text stringlengths 26 3.6k | page_title stringlengths 1 71 | source stringclasses 1
value | token_count int64 10 512 | id stringlengths 2 8 | url stringlengths 31 117 | topic stringclasses 4
values | section stringlengths 4 49 ⌀ | sublist stringclasses 9
values |
|---|---|---|---|---|---|---|---|---|
For children with asthma which is well-controlled on combination therapy of inhaled corticosteroids (ICS) and long-acting beta2-agonists (LABA), the benefits and harms of stopping LABA and stepping down to ICS-only therapy are uncertain. In adults who have stable asthma while they are taking a combination of LABA and inhaled corticosteroids (ICS), stopping LABA may increase the risk of asthma exacerbations that require treatment with corticosteroids by mouth. Stopping LABA probably makes little or no important difference to asthma control or asthma-related quality of life. Whether or not stopping LABA increases the risk of serious adverse events or exacerbations requiring an emergency department visit or hospitalization is uncertain.
Delivery methods
Medications are typically provided as metered-dose inhalers (MDIs) in combination with an inhaler spacer or as a dry powder inhaler. The spacer is a plastic cylinder that mixes the medication with air, making it easier to receive a full dose of the drug. A nebulizer may also be used. Nebulizers and spacers are equally effective in those with mild to moderate symptoms. However, insufficient evidence is available to determine whether a difference exists in those with severe disease. For delivering short-acting beta-agonists in acute asthma in children, spacers may have advantages compared to nebulisers, but children with life-threatening asthma have not been studied. There is no strong evidence for the use of intravenous LABA for adults or children who have acute asthma. There is insufficient evidence to directly compare the effectiveness of a metered-dose inhaler attached to a homemade spacer compared to commercially available spacer for treating children with asthma.
Adverse effects
Long-term use of inhaled corticosteroids at conventional doses carries a minor risk of adverse effects. Risks include thrush, the development of cataracts, and a slightly slowed rate of growth. Rinsing the mouth after the use of inhaled steroids can decrease the risk of thrush. Higher doses of inhaled steroids may result in lower bone mineral density. | Asthma | Wikipedia | 445 | 44905 | https://en.wikipedia.org/wiki/Asthma | Biology and health sciences | Illness and injury | null |
Others
Inflammation in the lungs can be estimated by the level of exhaled nitric oxide. The use of exhaled nitric oxide levels (FeNO) to guide asthma medication dosing may have small benefits for preventing asthma attacks but the potential benefits are not strong enough for this approach to be universally recommended as a method to guide asthma therapy in adults or children. | Asthma | Wikipedia | 70 | 44905 | https://en.wikipedia.org/wiki/Asthma | Biology and health sciences | Illness and injury | null |
When asthma is unresponsive to usual medications, other options are available for both emergency management and prevention of flareups. Additional options include:
Humidified oxygen to alleviate hypoxia if saturations fall below 92%.
Corticosteroids by mouth, with five days of prednisone being the same two days of dexamethasone. One review recommended a seven-day course of steroids.
Magnesium sulfate intravenous treatment increases bronchodilation when used in addition to other treatment in moderate severe acute asthma attacks. In adults intravenous treatment results in a reduction of hospital admissions. Low levels of evidence suggest that inhaled (nebulized) magnesium sulfate may have a small benefit for treating acute asthma in adults. Overall, high-quality evidence do not indicate a large benefit for combining magnesium sulfate with standard inhaled treatments for adults with asthma.
Heliox, a mixture of helium and oxygen, may also be considered in severe unresponsive cases.
Intravenous salbutamol is not supported by available evidence and is thus used only in extreme cases.
Methylxanthines (such as theophylline) were once widely used, but do not add significantly to the effects of inhaled beta-agonists. Their use in acute exacerbations is controversial.
The dissociative anaesthetic ketamine is theoretically useful if intubation and mechanical ventilation is needed in people who are approaching respiratory arrest; however, there is no evidence from clinical trials to support this. A 2012 Cochrane review found no significant benefit from the use of ketamine in severe acute asthma in children.
For those with severe persistent asthma not controlled by inhaled corticosteroids and LABAs, bronchial thermoplasty may be an option. It involves the delivery of controlled thermal energy to the airway wall during a series of bronchoscopies. While it may increase exacerbation frequency in the first few months it appears to decrease the subsequent rate. Effects beyond one year are unknown. | Asthma | Wikipedia | 417 | 44905 | https://en.wikipedia.org/wiki/Asthma | Biology and health sciences | Illness and injury | null |
Monoclonal antibody injections such as mepolizumab, dupilumab, or omalizumab may be useful in those with poorly controlled atopic asthma. However, these medications are expensive and their use is therefore reserved for those with severe symptoms to achieve cost-effectiveness. Monoclonal antibodies targeting interleukin-5 (IL-5) or its receptor (IL-5R), including mepolizumab, reslizumab or benralizumab, in addition to standard care in severe asthma is effective in reducing the rate of asthma exacerbations. There is limited evidence for improved health-related quality of life and lung function.
Evidence suggests that sublingual immunotherapy in those with both allergic rhinitis and asthma improve outcomes.
It is unclear if non-invasive positive pressure ventilation in children is of use as it has not been sufficiently studied. | Asthma | Wikipedia | 189 | 44905 | https://en.wikipedia.org/wiki/Asthma | Biology and health sciences | Illness and injury | null |
Adherence to asthma treatments
Staying with a treatment approach for preventing asthma exacerbations can be challenging, especially if the person is required to take medicine or treatments daily. Reasons for low adherence range from a conscious decision to not follow the suggested medical treatment regime for various reasons including avoiding potential side effects, misinformation, or other beliefs about the medication. Problems accessing the treatment and problems administering the treatment effectively can also result in lower adherence. Various approaches have been undertaken to try and improve adherence to treatments to help people prevent serious asthma exacerbations including digital interventions.
Alternative medicine
Many people with asthma, like those with other chronic disorders, use alternative treatments; surveys show that roughly 50% use some form of unconventional therapy. There is little data to support the effectiveness of most of these therapies.
Evidence is insufficient to support the usage of vitamin C or vitamin E for controlling asthma. There is tentative support for use of vitamin C in exercise induced bronchospasm. Fish oil dietary supplements (marine n-3 fatty acids) and reducing dietary sodium do not appear to help improve asthma control. In people with mild to moderate asthma, treatment with vitamin D supplementation or its hydroxylated metabolites does not reduce acute exacerbations or improve control. There is no strong evidence to suggest that vitamin D supplements improve day-to-day asthma symptoms or a person's lung function. There is no strong evidence to suggest that adults with asthma should avoid foods that contain monosodium glutamate (MSG). There have not been enough high-quality studies performed to determine if children with asthma should avoid eating food that contains MSG.
Acupuncture is not recommended for the treatment as there is insufficient evidence to support its use. Air ionizers show no evidence that they improve asthma symptoms or benefit lung function; this applied equally to positive and negative ion generators. Manual therapies, including osteopathic, chiropractic, physiotherapeutic and respiratory therapeutic manoeuvres, have insufficient evidence to support their use in treating asthma. Pulmonary rehabilitation, however, may improve quality of life and functional exercise capacity when compared to usual care for adults with asthma. The Buteyko breathing technique for controlling hyperventilation may result in a reduction in medication use; however, the technique does not have any effect on lung function. Thus an expert panel felt that evidence was insufficient to support its use. There is no clear evidence that breathing exercises are effective for treating children with asthma. | Asthma | Wikipedia | 512 | 44905 | https://en.wikipedia.org/wiki/Asthma | Biology and health sciences | Illness and injury | null |
Prognosis
The prognosis for asthma is generally good, especially for children with mild disease. Mortality has decreased over the last few decades due to better recognition and improvement in care. In 2010 the death rate was 170 per million for males and 90 per million for females. Rates vary between countries by 100-fold.
Globally it causes moderate or severe disability in 19.4 million people (16 million of which are in low and middle income countries). Of asthma diagnosed during childhood, half of cases will no longer carry the diagnosis after a decade. Airway remodelling is observed, but it is unknown whether these represent harmful or beneficial changes. More recent data find that severe asthma can result in airway remodelling and the "asthma with chronic obstructive pulmonary disease syndrome (ACOS)" that has a poor prognosis. Early treatment with corticosteroids seems to prevent or ameliorates a decline in lung function. Asthma in children also has negative effects on quality of life of their parents.
Epidemiology
In 2019, approximately 262 million people worldwide were affected by asthma and approximately 461,000 people died from the disease. Rates vary between countries with prevalences between 1 and 18%. It is more common in developed than developing countries. One thus sees lower rates in Asia, Eastern Europe and Africa. Within developed countries it is more common in those who are economically disadvantaged while in contrast in developing countries it is more common in the affluent. The reason for these differences is not well known. Low- and middle-income countries make up more than 80% of the mortality.
While asthma is twice as common in boys as girls, severe asthma occurs at equal rates. In contrast adult women have a higher rate of asthma than men and it is more common in the young than the old. In 2010, children with asthma experienced over 900,000 emergency department visits, making it the most common reason for admission to the hospital following an emergency department visit in the US in 2011.
Global rates of asthma have increased significantly between the 1960s and 2008 with it being recognized as a major public health problem since the 1970s. Rates of asthma have plateaued in the developed world since the mid-1990s with recent increases primarily in the developing world. Asthma affects approximately 7% of the population of the United States and 5% of people in the United Kingdom. Canada, Australia and New Zealand have rates of about 14–15%. | Asthma | Wikipedia | 494 | 44905 | https://en.wikipedia.org/wiki/Asthma | Biology and health sciences | Illness and injury | null |
The average death rate from 2011 to 2015 from asthma in the UK was about 50% higher than the average for the European Union and had increased by about 5% in that time. Children are more likely see a physician due to asthma symptoms after school starts in September.
Population-based epidemiological studies describe temporal associations between acute respiratory illnesses, asthma, and development of severe asthma with irreversible airflow limitation (known as the asthma-chronic obstructive pulmonary disease "overlap" syndrome, or ACOS). Additional prospective population-based data indicate that ACOS seems to represent a form of severe asthma, characterized by more frequent hospitalizations, and to be the result of early-onset asthma that has progressed to fixed airflow obstruction.
Economics
From 2000 to 2010, the average cost per asthma-related hospital stay in the United States for children remained relatively stable at about $3,600, whereas the average cost per asthma-related hospital stay for adults increased from $5,200 to $6,600. In 2010, Medicaid was the most frequent primary payer among children and adults aged 18–44 years in the United States; private insurance was the second most frequent payer. Among both children and adults in the lowest income communities in the United States there is a higher rate of hospital stays for asthma in 2010 than those in the highest income communities.
History
Asthma was recognized in ancient Egypt and was treated by drinking an incense mixture known as kyphi. It was officially named as a specific respiratory problem by Hippocrates circa 450 BC, with the Greek word for "panting" forming the basis of our modern name. In 200 BC it was believed to be at least partly related to the emotions. In the 12th century the Jewish physician-philosopher Maimonides wrote a treatise on asthma in Arabic, based partly on Arabic sources, in which he discussed the symptoms, proposed various dietary and other means of treatment, and emphasized the importance of climate and clean air. Traditional Chinese medicine also offered medication for asthma, as indicated by a surviving 14th-century manuscript curated by the Wellcome Foundation.
In 1873, one of the first papers in modern medicine on the subject tried to explain the pathophysiology of the disease while one in 1872, concluded that asthma can be cured by rubbing the chest with chloroform liniment. Medical treatment in 1880 included the use of intravenous doses of a drug called pilocarpine. | Asthma | Wikipedia | 498 | 44905 | https://en.wikipedia.org/wiki/Asthma | Biology and health sciences | Illness and injury | null |
In 1886, F. H. Bosworth theorized a connection between asthma and hay fever.
At the beginning of the 20th century, the focus was the avoidance of allergens as well as selective beta-2 adrenoceptor agonists were used as treatment strategies.
Epinephrine was first referred to in the treatment of asthma in 1905. Oral corticosteroids began to be used for the condition in 1950. The use of a pressurized metered-dose inhaler was developed in the mid-1950s for the administration of adrenaline and isoproterenol and was later used as a beta2-adrenergic agonist.
Inhaled corticosteroids and selective short-acting beta agonists came into wide use in the 1960s.
A well-documented case in the 19th century was that of young Theodore Roosevelt (1858–1919). At that time there was no effective treatment. Roosevelt's youth was in large part shaped by his poor health, partly related to his asthma. He experienced recurring nighttime asthma attacks that felt as if he was being smothered to death, terrifying the boy and his parents.
During the 1930s to 1950s, asthma was known as one of the "holy seven" psychosomatic illnesses. Its cause was considered to be psychological, with treatment often based on psychoanalysis and other talking cures. As these psychoanalysts interpreted the asthmatic wheeze as the suppressed cry of the child for its mother, they considered the treatment of depression to be especially important for individuals with asthma.
In January 2021, an appeal court in France overturned a deportation order against a 40-year-old Bangladeshi man, who was a patient of asthma. His lawyers had argued that the dangerous levels of pollution in Bangladesh could possibly lead to worsening of his health condition, or even premature death. | Asthma | Wikipedia | 375 | 44905 | https://en.wikipedia.org/wiki/Asthma | Biology and health sciences | Illness and injury | null |
Mahogany is a straight-grained, reddish-brown timber of three tropical hardwood species of the genus Swietenia, indigenous to the Americas and part of the pantropical chinaberry family, Meliaceae. Mahogany is used commercially for a wide variety of goods, due to its coloring and durable nature. It is naturally found within the Americas, but has also been imported to plantations across Asia and Oceania. The mahogany trade may have begun as early as the 16th century and flourished in the 17th and 18th centuries. In certain countries, mahogany is considered an invasive species.
Mahogany is wood from any of three tree species: Honduran or big-leaf mahogany (Swietenia macrophylla), West Indian or Cuban mahogany (Swietenia mahagoni), and Swietenia humilis. Honduran mahogany is the most widespread and the only genuine mahogany species commercially grown today. Mahogany is a valuable lumber used for paneling, furniture, boats, musical instruments, and other items. The United States is the leading importer of mahogany, while Peru is the largest exporter. Mahogany is the national tree of the Dominican Republic and Belize.
Swietenia species have been introduced in various countries outside the Americas since the 1800s, with many plantings becoming naturalized forests. All species of Swietenia are now listed by CITES and protected due to concerns over illegal logging and mismanagement. Mahogany species can crossbreed when they grow in proximity, and the hybrid between S. mahagoni and S. macrophylla is widely planted for timber.
The history of the American mahogany trade dates back to the 17th century when the wood was first noticed by Europeans during the Spanish colonization of the Americas. Mahogany became more popular in the 18th century when the British Parliament removed import duties on timber from British possessions, leading to increased exports to Europe and North America. Throughout the 18th and 19th centuries, mahogany from various regions was imported into Europe and North America, with Britain being the largest consumer.
By the late 19th century, African mahogany began to dominate the market, and by the early 20th century, the supply of American mahogany became scarcer. In response to concerns about the sustainability of mahogany, several species have been placed on CITES Appendices to regulate the trade.
Mahogany is known for its straight, fine grain and durability, making it a popular choice for fine furniture, boat construction, and musical instruments. However, the over-harvesting of mahogany and environmental concerns have led to a decrease in its use. | Mahogany | Wikipedia | 509 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
Etymology
The etymology of mahogany is uncertain and a subject of debate. The term first appeared in John Ogilby's "America" (1671), referring to a "curious and rich wood" from Jamaica. Initial mentions of the mahogany tree (as opposed to wood) date to 1731, with its first detailed description in 1743, attributed to Swietenia mahagoni by Kemp Malone in 1940. Malone suggested that mahogany originated as a generic term for 'wood' in a native Bahamian language. F. Bruce Lamb disagreed, pointing out that the Arawak language's word for wood is caoba. Lamb identified a West African origin for the word in the Yoruba oganwo, collectively m'oganwo (meaning one which is the tallest or most high) used for the Khaya genus of trees, whose timber is today called African mahogany. Lamb proposes that Yoruba and Igbo people brought to Jamaica as slaves identified the local trees of the Swietenia genus as m'oganwo, which developed into the Portuguese term mogano, which first appeared in print as the name of a river in 1661, before finally developing into the English mahogany in Jamaica between 1655 and 1670.
