
The central events of cell reproduction are chromosome duplication, which takes place in S (Synthetic) phase, followed by chromosome segregation and nuclear division (mitosis) and cell division (cytokinesis), which are collectively called M (Mitotic) phase. G1 is the gap between M and S phases, and G2 is the gap between S and M phases. In the fission yeast, the G2 phase is particularly extended, and cytokinesis (daughter-cell segregation) does not happen until a new S (Synthetic) phase is launched.
Fission yeast governs mitosis by mechanisms that are similar to those in multicellular animals. It normally proliferates in a haploid state. When starved, cells of opposite mating types (P and M) fuse to form a diploid zygote that immediately enters meiosis to generate four haploid spores. When conditions improve, these spores germinate to produce proliferating haploid cells.
Cytokinesis
The general features of cytokinesis are shown here. The site of cell division is determined before anaphase. The anaphase spindle (in green on the figure) is then positioned so that the segregated chromosomes are on opposite sides of the predetermined cleavage plane.
Size control
In fission yeast, where growth governs progression through G2/M, a wee1 mutation causes entry into mitosis at an abnormally small size, resulting in a shorter G2. G1 is lengthened, suggesting that progression through Start (beginning of cell cycle) is responsive to growth when the G2/M control is lost. Furthermore, cells in poor nutrient conditions grow slowly and therefore take longer to double in size and divide. Low nutrient levels also reset the growth threshold so that cell progresses through the cell cycle at a smaller size. Upon exposure to stressful conditions [heat (40 °C) or the oxidizing agent hydrogen peroxide] S. pombe cells undergo aging as measured by increased cell division time and increased probability of cell death. Finally, wee1 mutant fission yeast cells are smaller than wild-type cells, but take just as long to go through the cell cycle. This is possible because small yeast cells grow slower, that is, their added total mass per unit time is smaller than that of normal cells. | Schizosaccharomyces pombe | Wikipedia | 472 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
A spatial gradient is thought to coordinate cell size and mitotic entry in fission yeast.
The Pom1 protein kinase (green) is localized to the cell cortex, with the highest concentration at the cell tips. The cell-cycle regulators Cdr2, Cdr1 and Wee1 are present in cortical nodes in the middle of the cell (blue and red dots). a, In small cells, the Pom1 gradient reaches most of the cortical nodes (blue dots). Pom1 inhibits Cdr2, preventing Cdr2 and Cdr1 from inhibiting Wee1, and allowing Wee1 to phosphorylate Cdk1, thus inactivating cyclin-dependent kinase (CDK) activity and preventing entry into mitosis. b, In long cells, the Pom1 gradient does not reach the cortical nodes (red dots), and therefore Cdr2 and Cdr1 remain active in the nodes. Cdr2 and Cdr1 inhibit Wee1, preventing phosphorylation of Cdk1 and thereby leading to activation of CDK and mitotic entry. (This simplified diagram omits several other regulators of CDK activity.)
Mating-type switching
Fission yeast switches mating type by a replication-coupled recombination event, which takes place during S phase of the cell cycle. Fission yeast uses intrinsic asymmetry of the DNA replication process to switch the mating type; it was the first system where the direction of replication was shown to be required for the change of the cell type. Studies of the mating-type switching system lead to a discovery and characterization of a site-specific replication termination site RTS1, a site-specific replication pause site MPS1, and a novel type of chromosomal imprint, marking one of the sister chromatids at the mating-type locus mat1. In addition, work on the silenced donor region has led to great advances in understanding formation and maintenance of heterochromatin. | Schizosaccharomyces pombe | Wikipedia | 410 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
Responses to DNA damage
Schizosaccharomyces pombe is a facultative sexual microorganism that can undergo mating when nutrients are limiting. Exposure of S. pombe to hydrogen peroxide, an agent that causes oxidative stress leading to oxidative DNA damage, strongly induces mating and formation of meiotic spores. This finding suggests that meiosis, and particularly meiotic recombination, may be an adaptation for repairing DNA damage. Supporting this view is the finding that single base lesions of the type dU:dG in the DNA of S. pombe stimulate meiotic recombination. This recombination requires uracil-DNA glycosylase, an enzyme that removes uracil from the DNA backbone and initiates base excision repair. On the basis of this finding, it was proposed that base excision repair of either a uracil base, an abasic site, or a single-strand nick is sufficient to initiate recombination in S. pombe. Other experiments with S. pombe indicated that faulty processing of DNA replication intermediates, i.e. Okazaki fragments, causes DNA damages such as single-strand nicks or gaps, and that these stimulate meiotic recombination.
As a model system | Schizosaccharomyces pombe | Wikipedia | 268 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
Fission yeast has become a notable model system to study basic principles of a cell that can be used to understand more complex organisms like mammals and in particular humans. This single cell eukaryote is nonpathogenic and easily grown and manipulated in the lab. Fission yeast contains one of the smallest numbers of genes of a known genome sequence for a eukaryote, and has only three chromosomes in its genome. Many of the genes responsible for cell division and cellular organization in fission yeast cell are also found in the human's genome. Cell cycle regulation and division are crucial for growth and development of any cell. Fission yeast's conserved genes has been heavily studied and the reason for many recent biomedical developments. Fission yeast is also a practical model system to observe cell division because fission yeast's are cylindrically shaped single celled eukaryotes that divide and reproduce by medial fission. This can easily be seen using microscopy. Fission yeast also have an extremely short generation time, 2 to 4 hours, which also makes it an easy model system to observe and grow in the laboratory Fission yeast's simplicity in genomic structure yet similarities with mammalian genome, ease of ability to manipulate, and ability to be used for drug analysis is why fission yeast is making many contributions to biomedicine and cellular biology research, and a model system for genetic analysis.
Genome
Schizosaccharomyces pombe is often used to study cell division and growth because of conserved genomic regions also seen in humans including: heterochromatin proteins, large origins of replication, large centromeres, conserved cellular checkpoints, telomere function, gene splicing, and many other cellular processes. S. pombes genome was fully sequenced in 2002, the sixth eukaryotic genome to be sequenced as part of the Genome Project. An estimated 4,979 genes were discovered within three chromosomes containing about 14Mb of DNA. This DNA is contained within 3 different chromosomes in the nucleus with gaps in the centromeric (40kb) and telomeric (260kb) regions. After the initial sequencing of the fission yeast's genome, other previous non-sequenced regions of the genes have been sequenced. Structural and functional analysis of these gene regions can be found on large scale fission yeast databases such as PomBase. | Schizosaccharomyces pombe | Wikipedia | 473 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
Forty-three percent of the genes in the Genome Project were found to contain introns in 4,739 genes. Fission yeast does not have as many duplicated genes compared to budding yeast, only containing 5%, making fission yeast a great model genome to observe and gives researchers the ability to create more functional research approaches. S. pombes having a large number of introns gives opportunities for an increase of range of protein types produced from alternative splicing and genes that code for comparable genes in human.
81% of the three centromeres in fission yeast have been sequenced. The lengths of the three centromeres were found to be 34, 65, and 110 kb. This is 300–100 times longer than the centromeres of budding yeast. An extremely high level of conservation (97%) is also seen over 1,780-bp region in the DGS regions of the centromere. This elongation of centromeres and its conservative sequences makes fission yeast a practical model system to use to observe cell division and in humans because of their likeness.
PomBase reports over 69% of protein coding genes have human orthologs and over 500 of these are associated with human disease . This makes S. pombe a great system to use to study human genes and disease pathways, especially cell cycle and DNA checkpoint systems.
The genome of S. pombe contains meiotic drivers and drive suppressors called wtf genes.
Genetic diversity
Biodiversity and evolutionary study of fission yeast was carried out on 161 strains of Schizosaccharomyces pombe collected from 20 countries. Modeling of the evolutionary rate showed that all strains derived from a common ancestor that has lived since ~2,300 years ago. The study also identified a set of 57 strains of fission yeast that each differed by ≥1,900 SNPs, and all detected 57 strains of fission yeast were prototrophic (able to grow on the same minimal medium as the reference strain). A number of studies on S.pombe genome support the idea that the genetic diversity of fission yeast strains is slightly less than budding yeast. Indeed, only limited variations of S.pombe occur in proliferation in different environments. In addition, the amount of phenotypic variation segregating in fission yeast is less than that seen, in S. cerevisiae. Since most strains of fission yeast were isolated from brewed beverages, there is no ecological or historical context to this dispersal.
Cell cycle analysis | Schizosaccharomyces pombe | Wikipedia | 505 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
DNA replication in yeast has been increasingly studied by many researchers. Further understanding of DNA replication, gene expression, and conserved mechanisms in yeast can provide researchers with information on how these systems operate in mammalian cells in general and human cells in particular. Other stages, such as cellular growth and aging, are also observed in yeast in order to understand these mechanisms in more complex systems.
S. pombe stationary phase cells undergo chronological aging due to production of reactive oxygen species that cause DNA damages. Most such damages can ordinarily be repaired by DNA base excision repair and nucleotide excision repair. Defects in these repair processes lead to reduced survival.