Malone criticized this etymology, arguing that the proposed metamorphosis from the Yoruba m'oganwo to the Portuguese mogano to the English mahogany was a logical and linguistic stretch relying on the conversion of the singular oganwo to the collective m'oganwo, which Malone finds unlikely considering the tree's generally solitary nature. He also argues that Lamb's earliest identified use of the Portuguese mog(a)no, which is for a river that Lamb asserts must have been so named for the mahogany oganwo trees on its banks, could just as well have been named for any tall tree, since oganwo only means tall. Lamb, in turn, criticized Malone's methodology and perceived bias, and maintained that there is no evidence for mahogany as a generic word.
Description | Mahogany | Wikipedia | 412 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
Mahogany is a commercially important lumber prized for its beauty, durability, and color, and used for paneling and to make furniture, boats, musical instruments and other items. The leading importer of mahogany is the United States, followed by Britain; while the largest exporter today is Peru, which surpassed Brazil after that country banned mahogany exports in 2001. It is estimated that some 80 or 90 percent of Peruvian mahogany exported to the United States is illegally harvested, with the economic cost of illegal logging in Peru placed conservatively at $40–70 million USD annually. It was estimated that in 2000, some 57,000 mahogany trees were harvested to supply the U.S. furniture trade alone.
Mahogany is the national tree of the Dominican Republic and Belize. A mahogany tree with two woodcutters bearing an axe and a paddle also appears on the Belizean national coat of arms, under the national motto, , Latin for "under the shade I flourish."
The specific density of mahogany is 0.55. Mahogany, African: (500–850 kg/m3); Mahogany, Cuban: 660 kg/m3; Mahogany, Honduras: 650 kg/m3; Mahogany, Spanish: 850 kg/m3.
Species
The three species are:
Honduran or big-leaf mahogany (Swietenia macrophylla), with a range from Mexico to southern Amazonia in Brazil, the most widespread species of mahogany and the only genuine mahogany species commercially grown today. Illegal logging of S. macrophylla, and its highly destructive environmental effects, led to the species' placement in 2003 on Appendix II of Convention on International Trade in Endangered Species (CITES), the first time that a high-volume, high-value tree was listed on Appendix II.
West Indian or Cuban mahogany (Swietenia mahagoni), native to southern Florida and the Caribbean, formerly dominant in the mahogany trade, but not in widespread commercial use since World War II.
Swietenia humilis, a small and often twisted mahogany tree limited to seasonally dry forests in Pacific Central America that is of limited commercial utility. Some botanists believe that S. humilis is a mere variant of S. macrophylla. | Mahogany | Wikipedia | 445 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
Other species
While only the three Swietenia species are classified officially as "genuine mahogany", the Federal Trade Commission allows certain species of trees other than Swietenia to be sold as "mahoganies" in the U.S. timber trade. This is due to the long-standing usage of the terms. But it must be prefixed with another descriptor, and they are not allowed to be sold under the name "mahogany" alone.
Two names are allowed. The first is "African mahogany" for the five species of the genus Khaya (which also belong to the mahogany family), namely: K. anthotheca, K. grandifoliola, K. ivorensis, K. madagascariensis, and K. senegalensis. All of them are native to native to Africa and Madagascar. The second is the name "Philippine mahogany" for seven species (all native to the Philippines) in the genus Shorea and Parashorea (which are unrelated dipterocarps, more commonly known as "lauan" or "meranti"), namely:S. polysperma, S. negrosensis, S. contorta, S. ovata, S. almon, S. palosapis, and P. malaanonan. The timber from both "African mahoganies" and "Philippine mahoganies" as defined by the FTC, are very close in terms of appearance and properties to true mahoganies. No other species are allowed to be sold in the United States under the name "mahogany", aside from the three Swietenia species and the aforementioned exceptions. | Mahogany | Wikipedia | 340 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
Within the mahogany family, other closely-related members of other genera which also resemble mahoganies in terms of appearance and properties are also sometimes known as "mahoganies", though they can not be sold as such in the US timber trade. This includes some members of the genus Toona, namely: "Philippine mahogany" (Toona calantas, different from the above usage); "Indian mahogany" (Toona ciliata); "Chinese mahogany" (Toona sinensis); and Indonesian mahogany (Toona sureni);. However members of this genus are more usually known as "toons" or "red cedars." They have similar properties to true mahoganies but differ in appearance. Other species in the same family sometimes known as "mahoganies" include "Indian mahogany" (Chukrasia velutina, different from T. ciliata); "sipo mahogany" (Entandrophragma utile); "sapele mahogany" (Entandrophragma cylindricum); "royal mahogany" (Carapa guianensis); "white mahogany" (Turraeanthus africanus); "New Zealand mahogany" (Dysoxylum spectabile); "pink mahogany" (Guarea spp.); and "demerara mahogany" (Carapa guianensis).
Multiple other unrelated species are also known as "mahogany". These include the aforementioned Shorea species which does actually come close to true mahogany in terms of appearance and properties. But it also includes other species which do not resemble true mahogany at all and have very different wood properties, like the "Santos mahogany" (Myroxylon balsamum), "mountain mahogany" (Cercocarpus spp.), and "swamp mahogany" (Eucalyptus robusta). | Mahogany | Wikipedia | 383 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
Distribution
The natural distribution of these species within the Americas is geographically distinct. S. mahagoni grows on the West Indian islands as far north as the Bahamas, the Florida Keys and parts of Florida; S. humilis grows in the dry regions of the Pacific coast of Central America from south-western Mexico to Costa Rica; S. macrophylla grows in Central America from Yucatan southwards and into South America, extending as far as Peru, Bolivia and extreme western Brazil. In the 20th century various botanists attempted to further define S. macrophylla in South America as a new species, such as S. candollei Pittier and S. tessmannii Harms., but many authorities consider these spurious. According to Record and Hess, all of the mahogany of continental North and South America can be considered as one botanical species, Swietenia macrophylla King.
Both major species of Swietenia were introduced in several countries outside of the Americas during the 1800s and early 1900s using seeds from South America and the Caribbean. Many of these plantings became naturalized forests over time. | Mahogany | Wikipedia | 223 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
India had both S. macrophylla and S. mahagoni introduced in 1865 using seeds from West Indies. Both eventually became naturalized forests. Bangladesh had Honduran S. macrophylla introduced in 1872 and as with India it became naturalized in some areas. S. mahagoni and S. macrophylla were introduced in Indonesia in 1870 using seeds from India. S. macrophylla was included in plantation forests planted in Indonesia from the 1920s to the 1940s. Philippines had S. macrophylla introduced in 1907 and in 1913 as well as S. mahagoni in 1911, 1913, 1914, 1920 and 1922. Planting resumed in the late 1980s. It was planted with many other exotic tree species for the purpose of reforestation. S. macrophylla was planted in Sri Lanka in 1897 but it was left unmanaged until the 1950s when reforestation efforts initiated by the Sri Lankan government led to plantations being consciously developed. In the early 1900s S. mahagoni was planted on the islands of O'ahu and Maui in Hawaii but was neglected and became naturalized forests. Additionally, S. macrophylla was planted in 1922 on O'ahu and is now naturalized. Fiji had S. macrophylla introduced originally in 1911 as an ornamental species using seeds from Honduras and Belize. Fiji has become a major producer of mahogany in the 21st Century due to a robust plantation program spanning over 50 years. Harvesting began in 2003. | Mahogany | Wikipedia | 291 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
History
The name mahogany was initially associated only with those islands in the West Indies under British control (French colonists used the term acajou, while in the Spanish territories it was called caoba). The origin of the name is uncertain, but it could be a corruption of 'm'oganwo', the name used by the Yoruba and Ibo people of West Africa to describe trees of the genus Khaya, which is closely related to Swietenia. When transported to Jamaica as slaves, they gave the same name to the similar trees they saw there. Though this interpretation has been disputed, no one has suggested a more plausible origin. The indigenous Arawak name for the tree is not known. In 1671 the word mahogany appeared in print for the first time, in John Ogilby's America. Among botanists and naturalists, however, the tree was considered a type of cedar, and in 1759 was classified by Carl Linnaeus (1707–1778) as Cedrela mahagoni. The following year it was assigned to a new genus by Nicholas Joseph Jacquin (1727–1817), and named Swietenia mahagoni.
Until the 19th century all of the mahogany was regarded as one species, although varying in quality and character according to soil and climate. In 1836 the German botanist Joseph Gerhard Zuccarini (1797–1848) identified a second species while working on specimens collected on the Pacific coast of Mexico, and named it Swietenia humilis. In 1886 a third species, Swietenia macrophylla, was named by Sir George King (1840–1909) after studying specimens of Honduras mahogany planted in the Botanic Gardens in Calcutta, India. | Mahogany | Wikipedia | 348 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
Today, all species of Swietenia grown in their native locations are listed by CITES, and are therefore protected. After S. mahogani and S. macrophylla were added to CITES appendixes in 1992 and 1995 respectively international conservation programs began in earnest aided by a 1993 World Bank report entitled "Tropical Hardwood Marketing Strategies for Southeast Asia". Efforts to repopulate mahogany largely failed in its native locations due to attacks from the shoot borer Hypsipyla grandella and similarly failed in Africa due to the attacks by the equivalent Hypsipyla robusta. After so many years of mismanagement and illegal logging, Swietenia also suffered from genetic loss thus mutating and weakening the seeds. Additionally erosion in its native locations meant seeds could no longer even be planted. However, both species grew well in Asia and Asia Pacific due to the absence of these shoot borers and absence of other limitations. Plantation management progressed throughout the 1990s and 2000s in Asia and the South Pacific. Global supply of genuine mahogany has been increasing from these plantations, notably Fiji, and Philippines. For Swietenia macrophylla, the trees in these plantations are still relatively young compared to the trees being harvested from old growth forests in South America. Thus, the illegal trade of bigleaf mahogany continues apace.
History of American mahogany trade
In the 17th century, the buccaneer Alexandre Exquemelin recorded the use of mahogany or Caoba (Cedrela being the Spanish name) on Hispaniola for making canoes: "The Indians make these canoes without the use of any iron instruments, by only burning the trees at the bottom near the root, and afterwards governing the fire with such industry that nothing is burnt more than what they would have..."
The wood first came to the notice of Europeans with the beginning of Spanish colonisation in the Americas. A cross in the Cathedral at Santo Domingo, bearing the date 1514, is said to be mahogany, and Philip II of Spain apparently used the wood for the interior joinery of the palace El Escorial, begun in 1584. However, caoba, as the Taino Natives called the wood, was principally reserved for shipbuilding, and it was declared a royal monopoly at Havana in 1622. Hence very little of the mahogany growing in Spanish controlled territory found its way to Europe. | Mahogany | Wikipedia | 478 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
After the French established a colony in Saint Domingue (now Haiti), some mahogany from that island probably found its way to France, where joiners in the port cities of Saint-Malo, Nantes, La Rochelle and Bordeaux used the wood to a limited extent from about 1700. On the English-controlled islands, especially Jamaica and the Bahamas, mahogany was abundant but not exported in any quantity before 1700.
18th century
While the trade in mahogany from the Spanish and French territories in America remained moribund for most of the 18th century, this was not true for those islands under British control. The British Parliament passed an act of Parliament, the Naval Stores Act 1721 (8 Geo. 1. c. 12), which removed all import duties from timber imported into Britain from British possessions in the Americas. This immediately stimulated the trade in West Indian timbers including, most importantly, mahogany. Importations of mahogany into England (and excluding those to Scotland, which were recorded separately) reached 525 tons per annum by 1740, 3,688 tons by 1750, and more than 30,000 tons in 1788, the peak year of the 18th century trade.
At the same time, the Naval Stores Act 1721 had the effect of substantially increasing exports of mahogany from the West Indies to the British colonies in North America. Although initially regarded as a joinery wood, mahogany rapidly became the timber of choice for makers of high quality furniture in both the British Isles and the 13 colonies of North America.
Until the 1760s over 90 per cent of the mahogany imported into Britain came from Jamaica. Some of this was re-exported to continental Europe, but most was used by British furniture makers. Quantities of Jamaican mahogany also went to the North American colonies, but most of the wood used in American furniture came from the Bahamas. This was sometimes called Providence wood, after the main port of the islands, but more often madera or madeira, which was the West Indian name for mahogany.
In addition to Jamaica and Bahamas, all the British controlled islands exported some mahogany at various times, but the quantities were not large. The most significant third source was Black River and adjacent areas on the Mosquito Coast (now Republic of Honduras), from where quantities of mahogany were shipped from the 1740s onwards. This mahogany was known as 'Rattan mahogany', after the island of Ruatan, which was the main offshore entrepot for the British settlers in the area. | Mahogany | Wikipedia | 488 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
At the end of the Seven Years' War (1756–63), the mahogany trade began to change significantly. During the occupation of Havana by British forces between August 1762 and July 1763, quantities of Cuban or Havanna mahogany were sent to Britain, and after the city was restored to Spain in 1763, Cuba continued to export small quantities, mostly to ports on the north coast of Jamaica, from where it went to Britain. However, this mahogany was regarded as inferior to the Jamaican variety, and the trade remained sporadic until the 19th century.
Another variety new to the market was Hispaniola mahogany, also called 'Spanish' and 'St Domingo' mahogany. This was the result of the Free Port Act 1766 (6 Geo. 3. c. 49), which opened Kingston and other designated Jamaican ports to foreign vessels for the first time. The object was primarily to encourage importations of cotton from French plantations in Saint Domingue, but quantities of high quality mahogany were also shipped. These were then forwarded to Britain, where they entered the market in the late 1760s.
In terms of quantity, the most significant new addition to the mahogany trade was Honduras mahogany, also called 'baywood', after the Bay of Honduras. British settlers had been active in southern Yucatan since the beginning of the 18th century, despite the opposition of the Spanish, who claimed sovereignty over all of Central America.
Their main occupation was cutting logwood, a dyewood in high demand in Europe. The center of their activity and the primary point of export was Belize. Under Article XVII of the Treaty of Paris (1763), British cutters were for the first time given the right to cut logwood in Yucatan unmolested, within agreed limits. Such was the enthusiasm of the cutters that within a few years the European market was glutted, and the price of logwood collapsed.
However, the price of mahogany was still high after the war, and so the cutters turned to cutting mahogany. The first Honduras mahogany arrived in Kingston, Jamaica, in November 1763, and the first shipments arrived in Britain the following year.
By the 1790s most of the viable stocks of mahogany in Jamaica had been cut, and the market was divided between two principal sources or types of mahogany. Honduras mahogany was relatively cheap, plentiful, but rarely of the best quality. Hispaniola (also called Spanish or Santo Domingo) mahogany was the wood of choice for high quality work. | Mahogany | Wikipedia | 498 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
Data are lacking, but it is likely that the newly independent United States now received a good proportion of its mahogany from Cuba. In the last quarter of the 18th century France began to use mahogany more widely; they had ample supplies of high quality wood from Saint Domingue. The rest of Europe, where the wood was increasingly fashionable, obtained most of their wood from Britain.
Recent history
The French Revolution of 1789 and the wars that followed radically changed the mahogany trade, primarily due to the progressive collapse of the French and Spanish colonial empires, which allowed British traders into areas previously closed to them. Saint Domingue became the independent republic of Haiti, and from 1808, Spanish controlled Santo Domingo and Cuba were both open to British vessels for the first time.
From the 1820s mahogany from all these areas was imported into Europe and North America, with the majority of them going to Britain. In Central America British loggers moved northwest towards Mexico and south into Guatemala. Other areas of Central America as far south as Panama also began to be exploited.
The most important new development was the beginning of large scale logging in Mexico from the 1860s. Most mahogany was cut in the province of Tabasco and exported from a number of ports on the Gulf of Campeche, from Vera Cruz eastwards to Campeche and Sisal. By the end of the 19th century there was scarcely any part of Central America within reach of the coast untouched by logging, and activity also extended into Colombia, Venezuela, Peru and Brazil.