Cytokinesis is one of the components of cell division that is often observed in fission yeast. Well-conserved components of cytokinesis are observed in fission yeast and allow us to look at various genomic scenarios and pinpoint mutations. Cytokinesis is a permanent step and very crucial to the wellbeing of the cell. Contractile ring formation in particular is heavily studied by researchers using S. pombe as a model system. The contractile ring is highly conserved in both fission yeast and human cytokinesis. Mutations in cytokinesis can result in many malfunctions of the cell including cell death and development of cancerous cells. This is a complex process in human cell division, but in S. pombe simpler experiments can yield results that can then be applied for research in higher-order model systems such as humans.
One of the safety precautions that the cell takes to ensure precise cell division occurs is the cell-cycle checkpoint. These checkpoints ensure any mutagens are eliminated. This is done often by relay signals that stimulate ubiquitination of the targets and delay cytokinesis. Without mitotic check points such as these, mutagens are created and replicated, resulting in multitudes of cellular issues including cell death or tumorigenesis seen in cancerous cells. Paul Nurse, Leland Hartwell, and Tim Hunt were awarded the Nobel Prize in Physiology or Medicine in 2001. They discovered key conserved checkpoints that are crucial for a cell to divide properly. These findings have been linked to cancer and diseased cells and are a notable finding for biomedicine. | Schizosaccharomyces pombe | Wikipedia | 456 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
Researchers using fission yeast as a model system also look at organelle dynamics and responses and the possible correlations between yeast cells and mammalian cells. Mitochondria diseases, and various organelle systems such as the Golgi apparatus and endoplasmic reticulum, can be further understood, by observing fission yeast's chromosome dynamics and protein expression levels and regulation.
Meiotic recombination
RecA and RecA-like proteins are required for recombinational repair of DNA double-strand breaks. Five RecA-like proteins have been described in S. pombe that are linked to meiotic recombination, and all five RecA homologs appear to be required for normal levels of meiotic recombination.
Biomedical tool
However, there are limitations with using fission yeast as a model system: its multidrug resistance. "The MDR response involves overexpression of two types of drug efflux pumps, the ATP-binding cassette (ABC) family... and the major facilitator superfamily". Paul Nurse and some of his colleagues have recently created S. pombe strains sensitive to chemical inhibitors and common probes to see whether it is possible to use fission yeast as a model system of chemical drug research.
For example, Doxorubicin, a very common chemotherapeutic antibiotic, has many adverse side-effects. Researchers are looking for ways to further understand how doxorubicin works by observing the genes linked to resistance by using fission yeast as a model system. Links between doxorubicin adverse side-effects and chromosome metabolism and membrane transport were seen. Metabolic models for drug targeting are now being used in biotechnology, and further advances are expected in the future using the fission yeast model system.
Experimental approaches
Fission yeast is easily accessible, easily grown and manipulated to make mutants, and able to be maintained at either a haploid or diploid state. S. pombe is normally a haploid cell but, when put under stressful conditions, usually nitrogen deficiency, two cells will conjugate to form a diploid that later form four spores within a tetrad ascus. This process is easily visible and observable under any microscope and allows us to look at meiosis in a simpler model system to see how this phenomenon operates. | Schizosaccharomyces pombe | Wikipedia | 480 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
Virtually any genetics experiment or technique can, therefore, be applied to this model system such as: tetrad dissection, mutagens analysis, transformations, and microscopy techniques such as FRAP and FRET. New models, such as Tug-Of-War (gTOW), are also being used to analyze yeast robustness and observe gene expression. Making knock-in and knock-out genes is fairly easy and with the fission yeast's genome being sequenced this task is very accessible and well known. | Schizosaccharomyces pombe | Wikipedia | 105 | 318669 | https://en.wikipedia.org/wiki/Schizosaccharomyces%20pombe | Biology and health sciences | Basics | Plants |
The embryophytes () are a clade of plants, also known as Embryophyta () or land plants. They are the most familiar group of photoautotrophs that make up the vegetation on Earth's dry lands and wetlands. Embryophytes have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of freshwater charophyte green algae as a sister taxon of Charophyceae, Coleochaetophyceae and Zygnematophyceae. Embryophytes consist of the bryophytes and the polysporangiophytes. Living embryophytes include hornworts, liverworts, mosses, lycophytes, ferns, gymnosperms and angiosperms (flowering plants). Embryophytes have diplobiontic life cycles.
The embryophytes are informally called "land plants" because they thrive primarily in terrestrial habitats (despite some members having evolved secondarily to live once again in semiaquatic/aquatic habitats), while the related green algae are primarily aquatic. Embryophytes are complex multicellular eukaryotes with specialized reproductive organs. The name derives from their innovative characteristic of nurturing the young embryo sporophyte during the early stages of its multicellular development within the tissues of the parent gametophyte. With very few exceptions, embryophytes obtain biological energy by photosynthesis, using chlorophyll a and b to harvest the light energy in sunlight for carbon fixation from carbon dioxide and water in order to synthesize carbohydrates while releasing oxygen as a byproduct.
Description
The Embryophytes emerged either a half-billion years ago, at some time in the interval between the mid-Cambrian and early Ordovician, or almost a billion years ago, during the Tonian or Cryogenian, probably from freshwater charophytes, a clade of multicellular green algae similar to extant Klebsormidiophyceae. The emergence of the Embryophytes depleted atmospheric CO2 (a greenhouse gas), leading to global cooling, and thereby precipitating glaciations. Embryophytes are primarily adapted for life on land, although some are secondarily aquatic. Accordingly, they are often called land plants or terrestrial plants. | Embryophyte | Wikipedia | 480 | 318779 | https://en.wikipedia.org/wiki/Embryophyte | Biology and health sciences | Embryophytes (Land plants) except vascular plants | Plants |
On a microscopic level, the cells of charophytes are broadly similar to those of chlorophyte green algae, but differ in that in cell division the daughter nuclei are separated by a phragmoplast. They are eukaryotic, with a cell wall composed of cellulose and plastids surrounded by two membranes. The latter include chloroplasts, which conduct photosynthesis and store food in the form of starch, and are characteristically pigmented with chlorophylls a and b, generally giving them a bright green color. Embryophyte cells also generally have an enlarged central vacuole enclosed by a vacuolar membrane or tonoplast, which maintains cell turgor and keeps the plant rigid.
In common with all groups of multicellular algae they have a life cycle which involves alternation of generations. A multicellular haploid generation with a single set of chromosomes – the gametophyte – produces sperm and eggs which fuse and grow into a diploid multicellular generation with twice the number of chromosomes – the sporophyte which produces haploid spores at maturity. The spores divide repeatedly by mitosis and grow into a gametophyte, thus completing the cycle. Embryophytes have two features related to their reproductive cycles which distinguish them from all other plant lineages. Firstly, their gametophytes produce sperm and eggs in multicellular structures (called 'antheridia' and 'archegonia'), and fertilization of the ovum takes place within the archegonium rather than in the external environment. Secondly, the initial stage of development of the fertilized egg (the zygote) into a diploid multicellular sporophyte, takes place within the archegonium where it is both protected and provided with nutrition. This second feature is the origin of the term 'embryophyte' – the fertilized egg develops into a protected embryo, rather than dispersing as a single cell. In the bryophytes the sporophyte remains dependent on the gametophyte, while in all other embryophytes the sporophyte generation is dominant and capable of independent existence. | Embryophyte | Wikipedia | 454 | 318779 | https://en.wikipedia.org/wiki/Embryophyte | Biology and health sciences | Embryophytes (Land plants) except vascular plants | Plants |
Embryophytes also differ from algae by having metamers. Metamers are repeated units of development, in which each unit derives from a single cell, but the resulting product tissue or part is largely the same for each cell. The whole organism is thus constructed from similar, repeating parts or metamers. Accordingly, these plants are sometimes termed 'metaphytes' and classified as the group Metaphyta (but Haeckel's definition of Metaphyta places some algae in this group). In all land plants a disc-like structure called a phragmoplast forms where the cell will divide, a trait only found in the land plants in the streptophyte lineage, some species within their relatives Coleochaetales, Charales and Zygnematales, as well as within subaerial species of the algae order Trentepohliales, and appears to be essential in the adaptation towards a terrestrial life style.
Evolution
The green algae and land plants form a clade, the Viridiplantae. According to molecular clock estimates, the Viridiplantae split to into two clades: chlorophytes and streptophytes. The chlorophytes, with around 700 genera, were originally marine algae, although some groups have since spread into fresh water. The streptophyte algae (i.e. excluding the land plants) have around 122 genera; they adapted to fresh water very early in their evolutionary history and have not spread back into marine environments.
Some time during the Ordovician, streptophytes invaded the land and began the evolution of the embryophyte land plants. Present day embryophytes form a clade. Becker and Marin speculate that land plants evolved from streptophytes because living in fresh water pools pre-adapted them to tolerate a range of environmental conditions found on land, such as exposure to rain, tolerance of temperature variation, high levels of ultra-violet light, and seasonal dehydration.
The preponderance of molecular evidence as of 2006 suggested that the groups making up the embryophytes are related as shown in the cladogram below (based on Qiu et al. 2006 with additional names from Crane et al. 2004). | Embryophyte | Wikipedia | 468 | 318779 | https://en.wikipedia.org/wiki/Embryophyte | Biology and health sciences | Embryophytes (Land plants) except vascular plants | Plants |
An updated phylogeny of Embryophytes based on the work by Novíkov & Barabaš-Krasni 2015 and Hao and Xue 2013 with plant taxon authors from Anderson, Anderson & Cleal 2007 and some additional clade names. Puttick et al./Nishiyama et al. are used for the basal clades.