Trade in American mahogany probably reached a peak in the last quarter of the 19th century. Figures are not available for all countries, but Britain alone imported more than 80,000 tons in 1875. This figure was not matched again. From the 1880s, African mahogany (Khaya spp.), a related genus, began to be exported in increasing quantities from West Africa, and by the early 20th century it dominated the market. | Mahogany | Wikipedia | 381 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
In 1907 the total of mahogany from all sources imported into Europe was 159,830 tons, of which 121,743 tons were from West Africa. By this time mahogany from Cuba, Haiti and other West Indian sources had become increasingly difficult to obtain in commercial sizes, and by the late 20th century Central American and even South American mahogany was heading in a similar direction. In 1975 S. humilis was placed on CITES Appendix II (a list of species that would be in danger of extinction without strict regulation) followed by S. mahagoni in 1992. The most abundant species, S. macrophylla, was placed on Appendix III in 1995 and moved to Appendix II in 2003.
Uses
Mahogany has a straight, fine, and even grain, and is relatively free of voids and pockets. Its reddish-brown color darkens over time, and displays a reddish sheen when polished. It has excellent workability, and is very durable. Historically, the tree's girth allowed for wide boards from traditional mahogany species. These properties make it a favorable wood for crafting cabinets and furniture.
Much of the first-quality furniture made in the American colonies from the mid 18th century was made of mahogany, when the wood first became available to American craftsmen. Mahogany is still widely used for fine furniture; however, the rarity of Cuban mahogany, the over-harvesting of Honduras and Brazilian mahogany, and the protests by indigenous peoples and environmental organizations from the 1980s into the 2000s, have diminished their use. Recent mahogany production from Mexico and Fiji has a lighter color and density than South American production from the early 20th century.
Mahogany also resists wood rot, making it attractive in boat construction and outdoor decking. It is a tonewood, often used for musical instruments, particularly the backs, sides and necks of acoustic guitars, electric guitar bodies, and drum shells because of its ability to produce a very deep, warm tone compared to other commonly used woods, such as maple, alder, ash (Fraxinus) or spruce. Guitars featuring mahogany in their construction include many acoustic guitars from Martin, Taylor, and Gibson, and Gibson electric guitars such as the Les Paul and SG. In the 1930s Gibson used the wood to make banjo necks as well.
Mahogany as an invasive species
In the Philippines, environmentalists are calling for an end to the planting of mahogany because of its negative impact on the environment and wildlife, including possibly causing soil acidification and no net benefit to wildlife. | Mahogany | Wikipedia | 496 | 44928 | https://en.wikipedia.org/wiki/Mahogany | Biology and health sciences | Sapindales | null |
The common quail (Coturnix coturnix), or European quail, is a small ground-nesting game bird in the pheasant family Phasianidae. It is mainly migratory, breeding in the western Palearctic and wintering in Africa and southern India.
With its characteristic call of three repeated chirps (repeated three times in quick succession), this species of quail is more often heard than seen. It is widespread in Europe and North Africa, and is categorised by the IUCN as "least concern". It should not be confused with the Japanese quail (Coturnix japonica), native to Asia, which, although visually similar, has a call that is very distinct from that of the common quail. Like the Japanese quail, common quails are sometimes kept as poultry.
Taxonomy
The common quail was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Tetrao coturnix. The specific epithet coturnix is the Latin word for the common quail. This species is now placed in the genus Coturnix that was introduced in 1764 by the French naturalist François Alexandre Pierre de Garsault. The common quail was formerly considered to be conspecific with the Japanese quail (Coturnix japonica). The ranges of the two species meet in Mongolia and near Lake Baikal without apparent interbreeding and in captivity the offspring of crosses show reduced fertility. The Japanese quail is therefore now treated as a separate species.
Five subspecies are recognised:
C. c. coturnix (Linnaeus, 1758) – breeding in Europe and northwest Africa to Mongolia and north India, wintering in Africa and central, south India
C. c. conturbans Hartert, 1917 – Azores
C. c. inopinata Hartert, 1917 – Cape Verde Islands
C. c. africana Temminck & Schlegel, 1848 – sub-Saharan Africa and the three islands
C. c. erlangeri Zedlitz, 1912 – east and northeast Africa | Common quail | Wikipedia | 438 | 317350 | https://en.wikipedia.org/wiki/Common%20quail | Biology and health sciences | Galliformes | null |
Description
The common quail is a small compact gallinaceous bird in length with a wingspan of . The weight is . It is greatest before migration at the end of the breeding season. The female is generally slightly heavier than the male. It is streaked brown with a white eyestripe, and, in the male, a white chin. As befits its migratory nature, it has long wings, unlike the typically short-winged gamebirds. According to Online Etymology Dictionary, "small migratory game bird of the Old World, late 14c. (early 14c. as a surname, Quayle), from Old French quaille (Modern French caille), perhaps via Medieval Latin quaccula (source also of Provençal calha, Italian quaglia, Portuguese calha, Old Spanish coalla), or directly from a Germanic source (compare Dutch kwakkel, Old High German quahtala, German Wachtel, Old English wihtel), imitative of the bird's cry. Or the English word might have come up indigenously from Proto-Germanic."
Distribution and habitat
This is a terrestrial species, feeding on seeds and insects on the ground. It is notoriously difficult to see, keeping hidden in crops, and reluctant to fly, preferring to creep away instead. Even when flushed, it keeps low and soon drops back into cover. Often the only indication of its presence is the distinctive "wet-my-lips" repetitive song of the male. The call is uttered mostly in the mornings, evenings and sometimes at night. It is a strongly migratory bird, unlike most game birds.
The common quail has been introduced onto the island of Mauritius on several occasions but has failed to establish itself and is now probably extinct.
Behaviour and ecology
Breeding | Common quail | Wikipedia | 363 | 317350 | https://en.wikipedia.org/wiki/Common%20quail | Biology and health sciences | Galliformes | null |
Males generally arrive in the breeding area before the females. In northern Europe laying begins from the middle of May, and with repeat laying can continue to the end of August. The female forms a shallow scrape in the ground in diameter which is sparsely lined with vegetation. The eggs are laid at 24-hour intervals to form a clutch of between 8 and 13 eggs. These have an off-white to creamy yellow background with dark brown spots or blotches. Their average dimensions are with a weight of . The eggs are incubated by the female alone beginning after all the eggs are laid. The eggs hatch synchronously after 17–20 days. The young are precocial and shortly after hatching leave the nest and can feed themselves. They are cared for by the female who broods them while they are small. The young fledge when around 19 days of age but stay in the family group for 30–50 days. They generally first breed when one year old and only have a single brood.
Relationship to humans
The common quail is heavily hunted as game on passage through the Mediterranean area. Very large numbers are caught in nets along the Mediterranean coast of Egypt. It is estimated that in 2012, during the autumn migration, 3.4 million birds were caught in northern Sinai and perhaps as many as 12.9 million in the whole of Egypt.
This species over recent years has seen an increase in its propagation in the United States and Europe. However, most of this increase is with hobbyists. It is declining in parts of its range such as Ireland.
In 1537, Queen Jane Seymour, third wife of Henry VIII, then pregnant with the future King Edward VI, developed an insatiable craving for quail, and courtiers and diplomats abroad were ordered to find sufficient supplies for the Queen.
Poisoning
If common quails have eaten certain plants, although which plants is still in debate, the meat from quail can be poisonous, with one in four who consume poisonous flesh becoming ill with coturnism, which is characterized by muscle soreness, and which may lead to kidney failure.
In culture
In the Bible, the Book of Numbers chapter 11 describes a story of a huge mass of quails that were blown by a wind and were taken as meat by the Israelites in the wilderness.
Gallery | Common quail | Wikipedia | 466 | 317350 | https://en.wikipedia.org/wiki/Common%20quail | Biology and health sciences | Galliformes | null |
Menthol is an organic compound, specifically a monoterpenoid, that occurs naturally in the oils of several plants in the mint family, such as corn mint and peppermint. It is a white or clear waxy crystalline substance that is solid at room temperature and melts slightly above. The main form of menthol occurring in nature is (−)-menthol, which is assigned the (1R,2S,5R) configuration.
For many people, menthol produces a cooling sensation when inhaled, eaten, or applied to the skin, and mint plants have been used for centuries for topical pain relief and as a food flavoring. Menthol has local anesthetic and counterirritant qualities, and it is widely used to relieve minor throat irritation. Menthol also acts as a weak κ-opioid receptor agonist.
Structure
Natural menthol exists as one pure stereoisomer, nearly always the (1R,2S,5R) form (bottom left corner of the diagram below). The eight possible stereoisomers are:
In the natural compound, the isopropyl group is in the trans orientation to both the methyl and hydroxyl groups. Thus, it can be drawn in any of the ways shown:
The (+)- and (−)-enantiomers of menthol are the most stable among these based on their cyclohexane conformations. With the ring itself in a chair conformation, all three bulky groups can orient in equatorial positions.
The two crystal forms for racemic menthol have melting points of 28 °C and 38 °C. Pure (−)-menthol has four crystal forms, of which the most stable is the α form, the familiar broad needles.
Biological properties
Menthol's ability to chemically trigger the cold-sensitive TRPM8 receptors in the skin is responsible for the well-known cooling sensation it provokes when inhaled, eaten, or applied to the skin. In this sense, it is similar to capsaicin, the chemical responsible for the spiciness of hot chilis (which stimulates heat sensors, also without causing an actual change in temperature).
Menthol's analgesic properties are mediated through a selective activation of κ-opioid receptors. Menthol blocks calcium channels and voltage-sensitive sodium channels, reducing neural activity that may stimulate muscles. | Menthol | Wikipedia | 497 | 317380 | https://en.wikipedia.org/wiki/Menthol | Physical sciences | Terpenes and terpenoids | Chemistry |
Some studies show that menthol acts as a GABAA receptor positive allosteric modulator and increases GABAergic transmission in PAG neurons. Menthol has anesthetic properties similar to, though less potent than, propofol because it interacts with the same sites on the GABAA receptor. Menthol may also enhance the activity of glycine receptors and negatively modulate 5-HT3 receptors and nAChRs.
Menthol is widely used in dental care as a topical antibacterial agent, effective against several types of streptococci and lactobacilli. Menthol also lowers blood pressure and antagonizes vasoconstriction through TRPM8 activation.
Occurrence
Mentha arvensis (wild mint) is the primary species of mint used to make natural menthol crystals and natural menthol flakes. This species is primarily grown in the Uttar Pradesh region in India.
Menthol occurs naturally in peppermint oil (along with a little menthone, the ester menthyl acetate and other compounds), obtained from Mentha × piperita (peppermint). Japanese menthol also contains a small percentage of the 1-epimer neomenthol.
Biosynthesis
The biosynthesis of menthol has been investigated in Mentha × piperita and the enzymes involved in have been identified and characterized. It begins with the synthesis of the terpene limonene, followed by hydroxylation, and then several reduction and isomerization steps.
More specifically, the biosynthesis of (−)-menthol takes place in the secretory gland cells of the peppermint plant. The steps of the biosynthetic pathway are as follows: | Menthol | Wikipedia | 370 | 317380 | https://en.wikipedia.org/wiki/Menthol | Physical sciences | Terpenes and terpenoids | Chemistry |
Geranyl diphosphate synthase (GPPS) first catalyzes the reaction of IPP and DMAPP into geranyl diphosphate.
(−)-limonene synthase (LS) catalyzes the cyclization of geranyl diphosphate to (−)-limonene.
(−)-Limonene-3-hydroxylase (L3OH), using O2 and then nicotinamide adenine dinucleotide phosphate (NADPH) catalyzes the allylic hydroxylation of (−)-limonene at the 3 position to (−)-trans-isopiperitenol.
(−)-trans-Isopiperitenol dehydrogenase (iPD) further oxidizes the hydroxyl group on the 3 position using NAD+ to make (−)-isopiperitenone.
(−)-Isopiperitenone reductase (iPR) then reduces the double bond between carbons 1 and 2 using NADPH to form (+)-cis-isopulegone.
(+)-cis-Isopulegone isomerase (iPI) then isomerizes the remaining double bond to form (+)-pulegone.
(+)-Pulegone reductase (PR) reduces this double bond using NADPH to form (−)-menthone.
(−)-Menthone reductase (MR) then reduces the carbonyl group using NADPH to form (−)-menthol.
Production
Natural menthol is obtained by freezing peppermint oil. The resultant crystals of menthol are then separated by filtration.
Total world production of menthol in 1998 was 12,000 tonnes of which 2,500 tonnes was synthetic. In 2005, the annual production of synthetic menthol was almost double. Prices are in the $10–20/kg range with peaks in the $40/kg region but have reached as high as $100/kg. In 1985, it was estimated that China produced most of the world's supply of natural menthol, although it appears that India has pushed China into second place. | Menthol | Wikipedia | 460 | 317380 | https://en.wikipedia.org/wiki/Menthol | Physical sciences | Terpenes and terpenoids | Chemistry |
Menthol is manufactured as a single enantiomer (94% e.e.) on the scale of 3,000 tonnes per year by Takasago International Corporation. The process involves an asymmetric synthesis developed by a team led by Ryōji Noyori, who won the 2001 Nobel Prize for Chemistry in recognition of his work on this process:
The process begins by forming an allylic amine from myrcene, which undergoes asymmetric isomerisation in the presence of a BINAP rhodium complex to give (after hydrolysis) enantiomerically pure R-citronellal. This is cyclised by a carbonyl-ene-reaction initiated by zinc bromide to , which is then hydrogenated to give pure (1R,2S,5R)-menthol.
Another commercial process is the Haarmann–Reimer process (after the company Haarmann & Reimer, now part of Symrise) This process starts from m-cresol which is alkylated with propene to thymol. This compound is hydrogenated in the next step. Racemic menthol is isolated by fractional distillation. The enantiomers are separated by chiral resolution in reaction with methyl benzoate, selective crystallisation followed by hydrolysis.
Racemic menthol can also be formed by hydrogenation of thymol, menthone, or pulegone. In both cases with further processing (crystallizative entrainment resolution of the menthyl benzoate conglomerate) it is possible to concentrate the L-enantiomer, however this tends to be less efficient, although the higher processing costs may be offset by lower raw material costs. A further advantage of this process is that D-menthol becomes inexpensively available for use as a chiral auxiliary, along with the more usual L-antipode.
Applications
Menthol is included in many products, and for a variety of reasons.
Cosmetic
In some beauty products such as hair conditioners, based on natural ingredients (e.g., St. Ives). | Menthol | Wikipedia | 442 | 317380 | https://en.wikipedia.org/wiki/Menthol | Physical sciences | Terpenes and terpenoids | Chemistry |
Medical
As an antipruritic to reduce itching.
As a topical analgesic, it is used to relieve minor aches and pains, such as muscle cramps, sprains, headaches and similar conditions, alone or combined with chemicals such as camphor, eucalyptus oil or capsaicin. In Europe, it tends to appear as a gel or a cream, while in the U.S., patches and body sleeves are very frequently used, e.g.: Tiger Balm, or IcyHot patches or knee/elbow sleeves.
As a penetration enhancer in transdermal drug delivery.
In decongestants for chest and sinuses (cream, patch or nose inhaler).
Examples: Vicks VapoRub, Mentholatum, Axe Brand, VapoRem, Mentisan.
In certain medications used to treat sunburns, as it provides a cooling sensation (then often associated with aloe).
Commonly used in oral hygiene products and bad-breath remedies, such as mouthwash, toothpaste, mouth and tongue sprays, and more generally as a food flavor agent; such as in chewing gum and candy.
In first aid products such as "mineral ice" to produce a cooling effect as a substitute for real ice in the absence of water or electricity (pouch, body patch/sleeve or cream).
In nonprescription products for short-term relief of minor sore throat and minor mouth or throat irritation e.g.: lip balms and cough medicines.
A recent study showed improvement in Alzheimer's symptoms and cognition improvements in mice. | Menthol | Wikipedia | 327 | 317380 | https://en.wikipedia.org/wiki/Menthol | Physical sciences | Terpenes and terpenoids | Chemistry |
Others
In aftershave products to relieve razor burn.
As a smoking tobacco additive in some cigarette brands, for flavor, and to reduce throat and sinus irritation caused by smoking. Menthol also increases nicotine receptor density, increasing the addictive potential of tobacco products.
As a pesticide against tracheal mites of honey bees.
In perfumery, menthol is used to prepare menthyl esters to emphasize floral notes (especially rose).
In various patches ranging from fever-reducing patches applied to children's foreheads to "foot patches" to relieve numerous ailments (the latter being much more frequent and elaborate in Asia, especially Japan: some varieties use "functional protrusions", or small bumps to massage one's feet as well as soothing them and cooling them down).