Diversity
Non-vascular land plants
The non-vascular land plants, namely the mosses (Bryophyta), hornworts (Anthocerotophyta), and liverworts (Marchantiophyta), are relatively small plants, often confined to environments that are humid or at least seasonally moist. They are limited by their reliance on water needed to disperse their gametes; a few are truly aquatic. Most are tropical, but there are many arctic species. They may locally dominate the ground cover in tundra and Arctic–alpine habitats or the epiphyte flora in rain forest habitats.
They are usually studied together because of their many similarities. All three groups share a haploid-dominant (gametophyte) life cycle and unbranched sporophytes (the plant's diploid generation). These traits appear to be common to all early diverging lineages of non-vascular plants on the land. Their life-cycle is strongly dominated by the haploid gametophyte generation. The sporophyte remains small and dependent on the parent gametophyte for its entire brief life. All other living groups of land plants have a life cycle dominated by the diploid sporophyte generation. It is in the diploid sporophyte that vascular tissue develops. In some ways, the term "non-vascular" is a misnomer. Some mosses and liverworts do produce a special type of vascular tissue composed of complex water-conducting cells. However, this tissue differs from that of "vascular" plants in that these water-conducting cells are not lignified. It is unlikely that water-conducting cells in the mosses is homologous with the vascular tissue in "vascular" plants. | Embryophyte | Wikipedia | 433 | 318779 | https://en.wikipedia.org/wiki/Embryophyte | Biology and health sciences | Embryophytes (Land plants) except vascular plants | Plants |
Like the vascular plants, they have differentiated stems, and although these are most often no more than a few centimeters tall, they provide mechanical support. Most have leaves, although these typically are one cell thick and lack veins. They lack true roots or any deep anchoring structures. Some species grow a filamentous network of horizontal stems, but these have a primary function of mechanical attachment rather than extraction of soil nutrients (Palaeos 2008).
Rise of vascular plants
During the Silurian and Devonian periods (around ), plants evolved which possessed true vascular tissue, including cells with walls strengthened by lignin (tracheids). Some extinct early plants appear to be between the grade of organization of bryophytes and that of true vascular plants (eutracheophytes). Genera such as Horneophyton have water-conducting tissue more like that of mosses, but a different life-cycle in which the sporophyte is branched and more developed than the gametophyte. Genera such as Rhynia have a similar life-cycle but have simple tracheids and so are a kind of vascular plant. It was assumed that the gametophyte dominant phase seen in bryophytes used to be the ancestral condition in terrestrial plants, and that the sporophyte dominant stage in vascular plants was a derived trait. However, the gametophyte and sporophyte stages were probably equally independent from each other, and that the mosses and vascular plants in that case are both derived, and have evolved in opposite directions.
During the Devonian period, vascular plants diversified and spread to many different land environments. In addition to vascular tissues which transport water throughout the body, tracheophytes have an outer layer or cuticle that resists drying out. The sporophyte is the dominant generation, and in modern species develops leaves, stems and roots, while the gametophyte remains very small.
Lycophytes and euphyllophytes | Embryophyte | Wikipedia | 409 | 318779 | https://en.wikipedia.org/wiki/Embryophyte | Biology and health sciences | Embryophytes (Land plants) except vascular plants | Plants |
All the vascular plants which disperse through spores were once thought to be related (and were often grouped as 'ferns and allies'). However, recent research suggests that leaves evolved quite separately in two different lineages. The lycophytes or lycopodiophytes – modern clubmosses, spikemosses and quillworts – make up less than 1% of living vascular plants. They have small leaves, often called 'microphylls' or 'lycophylls', which are borne all along the stems in the clubmosses and spikemosses, and which effectively grow from the base, via an intercalary meristem. It is believed that microphylls evolved from outgrowths on stems, such as spines, which later acquired veins (vascular traces).
Although the living lycophytes are all relatively small and inconspicuous plants, more common in the moist tropics than in temperate regions, during the Carboniferous period tree-like lycophytes (such as Lepidodendron) formed huge forests that dominated the landscape.
The euphyllophytes, making up more than 99% of living vascular plant species, have large 'true' leaves (megaphylls), which effectively grow from the sides or the apex, via marginal or apical meristems. One theory is that megaphylls evolved from three-dimensional branching systems by first '' – flattening to produce a two dimensional branched structure – and then 'webbing' – tissue growing out between the flattened branches. Others have questioned whether megaphylls evolved in the same way in different groups.
Ferns and horsetails
The ferns and horsetails (the Polypodiophyta) form a clade; they use spores as their main method of dispersal. Traditionally, whisk ferns and horsetails were historically treated as distinct from 'true' ferns. Living whisk ferns and horsetails do not have the large leaves (megaphylls) which would be expected of euphyllophytes. This has probably resulted from reduction, as evidenced by early fossil horsetails, in which the leaves are broad with branching veins.
Ferns are a large and diverse group, with some 12,000 species. A stereotypical fern has broad, much divided leaves, which grow by unrolling.
Seed plants | Embryophyte | Wikipedia | 479 | 318779 | https://en.wikipedia.org/wiki/Embryophyte | Biology and health sciences | Embryophytes (Land plants) except vascular plants | Plants |
Seed plants, which first appeared in the fossil record towards the end of the Paleozoic era, reproduce using desiccation-resistant capsules called seeds. Starting from a plant which disperses by spores, highly complex changes are needed to produce seeds. The sporophyte has two kinds of spore-forming organs or sporangia. One kind, the megasporangium, produces only a single large spore, a megaspore. This sporangium is surrounded by sheathing layers or integuments which form the seed coat. Within the seed coat, the megaspore develops into a tiny gametophyte, which in turn produces one or more egg cells. Before fertilization, the sporangium and its contents plus its coat is called an ovule; after fertilization a seed. In parallel to these developments, the other kind of sporangium, the microsporangium, produces microspores. A tiny gametophyte develops inside the wall of a microspore, producing a pollen grain. Pollen grains can be physically transferred between plants by the wind or animals, most commonly insects. Pollen grains can also transfer to an ovule of the same plant, either with the same flower or between two flowers of the same plant (self-fertilization). When a pollen grain reaches an ovule, it enters via a microscopic gap in the coat, the micropyle. The tiny gametophyte inside the pollen grain then produces sperm cells which move to the egg cell and fertilize it. Seed plants include two clades with living members, the gymnosperms and the angiosperms or flowering plants. In gymnosperms, the ovules or seeds are not further enclosed. In angiosperms, they are enclosed within the carpel. Angiosperms typically also have other, secondary structures, such as petals, which together form a flower.
Meiosis in sexual land plants provides a direct mechanism for repairing DNA in reproductive tissues. Sexual reproduction appears to be needed for maintaining long-term genomic integrity and only infrequent combinations of extrinsic and intrinsic factors allow for shifts to asexuality. | Embryophyte | Wikipedia | 460 | 318779 | https://en.wikipedia.org/wiki/Embryophyte | Biology and health sciences | Embryophytes (Land plants) except vascular plants | Plants |
Iceland spar, formerly called Iceland crystal ( , ) and also called optical calcite, is a transparent variety of calcite, or crystallized calcium carbonate, originally brought from Iceland, and used in demonstrating the polarization of light.
Formation and composition
Iceland spar is a colourless, transparent variety of calcium carbonate (CaCO3). It crystallizes in the trigonal system, typically forming rhombohedral crystals. It has a Mohs hardness of 3 and exhibits double refraction, splitting a ray of light into two rays that travel at different speeds and directions.
Iceland spar forms in sedimentary environments, mainly limestone and dolomite rocks, but it also forms in hydrothermal veins and evaporite deposits. It precipitates from solutions rich in calcium and carbonate ions, influenced by temperature, pressure, and impurities.
The most common crystal structure of Iceland spar is rhombohedral, but other structures, such as scalenohedral or prismatic, can form depending on formation conditions. Iceland spar is primarily found in Iceland but can occur in different parts of the world with suitable geological conditions.
Characteristics and optical properties
Iceland spar is characterized by its large, readily cleavable crystals, easily divided into parallelepipeds. This feature makes it easily identifiable and workable. One of the most remarkable properties of Iceland spar is its birefringence, where the crystal's refractive index differs for light of different polarizations. When a ray of unpolarized light passes through the crystal, it is divided into two rays of mutually perpendicular polarization directed at various angles. This double refraction causes objects seen through the crystal to appear doubled.
Iceland spar possesses several optical properties other than double refraction and birefringence. It is highly transparent to visible light, allowing light to pass through with minimal absorption or scattering, which is ideal for optical applications requiring clarity. Iceland spar can produce vivid colours when viewed under polarized light due to its birefringent nature. This effect is known as the "Becke line" and can be used to determine a mineral's refractive index. Additionally, Iceland spar is optically active, meaning it can rotate the plane of polarization of light passing through it, a property resulting from its asymmetrical atomic arrangement. These optical properties contribute to the mineral's scientific use and aesthetic appeal. | Iceland spar | Wikipedia | 490 | 318869 | https://en.wikipedia.org/wiki/Iceland%20spar | Physical sciences | Minerals | Earth science |
Historical significance
Iceland spar holds historical importance in optics and the study of light. One of its most notable properties is its ability to exhibit double refraction. This phenomenon was first described by the Danish scientist Erasmus Bartholin in 1669, who observed it in a specimen of Iceland spar.
The study of double refraction in Iceland spar played a role in developing the wave theory of light. Scientists such as Christiaan Huygens, Isaac Newton, and Sir George Stokes studied this phenomenon and contributed to the understanding of light as a wave. Huygens, in particular, used double refraction to support his wave theory of light, in contrast to Newton's corpuscular theory. Augustin-Jean Fresnel published a complete explanation of double refraction in light polarization in the 1820s.
The understanding of double refraction in Iceland spar also led to the development of polarized light microscopy, which is used in various scientific fields to study the properties of materials. Iceland spar has been used historically in optical instruments like polarizing microscopes and navigation equipment.
Mining
Mines producing Iceland spar include many mines producing related calcite and aragonite. Iceland spar occurs in various locations worldwide, historically named after Iceland due to its abundance on the island. Other productive sources include China and the greater Sonoran Desert region, in Santa Eulalia, Chihuahua, Mexico, and New Mexico, United States. The clearest specimens, as well as the largest, have been from the Helgustaðir mine in Iceland.
Surveying tools and techniques are combined to reduce the risk and cost of exploration to identify deposits. Geological maps and remote sensing techniques, such as satellite imagery and aerial photography, are used for initial exploration and regional assessment to identify potential areas for further exploration. Geophysical surveys, including magnetometry, gravity surveys, and electromagnetic surveys, are then employed to detect anomalies indicating mineralization. Field mapping of surface geology and mineralogy also plays a role in identifying potential mineralization zones.
The mining process for Iceland spar varies based on the specific geological conditions of the deposit. Open-pit mining or quarrying is common for surface deposits. Once extracted, the calcite is processed to remove impurities, prepared for various applications, including optical instruments and jewelry, and used as a source of calcium carbonate in industries like construction and agriculture. | Iceland spar | Wikipedia | 475 | 318869 | https://en.wikipedia.org/wiki/Iceland%20spar | Physical sciences | Minerals | Earth science |
Environmental issues
Some potential environmental issues associated with Iceland spar mining include habitat destruction, water pollution, air pollution, soil degradation, and visual impact. Mining activities can destroy natural habitats, mainly if the mining site is located in ecologically sensitive areas, leading to the loss of biodiversity and disrupting local ecosystems. Water sources can be contaminated through the discharge of chemicals used in the extraction and processing of minerals, impacting aquatic life and water quality. Mining activities can also lead to soil erosion and degradation, mainly if proper land reclamation measures are not implemented after mining ceases. Open-pit mining operations can have a significant visual impact on the landscape, altering the natural scenery of an area. These measures may include erosion control, environmentally friendly mining techniques, and the reclamation of mined areas to restore them to a natural state.
Health concerns
Mining, including Iceland spar mining, poses various health risks to workers and nearby communities. Some key health concerns associated with mining activities include respiratory issues, noise-induced hearing loss, chemical exposure, musculoskeletal disorders, injuries and accidents, and mental health issues. Dust generated during mining operations can contain harmful particles, leading to respiratory problems. The high noise levels generated by mining activities can cause hearing loss over time if proper protective measures are not in place. Miners may also be exposed to harmful chemicals used in the extraction and processing of minerals, which can cause various health issues. The physical demands of mining work, such as heavy lifting and repetitive motions, can result in musculoskeletal disorders. Injuries and accidents are also common risks in mining, including falls, equipment-related incidents, and mine collapses. The demanding nature of mining work, along with long hours and isolation, can contribute to mental health issues such as stress, anxiety, and depression. Mining companies must implement health and safety measures to mitigate these risks to protect workers and nearby communities, including personal protective equipment, dust control measures, and health and safety training. Regularly monitoring air quality, noise levels, and other potential hazards is essential to ensure a safe working environment.
Uses
Iceland spar has been historically used in telecommunications due to its unique optical properties. One of its key features, birefringence, made it worthwhile in early optical technologies, such as developing optical instruments like polarizing microscopes and constructing optical rangefinders and gunsights. | Iceland spar | Wikipedia | 474 | 318869 | https://en.wikipedia.org/wiki/Iceland%20spar | Physical sciences | Minerals | Earth science |
While uncommon, Iceland spar has historically been used in navigation as a polarizing filter to determine the sun's direction on overcast days. It has been speculated that the sunstone (, a different mineral from the gem-quality sunstone) mentioned in medieval Icelandic texts, such as Rauðúlfs þáttr, was Iceland spar, and that Vikings used its light-polarizing property to tell the direction of the sun on cloudy days for navigational purposes. The polarization of sunlight in the Arctic can be detected, and the direction of the sun identified to within a few degrees in both cloudy and twilight conditions using the sunstone and the naked eye. The process involves moving the stone across the visual field to reveal a yellow entoptic pattern on the fovea of the eye, probably Haidinger's brush. The recovery of an Iceland spar sunstone from a ship of the Elizabethan era that sank in 1592 off Alderney suggests that this navigational technology may have persisted after the invention of the magnetic compass.
William Nicol (1770–1851) invented the first polarizing prism, using Iceland spar to create his Nicol prism.
Modern applications
Despite being historically significant, Iceland spar still holds an essential place in modern applications. Due to its optical properties, Iceland spar is still used in instruments like polarizing microscopes, lenses, and filters. Iceland spar is also used in optical instruments for geological and biological microscopy as its birefringence helps to reveal material structure. It is also a practical tool used in education and research to demonstrate optical principles. Though its applications are less widespread than in the past, Iceland spar continues to contribute to various scientific and technological endeavours.
As a type of calcite, Iceland spar can be used in construction as a building material in cement and concrete. Its high purity and brightness make it an ideal filler in paints and coatings. In metallurgy, calcite acts as a flux to lower the melting point of metals during smelting and refining. Additionally, it is used in agriculture as a soil conditioner and neutralizer to adjust soil pH levels and improve crop yields. Calcite also contributes to environmental remediation efforts, treating acidic water and soil by neutralizing acidity and removing heavy metals. | Iceland spar | Wikipedia | 469 | 318869 | https://en.wikipedia.org/wiki/Iceland%20spar | Physical sciences | Minerals | Earth science |
Geological significance
Due to Iceland spar typically forming in sedimentary environments, particularly limestone and dolomite rocks, its formation is closely tied to these carbonate rocks' deposition and diagenesis (compaction and cementation). Studying Iceland spar can provide valuable information about past environmental conditions, such as the presence of ancient seas and marine life, as carbonate rocks like limestone often form in marine environments. The presence of Iceland spar can also indicate the presence of hydrothermal activity, as calcite can form in hydrothermal veins.
Conservation and protection
Due to their scientific and historical significance, conservation efforts related to Iceland spar primarily focus on preserving specimens and mining sites. One of the challenges in preserving Iceland spar specimens is the risk of damage during extraction, handling, and storage. Mining sites that yield high-quality Iceland spar specimens are also of interest for conservation. These sites may be designated protected areas to prevent overexploitation.
Cultural impact
The Thomas Pynchon novel Against the Day uses the doubling effect of Iceland spar as a theme. | Iceland spar | Wikipedia | 210 | 318869 | https://en.wikipedia.org/wiki/Iceland%20spar | Physical sciences | Minerals | Earth science |
A deodorant is a substance applied to the body to prevent or mask body odor caused by bacterial breakdown of perspiration, for example in the armpits, groin, or feet. A subclass of deodorants, called antiperspirants, prevents sweating itself, typically by blocking sweat glands. Antiperspirants are used on a wider range of body parts, at any place where sweat would be inconvenient or unsafe, since unwanted sweating can interfere with comfort, vision, and grip (due to slipping). Other types of deodorant allow sweating but prevent bacterial action on sweat, since human sweat only has a noticeable smell when it is decomposed by bacteria.
In the United States, the Food and Drug Administration classifies and regulates most deodorants as cosmetics, but classifies antiperspirants as over-the-counter drugs.
The first commercial deodorant, Mum, was introduced and patented in the late nineteenth century by an inventor in Philadelphia, Pennsylvania, Edna Murphey. The product was briefly withdrawn from the market in the US. The modern formulation of the antiperspirant was patented by Jules Montenier on January 28, 1941. This formulation was first found in "Stopette" deodorant spray, which Time magazine called "the best-selling deodorant of the early 1950s".
Use of deodorant with aluminium compounds has been suspected of being linked to breast cancer, but research has not proven any such link.
Overview
The human body produces perspiration (sweat) via two types of sweat gland: eccrine sweat glands which cover much of the skin and produce watery odourless sweat, and apocrine sweat glands in the armpits and groin, which produce a more oily "heavy" sweat containing a proportion of waste proteins, fatty acids and carbohydrates, that can be metabolized by bacteria to produce compounds that cause body odor. In addition, the vagina produces secretions which are not a form of sweat but may be undesired and also masked with deodorants. | Deodorant | Wikipedia | 439 | 318895 | https://en.wikipedia.org/wiki/Deodorant | Biology and health sciences | Hygiene products | Health |
Human perspiration of all types is largely odorless until its organic components are fermented by bacteria that thrive in hot, humid environments. The human underarm is among the most consistently warm areas on the surface of the human body, and sweat glands readily provide moisture containing a fraction of organic matter, which when excreted, has a vital cooling effect. When adult armpits are washed with alkaline pH soap, the skin loses its protective acid mantle (pH 4.5–6), raising the skin pH and disrupting the skin barrier. Many bacteria are adapted to the slightly alkaline environment within the human body, so they can thrive within this elevated pH environment. This makes the skin more than usually susceptible to bacterial colonization. Bacteria on the skin feed on the waste proteins and fatty acids in the sweat from the apocrine glands and on dead skin and hair cells, releasing trans-3-methyl-2-hexenoic acid in their waste, which is the primary cause of body odor.