As an antispasmodic and smooth muscle relaxant in upper gastrointestinal endoscopy.
Organic chemistry
In organic chemistry, menthol is used as a chiral auxiliary in asymmetric synthesis. For example, sulfinate esters made from sulfinyl chlorides and menthol can be used to make enantiomerically pure sulfoxides by reaction with organolithium reagents or Grignard reagents. Menthol reacts with chiral carboxylic acids to give diastereomic menthyl esters, which are useful for chiral resolution.
It can be used as a catalyst for sodium production for the amateur chemist via the alcohol catalysed magnesium reduction process.
Menthol is potentially ergogenic (performance enhancing) for athletic performance in hot environments
Reactions
Menthol reacts in many ways like a normal secondary alcohol. It is oxidised to menthone by oxidising agents such as chromic acid, dichromate, or by calcium hypochlorite, in a green chemistry route. Under some conditions the oxidation using Cr(VI) compounds can go further and break open the ring. Menthol is easily dehydrated to give mainly 3-menthene, by the action of 2% sulfuric acid. Phosphorus pentachloride (PCl5) gives menthyl chloride. | Menthol | Wikipedia | 457 | 317380 | https://en.wikipedia.org/wiki/Menthol | Physical sciences | Terpenes and terpenoids | Chemistry |
History
In the West, menthol was first isolated in 1771, by the German, Hieronymus David Gaubius. Early characterizations were done by Oppenheim, Beckett, Moriya, and Atkinson. It was named by F. L. Alphons Oppenheim (1833–1877) in 1861.
Compendial status
United States Pharmacopeia 23
Japanese Pharmacopoeia 15
Food Chemicals Codex
Safety
The estimated lethal dose for menthol (and peppermint oil) in humans may be as low as LD=50–500 mg/kg. In the rat, 3300 mg/kg. In the mouse, 3400 mg/kg. In the cat, 800 mg/kg.
Survival after doses of 8 to 9 g has been reported. Overdose effects are abdominal pain, ataxia, atrial fibrillation, bradycardia, coma, dizziness, lethargy, nausea, skin rash, tremor, vomiting, and vertigo. | Menthol | Wikipedia | 202 | 317380 | https://en.wikipedia.org/wiki/Menthol | Physical sciences | Terpenes and terpenoids | Chemistry |
An image scanner (often abbreviated to just scanner) is a device that optically scans images, printed text, handwriting, or an object and converts it to a digital image. The most common type of scanner used in the home and the office is the flatbed scanner, where the document is placed on a glass bed. A sheetfed scanner, which moves the page across an image sensor using a series of rollers, may be used to scan one page of a document at a time or multiple pages, as in an automatic document feeder. A handheld scanner is a portable version of an image scanner that can be used on any flat surface. Scans are typically downloaded to the computer that the scanner is connected to, although some scanners are able to store scans on standalone flash media (e.g., memory cards and USB drives).
Modern scanners typically use a charge-coupled device (CCD) or a contact image sensor (CIS) as the image sensor, whereas drum scanners, developed earlier and still used for the highest possible image quality, use a photomultiplier tube (PMT) as the image sensor. Document cameras, which use commodity or specialized high-resolution cameras, photograph documents all at once.
History
Precursors
Image scanners are considered the successors of early facsimile (fax) machines. The earliest attempt at a fax machine was patented in 1843 by the Scottish clockmaker Alexander Bain but never put into production. In his design, a metal stylus linked to a pendulum scans across a copper plate with a raised image. When the stylus makes contact with a raised part of the plate, it sends a pulse across a pair of wires to a receiver containing an electrode linked to another pendulum. A piece of paper impregnated with an electrochemically sensitive solution resides underneath the electrode and changes color whenever a pulse reaches the electrode. A gear advances the copper plate and paper in tandem with each swing of the pendulum; over time, the result is a perfect reproduction of the copper plate. In Bain's system, it is critical that the pendulums of the transceiver and receiver are in perfect step, or else the reproduced image will be distorted. | Image scanner | Wikipedia | 445 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
In 1847, the English physicist Frederick Bakewell developed the first working fax machine. Bakewell's machine was similar to Bain's but used a revolving drum coated in tinfoil, with non-conductive ink painted on the foil and a stylus that scans across the drum and sends a pulse down a pair of wires when it contacts a conductive point on the foil. The receiver contains an electrode that touches a sheet of chemically treated paper, which changes color when the electrode receives a pulse; the result is a reverse contrast (white-on-blue) reproduction of the original image. Bakewell's fax machine was marginally more successful than Bain's but suffered from the same synchronization issues. In 1862, Giovanni Caselli solved this with the pantelegraph, the first fax machine put into regular service. Largely based on Bain's design, it ensured complete synchronization by flanking the pendulums of both the transceiver and receiver between two magnetic regulators, which become magnetized with each swing of the pendulum and become demagnetized when the pendulum reaches the maxima and minima of each oscillation.
In 1893, the American engineer Elisha Gray introduced the telautograph, the first widely commercially successful fax machine that used linkage bars translating x- and y-axis motion at the receiver to scan a pen across the paper and strike it only when actuated by the stylus moving across the transceiver drum. Because it could use commodity stationery paper, it became popular in business and hospitals. In 1902, the German engineer Arthur Korn introduced the phototelautograph, a fax machine that used a light-sensitive selenium cell to scan a paper to be copied, instead of relying on a metallic drum and stylus. It was even more commercially successful than Gray's machine and became the basis for telephotography machines used by newspapers around the world from the early 1900s onward. | Image scanner | Wikipedia | 406 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
Analog era
Alexander Murray and Richard Morse invented and patented the first analog color scanner at Eastman Kodak in 1937. Intended for color separation at printing presses, their machine was an analog drum scanner that imaged a color transparency mounted in the drum, with a light source placed underneath the film, and three photocells with red, green, and blue color filters reading each spot on the transparency to translate the image into three electronic signals. In Murray and Morse's initial design, the drum was connected to three lathes that etched cyan, magenta, and yellow (CMY) halftone dots onto three offset cylinders directly. The rights to the patent were sold to Printing Developments Incorporated (P.D.I.) in 1946, who improved on the design by using a photomultiplier tube to image the points on the negative, which produced an amplified signal that was then fed to a single-purpose computer that processed the RGB signals into color-corrected cyan, magenta, yellow, and black (CMYK) values. The processed signals are then sent to four lathes that etch CMYK halftone dots onto the offset cylinders. | Image scanner | Wikipedia | 234 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
In 1948, Arthur Hardy of the Interchemical Corporation and F. L. Wurzburg of the Massachusetts Institute of Technology invented the first analog, color flatbed image scanner, intended for producing color-corrected lithographic plates from a color negative. In this system, three color-separated plates (of CMY values) are prepared from a color negative via dot etching and placed in the scanner bed. Above each plate are rigidly fixed, equidistant light beam projectors that focus a beam of light onto one corner of the plate. The entire bed with all three plates moves horizontally, back and forth, to reach the opposite corners of the plate; with each horiztonal oscillation of the bed, the bed moves down one step to cover the entire vertical area of the plate. While this is happening, the beam of light focused on a given spot on the plate gets reflected and bounced off to a photocell adjacent to the projector. Each photocell connects to an analog image processor, which evaluates the reflectance of the combined CMY values using Neugebauer equations and outputs a signal to a light projector hovering over a fourth, unexposed lithographic plate. This plate receives a color-corrected, continuous-tone dot-etch of either the cyan, magenta, or yellow values. The fourth plate is replaced with another unexposed plate, and the process repeats until three color-corrected plates, of cyan, magenta and yellow, are produced. In the 1950s, the Radio Corporation of America (RCA) took Hardy and Wurzburg's patent and replaced the projector-and-photocell arrangement with a video camera tube focusing on one spot of the plate.
Digital era | Image scanner | Wikipedia | 357 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
The first digital imaging system was the Bartlane system in 1920. Named after the pair who invented it, Harry G. Bartholomew and Maynard D. McFarlane, the Bartlane system used zinc plates etched with an image from a film negative projected at five different exposure levels to correspond to five quantization levels. All five plates are affixed to a long, motor-driven rotating cylinder, with five equidistant contacts scanning over each plate at the same starting position. The Bartlane system was initially used exclusively by telegraph, with the five-bit Baudot code used to transmit the grayscale digital image. In 1921, the system was modified for offline use, with a five-bit paper tape punch punching holes depending on whether its connections to the contacts are bridged or not. The result was a stored digital image with five gray levels. Reproduction of the image was achieved with a lamp passing over the punched holes, exposing five different intensities of light onto a film negative.
The first scanner to store its images digitally onto a computer was a drum scanner built in 1957 at the National Bureau of Standards (NBS, later NIST) by a team led by Russell A. Kirsch. It used a photomultiplier tube to detect light at a given point and produced an amplified signal that a computer could read and store into memory. The computer of choice at the time was the SEAC mainframe; the maximum horizontal resolution that the SEAC was capable of processing was 176 pixels. The first image ever scanned on this machine was a photograph of Kirsch's three-month-old son, Walden.
In 1969, Dacom introduced the 111 fax machine, which was the first digital fax machine to employ data compression using an on-board computer. It employed a flatbed design with a continuous feed capable of scanning up to letter paper in 1-bit monochrome (black and white). | Image scanner | Wikipedia | 393 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
The first flatbed scanner used for digital image processing was the Autokon 8400, introduced by ECRM Inc., a subsidiary of AM International, in 1975. The Autokon 8400 used a laser beam to scan pages up to 11 by 14 inches at a maximum resolution of 1000 lines per inch. Although it was only capable of scanning in 1-bit monochrome, the on-board processor was capable of halftoning, unsharp masking, contrast adjustment, and anamorphic distortions, among other features. The Autokon 8400 could either be connected to a film recorder to create a negative for producing plates or connected to a mainframe or minicomputer for further image processing and digital storage. The Autokon 8400 enjoyed widespread use in newspapers—ECRM shipped 1,000 units to newspaper publishers by 1985—but its limited resolution and maximum scan size made it unsuitable for commercial printing. In 1982, ECRM introduced the Autokon 8500, capable of scanning up to 1200 lines per inch. Four of ECRM's competitors introduced commercial flatbed scanners that year, including Scitex, Agfa-Gevaert, and Linotype-Hell, all of which were capable of scanning larger prints at higher resolutions. ECRM introduced the Autokon 1000DE in 1985 to address the shortcomings of the Autokon 8400/8500. The 1000DE (digital enhancement) used a microprocessor to produce the sharpening effect as against the 8400 which used analogue electronics and an optical method to create sharpening. The Autokon 1000DE had a touchpad rather than analogue rotary controls. The Autokon 1000DE had applications in both commercial and newspaper environments where only a single halftone was required ie black and white. Whilst typically the Autokon 8400 was a standalone output device that scanned and then output to either photosensitive, roll format bromide paper or film, the Autokon 1000DE was often connected to Apple Macintoshes or PCs via a dedicated interface such as those from HighWater Designs. The last Autokon was a wider format, online only device which utilised both a red and green laser to improve the response to the scanning of colour photographs. | Image scanner | Wikipedia | 446 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
In 1977, Raymond Kurzweil, of his start-up company Kurzweil Computer Products, released the Kurzweil Reading Machine, which was the first flatbed scanner with a charge-coupled device (CCD) imaging element. The Kurzweil Reading Machine was invented to assist blind people in reading books that had not been translated to braille. It comprised the image scanner and a Data General Nova minicomputer—the latter performing the image processing, optical character recognition (OCR), and speech synthesis.
The first scanners for personal computers appeared in the mid-1980s, starting with ThunderScan for the Macintosh in December 1984. Designed by Andy Hertzfeld and released by Thunderware Inc., the ThunderScan contains a specialized image sensor built into a plastic housing the same shape as the ink ribbon cartridge of Apple's ImageWriter printer. The ThunderScan slots into the ImageWriter's ribbon carrier and connects to both the ImageWriter and the Macintosh simultaneously. The ImageWriter's carriage, controlled by the ThunderScan, moves left-to-right to scan one 200-dpi (dots per inch) line at a time, with the carriage return serving to advance the scanner down the print to be scanned. The ThunderScan was the Macintosh's first scanner and sold well but operated very slowly and was only capable of scanning prints at 1-bit monochrome. In 1999, Canon iterated on this idea with the IS-22, a cartridge that fit into their inkjet printers to convert them into sheetfed scanners. | Image scanner | Wikipedia | 318 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
In early 1985, the first flatbed scanner for the IBM PC, the Datacopy Model 700, was released. Based on a CCD imaging element, the Model 700 was capable of scanning letter-sized documents at a maximum resolution of 200 dpi at 1-bit monochrome. The Model 700 came with a special interface card for connecting to the PC, and an optional, aftermarket OCR software card and software package were sold for the Model 700. In April 1985, LaserFAX Inc. introduced the first CCD-based color flatbed scanner, the SpectraSCAN 200, for the IBM PC. The SpectraSCAN 200 worked by placing color filters over the CCD and taking four passes (three for each primary color and one for black) per scan to build up a color reproduction. The SpectraSCAN 200 took between two and three minutes to produce a scan of a letter-sized print at 200-dpi; its grayscale counterpart, the DS-200, took only 30 seconds to make a scan at the same size and resolution.
The first relatively affordable flatbed scanner for personal computers appeared in February 1987 with Hewlett-Packard's ScanJet, which was capable of scanning 4-bit (64-shade) grayscale images at a maximum resolution of 300 dpi. By the beginning of 1988, the ScanJet had accounted for 27 percent of all scanner sales in terms of dollar volume, per Gartner Dataquest. In February 1989, the company introduced the ScanJet Plus, which increased the bit depth to 8 bits (256 shades) while costing only US$200 more than the original ScanJet's $1990 (). This led to a massive price drop in grayscale scanners with equivalent or lesser features in the market. The number of third-party developers producing software and hardware supporting these scanners jumped dramatically in turn, effectively popularizing the scanner for the personal computer user. By 1999, the cost of the average color-capable scanner had dropped to $300 (). That year, Computer Shopper declared 1999 "the year that scanners finally became a mainstream commodity".
Types
Flatbed | Image scanner | Wikipedia | 435 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
A flatbed scanner is a type of scanner that provides a glass bed (platen) on which the object to be scanned lies motionless. The scanning element moves vertically from under the glass, scanning either the entirety of the platen or a predetermined portion. The driver software for most flatbed scanners allows users to prescan their documents—in essence, to take a quick, low-resolution pass at a document in order to judge what area of the document should be scanned (if not the entirety of it), before scanning it at a higher resolution. Some flatbed scanners incorporate sheet-feeding mechanisms called automatic document feeders (ADFs) that use the same scanning element as the flatbed portion.
This type of scanner is sometimes called a reflective scanner, because it works by shining white light onto the object to be scanned and reading the intensity and color of light that is reflected from it, usually a line at a time. They are designed for scanning prints or other flat, opaque materials, but some have available transparency adapters, which—for a number of reasons—in most cases, are not very well suited to scanning film.
Sheetfed
A sheetfed scanner, also known as a document feeder, is a type of scanner that uses motor-driven rollers to move one single sheet of paper at a time past a stationary scanning element (two scanning elements, in the case of scanners with duplex functionality). Unlike flatbed scanners, sheetfed scanners are not equipped to scan bound material such as books or magazines, nor are they suitable for any material thicker than plain printer paper. Some sheetfed scanners, called automatic document feeders (ADFs), are capable of scanning several sheets in one session, although others only accept one page at a time. Some sheetfed scanners are portable, powered by batteries, and have their own storage, eventually transferring stored scans to a computer.
Handheld | Image scanner | Wikipedia | 390 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
A handheld scanner is a type of scanner that must be manually dragged or gilded by hand across the surface of the object to be scanned. Scanning documents in this manner requires a steady hand, as an uneven scanning rate produces distorted images. Some handheld scanners have an indicator light on the scanner for this purpose, actuating if the user is moving the scanner too fast. They typically have at least one button that starts the scan when pressed; it is held by the user for the duration of the scan. Some other handheld scanners have switches to set the optical resolution, as well as a roller, which generates a clock pulse for synchronization with the computer. Older hand scanners were monochrome, and produced light from an array of green LEDs to illuminate the image; later ones scan in monochrome or color, as desired. A hand scanner may also have a small window through which the document being scanned could be viewed. As hand scanners are much narrower than most normal document or book sizes, software (or the end user) needed to combine several narrow "strips" of scanned documents to produce the finished article.