Underarm hair wicks the moisture away from the skin and aids in keeping the skin dry enough to prevent or diminish bacterial colonization. The hair is less susceptible to bacterial growth and therefore reduces bacterial odor. The apocrine sweat glands are inactive until puberty, which is why body odor often only becomes noticeable at that time.
Deodorant products work in one of two ways – by preventing sweat from occurring, or by allowing it to occur but preventing bacterial activity that decomposes sweat on the skin.
History
Modern deodorants
In 1888, the first modern commercial deodorant, Mum, was developed and patented by a U.S. inventor in Philadelphia, Pennsylvania, Edna Murphey; the small company was bought by Bristol-Myers in 1931. In the late 1940s, Helen Barnett Diserens developed an underarm applicator based on the newly invented ball-point pen. In 1952, the company began marketing the product under the name Ban Roll-On. The product was briefly withdrawn from the market in the U.S., but it is once again available at retailers in the U.S. under the brand Ban. In the UK it is sold under the names Mum Solid and Mum Pump Spray. Chattem acquired the Ban deodorant brand in 1998 and subsequently sold it to Kao Corporation in 2000. | Deodorant | Wikipedia | 483 | 318895 | https://en.wikipedia.org/wiki/Deodorant | Biology and health sciences | Hygiene products | Health |
In 1903, the first commercial antiperspirant was Everdry. The modern formulation of the antiperspirant was patented by Jules Montenier on January 28, 1941. This patent addressed the problem of the excessive acidity of aluminum chloride and its excessive irritation of the skin, by combining it with a soluble nitrile or a similar compound. This formulation was first found in "Stopette" deodorant spray, which Time magazine called "the best-selling deodorant of the early 1950s". "Stopette" gained its prominence as the first and long-time sponsor of the game show What's My Line?; it was later eclipsed by many other brands once the 1941 patent expired.
Between 1942 and 1957, the market for deodorants increased 600 times to become a $70 million market. Deodorants were originally marketed primarily to women, but by 1957 the market had expanded to male users, and estimates were that 50% of men were using deodorants by that date. The Ban Roll-On product led the market in sales.
In the early 1960s, the first aerosol antiperspirant in the marketplace was Gillette's Right Guard, whose brand was later sold to Henkel in 2006. Aerosols were popular because they let the user dispense a spray without coming in contact with the underarm area. By the late 1960s, half of all the antiperspirants sold in the U.S. were aerosols, and continued to grow in all sales to 82% by the early 1970s. However, the late 1970s saw two developments which greatly reduced the popularity of these products. First, in 1977 the U.S. Food and Drug Administration banned the active ingredient used in aerosols, aluminium zirconium chemicals, due to safety concerns over long term inhalation. Second, the U.S. Environmental Protection Agency limited the use of chlorofluorocarbon (CFC) propellants used in aerosols due to awareness that these gases can contribute to depleting the ozone layer. As the popularity of aerosols slowly decreased, stick antiperspirants became more popular.
Classification | Deodorant | Wikipedia | 449 | 318895 | https://en.wikipedia.org/wiki/Deodorant | Biology and health sciences | Hygiene products | Health |
Deodorant
In the United States, deodorants are classified and regulated as cosmetics by the U.S. Food and Drug Administration (FDA) and are designed to eliminate odor. Deodorants are often alcohol-based. Alcohol initially stimulates sweating but may also temporarily kill bacteria. Other active ingredients in deodorants include sodium stearate, sodium chloride, and stearyl alcohol. Deodorants can be formulated with other, more persistent antimicrobials such as triclosan that slow bacterial growth or with metal chelant compounds such as EDTA. Deodorants may contain perfume fragrances or natural essential oils intended to mask the odor of perspiration. Some of the first patented deodorants used zinc oxide, acids, ammonium chloride, sodium bicarbonate, and formaldehyde (which is now known as a carcinogen), and some of these ingredients were messy, irritating to the skin.
Over-the-counter products, often labeled as "natural deodorant crystal", contain the chemical rock crystals potassium alum or ammonium alum, which prevents bacterial action on sweat. These have gained popularity as an alternative health product, in spite of concerns about possible risks related to aluminum (see below – all alum salts contain aluminum in the form of aluminum sulphate salts) and contact dermatitis.
Vaginal deodorant, in the form of sprays, suppositories, and wipes, is often used by women to mask vaginal secretions. Vaginal deodorants can sometimes cause dermatitis.
Deodorant antiperspirant | Deodorant | Wikipedia | 342 | 318895 | https://en.wikipedia.org/wiki/Deodorant | Biology and health sciences | Hygiene products | Health |
In the United States, deodorants combined with antiperspirant agents are classified as drugs by the FDA. Antiperspirants attempt to stop or significantly reduce perspiration and thus reduce the moist climate in which bacteria thrive. Aluminium chloride, aluminium chlorohydrate, and aluminium-zirconium compounds, most notably aluminium zirconium tetrachlorohydrex gly are frequently used in antiperspirants. Aluminium chlorohydrate and aluminium-zirconium tetrachlorohydrate gly are the most frequent active ingredients in commercial antiperspirants. Aluminium-based complexes react with the electrolytes in the sweat to form a gel plug in the duct of the sweat gland. The plugs prevent the gland from excreting liquid and are removed over time by the natural sloughing of the skin. The metal salts work in another way to prevent sweat from reaching the surface of the skin: the aluminium salts interact with the keratin fibrils in the sweat ducts and form a physical plug that prevents sweat from reaching the skin's surface. Aluminium salts also have a slight astringent effect on the pores; causing them to contract, further preventing sweat from reaching the surface of the skin. The blockage of a large number of sweat glands reduces the amount of sweat produced in the underarms, though this may vary from person to person. Methenamine in the form of cream or spray is effective in the treatment of excessive sweating and attendant odor. Antiperspirants are usually best applied before bed.
Product formulations and formats
Formulations
Common and historical formulations for deodorants include the following active ingredients: | Deodorant | Wikipedia | 355 | 318895 | https://en.wikipedia.org/wiki/Deodorant | Biology and health sciences | Hygiene products | Health |
Aluminum salts (aluminum chlorohydrate, aluminum zirconium tetrachlorohydrex gly, and others) – used as the basis for almost all non-prescription (everyday) antiperspirants. The aluminum reacts within the sweat gland to form a colloid which physically prevents sweating.
Alum (typically potassium alum or ammonium alum, also described as "rock alum", or "rock crystal", or "natural deodorant"). Alum is a natural crystalline product widely used both historically and in modern times as a deodorant, because it inhibits bacterial action. The word 'alum' is a historical term for aluminum sulfate salts, therefore all alum products will contain aluminum, albeit in a different chemical form from antiperspirants.
Bactericidal products such as triclosan (TCS), octenidine dihydrochloride, and parabens kill bacteria on the skin.
Alcohols and related compounds such as propylene glycol – these products can have both drying and bactericidal effects.
Methenamine (hexamethylenetetramine, also known as hexamine or urotropin) is a powerful antiperspirant, often used for severe sweat-related issues, as well as prevention of sweating within the sockets of prosthetic devices used by amputees.
Acidifiers and pH neutral products – deodorants that prevent bacterial action by enhancing (or at least, not depleting) the skin's natural slight acidity, known as the acid mantle, which naturally reduces bacterial action but can be compromised by typically alkaline soaps and skin products.
Masking scents – other strong or overriding scents of a pleasing type may be used, used to mask bodily odors. Typically these are strongly smelling plant extracts or synthetic aromas.
Activated charcoal and other products capable of absorbing sweat and/or smell. Although charcoal most often has a black color, the activated charcoal used in deodorants may be a very light color for aesthetic reasons. | Deodorant | Wikipedia | 436 | 318895 | https://en.wikipedia.org/wiki/Deodorant | Biology and health sciences | Hygiene products | Health |
Less commonly used, products such as milk of magnesia (a thick liquid suspension of magnesium hydroxide) are sometimes used as deodorants. Many milk of magnesia products contain small amounts of sodium hypochlorite (bleach) at very low levels that are safe for ingestion and skin application. Sodium hypochlorite is a powerful bactericide, and it is possible that its presence in a product that can dry onto the skin, may explain this use as a deodorant. (Safety info: bleach is caustic and extremely poisonous, and can be lethal, in higher concentrations.) | Deodorant | Wikipedia | 132 | 318895 | https://en.wikipedia.org/wiki/Deodorant | Biology and health sciences | Hygiene products | Health |
Formats
Deodorants and antiperspirants come in many forms. What is commonly used varies in different countries. In Europe, aerosol sprays are popular, as are cream and roll-on forms. In North America, solid or gel forms are dominant.
Health effects
After using a deodorant containing zirconium, the skin may develop an allergic, axillary granuloma response. Antiperspirants with propylene glycol, when applied to the axillae, can cause irritation and may promote sensitization to other ingredients in the antiperspirant. Deodorant crystals containing synthetically made potassium alum were found to be a weak irritant to the skin. Unscented deodorant is available for those with sensitive skin. Frequent use of deodorants was associated with blood concentrations of the synthetic musk galaxolide.
Aluminum
Many deodorants and antiperspirants contain aluminium in the form of aluminium salts such as aluminium chlorohydrate.
The US Food and Drug Administration, in a 2003 paper discussing deodorant safety, concluded that "despite many investigators looking at this issue, the agency does not find data from topical and inhalation chronic exposure animal and human studies submitted to date sufficient to change the monograph status of aluminum containing antiperspirants", therefore allowing their use and stating they will keep monitoring the scientific literature. Members of the Scientific Committee on Consumer Safety (SCCS) of the European Commission concluded similarly in 2015, that "due to the lack of adequate data on dermal penetration to estimate the internal dose of aluminium following cosmetic uses, risk assessment cannot be performed." In the light of new data in 2020 the SCCS considered aluminium compounds safe up to 6.25% in non-spray deodorants or non-spray antiperspirants and 10.60% in spray deodorants or spray antiperspirants.
Myths and claims related to aluminium compounds in deodorants
Common myths and marketing claims for aluminium in deodorants (including aluminum in alum products) include claims: | Deodorant | Wikipedia | 440 | 318895 | https://en.wikipedia.org/wiki/Deodorant | Biology and health sciences | Hygiene products | Health |
That aluminium in deodorants applied to the skin is a risk factor for some cancers (notably breast cancer) and some forms of dementia
That aluminium in antiperspirants can enter the body (possibly through shaving cuts)
That aluminium in alum "natural deodorant" products is "safer" because it is "too large" to enter the body
Of note, the parts of the body which are commonly shaved and also commonly treated with deodorants, such as the armpits, contain substantial deposits of subcutaneous fat. Shaving cuts would be extremely unlikely to penetrate sufficiently beyond the very outer layers of the skin, for much if any product to enter the bloodstream.
Alzheimer's disease
A 2014 review of 469 peer-reviewed studies examining the effect of exposure to aluminum products concluded "that health risks posed by exposure to inorganic depend on its physical and chemical forms and that the response varies with route of administration, magnitude, duration and frequency of exposure. These results support previous conclusions that there is little evidence that exposure to metallic Al, the Al oxides or its salts increases risk for Alzheimer's disease, genetic damage or cancer".
Breast cancer
The claim that breast cancer is believed to be linked with deodorant use has been widely circulated and appears to originate from a spam email sent in 1999; however, there is no evidence to support the existence of such a link. The myth circulates in two forms:
Antiperspirants block the "purging" of toxins which build up in the body and cause breast cancer: As sweat glands simply do not have this function, the claim is scientifically implausible. Perspiration from the eccrine sweat glands is 99% water, with some salt (sodium chloride) and only trace amounts of lactic acid (almost entirely processed in the liver), urea (almost entirely excreted by the kidneys), and only very small amounts of all other components. Perspiration from the apocrine sweat glands (those in the armpits and groin, which are more responsible for body odor) also include waste proteins, carbohydrates, and fatty acids which would otherwise be processed by other organs such as the liver. | Deodorant | Wikipedia | 461 | 318895 | https://en.wikipedia.org/wiki/Deodorant | Biology and health sciences | Hygiene products | Health |
It is possible that there has been confusion between sweat glands, and the lymph nodes deep within the armpits which form part of the immune system and help filter toxins, but if so, there is no evidence at all of such "blocking" of lymph nodes, nor any scientifically plausible route by which this could result from deodorant use.
Aluminum in antiperspirants can enter the body (possibly through cuts) and cause breast cancer: There is no current evidence to support this claim, nor any convincing evidence that it is true. A fact often cited to back up this claim is that more breast cancers occur in the part of the breast near the armpits. However, breast tissue is not evenly spread out, and the part of the breast near the armpit (the Tail of Spence) simply contains much more breast tissue than the other quadrants, making it much more likely that any cancer would occur in that location. See above for current scientific knowledge regarding aluminum in deodorants.
The National Cancer Institute states that "no scientific evidence links the use of these products to the development of breast cancer" and that "no clear evidence that the use of aluminum-containing underarm antiperspirants or cosmetics increases the risk of breast cancer", but also concludes that studies of antiperspirants and deodorants and breast cancer have provided conflicting results, additional research would be needed to determine whether a relationship exists".
Another constituent of deodorant products that has given cause for concern are parabens, a chemical additive. However parabens do not cause cancer.
Kidney dysfunction
The FDA has "acknowledge[d] that small amounts of aluminum can be absorbed from the gastrointestinal tract and through the skin", leading to a warning "that people with kidney disease may not be aware that the daily use of antiperspirant drug products containing aluminum may put them at a higher risk because of exposure to aluminum in the product." The agency warns people with kidney dysfunction to consult a doctor before using antiperspirants containing aluminum.
Aerosol burns and frostbite
If aerosol deodorant is held close to the skin for long enough, it can cause an aerosol burn—a form of frostbite. In controlled tests, spray deodorants have been shown to cause temperature drops of over 60 °C in a short period of time. | Deodorant | Wikipedia | 493 | 318895 | https://en.wikipedia.org/wiki/Deodorant | Biology and health sciences | Hygiene products | Health |
Clothing
Aluminium zirconium tetrachlorohydrex gly, a common antiperspirant, can react with sweat to create yellow stains on clothing. Underarm liners are an antiperspirant alternative that does not leave stains. | Deodorant | Wikipedia | 52 | 318895 | https://en.wikipedia.org/wiki/Deodorant | Biology and health sciences | Hygiene products | Health |
An endorheic basin ( ; also endoreic basin and endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water (e.g. rivers and oceans); instead, the water drainage flows into permanent and seasonal lakes and swamps that equilibrate through evaporation. Endorheic basins are also called closed basins, terminal basins, and internal drainage systems.
Endorheic regions contrast with open lakes (exorheic regions), where surface waters eventually drain into the ocean. In general, water basins with subsurface outflows that lead to the ocean are not considered endorheic; but cryptorheic. Endorheic basins constitute local base levels, defining a limit of the erosion and deposition processes of nearby areas. Endorheic water bodies include the Caspian Sea, which is the world's largest inland body of water.
Etymology
The term endorheic derives from the French word , which combines ( 'within') and 'flow'.
Endorheic lakes
Endorheic lakes (terminal lakes) are bodies of water that do not flow into an ocean or a sea. Most of the water that falls to Earth percolates into the oceans and the seas by way of a network of rivers, lakes, and wetlands. Analogous to endorheic lakes is the class of bodies of water located in closed watersheds (endorheic watersheds) where the local topography prevents the drainage of water into the oceans and the seas. These endorheic watersheds (containing water in rivers or lakes that form a balance of surface inflows, evaporation and seepage) are often called sinks. | Endorheic basin | Wikipedia | 357 | 318980 | https://en.wikipedia.org/wiki/Endorheic%20basin | Physical sciences | Hydrology | Earth science |
Endorheic lakes are typically located in the interior of a landmass, far from an ocean, and in areas of relatively low rainfall. Their watersheds are often confined by natural geologic land formations such as a mountain range, cutting off water egress to the ocean. The inland water flows into dry watersheds where the water evaporates, leaving a high concentration of minerals and other inflow erosion products. Over time this input of erosion products can cause the endorheic lake to become relatively saline (a "salt lake"). Since the main outflow pathways of these lakes are chiefly through evaporation and seepage, endorheic lakes are usually more sensitive to environmental pollutant inputs than water bodies that have access to oceans, as pollution can be trapped in them and accumulate over time.
Occurrence
Endorheic regions can occur in any climate but are most commonly found in desert locations. This reflects the balance between tectonic subsidence and rates of evaporation and sedimentation. Where the basin floor is dropping more rapidly than water and sediments can accumulate, any lake in the basin will remain below the sill level (the level at which water can find a path out of the basin). Low rainfall or rapid evaporation in the watershed favor this case. In areas where rainfall is higher, riparian erosion will generally carve drainage channels (particularly in times of flood), or cause the water level in the terminal lake to rise until it finds an outlet, breaking the enclosed endorheic hydrological system's geographical barrier and opening it to the surrounding terrain. The Black Sea was likely such a lake, having once been an independent hydrological system before the Mediterranean Sea broke through the terrain separating the two. Lake Bonneville was another such lake, overflowing its basin in the Bonneville flood. The Malheur/Harney lake system in Oregon is normally cut off from drainage to the ocean, but has an outflow channel to the Malheur River. This is presently dry, but may have flowed as recently as 1,000 years ago.
Examples of relatively humid regions in endorheic basins often exist at high elevation. These regions tend to be marshy and are subject to substantial flooding in wet years. The area containing Mexico City is one such case, with annual precipitation of and characterized by waterlogged soils that require draining. | Endorheic basin | Wikipedia | 487 | 318980 | https://en.wikipedia.org/wiki/Endorheic%20basin | Physical sciences | Hydrology | Earth science |
Endorheic regions tend to be far inland with their boundaries defined by mountains or other geological features that block their access to oceans. Since the inflowing water can evacuate only through seepage or evaporation, dried minerals or other products collect in the basin, eventually making the water saline and also making the basin vulnerable to pollution. Continents vary in their concentration of endorheic regions due to conditions of geography and climate. Australia has the highest percentage of endorheic regions at 21 per cent while North America has the least at five per cent. Approximately 18 per cent of the Earth's land drains to endorheic lakes or seas, the largest of these land areas being the interior of Asia.