Inexpensive, portable, battery-powered or USB-powered wand scanners and pen scanners, typically capable of scanning an area as wide as a normal letter and much longer, remain available . Some computer mice can also scan documents.
Drum
A drum scanner is a type of scanner that uses a clear, motor-driven rotating cylinder (drum) onto which a print, a film negative, a transparency, or any other flat object is taped or otherwise secured. A beam of light either projects past, or reflects off, the material to be scanned onto a series of mirrors, which focus the beam onto the drum scanner's photomultiplier tube (PMT). After one revolution, the beam of light moves down a single step. When scanning transparent media, such as negatives, a light beam is directed from within the cylinder onto the media; when scanning opaque items, a light beam from above is reflected off the surface of the media. When only one PMT is present, three passes of the image are required for a full-color RGB scan. When three PMTs are present, only a single pass is required. | Image scanner | Wikipedia | 457 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
The photomultiplier tubes of drum scanners offer superior dynamic range to that of CCD sensors. For this reason, drum scanners can extract more detail from very dark shadow areas of a transparency than flatbed scanners using CCD sensors. The smaller dynamic range of the CCD sensors (versus photomultiplier tubes) can lead to loss of shadow detail, especially when scanning very dense transparency film. Drum scanners are also able to resolve true detail in excess of 10000 dpi, producing higher-resolution scans than any CCD scanner.
Overhead
An overhead scanner is a type of scanner that places the scanning element in a housing on top of a vertical post, hovering above the document or object to be scanned, which lies stationary on an open-air bed. Chinon Industries patented a specific type of overhead scanner, which uses a rotating mirror to reflect the contents of the bed onto a linear CCD, in 1987. Although very flexible—allowing users to scan not only two-dimensional prints and documents but any 3D object, of any size—the Chinon design required the user to provide uniform illumination of the object to be scanned and was more cumbersome to set up.
A more modern type of overhead scanner is a document camera (also known as a video scanner), which uses a digital camera to capture a document all at once. Most document cameras output live video of the document and are usually reserved for displaying documents to a live audience, but they may also be used as replacements for image scanners, capturing a single frame of the output as an image file. Document cameras may even use the same APIs as scanners when connected to computers. A planetary scanner is a type of very-high-resolution document camera used for capturing certain fragile documents. A book scanner is another kind of document camera, pairing a digital camera with a scanning area defined by a mat to assist in scanning books. Some more advanced models of book scanners project a laser onto the page for calibration and software skew correction.
Film | Image scanner | Wikipedia | 412 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
A film scanner, also known as a slide scanner or a transparency scanner, is a type of specialized flatbed scanner specifically for scanning film negatives and slides. A typical film scanner works by passing a narrowly focused beam of light through the film and reading the intensity and color of the light that emerges. The lowest-cost dedicated film scanners can be had for less than $50, and they might be sufficient for modest needs. From there they inch up in staggered levels of quality and advanced features upward of five figures.
Portable
Image scanners are usually used in conjunction with a computer which controls the scanner and stores scans. Small portable scanners, either sheetfed or handheld and operated by batteries and with storage capability, are available for use away from a computer; stored scans can be transferred later. Many can scan both small documents such as business cards and till receipts, as well as letter-sized documents.
Software scanners
The higher-resolution cameras fitted to some smartphones can produce reasonable quality document scans by taking a photograph with the phone's camera and post-processing it with a scanning app, a range of which are available for most phone operating systems, to whiten the background of a page, correct perspective distortion so that the shape of a rectangular document is corrected, convert to black-and-white, etc. Many such apps can scan multiple-page documents with successive camera exposures and output them either as a single file or multiple-page files. Some smartphone scanning apps can save documents directly to online storage locations, such as Dropbox and Evernote, send via email, or fax documents via email-to-fax gateways.
Smartphone scanner apps can be broadly divided into three categories:
Document scanning apps primarily designed to handle documents and output PDF, and sometimes JPEG, files
Photo scanning apps that output JPEG files, and have editing functions useful for photo rather than document editing;
Barcode-like QR code scanning apps that then search the internet for information associated with the code.
Scanning elements
Charge-coupled device (CCD)
Scanners equipped with charge-coupled device (CCD) scanning elements require a sophisticated series of mirrors and lenses to reproduce an image, but the result of this complexity is a much higher-quality scan. Because CCDs have a much greater depth of field, they are more forgiving when it comes to scanning documents that are difficult to get perfectly flat against the platen (such as bound books).
Contact image sensor (CIS) | Image scanner | Wikipedia | 500 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
Scanners equipped with contact image sensor (CIS) scanning elements are designed to be in near-direct contact with the document to be scanned and thus do not require the complex optics of CCDs scanners. However, their depth of field is much worse, resulting in blurry scans if the scanned document is not perfectly flush against the platten. Because the sensors require far less power than CCD scanners, CIS scanners are able to be manufactured down to a low cost and are typically much lighter in weight and depth than CCD scanners.
Photomultiplier tube (PMT)
Scanners equipped with photomultiplier tubes (PMT) are nearly exclusively drum scanners.
Scan quality
Color scanners typically read RGB (red-green-blue) color data from the array. This data is then processed with some proprietary algorithm to correct for different exposure conditions, and sent to the computer via the device's input/output interface (usually USB, previous to which was SCSI or bidirectional parallel port in older units).
Color depth varies depending on the scanning array characteristics, but is usually at least 24 bits. High-quality models have 36-48 bits of color depth.
Another qualifying parameter for a scanner is its resolution, measured in pixels per inch (ppi), sometimes more accurately referred to as samples per inch (spi). Instead of using the scanner's true optical resolution, the only meaningful parameter, manufacturers like to refer to the interpolated resolution, which is much higher thanks to software interpolation. , a high-end flatbed scanner can scan up to 5400 ppi and drum scanners have an optical resolution of between 3000 and 24000 ppi.
Effective resolution refers to the true resolution of a scanner, and is determined by using a resolution test chart. The effective resolution of most all consumer flatbed scanners is considerably lower than the manufactures' given optical resolution.
Manufacturers often claim interpolated resolutions as high as 19200 ppi; but such numbers carry little meaningful value because the number of possible interpolated pixels is unlimited, and doing so does not increase the level of captured detail. | Image scanner | Wikipedia | 440 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
The size of the file created increases with the square of the resolution; doubling the resolution quadruples the file size. A resolution must be chosen that is within the capabilities of the equipment, preserves sufficient detail, and does not produce a file of excessive size. The file size can be reduced for a given resolution by using "lossy" compression methods such as JPEG, at some cost in quality. If the best possible quality is required lossless compression should be used; reduced-quality files of smaller size can be produced from such an image when required (e.g., image designed to be printed on a full page, and a much smaller file to be displayed as part of a fast-loading web page).
Purity can be diminished by scanner noise, optical flare, poor analog to digital conversion, scratches, dust, Newton's rings, out-of-focus sensors, improper scanner operation, and poor software. Drum scanners are said to produce the purest digital representations of the film, followed by high-end film scanners that use the larger Kodak Tri-Linear sensors.
The third important parameter for a scanner is its dynamic range (also known as density range). A high-density range means that the scanner is able to record shadow details and brightness details in one scan. Density of film is measured on a base 10 log scale and varies between 0.0 (transparent) and 5.0, about 16 stops. Density range is the space taken up in the 0 to 5 scale, and Dmin and Dmax denote where the least dense and most dense measurements on a negative or positive film. The density range of negative film is up to 3.6d, while slide film dynamic range is 2.4d. Color negative density range after processing is 2.0d thanks to the compression of the 12 stops into a small density range. Dmax will be the densest on slide film for shadows, and densest on negative film for highlights. Some slide films can have a Dmax close to 4.0d with proper exposure, and so can black-and-white negative film. | Image scanner | Wikipedia | 429 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
Consumer-level flatbed photo scanners have a dynamic range in the 2.0–3.0 range, which can be inadequate for scanning all types of photographic film, as Dmax can be and often is between 3.0d and 4.0d with traditional black-and-white film. Color film compresses its 12 stops of a possible 16 stops (film latitude) into just 2.0d of space via the process of dye coupling and removal of all silver from the emulsion. Kodak Vision 3 has 18 stops. So, color-negative film scans the easiest of all film types on the widest range of scanners. Because traditional black-and-white film retains the image creating silver after processing, density range can be almost twice that of color film. This makes scanning traditional black-and-white film more difficult and requires a scanner with at least a 3.6d dynamic range, but also a Dmax between 4.0d to 5.0d. High-end (photo lab) flatbed scanners can reach a dynamic range of 3.7, and Dmax around 4.0d. Dedicated film scanners have a dynamic range between 3.0d–4.0d. Office document scanners can have a dynamic range of less than 2.0d. Drum scanners have a dynamic range of 3.6–4.5.
For scanning film, is a technique used to remove the effects of dust and scratches on images scanned from film; many modern scanners incorporate this feature. It works by scanning the film with infrared light; the dyes in typical color film emulsions are transparent to infrared light, but dust and scratches are not, and block infrared; scanner software can use the visible and infrared information to detect scratches and process the image to greatly reduce their visibility, considering their position, size, shape, and surroundings. Scanner manufacturers usually have their own names attached to this technique. For example, Epson, Minolta, Nikon, Konica Minolta, Microtek, and others use Digital ICE, while Canon uses its own system, FARE (Film Automatic Retouching and Enhancement). Plustek uses LaserSoft Imaging iSRD. Some independent software developers design infrared cleaning tools.
By combining full-color imagery with 3D models, modern hand-held scanners are able to completely reproduce objects electronically. The addition of 3D color printers enables accurate miniaturization of these objects, with applications across many industries and professions. | Image scanner | Wikipedia | 509 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
For scanner apps, the scan quality is highly dependent on the quality of the phone camera and on the framing chosen by the user of the app.
Connectivity
Scans must virtually always be transferred from the scanner to a computer or information storage system for further processing or storage. There are two basic issues: (1) how the scanner is physically connected to the computer and (2) how the application retrieves the information from the scanner.
Direct connection
The file size of a scan can go up to about 100 MB for a 600 dpi, 23 × 28 cm (slightly larger than A4 paper) uncompressed 24-bit image. Scanned files must be transferred and stored. Scanners can generate this volume of data in a matter of seconds, making a fast connection desirable. | Image scanner | Wikipedia | 154 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
Scanners communicate to their host computer using one of the following physical interfaces, listing roughly from slow to fast:
Parallel port – Connecting through a parallel port is the slowest common transfer method. Early scanners had parallel port connections that could not transfer data faster than 70 kilobytes/second. The primary advantage of the parallel port connection was economic and user skill level: it avoided adding an interface card to the computer.
GPIB – General Purpose Interface Bus. Certain drum scanners like the Howtek D4000 featured both a SCSI and GPIB interface. The latter conforms to the IEEE-488 standard, introduced in the mid-1970s. The GPIB interface has only been used by a few scanner manufacturers, mostly serving the DOS/Windows environment. For Apple Macintosh systems, National Instruments provided a NuBus GPIB interface card.
Small Computer System Interface (SCSI) – SCSI is rarely used since the early 21st century, supported only by computers with a SCSI interface, either on a card or built-in. During the evolution of the SCSI standard, speeds increased. Widely available and easily set up USB and Firewire largely supplanted SCSI.
Universal Serial Bus (USB) – USB scanners can transfer data quickly. The early USB 1.1 standard could transfer data at 1.5 megabytes per second (slower than SCSI), but the later USB 2.0/3.0 standards can transfer at more than 20/60 megabytes per second in practice.
FireWire – Also known as IEEE-1394, FireWire is an interface of comparable speed to USB 2.0. Possible FireWire speeds are 25, 50, and 100, 400, and 800 megabits per second, but devices may not support all speeds.
Proprietary interfaces – Bespoke interfaces were used on some early scanners that used a proprietary interface card rather than a standard interface.
Indirect connection
During the early 1990s professional flatbed scanners were available over a local computer network. This proved useful to publishers, print shops, etc. This functionality largely fell out of use as the cost of flatbed scanners reduced enough to make sharing unnecessary.
From 2000 all-in-one multi-purpose devices became available which were suitable for both small offices and consumers, with printing, scanning, copying, and fax capability in a single apparatus that can be made available to all members of a workgroup. | Image scanner | Wikipedia | 493 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
Battery-powered portable scanners store scans on internal memory; they can later be transferred to a computer either by direct connection, typically USB, or in some cases a memory card may be removed from the scanner and plugged into the computer.
Applications programming interface
A raster image editor must be able to communicate with a scanner. There are many different scanners, and many of those scanners use different protocols. In order to simplify applications programming, some application programming interfaces (APIs) were developed. The API presents a uniform interface to the scanner. This means that the application does not need to know the specific details of the scanner in order to access it directly. For example, Adobe Photoshop supports the TWAIN standard; therefore in theory Photoshop can acquire an image from any scanner that has a TWAIN driver.
In practice, there are often problems with an application communicating with a scanner. Either the application or the scanner manufacturer (or both) may have faults in their implementation of the API.
Typically, the API is implemented as a dynamically linked library. Each scanner manufacturer provides software that translates the API procedure calls into primitive commands that are issued to a hardware controller (such as the SCSI, USB, or FireWire controller). The manufacturer's part of the API is commonly called a device driver, but that designation is not strictly accurate: the API does not run in kernel mode and does not directly access the device. Rather the scanner API library translates application requests into hardware requests.
Common scanner software API include:
TWAIN – An API used by most scanners. Originally used for low-end and home-use equipment, it is now widely used for large-volume scanning.
SANE (Scanner Access Now Easy) – A free/open-source API for accessing scanners. Originally developed for Unix and Linux operating systems, it has been ported to OS/2, Mac OS X, and Microsoft Windows. Unlike TWAIN, SANE does not handle the user interface. This allows batch scans and transparent network access without any special support from the device driver.
Windows Image Acquisition (WIA) – An API provided by Microsoft for use on Microsoft Windows.
Image and Scanner Interface Specification (ISIS) – Created by Pixel Translations, which still uses SCSI-2 for performance reasons, ISIS is used by large, departmental-scale, machines. | Image scanner | Wikipedia | 469 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
Bundled applications
Although no software beyond a scanning utility is a feature of any scanner, many scanners come bundled with software. Typically, in addition to the scanning utility, some type of raster image editor (such as Photoshop or GIMP) and optical character recognition (OCR) software are supplied. OCR software converts graphical images of text into standard text that can be edited using common word-processing and text-editing software; accuracy is rarely perfect.
Output data
Some scanners, especially those designed for scanning printed documents, only work in black and white, but most modern scanners work in color. For the latter, the scanned result is a non-compressed RGB image, which can be transferred to a computer's memory. The color output of different scanners is not the same due to the spectral response of their sensing elements, the nature of their light source, and the correction applied by the scanning software. While most image sensors have a linear response, the output values are usually gamma-compressed. Some scanners compress and clean up the image using embedded firmware. Once on the computer, the image can be processed with a raster graphics editor (such as Photoshop) and saved on a storage device (such as a hard disk).
Scans may be stored uncompressed in image file formats such as BMP; stored losslessly compressed in file formats such as TIFF and PNG; stored lossy-compressed in file formats such as JPEG; or stored as embedded images or converted to vector graphics within a PDF. Optical character recognition (OCR) software allows a scanned image of text to be converted into editable text with reasonable accuracy, so long as the text is cleanly printed and in a typeface and size that can be read by the software. OCR capability may be integrated into the scanning software, or the scanned image file can be processed with a separate OCR program.
Specific uses
Document processing
Document processing requirements differ from those of image scanning. These requirements include scanning speed, automated paper feed, and the ability to automatically scan both the front and the back of a document. On the other hand, image scanning typically requires the ability to handle fragile and or three-dimensional objects as well as scan at a much higher resolution. | Image scanner | Wikipedia | 458 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
Document scanners have document feeders, usually larger than those sometimes found on copiers or all-purpose scanners. Scans are made at high speed, from 20 up to 420 pages per minute, often in grayscale, although many scanners support color. Many scanners can scan both sides of double-sided originals (duplex operation). Sophisticated document scanners have firmware or software that cleans up scans of text as they are produced, eliminating accidental marks and sharpening type; this would be unacceptable for photographic work, where marks cannot reliably be distinguished from desired fine detail. Files created are compressed as they are made.