In deserts, water inflow is low and loss to solar evaporation high, drastically reducing the formation of complete drainage systems. In the extreme case, where there is no discernible drainage system, the basin is described as arheic. Closed water flow areas often lead to the concentration of salts and other minerals in the basin. Minerals leached from the surrounding rocks are deposited in the basin, and left behind when the water evaporates. Thus endorheic basins often contain extensive salt pans (also called salt flats, salt lakes, alkali flats, dry lake beds, or playas). These areas tend to be large, flat hardened surfaces and are sometimes used for aviation runways, or land speed record attempts, because of their extensive areas of perfectly level terrain.
Both permanent and seasonal endorheic lakes can form in endorheic basins. Some endorheic basins are essentially stable because climate change has reduced precipitation to the degree that a lake no longer forms. Even most permanent endorheic lakes change size and shape dramatically over time, often becoming much smaller or breaking into several smaller parts during the dry season. As humans have expanded into previously uninhabitable desert areas, the river systems that feed many endorheic lakes have been altered by the construction of dams and aqueducts. As a result, many endorheic lakes in developed or developing countries have contracted dramatically, resulting in increased salinity, higher concentrations of pollutants, and the disruption of ecosystems. | Endorheic basin | Wikipedia | 454 | 318980 | https://en.wikipedia.org/wiki/Endorheic%20basin | Physical sciences | Hydrology | Earth science |
Even within exorheic basins, there can be "non-contributing", low-lying areas that trap runoff and prevent it from contributing to flows downstream during years of average or below-average runoff. In flat river basins, non-contributing areas can be a large fraction of the river basin, e.g. Lake Winnipeg's basin. A lake may be endorheic during dry years and can overflow its basin during wet years, e.g., the former Tulare Lake.
Because the Earth's climate has recently been through a warming and drying phase with the end of the Ice Ages, many endorheic areas such as Death Valley that are now dry deserts were large lakes relatively recently. During the last ice age, the Sahara may have contained lakes larger than any now existing.
Climate change coupled with the mismanagement of water in these endorheic regions has led to devastating losses in ecosystem services and toxic surges of pollutants. The desiccation of saline lakes produces fine dust particles that impair agriculture productivity and harm human health. Anthropogenic activity has also caused a redistribution of water from these hydrologically landlocked basins such that endorheic water loss has contributed to sea level rise, and it is estimated that most of the terrestrial water lost ends up in the ocean. In regions such as Central Asia, where people depend on endorheic basins and other surface water sources to satisfy their water needs, human activity greatly impacts the availability of that water.
Notable endorheic basins and lakes
Africa
Large endorheic regions in Africa are located in the Sahara Desert, the Sahel, the Kalahari Desert, and the East African Rift: | Endorheic basin | Wikipedia | 350 | 318980 | https://en.wikipedia.org/wiki/Endorheic%20basin | Physical sciences | Hydrology | Earth science |
Chad Basin, in the northern centre of Africa. It covers an area of approximately 2.434 million km2.
Qattara Depression, in Egypt.
Chott Melrhir, in Algeria.
Chott el Djerid, in Tunisia.
The Okavango River, in the Kalahari Desert, is part of an endorheic basin region, the Okavango Basin, that also includes the Okavango Delta, Lake Ngami, the Nata River, and a number of salt pans such as Makgadikgadi Pan.
Etosha Pan in Namibia's Etosha National Park.
Turkana Basin, in Kenya, whose basin includes the Omo River of Ethiopia.
Lake Chilwa, in Malawi.
Afar Depression, in Eritrea, Ethiopia, and Djibouti, which contains the Awash River
Some Rift Valley lakes, such as Lake Abijatta, Lake Chew Bahir, Lake Shala, Lake Chamo, and Lake Awasa.
Lake Mweru Wantipa, in Zambia.
Lake Magadi, in Kenya.
Lake Rukwa, in Tanzania.
Antarctica
Endorheic lakes exist in Antarctica's McMurdo Dry Valleys, Victoria Land, the largest ice-free area.
Don Juan Pond in Wright Valley is fed by groundwater from a rock glacier and remains unfrozen throughout the year.
Lake Vanda in Wright Valley has a perennial ice cover, the edges of which melt in the summer, allowing flow from the longest river in Antarctica, the Onyx River. The lake is over 70 m deep and is hypersaline.
Lake Bonney is in Taylor Valley and has a perennial ice cover and two lobes separated by the Bonney Riegel. Glacial melt and discharge from Blood Falls feed the lake. Its unique glacial history has resulted in hypersaline brine in the bottom waters and fresh water at the surface.
Lake Hoare, in Taylor Valley, is the freshest of the Dry Valley lakes, receiving its melt almost exclusively from the Canada Glacier. The lake has an ice cover and forms a moat during the Austral summer.
Lake Fryxell is adjacent to the Ross Sea in Taylor Valley. The lake has an ice cover and receives its water from numerous glacial meltwater streams for approximately six weeks out of the year. Its salinity increases with depth.
Asia | Endorheic basin | Wikipedia | 481 | 318980 | https://en.wikipedia.org/wiki/Endorheic%20basin | Physical sciences | Hydrology | Earth science |
Much of Western and Central Asia is a giant endorheic region made up of a number of contiguous closed basins. The region contains several basins and terminal lakes, including:
The Caspian Sea, the largest lake on Earth. A large part of western Russia, drained by the Volga River, is part of the Caspian basin.
Lake Urmia in Western Azerbaijan Province of Iran.
The Aral Sea, whose tributary rivers have been diverted, leading to a dramatic shrinkage of the lake. The resulting ecological disaster has brought the plight of internal drainage basins to public attention.
Lake Balkhash, in Kazakhstan.
Issyk-Kul Lake and Chatyr-Kul Lake in Kyrgyzstan.
Lop Lake, in the Tarim Basin of China's Xinjiang Uygur Autonomous Region.
The Dzungarian Basin in Xinjiang, separated from the Tarim Basin by the Tian Shan. The most notable terminal lake in the basin is the Manas Lake.
The Central Asian Internal Drainage Basin, in southern and western Mongolia, contains a series of closed drainage basins, such as the Khyargas Nuur basin, the Uvs Nuur basin, which includes Üüreg Lake, and the Pu-Lun-To River Basin.
Qaidam Basin, in Qinghai Province, China, as well as nearby Qinghai Lake.
Sistan Basin covering areas of Iran and Afghanistan
Pangong Tso and Aksai Chin Lake on the China-India border
Many small lakes and rivers of the Iranian Plateau, including Gavkhouni marshes and Namak Lake.
Other endorheic lakes and basins in Asia include:
The Dead Sea, the lowest surface point on Earth and one of its saltiest bodies of water lies between Israel and Jordan.
Sambhar Lake, in Rajasthan, north-western India
Lake Van in eastern Turkey
Sabkhat al-Jabbul, extensive salt flats and a lake in Syria.
Solar Lake, Sinai, near the Israeli-Egypt border.
Lake Tuz, in Turkey, in south part of Central Anatolia Region.
Sawa lake in Iraq, in Muthanna Governorate.
Australia
Australia, being very dry and having exceedingly low runoff ratios due to its ancient soils, has many endorheic drainages. The most important are: | Endorheic basin | Wikipedia | 459 | 318980 | https://en.wikipedia.org/wiki/Endorheic%20basin | Physical sciences | Hydrology | Earth science |
Lake Eyre basin, which drains into the highly variable Lake Eyre and includes Lake Frome.
Lake Torrens, usually an endorheic lake to the west of the Flinders Ranges in South Australia, that flows to the sea after extreme rainfall events.
Lake Corangamite, a highly saline crater lake in western Victoria.
Lake George, formerly connected to the Murray-Darling Basin
Europe
Though a large portion of Europe drains to the endorheic Caspian Sea, Europe's wet climate means it contains relatively few terminal lakes itself: any such basin is likely to continue to fill until it reaches an overflow level connecting it with an outlet or erodes the barrier blocking its exit.
There are some seemingly endorheic lakes, but they are cryptorheic, being drained either through manmade canals, via karstic phenomena, or other subsurface seepage.
Lake Neusiedl, in Austria and Hungary.
Lake Trasimeno, in Italy.
Fucine Lake, in Italy. Now drained.
Lake Velence, in Hungary.
Lake Prespa, between Albania, Greece and North Macedonia.
Rahasane Turlough, the largest turlough in Ireland.
Laacher See, in Germany.
The Lasithi Plateau in Crete, Greece, is a high endorheic plateau.
A few minor true endorheic lakes exist in Spain (e.g. Laguna de Gallocanta, Estany de Banyoles), Italy, Cyprus (Larnaca and Akrotiri salt lakes) and Greece.
North and Central America | Endorheic basin | Wikipedia | 320 | 318980 | https://en.wikipedia.org/wiki/Endorheic%20basin | Physical sciences | Hydrology | Earth science |
The Great Basin is North America's largest and the world's ninth largest endorheic basin, covering nearly all of Nevada, much of Oregon and Utah, and portions of California, Idaho, and Wyoming. Notable enclosed basins include Death Valley, the hottest location on Earth; the Black Rock Desert and Bonneville Salt Flats, location of many of the new vehicle land speed records set since the 1930s; the Great Salt Lake, remnant of Lake Bonneville; and the Salton Sea.
The Valley of Mexico. In Pre-Columbian times, the Valley was substantially covered with five lakes, including Lake Texcoco, Lake Xochimilco, and Lake Chalco.
Guzmán Basin, in northern Mexico and the southwestern United States. The Mimbres River of New Mexico drains into this basin.
Lago Atitlán, a volcanic caldera lake in the highlands of Guatemala. It is cryptorheic.
Lago Coatepeque, El Salvador.
Bolsón de Mapimí, in northern Mexico.
Willcox Playa of southern Arizona.
Tulare Lake in the San Joaquin Valley in Central California, fed by the Kaweah and Tule Rivers plus southern distributaries of the Kings. Historically, it would drain into the San Joaquin River in very wet years. Agricultural development and irrigation diversions have left the lake dry.
Buena Vista Lake at the southmost end of the San Joaquin Valley in Southern California, fed by the Kern River. Historically, it would drain into Tulare Lake and the San Joaquin River in exceptionally wet years. Agricultural development and irrigation diversions have left the lake dry.
Crater Lake, in Oregon, a cryptorheic lake with subsurface drainage to the Wood River. It is filled directly by rain and snow and has very little mineral or salt buildup.
The Great Divide Basin in Wyoming, a small endorheic basin that straddles the Continental Divide of the Americas.
Devils Lake, in North Dakota.
Devil's Lake, in Wisconsin, cryptorheic.
Tule Lake and the Lost River basin in California and Oregon.
Little Manitou Lake in Saskatchewan.
Old Wives Lake, on the Laurentian Divide in Saskatchewan.
Quill Lakes, in Saskatchewan.
Pakowki Lake, on the Laurentian Divide in Alberta.
Paynes Prairie, in Florida. Since 1927, it has been drained by canal to the Atlantic Ocean via the River Styx.
Spotted Lake, Osoyoos, British Columbia, Canada. | Endorheic basin | Wikipedia | 506 | 318980 | https://en.wikipedia.org/wiki/Endorheic%20basin | Physical sciences | Hydrology | Earth science |
Several lakes on the western Chilcotin Plateau sit on the divide between the Fraser River drainage to the east and the Homathko drainage to the west. Such examples include Choelquoit Lake, Eagle Lake, and Martin lake.
Frame Lake in Yellowknife, capital of Canada's Northwest Territories.
New Mexico has several desert endorheic basins, including:
The Tularosa Basin, a rift valley.
Zuñi Salt Lake, a maar.
The Mimbres River Basin, in Grant County.
The San Agustin Basin, in Catron and Socorro Counties.
Lago Enriquillo on the island of Hispaniola in the Caribbean Sea. | Endorheic basin | Wikipedia | 138 | 318980 | https://en.wikipedia.org/wiki/Endorheic%20basin | Physical sciences | Hydrology | Earth science |
Many small lakes and ponds in North Dakota and the Northern Great Plains are endorheic, and some have salt encrustations along their shores.
South America
Laguna del Carbón, in Gran Bajo de San Julián, Argentina – the lowest point in the Western and Southern hemispheres
Lake Mar Chiquita in Argentina.
The Altiplano includes a number of closed basins such as the Salar de Coipasa, and Titicaca–Poopó system.
Lake Valencia, in Venezuela.
Salar de Atacama, in the Atacama Desert, Chile.
Ancient
Some of Earth's ancient endorheic systems and lakes include:
The Black Sea, until its merger with the Mediterranean.
The Mediterranean Sea itself and all its tributary basins, during its Messinian desiccation (approximately five million years ago) as it became disconnected from the Atlantic Ocean.
The Orcadian Basin in Scotland during the Devonian period. Now identifiable as lacustrine sediments buried around and off the coast.
Lake Tanganyika in Africa. Currently high enough to connect to rivers entering the sea.
Lake Lahontan in North America.
Lake Bonneville in North America. The basin was not always endorheic; at times, it overflowed through Red Rock Pass to the Snake River and the sea.
Lake Chewaucan in North America.
Tularosa Basin and Lake Cabeza de Vaca in North America. The basin was formerly much larger than it is today, including the ancestral Rio Grande north of Texas, which fed a large lake area.
Ebro and Duero basins, draining most of northern Spain during the Neogene and perhaps Pliocene. Climate change and erosion of the Catalan coastal mountains, as well as the deposition of alluvium in the terminal lake, allowed the Ebro basin to overflow into the sea during the middle-to-late Miocene. | Endorheic basin | Wikipedia | 385 | 318980 | https://en.wikipedia.org/wiki/Endorheic%20basin | Physical sciences | Hydrology | Earth science |
The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on, unbarred, and counterclockwise spiral galaxy located from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and was communicated that year to Charles Messier, who verified its position for inclusion in the Messier Catalogue as one of its final entries.
On February 28, 2006, NASA and the European Space Agency released a very detailed image of the Pinwheel Galaxy, which was the largest and most detailed image of a galaxy by Hubble Space Telescope at the time. The image was composed of 51 individual exposures, plus some extra ground-based photos.
Discovery
Pierre Méchain, the discoverer of the galaxy, described it as a "nebula without star, very obscure and pretty large, 6' to 7' in diameter, between the left hand of Bootes and the tail of the great Bear. It is difficult to distinguish when one lits the [grating] wires."
William Herschel wrote in 1784 that the galaxy was one of several which "...in my 7-, 10-, and 20-feet [focal length] reflectors shewed a mottled kind of nebulosity, which I shall call resolvable; so that I expect my present telescope will, perhaps, render the stars visible of which I suppose them to be composed."
Lord Rosse observed the galaxy in his 72-inch-diameter Newtonian reflector during the second half of the 19th century. He was the first to make extensive note of the spiral structure and made several sketches.
Though the galaxy can be detected with binoculars or a small telescope, to observe the spiral structure in a telescope without a camera requires a fairly large instrument, very dark skies, and a low-power eyepiece.
Structure and composition
M101 is a large galaxy, with a diameter of 170,000 light-years. By comparison, the Milky Way has a diameter of 87,400 light-years. It has around a trillion stars. It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses. Its characteristics can be compared to those of Andromeda Galaxy. | Pinwheel Galaxy | Wikipedia | 465 | 319122 | https://en.wikipedia.org/wiki/Pinwheel%20Galaxy | Physical sciences | Notable galaxies | null |
M101 has a high population of H II regions, many of which are very large and bright. H II regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force where stars form. H II regions are ionized by large numbers of extremely bright and hot young stars; those in M101 are capable of creating hot superbubbles. In a 1990 study, 1,264 H II regions were cataloged in the galaxy. Three are prominent enough to receive New General Catalogue numbers—NGC 5461, NGC 5462, and NGC 5471.
M101 is asymmetrical due to the tidal forces from interactions with its companion galaxies. These gravitational interactions compress interstellar hydrogen gas, which then triggers strong star formation activity in M101's spiral arms that can be detected in ultraviolet images.
In 2001, the X-ray source P98, located in M101, was identified as an ultra-luminous X-ray source—a source more powerful than any single star but less powerful than a whole galaxy—using the Chandra X-ray Observatory. It received the designation M101 ULX-1. In 2005, Hubble and XMM-Newton observations showed the presence of an optical counterpart, strongly indicating that M101 ULX-1 is an X-ray binary. Further observations showed that the system deviated from expected models—the black hole is just 20 to 30 solar masses, and consumes material (including captured stellar wind) at a higher rate than theory suggests.
It is estimated that M101 has about 150 globular clusters, the same as the number of the Milky Way's globular clusters.
Companion galaxies
M101 has six prominent companion galaxies: NGC 5204, NGC 5474, NGC 5477, NGC 5585, UGC 8837 and UGC 9405. As stated above, the gravitational interaction between it and its satellites may have spawned its grand design pattern. The galaxy has probably distorted the second-listed companion. The list comprises most or all of the M101 Group. | Pinwheel Galaxy | Wikipedia | 422 | 319122 | https://en.wikipedia.org/wiki/Pinwheel%20Galaxy | Physical sciences | Notable galaxies | null |
Supernovae and luminous red nova
Six internal supernovae have been recorded:
SN 1909A was discovered by Max Wolf in January 1909 and reached magnitude 12.1.
SN 1951H was discovered by Milton Humason on 1 September 1951 and reached magnitude 17.5.
SN 1970G (typeII, mag. 11.5) was discovered by Miklós Lovas on 30 July 1970.
On August 24, 2011, a Type Ia supernova, SN 2011fe, initially designated PTF 11kly, was discovered in M101. It had visual magnitude 17.2 at discovery and reached 9.9 at its peak.
On February 10, 2015, a luminous red nova, known as M101 OT2015-1 was discovered in the Pinwheel Galaxy.
On May 19, 2023, SN 2023ixf was discovered in M101, and immediately classified as a Type II supernova. | Pinwheel Galaxy | Wikipedia | 190 | 319122 | https://en.wikipedia.org/wiki/Pinwheel%20Galaxy | Physical sciences | Notable galaxies | null |
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