The resolution used is usually from 150 to 300 dpi, although the hardware may be capable of 600 or higher resolution; this produces images of text good enough to read and for OCR, without the higher demands on storage space required by higher-resolution images.
Document scans are often processed using OCR technology to create editable and searchable files. Most scanners use ISIS or TWAIN device drivers to scan documents into TIFF format so that the scanned pages can be fed into a document management system that will handle the archiving and retrieval of the scanned pages. Lossy JPEG compression, which is very efficient for pictures, is undesirable for text documents, as slanted straight edges take on a jagged appearance, and solid black (or other color) text on a light background compresses well with lossless compression formats.
While paper feeding and scanning can be done automatically and quickly, preparation and indexing are necessary and require much work by humans. Preparation involves manually inspecting the papers to be scanned and making sure that they are in order, unfolded, without staples or anything else that might jam the scanner. Additionally, some industries such as legal and medical may require documents to have Bates Numbering or some other mark giving a document identification number and date/time of the document scan.
Indexing involves associating relevant keywords to files so that they can be retrieved by content. This process can sometimes be automated to some extent, but it often requires manual labour performed by data-entry clerks. One common practice is the use of barcode-recognition technology: during preparation, barcode sheets with folder names or index information are inserted into the document files, folders, and document groups. Using automatic batch scanning, the documents are saved into appropriate folders, and an index is created for integration into document management systems. | Image scanner | Wikipedia | 496 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
A specialized form of document scanning is book scanning. Technical difficulties arise from the books usually being bound and sometimes fragile and irreplaceable, but some manufacturers have developed specialized machinery to deal with this. Often special robotic mechanisms are used to automate the page-turning and scanning process.
Other uses
Flatbed scanners have been used as digital backs for large-format cameras to create high-resolution digital images of static subjects. A modified flatbed scanner has been used for documentation and quantification of thin layer chromatograms detected by fluorescence quenching on silica gel layers containing an ultraviolet (UV) indicator. The ChromImage is allegedly the first commercial flatbed scanner densitometer. It enables acquisition of TLC plate images and quantification of chromatograms by use of Galaxie-TLC software. Other than being turned into densitometers, flatbed scanners were also turned into colorimeters using different methods. Trichromatic Color Analyser is allegedly the first distributable system using a flatbed scanner as a tristimulus colorimetric device.
Flatbed scanners may also be used to create artwork directly, in a practice known as scanography.
In the biomedical research field, detection devices for DNA microarrays are also referred to as scanners. These scanners are high-resolution systems (up to 1 μm/pixel), similar to microscopes. Detection is performed using CCDs or photomultiplier tubes.
In pathology, scanners are used to capture glass slides with tissue from biopsies and other kinds of sampling, allowing for various methods of digital pathology such as telepathology and the application of artificial intelligence for interpretation. | Image scanner | Wikipedia | 355 | 317625 | https://en.wikipedia.org/wiki/Image%20scanner | Technology | Media and communication | null |
In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is a process by which an animal casts off parts of its body to serve some beneficial purpose, either at specific times of the year, or at specific points in its life cycle.
In medieval times, it was also known as "mewing" (from the French verb "muer", to moult), a term that lives on in the name of Britain's Royal Mews where the King's hawks used to be kept during moulting time before becoming horse stables after Tudor times.
Moulting can involve shedding the epidermis (skin), pelage (hair, feathers, fur, wool), or other external layer. In some groups, other body parts may be shed, for example, the entire exoskeleton in arthropods, including the wings in some insects.
Examples
In birds
In birds, moulting is the periodic replacement of feathers by shedding old feathers while producing new ones. Feathers are dead structures at maturity which are gradually abraded and need to be replaced. Adult birds moult at least once a year, although many moult twice and a few three times each year. It is generally a slow process: birds rarely shed all their feathers at any one time. The bird must retain sufficient feathers to regulate its body temperature and repel moisture. The number and area of feathers that are shed varies. In some moulting periods, a bird may renew only the feathers on the head and body, shedding the wing and tail feathers during a later moulting period.
Some species of bird become flightless during an annual "wing moult" and must seek a protected habitat with a reliable food supply during that time. While the plumage may appear thin or uneven during the moult, the bird's general shape is maintained despite the loss of apparently many feathers; bald spots are typically signs of unrelated illnesses, such as gross injuries, parasites, feather pecking (especially in commercial poultry), or (in pet birds) feather plucking. Some birds will drop feathers, especially tail feathers, in what is called a "fright moult". | Moulting | Wikipedia | 470 | 317695 | https://en.wikipedia.org/wiki/Moulting | Biology and health sciences | Animal ontogeny | null |
The process of moulting in birds is as follows: First, the bird begins to shed some old feathers, then pin feathers grow in to replace the old feathers. As the pin feathers become full feathers, other feathers are shed. This is a cyclical process that occurs in many phases. It is usually symmetrical, with feather loss equal on each side of the body. Because feathers make up 4–12% of a bird's body weight, it takes a large amount of energy to replace them.
For this reason, moults often occur immediately after the breeding season, but while food is still abundant. The plumage produced during this time is called postnuptial plumage. Prenuptial moulting occurs in red-collared widowbirds where the males replace their nonbreeding plumage with breeding plumage. It is thought that large birds can advance the moult of severely damaged feathers.
Determining the process birds go through during moult can be useful in understanding breeding, migration and foraging strategies. One non-invasive method of studying moult in birds is through using field photography. The evolutionary and ecological forces driving moult can also be investigated using intrinsic markers such as stable hydrogen isotope (δ2H) analysis. In some tropical birds, such as the common bulbul, breeding seasonality is weak at the population level, instead moult can show high seasonality with individuals probably under strong selection to match moult with peak environmental conditions.
A 2023 paleontological analysis concluded that moulting probably evolved late in the evolutionary lineage of birds.
Forced moulting
In some countries, flocks of commercial layer hens are force-moulted to reinvigorate egg-laying. This usually involves complete withdrawal of their food and sometimes water for 7–14 days or up to 28 days under experimental conditions, which presumably reflect standard farming practice in some countries. This causes a body weight loss of 25 to 35%, which stimulates the hen to lose her feathers, but also reinvigorates egg-production. | Moulting | Wikipedia | 411 | 317695 | https://en.wikipedia.org/wiki/Moulting | Biology and health sciences | Animal ontogeny | null |
Some flocks may be force-moulted several times. In 2003, more than 75% of all flocks were force-moulted in the US. Other methods of inducing a moult include low-density diets (e.g. grape pomace, cotton seed meal, alfalfa meal) or dietary manipulation to create an imbalance of a particular nutrient(s). The most important among these include manipulation of minerals including sodium (Na), calcium (Ca), iodine (I) and zinc (Zn), with full or partially reduced dietary intakes.
In reptiles and amphibians
Squamates periodically engage in moulting, as their skin is scaly. The most familiar example of moulting in such reptiles is when snakes "shed their skin". This is usually achieved by the snake rubbing its head against a hard object, such as a rock (or between two rocks) or piece of wood, causing the already stretched skin to split.
At this point, the snake continues to rub its skin on objects, causing the end nearest the head to peel back on itself, until the snake is able to crawl out of its skin, effectively turning the moulted skin inside-out. This is similar to how one might remove a sock from one's foot by grabbing the open end and pulling it over itself. The snake's skin is often left in one piece after the moulting process, including the discarded brille (ocular scale), so that the moult is vital for maintaining the animal's quality of vision. The skins of lizards, in contrast, generally fall off in pieces.
Both frogs and salamanders moult regularly and consume the skin, with some species moulting in pieces and others in one piece.
In arthropods
In arthropods, such as insects, arachnids and crustaceans, moulting is the shedding of the exoskeleton, which is often called its shell, typically to let the organism grow. This process is called ecdysis. Most Arthropoda with soft, flexible skins also undergo ecdysis. Ecdysis permits metamorphosis, the sometimes radical difference between the morphology of successive instars. | Moulting | Wikipedia | 466 | 317695 | https://en.wikipedia.org/wiki/Moulting | Biology and health sciences | Animal ontogeny | null |
A new skin can replace structures, such as by providing new external lenses for eyes. The new exoskeleton is initially soft but hardens after the moulting of the old exoskeleton. The old exoskeleton is called an exuviae. While moulting, insects cannot breathe. In the crustacean Ovalipes catharus molting must occur before they mate.
In dogs
Most dogs moult twice each year, in the spring and autumn, depending on the breed, environment and temperature. Dogs shedding much more than usual are known as "blow coats" or "blowing coats".
Gallery | Moulting | Wikipedia | 133 | 317695 | https://en.wikipedia.org/wiki/Moulting | Biology and health sciences | Animal ontogeny | null |
A clothes dryer (tumble dryer, drying machine, or simply dryer) is a powered household appliance that is used to remove moisture from a load of clothing, bedding and other textiles, usually after they are washed in the washing machine.
Many dryers consist of a rotating drum called a "tumbler" through which heated air is circulated to evaporate moisture while the tumbler is rotated to maintain air space between the articles. Using such a machine may cause clothes to shrink or become less soft (due to loss of short soft fibers). A simpler non-rotating machine called a "drying cabinet" may be used for delicate fabrics and other items not suitable for a tumble dryer. Other machines include steam to de-shrink clothes and avoid ironing.
Tumble dryers
Tumble dryers continuously draw in the ambient air around them and heat it before passing it through the tumbler. The resulting hot, humid air is usually vented outside to make room for more air to continue the drying process.
Tumble dryers are sometimes integrated with a washing machine, in the form of washer-dryer combos, which are essentially a front loading washing machine with an integrated dryer or (in the US) a laundry center, which stacks the dryer on top of the washer and integrates the controls for both machines into a single control panel. Often the washer and dryer functions will have a different capacity, with the dryer usually having a lower capacity than the washer. Tumble dryers can also be top loading, in which the drum is loaded from the top of the machine and the drum's end supports are in the left and right sides, instead of the more conventional front and rear. They can be as thin as in width, and may include detachable stationary racks for drying items like plush toys and footwear.
Ventless dryers
Spin dryers
These centrifuge machines simply spin their drums much faster than a typical washer could, in order to extract additional water from the load. They may remove more water in two minutes than a heated tumbler dryer can in twenty, thus saving significant amounts of time and energy. Although spinning alone will not completely dry clothing, this additional step saves a worthwhile amount of time and energy for large laundry operations such as those of hospitals. | Clothes dryer | Wikipedia | 471 | 317900 | https://en.wikipedia.org/wiki/Clothes%20dryer | Technology | Household appliances | null |
Condenser dryers
Just as in a tumble dryer, condenser or condensation dryers pass heated air through the load. However, instead of exhausting this air, the dryer uses a heat exchanger to cool the air and condense the water vapor into either a drain pipe or a collection tank. The drier air is run through the loop again. The heat exchanger typically uses ambient air as its coolant, therefore the heat produced by the dryer will go into the immediate surroundings instead of the outside, increasing the room temperature. In some designs, cold water is used in the heat exchanger, eliminating this heating, but requiring increased water usage.
In terms of energy use, condenser dryers typically require around 2 kilowatt hours (kW⋅h) of energy per average load.
Because the heat exchange process simply cools the internal air using ambient air (or cold water in some cases), it will not dry the air in the internal loop to as low a level of humidity as typical fresh, ambient air. As a consequence of the increased humidity of the air used to dry the load, this type of dryer requires somewhat more time than a tumble dryer. Condenser dryers are a particularly attractive option where long, intricate ducting would be required to vent the dryer.
Heat pump dryers
A closed-cycle heat pump clothes dryer uses a heat pump to dehumidify the processing air. Such dryers typically use under half the energy per load of a condenser dryer. | Clothes dryer | Wikipedia | 316 | 317900 | https://en.wikipedia.org/wiki/Clothes%20dryer | Technology | Household appliances | null |
Whereas condensation dryers use a passive heat exchanger cooled by ambient air, these dryers use a heat pump. The hot, humid air from the tumbler is passed through a heat pump where the cold side condenses the water vapor into either a drain pipe or a collection tank and the hot side reheats the air afterward for re-use. In this way not only does the dryer avoid the need for ducting, but it also conserves much of its heat within the dryer instead of exhausting it into the surroundings. Heat pump dryers can, therefore, use up to 50% less energy required by either condensation or conventional electric dryers. Heat pump dryers use about 1 kW⋅h of energy to dry an average load instead of 2 kW⋅h for a condenser dryer, or from 3 to 9 kW⋅h, for a conventional electric dryer. Domestic heat pump dryers are designed to work in typical ambient temperatures from . Below , drying times significantly increase.
As with condensation dryers, the heat exchanger will not dry the internal air to as low a level of humidity as the typical ambient air. With respect to ambient air, the higher humidity of the air used to dry the clothes has the effect of increasing drying times; however, because heat pump dryers conserve much of the heat of the air they use, the already-hot air can be cycled more quickly, possibly leading to shorter drying times than tumble dryers, depending on the model.
Mechanical steam compression dryers
A new type of dryer in development, these machines are a more advanced version of heat pump dryers. Instead of using hot air to dry the clothing, mechanical steam compression dryers use water recovered from the clothing in the form of steam. First, the tumbler and its contents are heated to . The wet steam that results purges the system of air and is the only remaining atmosphere in the tumbler.
As wet steam exits the tumbler, it is mechanically compressed (hence the name) to extract water vapor and transfer the heat of vaporization to the remaining gaseous steam. This pressurized, gaseous steam is then allowed to expand, and is superheated before being injected back into the tumbler where its heat causes more water to vaporize from the clothing, creating more wet steam and restarting the cycle. | Clothes dryer | Wikipedia | 482 | 317900 | https://en.wikipedia.org/wiki/Clothes%20dryer | Technology | Household appliances | null |
Like heat pump dryers, mechanical steam compression dryers recycle much of the heat used to dry the clothes, and they operate in a very similar range of efficiency as heat pump dryers. Both types can be over twice as efficient as conventional tumble dryers. The considerably higher temperatures used in mechanical steam compression dryers result in drying times on the order of half as long as those of heat pump dryers.
Convectant drying
Marketed by some manufacturers as a "static clothes drying technique", convectant dryers simply consist of a heating unit at the bottom, a vertical chamber, and a vent at top. The unit heats air at the bottom, reducing its relative humidity, and the natural tendency of hot air to rise brings this low-humidity air into contact with the clothes. This design is slower than conventional tumble dryers, but relatively energy-efficient if well-implemented. It works particularly well in cold and humid environments, where it dries clothes substantially faster than line-drying. In hot and dry weather, the performance delta over line-drying is negligible.
Given that this is a relatively simple and cheap technique to materialize, most consumer products showcase the added benefit of portability and/or modularity. Newer designs implement a fan heater at the bottom to pump hot air into the vertical drying rack chamber. Temperatures in excess of can be reached inside these "hot air balloons," yet lint, static cling, and shrinkage are minimal. Upfront cost is significantly lower than tumble, condenser and heat pump designs.
If used in combination with washing machines featuring fast spin cycles (800+ rpm) or spin dryers, the cost-effectiveness of this technique has the potential to render tumble dryer-like designs obsolete in single-person and small family households. One disadvantage is that the moisture from the clothes is released into the immediate surroundings. Proper ventilation or a complementary dehumidifier is recommended for indoor use. It also cannot compete with the tumble dryer's capacity to dry multiple loads of wet clothing in a single day.
Solar clothes dryer
The solar dryer is a box-shaped stationary construction which encloses a second compartment where the clothes are held. It uses the sun's heat without direct sunlight reaching the clothes. Alternatively, a solar heating box may be used to heat air that is driven through a conventional tumbler dryer. | Clothes dryer | Wikipedia | 489 | 317900 | https://en.wikipedia.org/wiki/Clothes%20dryer | Technology | Household appliances | null |
Microwave dryers
Japanese manufacturers have developed highly efficient clothes dryers that use microwave radiation to dry the clothes (though a vast majority of Japanese air dry their laundry). Most of the drying is done using microwaves to evaporate the water, but the final drying is done by convection heating, to avoid problems of arcing with metal pieces in the laundry. There are a number of advantages: shorter drying times (25% less), energy savings (17–25% less), and lower drying temperatures. Some analysts think that the arcing and fabric damage is a factor preventing microwave dryers from being developed for the US market.
Ultrasonic dryers
Ultrasonic dryers use high-frequency signals to drive piezoelectric actuators in order to mechanically shake the clothes, releasing water in the form of a mist which is then removed from the drum. They have the potential to significantly cut energy consumption while needing only one-third of the time needed by a conventional electric dryer for a given load. They also do not have the same issues related with lint in most other types of dryers.
Hybrid dryers
Some manufacturers, like LG Electronics and Whirlpool, have introduced hybrid dryers, that offer the user the option of using either a heat pump or a traditional electric heating element for drying the user's clothes. Hybrid dryers can also use a heat pump and a heating element at the same time to dry clothes faster.
Static electricity
Clothes dryers can cause static cling through the triboelectric effect. This can be a minor nuisance and is often a symptom of over-drying textiles to below their equilibrium moisture level, particularly when using synthetic materials. Fabric conditioning products such as dryer sheets are marketed to dissipate this static charge, depositing surfactants onto the fabric load by mechanical abrasion during tumbling. Modern dryers often have improved temperature and humidity sensors and electronic controls which aim to stop the drying cycle once textiles are sufficiently dry, avoiding over-drying and the static charge and energy wastage this causes.
Pest control use
Drying at a minimum of heat for thirty minutes kills many parasites including house dust mites, bed bugs, and scabies mites and their eggs; a bit more than ten minutes kills ticks. Simply washing drowns dust mites, and exposure to direct sunlight for three hours kills their eggs.
Lint build-up (tumble dryers) | Clothes dryer | Wikipedia | 494 | 317900 | https://en.wikipedia.org/wiki/Clothes%20dryer | Technology | Household appliances | null |
Moisture and lint are byproducts of the tumble drying process and are pulled from the drum by a fan motor and then pushed through the remaining exhaust conduit to the exterior termination fitting. Typical exhaust conduit comprises flex transition hose found immediately behind the dryer, the rigid galvanized pipe and elbow fittings found within the wall framing, and the vent duct hood found outside the house.
A clean, unobstructed dryer vent improves both the efficiency and safety of the dryer. As the dryer duct pipe becomes partially obstructed and filled with lint, drying time markedly increases and causes the dryer to waste energy. A blocked vent increases the internal temperature and may result in a fire. Clothes dryers are one of the more costly home appliances to operate.
Several factors can contribute to or accelerate rapid lint build-up. These include long or restrictive ducts, bird or rodent nests in the termination, crushed or kinked flex transition hose, terminations with screen-like features, and condensation within the duct due to un-insulated ducts traveling through cold spaces such as a crawl space or attic. If plastic flaps are at the outside end of the duct, one may be able to flex, bend, and temporarily remove the plastic flaps, clean the inside surface of the flaps, clean the last foot or so of the duct, and reattach the plastic flaps. The plastic flaps keep insects, birds, and snakes out of the dryer vent pipe. During cold weather, the warm wet air condenses on the plastic flaps, and minor trace amounts of lint sticks to the wet inside part of the plastic flaps at the outside of the building.
Ventless dryers include multi-stage lint filtration systems and some even include automatic evaporator and condenser cleaning functions that can run even while the dryer is running. The evaporator and condenser are usually cleaned with running water. These systems are necessary, in order to prevent lint from building up inside the dryer and evaporator and condenser coils.
Aftermarket add-on lint and moisture traps can be attached to the dryer duct pipe, on machines originally manufactured as outside-venting, to facilitate installation where an outside vent is not available. Increased humidity at the location of installation is a drawback to this method. | Clothes dryer | Wikipedia | 487 | 317900 | https://en.wikipedia.org/wiki/Clothes%20dryer | Technology | Household appliances | null |
Safety
Dryers expose flammable materials to heat. Underwriters Laboratories recommends cleaning the lint filter after every cycle for safety and energy efficiency, provision of adequate ventilation, and cleaning of the duct at regular intervals. UL also recommends that dryers not be used for glass fiber, rubber, foam or plastic items, or any item that has had a flammable substance spilled on it.
In the United States, an estimate from the US Fire Administration in a 2012 report estimated that from 2008 to 2010, fire departments responded to an estimated 2,900 clothes dryer fires in residential buildings each year across the nation. These fires resulted in an annual average loss of 5 deaths, 100 injuries, and $35 million in property loss. The Fire Administration attributes "Failure to clean" (34%) as the leading factor contributing to clothes dryer fires in residential buildings, and observed that new home construction trends place clothes dryers and washing machines in more hazardous locations away from outside walls, such as in bedrooms, second-floor hallways, bathrooms, and kitchens.
To address the problem of clothes dryer fires, a fire suppression system can be used with sensors to detect the change in temperature when a blaze starts in a dryer drum. These sensors then activate a water vapor mechanism to put out the fire.
Environmental impact
The environmental impact of clothes dryers is especially severe in the US and Canada, where over 80% of all homes have a clothes dryer. According to the US Environmental Protection Agency, if all residential clothes dryers sold in the US were energy efficient, "the utility cost savings would grow to more than $1.5 billion each year and more than 10 billion kilograms (22 billion pounds) of annual greenhouse gas emissions would be prevented”.
Clothes dryers are second only to refrigerators and freezers as the largest residential electrical energy consumers in America.
In the European Union, the EU energy labeling system is applied to dryers; dryers are classified with a label from A+++ (best) to G (worst) according to the amount of energy used per kilogram of clothes (kW⋅h/kg). Sensor dryers can automatically sense that clothes are dry and switch off. This means over-drying is not as frequent. Most of the European market sells sensor dryers now, and they are normally available in condenser and vented dryers. | Clothes dryer | Wikipedia | 480 | 317900 | https://en.wikipedia.org/wiki/Clothes%20dryer | Technology | Household appliances | null |
History
A hand-cranked clothes dryer was created in 1800 by M. Pochon from France. Henry W. Altorfer invented and patented an electric clothes dryer in 1937. J. Ross Moore, an inventor from North Dakota, developed designs for automatic clothes dryers and published his design for an electrically operated dryer in 1938. Industrial designer Brooks Stevens developed an electric dryer with a glass window in the early 1940s. | Clothes dryer | Wikipedia | 87 | 317900 | https://en.wikipedia.org/wiki/Clothes%20dryer | Technology | Household appliances | null |
The megamouth shark (Megachasma pelagios) is a species of deepwater shark. Rarely seen by humans, it measures around long and is the smallest of the three extant filter-feeding sharks alongside the relatively larger whale shark and basking shark. According to Sharkman's World Organization a total of 286 specimens have been observed or caught since its discovery in 1976. Like the other two planktivorous sharks, it swims with its mouth wide open, filtering water for plankton and jellyfish. It is recognizable from its large head with rubbery lips. The megamouth is so unlike any other type of shark that it is usually considered to be the sole extant species in the family Megachasmidae, though some scientists have suggested it may belong in the family Cetorhinidae.
Taxonomy and evolution
The first megamouth shark was captured on November 15, 1976, about 25 miles northeast of Kahuku, Hawaii, when it became entangled in the sea anchor of United States Navy ship AFB-14 at a depth of about 165 m (541 ft). The species was identified as being of a new genus within the planktivorous shark species. Examination of the , specimen by Leighton Taylor showed it to be an entirely unknown type of shark, making it – along with the coelacanth – one of the more sensational discoveries in 20th-century ichthyology. The pectoral fin of the megamouth shark was studied, along with its skeletal and muscular system, to show its phylogenetic relationship to the other two sharks.
, only 99 megamouth specimens had been caught or sighted. They have been found in the Pacific, Atlantic, and Indian Oceans. Japan, the Philippines and Taiwan have each yielded at least 10 specimens, the most of any single area, amounting to more than half the worldwide total. Specimens have also been sighted in or come out of the waters near Hawaii, California, Mexico, Indonesia, Australia, Brazil, Senegal, South Africa, Puerto Rico, Ecuador, and possibly Vietnam. | Megamouth shark | Wikipedia | 409 | 318020 | https://en.wikipedia.org/wiki/Megamouth%20shark | Biology and health sciences | Sharks | Animals |
Researchers have predicted the feeding patterns of megamouth sharks in relation to the other two planktivorous sharks; the three planktivorous sharks have ram feeding in common, as it evolved from ram feeding swimming-type ancestors that developed their filtering mechanism to capture small prey like plankton. In addition to the living M. pelagios, however, two extinct megamouth species – the Priabonian M. alisonae and the Oligocene–Miocene M. applegatei – have also recently been proposed on the basis of fossilized tooth remains. An early ancestor of the recent species Megachasma pelagios was reported from the early Miocene (Burdigalian) of Belgium. However, the Cretaceous-aged M. comanchensis has been recently reclassified as an odontaspid shark in the genus Pseudomegachasma, and is in fact unrelated to the megamouth shark despite similar teeth morphology. The megamouth's filter-feeding adaptations likely evolved independently from other extant filter-feeding sharks, even the lamniform basking shark, making it an example of convergent evolution.
Description
The appearance of the megamouth is distinctive, but little else is known about it. It has a brownish-black colour on top, is white underneath, and has an asymmetrical tail with a long upper lobe, similar to that of the thresher shark. The interior of its gill slits are lined with finger-like gill rakers that capture its food. A relatively poor swimmer, the megamouth has a soft, flabby body and lacks caudal keels. The megamouth is considerably less active than the other filter-feeding sharks, the basking shark and the whale shark. The megamouth has a stout body and a long, wide bulbous head.
Megamouths are large sharks, able to grow to in length. Mature males average at and females at . Weights of up to have been reported. A 2019 study suggested that it would have reached in maximum length. Megamouth sharks can be found as far northward as northern Japan; southern California (LACM 43745-1) and near Punta Eugenia, Baja California, and Hawaii. Megamouth sharks can be found at a depth of up to 1,000 m (3,280 ft). Megamouth sharks are dark blue, brownish-black, or gray above, lighter below; with a white band along the upper jaw; while the posterior margin of its fins are white. | Megamouth shark | Wikipedia | 503 | 318020 | https://en.wikipedia.org/wiki/Megamouth%20shark | Biology and health sciences | Sharks | Animals |
As their name implies, megamouths have a large mouth with small teeth, and a broad, rounded snout, causing observers to occasionally mistake the megamouth for a young orca. The protruding inside of the upper lip is a brilliant silvery-white, which is very visible when the mouth is open. This lip was initially thought to be possibly embedded by luminous photophores when the first shark was examined in the early 1980s, which may act as a lure for plankton, while the team examining the second shark in the mid-1980s instead proposed that the lower lip might glow with the white band used as a reflector of sorts, but neither theory has been proven. In 2020, a study concluded that this species of shark does not in fact produce any light; the white band was found to merely be highly reflective of light. This white band is present in both sexes and could be either a feeding mechanism or possibly be used as a means of identifying other individuals of megamouth sharks. Their mouths can reach up to in width. Megamouth sharks have up to 50 rows of teeth in their upper-jaw and up to 75 rows of teeth in their lower-jaw.
Behavior
In 1990, a 4.9-m (16-foot) male megamouth shark was caught near the surface off Dana Point, California. This individual was eventually released with a small radio tag attached to its soft body. The tag relayed depth and time information over a two-day period. During the day, the shark swam at a depth around , but as the sun set, it would ascend and spend the night at depths between . Both day and night, its progress was very slow, around . This pattern of vertical migration is seen in many marine animals as they track the movement of plankton in the water column. The shark captured in March 2009 was reportedly netted at a depth of .
Reproduction
Reproduction is ovoviviparous, meaning that the young sharks develop in eggs that remain within the mother's body until they hatch. Tissue samples were obtained from twenty-seven megamouths caught in a two-year period off the Hualien coast (eastern Taiwan), and two caught in Baja California, Mexico, and samples taken from GenBank to perform a population genetic analyses of the megamouth shark; the results indicated no genetic diversity between populations found in different geographical locations, which indicates the species forms a single, highly migratory, interbreeding population. | Megamouth shark | Wikipedia | 494 | 318020 | https://en.wikipedia.org/wiki/Megamouth%20shark | Biology and health sciences | Sharks | Animals |
The Lamniformes (, from Greek lamna "fish of prey") are an order of sharks commonly known as mackerel sharks (which may also refer specifically to the family Lamnidae). It includes some of the most familiar species of sharks, such as the great white as well as less familiar ones, such as the goblin shark and megamouth shark.
Members of the order are distinguished by possessing two dorsal fins, an anal fin, five gill slits, eyes without nictitating membranes, and a mouth extending behind the eyes. Species in two families of Lamniformes – Lamnidae and Alopiidae – are distinguished for maintaining a higher body temperature than the surrounding waters.
Members of the group include macropredators, generally of medium-large size, including the largest macropredatory shark ever, the extinct Otodus megalodon, as well as large planktivores.
Although some authors have argued that the Late Jurassic Palaeocarcharias should be considered the oldest known lamniform, this is disputed. The earliest unambiguous records of lamniformes are from the Early Cretaceous. Lamniformes underwent a major adaptive radiation during the Cretaceous and became prominent elements of oceanic ecosystems. They reached their highest diversity during the Late Cretaceous, but severely declined during the K-Pg extinction, before rebounding to a high but lower diversity peak during the Paleogene. Lamniformes have severely declined over the last 20 million years, with only 15 species alive today, compared to over 290 extant species in the Carcharhiniformes, which have evolved into medium and large body sizes during the same timeframe. The causes of the decline are uncertain, but are likely to have involved both biotic factors like competition and non-biotic factors like temperature and sea level.
Species
The order Lamniformes includes 10 families with 22 species, with a total of seven living families and 15 living species:
Order Lamniformes
Family Alopiidae Bonaparte, 1838 (thresher sharks)
Genus Alopias Rafinesque, 1810
Alopias pelagicus Nakamura, 1935 (pelagic thresher)
Alopias superciliosus R. T. Lowe, 1841 (bigeye thresher)
Alopias vulpinus (Bonnaterre, 1788) (common thresher)
Family †Anacoracidae Capetta, 1987 (extinct, Cretaceous period)
Genus †Squalicorax (crow sharks) | Lamniformes | Wikipedia | 508 | 318037 | https://en.wikipedia.org/wiki/Lamniformes | Biology and health sciences | Sharks | Animals |
Genus †Scindocorax
Genus †Nanocorax
Genus †Ptychocorax
Family †Aquilolamnidae Vullo et al., 2021? (eagle sharks) (extinct, Late Cretaceous period)
Genus †Aquilolamna Vullo et al., 2021
†Aquilolamna milarcae Vullo et al., 2021
Family Cetorhinidae Gill, 1862
Genus Cetorhinus Blainville, 1816
Cetorhinus maximus (Gunnerus, 1765) (basking shark)
†Cetorhinus huddlestoni (Welton, 2014)
†Cetorhinus piersoni (Welton, 2015)
Genus †Keasius (Welton, 2013)
Family †Eoptolamnidae (extinct, Late Cretaceous period)
Genus †Eoptolamna
†Eoptolamna eccentrolopha
Genus †Leptostyrax
†Leptostyrax macrorhiza
Genus †Protolamna
†Protolamna sokolovi
†Protolamna borodini
†Protolamna carteri
†Protolamna compressidens
†Protolamna gigantea
†Protolamna roanokeensis
Family Lamnidae J. P. Müller and Henle, 1838 (mackerel sharks or white sharks)
Genus Carcharodon A. Smith, 1838
Carcharodon carcharias (Linnaeus, 1758) (great white shark)
†Carcharodon hubbelli Ehret, Macfadden, Jones, Devries, Foster & Salas-Gismondi, 2012 (Hubbell's white shark)
†Carcharodon caifassii Lawley, 1876
†Carcharodon carcharias-f Linnaeus, 1758
Genus Isurus Rafinesque, 1810
Isurus oxyrinchus Rafinesque, 1810 (shortfin mako)
Isurus paucus Guitart-Manday, 1966 (longfin mako)
Genus Lamna Cuvier, 1816
Lamna ditropis Hubbs & Follett, 1947 (salmon shark)
Lamna nasus (Bonnaterre, 1788) (porbeagle)
Family †Otodontidae Gluckman, 1964 (extinct, Late Cretaceous to Pliocene) (megatoothed sharks)
Genus †Cretalamna Gluckman, 1958
Genus †Otodus (Agassiz, 1843)
†Otodus obliquus (Agassiz, 1838) | Lamniformes | Wikipedia | 505 | 318037 | https://en.wikipedia.org/wiki/Lamniformes | Biology and health sciences | Sharks | Animals |
†Otodus angustidens (Agassiz, 1843)
†Otodus chubutensis (Agassiz, 1843)
†Otodus megalodon (Agassiz, 1843) (megalodon)
†Otodus auriculatus (Jordan, 1923)
†Otodus sokolovi (Zhelezko and Kozlov, 1999)
†Otodus poseidoni (Zhelezko and Kozlov, 1999)
†Otodus minor (Giebel, 1943)
†Otodus hastalis (Lawley, 876)
†Otodus limhamnensis (Davis, 1890)
†Otodus debrayi (Leriche, 1906)
†Otodus naidini (Zhelezko in Zhelezko & Kozlov)
Genus †Megaselachus
†Megaselachus subauriculatus? (Glickman, 1964)
Genus †Megalolamna Shimada et al., 2016
Genus †Palaeocarcharodon Casieer, 1960
Genus †Kenolamna Siversson, 2017
Family Megachasmidae Taylor, Compagno & Struhsaker, 1983
Genus Megachasma Taylor, Compagno & Struhsaker, 1983
Megachasma pelagios Taylor, Compagno & Struhsaker, 1983 (megamouth shark)
Family Mitsukurinidae D. S. Jordan, 1898
Genus Mitsukurina D. S. Jordan, 1898
Mitsukurina owstoni D. S. Jordan, 1898 (goblin shark)
Family Odontaspididae Müller & Henle, 1839
Genus Carcharias Rafinesque, 1810
Carcharias taurus Rafinesque, 1810 (sand tiger shark)
Genus Odontaspis Agassiz, 1838
Odontaspis ferox (Risso, 1810) (smalltooth sand tiger)
Odontaspis noronhai (Maul, 1955) (bigeye sand tiger)
Family Pseudocarchariidae Compagno, 1973
Genus Pseudocarcharias Cadenat, 1963
Pseudocarcharias kamoharai (Matsubara, 1936) (crocodile shark)
Family †Cardabiodontidae (extinct, Late Cretaceous period)
Genus †Cardabiodon Siverson, 1999
†Cardabiodon ricki Siverson, 1999
†Cardabiodon venator Siverson and Lindgren, 2005 | Lamniformes | Wikipedia | 511 | 318037 | https://en.wikipedia.org/wiki/Lamniformes | Biology and health sciences | Sharks | Animals |
Genus †Dwardius Siverson, 1999
Genus †Parotodus? Cappetta, 1980
Family †Cretoxyrhinidae (extinct, Late Cretaceous period)
Genus †Cretoxyrhina Agassiz, 1843
†Cretoxyrhina vraconensis Zhelezko, 2000
†Cretoxyrhina denticulata Glückman, 1957
†Cretoxyrhina agassizensis Underwood and Cumbaa, 2010
†Cretoxyrhina mantelli Agassiz, 1843 (ginsu shark)
Family †Serratolamnidae
Genus †Serratolamna
Family †Ptychodontidae (extinct, Cretaceous period)
Genus †Ptychodus (16+ species) | Lamniformes | Wikipedia | 149 | 318037 | https://en.wikipedia.org/wiki/Lamniformes | Biology and health sciences | Sharks | Animals |
Phylogeny
Below is a cladogram showing relationships within Lamniformes. The topology of extant families is based on Vella & Vella (2020) and the placements of Cretoxyrhinidae and Otodontidae are based on Ferrón (2017), Cooper (2020), and Greenfield (2022).
Sustainable consumption
In 2010, Greenpeace International added the shortfin mako shark (Isurus oxyrinchus) to its seafood red list. | Lamniformes | Wikipedia | 101 | 318037 | https://en.wikipedia.org/wiki/Lamniformes | Biology and health sciences | Sharks | Animals |
In chemistry, the law of mass action is the proposition that the rate of a chemical reaction is directly proportional to the product of the activities or concentrations of the reactants. It explains and predicts behaviors of solutions in dynamic equilibrium. Specifically, it implies that for a chemical reaction mixture that is in equilibrium, the ratio between the concentration of reactants and products is constant.
Two aspects are involved in the initial formulation of the law: 1) the equilibrium aspect, concerning the composition of a reaction mixture at equilibrium and 2) the kinetic aspect concerning the rate equations for elementary reactions. Both aspects stem from the research performed by Cato M. Guldberg and Peter Waage between 1864 and 1879 in which equilibrium constants were derived by using kinetic data and the rate equation which they had proposed. Guldberg and Waage also recognized that chemical equilibrium is a dynamic process in which rates of reaction for the forward and backward reactions must be equal at chemical equilibrium. In order to derive the expression of the equilibrium constant appealing to kinetics, the expression of the rate equation must be used. The expression of the rate equations was rediscovered independently by Jacobus Henricus van 't Hoff.
The law is a statement about equilibrium and gives an expression for the equilibrium constant, a quantity characterizing chemical equilibrium. In modern chemistry this is derived using equilibrium thermodynamics. It can also be derived with the concept of chemical potential.
History
Two chemists generally expressed the composition of a mixture in terms of numerical values relating the amount of the product to describe the equilibrium state.
Cato Maximilian Guldberg and Peter Waage, building on Claude Louis Berthollet's ideas about reversible chemical reactions, proposed the law of mass action in 1864. These papers, in Danish, went largely unnoticed, as did the later publication (in French) of 1867 which contained a modified law and the experimental data on which that law was based.
In 1877 van 't Hoff independently came to similar conclusions, but was unaware of the earlier work, which prompted Guldberg and Waage to give a fuller and further developed account of their work, in German, in 1879. Van 't Hoff then accepted their priority.
1864 | Law of mass action | Wikipedia | 445 | 318051 | https://en.wikipedia.org/wiki/Law%20of%20mass%20action | Physical sciences | Kinetics | Chemistry |
The equilibrium state (composition)
In their first paper, Guldberg and Waage suggested that in a reaction such as
A + B <=> A' + B'
the "chemical affinity" or "reaction force" between A and B did not just depend on the chemical nature of the reactants, as had previously been supposed, but also depended on the amount of each reactant in a reaction mixture. Thus the law of mass action was first stated as follows:
When two reactants, A and B, react together at a given temperature in a "substitution reaction," the affinity, or chemical force between them, is proportional to the active masses, [A] and [B], each raised to a particular power
.
In this context a substitution reaction was one such as {alcohol} + acid <=> {ester} + water. Active mass was defined in the 1879 paper as "the amount of substance in the sphere of action". For species in solution active mass is equal to concentration. For solids, active mass is taken as a constant. , a and b were regarded as empirical constants, to be determined by experiment.
At equilibrium, the chemical force driving the forward reaction must be equal to the chemical force driving the reverse reaction. Writing the initial active masses of A,B, A' and B' as p, q, p' and q' and the dissociated active mass at equilibrium as , this equality is represented by
represents the amount of reagents A and B that has been converted into A' and B'. Calculations based on this equation are reported in the second paper.
Dynamic approach to the equilibrium state
The third paper of 1864 was concerned with the kinetics of the same equilibrium system. Writing the dissociated active mass at some point in time as x, the rate of reaction was given as
Likewise the reverse reaction of A' with B' proceeded at a rate given by
The overall rate of conversion is the difference between these rates, so at equilibrium (when the composition stops changing) the two rates of reaction must be equal. Hence
... | Law of mass action | Wikipedia | 427 | 318051 | https://en.wikipedia.org/wiki/Law%20of%20mass%20action | Physical sciences | Kinetics | Chemistry |
1867
The rate expressions given in Guldberg and Waage's 1864 paper could not be differentiated, so they were simplified as follows. The chemical force was assumed to be directly proportional to the product of the active masses of the reactants.
This is equivalent to setting the exponents a and b of the earlier theory to one. The proportionality constant was called an affinity constant, k. The equilibrium condition for an "ideal" reaction was thus given the simplified form
[A]eq, [B]eq etc. are the active masses at equilibrium. In terms of the initial amounts reagents p,q etc. this becomes
The ratio of the affinity coefficients, k'/k, can be recognized as an equilibrium constant. Turning to the kinetic aspect, it was suggested that the velocity of reaction, v, is proportional to the sum of chemical affinities (forces). In its simplest form this results in the expression
where is the proportionality constant. Actually, Guldberg and Waage used a more complicated expression which allowed for interaction between A and A', etc. By making certain simplifying approximations to those more complicated expressions, the rate equation could be integrated and hence the equilibrium quantity could be calculated. The extensive calculations in the 1867 paper gave support to the simplified concept, namely,
The rate of a reaction is proportional to the product of the active masses of the reagents involved.
This is an alternative statement of the law of mass action.
1879
In the 1879 paper the assumption that reaction rate was proportional to the product of concentrations was justified microscopically in terms of the frequency of independent collisions, as had been developed for gas kinetics by Boltzmann in 1872 (Boltzmann equation). It was also proposed that the original theory of the equilibrium condition could be generalised to apply to any arbitrary chemical equilibrium.
The exponents α, β etc. are explicitly identified for the first time as the stoichiometric coefficients for the reaction. | Law of mass action | Wikipedia | 403 | 318051 | https://en.wikipedia.org/wiki/Law%20of%20mass%20action | Physical sciences | Kinetics | Chemistry |
Modern statement of the law
The affinity constants, k+ and k−, of the 1879 paper can now be recognised as rate constants. The equilibrium constant, K, was derived by setting the rates of forward and backward reactions to be equal. This also meant that the chemical affinities for the forward and backward reactions are equal. The resultant expression
is correct even from the modern perspective, apart from the use of concentrations instead of activities (the concept of chemical activity was developed by Josiah Willard Gibbs, in the 1870s, but was not widely known in Europe until the 1890s). The derivation from the reaction rate expressions is no longer considered to be valid. Nevertheless, Guldberg and Waage were on the right track when they suggested that the driving force for both forward and backward reactions is equal when the mixture is at equilibrium. The term they used for this force was chemical affinity. Today the expression for the equilibrium constant is derived by setting the chemical potential of forward and backward reactions to be equal. The generalisation of the law of mass action, in terms of affinity, to equilibria of arbitrary stoichiometry was a bold and correct conjecture.
The hypothesis that reaction rate is proportional to reactant concentrations is, strictly speaking, only true for elementary reactions (reactions with a single mechanistic step), but the empirical rate expression
is also applicable to second order reactions that may not be concerted reactions. Guldberg and Waage were fortunate in that reactions such as ester formation and hydrolysis, on which they originally based their theory, do indeed follow this rate expression.
In general many reactions occur with the formation of reactive intermediates, and/or through parallel reaction pathways. However, all reactions can be represented as a series of elementary reactions and, if the mechanism is known in detail, the rate equation for each individual step is given by the expression so that the overall rate equation can be derived from the individual steps. When this is done the equilibrium constant is obtained correctly from the rate equations for forward and backward reaction rates. | Law of mass action | Wikipedia | 413 | 318051 | https://en.wikipedia.org/wiki/Law%20of%20mass%20action | Physical sciences | Kinetics | Chemistry |
In biochemistry, there has been significant interest in the appropriate mathematical model for chemical reactions occurring in the intracellular medium. This is in contrast to the initial work done on chemical kinetics, which was in simplified systems where reactants were in a relatively dilute, pH-buffered, aqueous solution. In more complex environments, where bound particles may be prevented from disassociation by their surroundings, or diffusion is slow or anomalous, the model of mass action does not always describe the behavior of the reaction kinetics accurately. Several attempts have been made to modify the mass action model, but consensus has yet to be reached. Popular modifications replace the rate constants with functions of time and concentration. As an alternative to these mathematical constructs, one school of thought is that the mass action model can be valid in intracellular environments under certain conditions, but with different rates than would be found in a dilute, simple environment .
The fact that Guldberg and Waage developed their concepts in steps from 1864 to 1867 and 1879 has resulted in much confusion in the literature as to which equation the law of mass action refers. It has been a source of some textbook errors. Thus, today the "law of mass action" sometimes refers to the (correct) equilibrium constant formula,
and at other times to the (usually incorrect) rate formula.
Applications to other fields
In semiconductor physics
The law of mass action also has implications in semiconductor physics. Regardless of doping, the product of electron and hole densities is a constant at equilibrium. This constant depends on the thermal energy of the system (i.e. the product of the Boltzmann constant, , and temperature, ), as well as the band gap (the energy separation between conduction and valence bands, ) and effective density of states in the valence and conduction bands. When the equilibrium electron and hole densities are equal, their density is called the intrinsic carrier density as this would be the value of and in a perfect crystal. Note that the final product is independent of the Fermi level :
Diffusion in condensed matter
Yakov Frenkel represented diffusion process in condensed matter as an ensemble of elementary jumps and quasichemical interactions of particles and defects. Henry Eyring applied his theory of absolute reaction rates to this quasichemical representation of diffusion. Mass action law for diffusion leads to various nonlinear versions of Fick's law.
In mathematical ecology | Law of mass action | Wikipedia | 486 | 318051 | https://en.wikipedia.org/wiki/Law%20of%20mass%20action | Physical sciences | Kinetics | Chemistry |
The Lotka–Volterra equations describe dynamics of the predator-prey systems. The rate of predation upon the prey is assumed to be proportional to the rate at which the predators and the prey meet; this rate is evaluated as xy, where x is the number of prey, y is the number of predator. This is a typical example of the law of mass action.
In mathematical epidemiology
The law of mass action forms the basis of the compartmental model of disease spread in mathematical epidemiology, in which a population of humans, animals or other individuals is divided into categories of susceptible, infected, and recovered (immune). The principle of mass action is at the heart of the transmission term of compartmental models in epidemiology, which provide a useful abstraction of disease dynamics. The law of mass action formulation of the SIR model corresponds to the following "quasichemical" system of elementary reactions:
The list of components is S (susceptible individuals), I (infected individuals), and R (removed individuals, or just recovered ones if we neglect lethality);
The list of elementary reactions is
S + I -> 2I
I -> R.
If the immunity is unstable then the transition from R to S should be added that closes the cycle (SIRS model):
R -> S.
A rich system of law of mass action models was developed in mathematical epidemiology by adding components and elementary reactions.
Individuals in human or animal populations unlike molecules in an ideal solution do not mix homogeneously. There are some disease examples in which this non-homogeneity is great enough such that the outputs of the classical SIR model and their simple generalizations like SIS or SEIR, are invalid. For these situations, more sophisticated compartmental models or distributed reaction-diffusion models may be useful. | Law of mass action | Wikipedia | 370 | 318051 | https://en.wikipedia.org/wiki/Law%20of%20mass%20action | Physical sciences | Kinetics | Chemistry |
The goblin shark (Mitsukurina owstoni) is a rare species of deep-sea shark. Sometimes called a "living fossil", it is the only extant representative of the family Mitsukurinidae, a lineage some 125 million years old. This pink-skinned animal has a distinctive profile with an elongated, flat snout, and highly protrusible jaws containing prominent nail-like teeth. It is usually between long when mature, though it can grow considerably larger such as one captured in 2000 that is thought to have measured . Goblin sharks are benthopelagic creatures that inhabit upper continental slopes, submarine canyons, and seamounts throughout the world at depths greater than , with adults found deeper than juveniles. Some researchers believe that these sharks could also dive to depths of up to , for short periods of time.
Various anatomical features of the goblin shark, such as its flabby body and small fins, suggest that it is sluggish in nature. This species hunts for teleost fishes, cephalopods, and crustaceans both near the sea floor and in the middle of the water column. Its long snout is covered with ampullae of Lorenzini that enable it to sense minute electric fields produced by nearby prey, which it can snatch up by rapidly extending its jaws. Small numbers of goblin sharks are unintentionally caught by deepwater fisheries. The International Union for Conservation of Nature (IUCN) has assessed it as Least Concern, despite its rarity, citing its wide distribution and low incidence of capture.
Taxonomy
American ichthyologist David Starr Jordan described the goblin shark in an 1898 issue of Proceedings of the California Academy of Sciences, recognizing the peculiar fish not only as a new species, but also a new genus and family. He based his account on an immature male caught in Sagami Bay near Yokohama, Japan. The specimen had been acquired by shipmaster and naturalist Alan Owston, who had given it to Professor Kakichi Mitsukuri at the University of Tokyo, who in turn brought it to Jordan. Jordan named the shark Mitsukurina owstoni in honor of these two men.
The common name "goblin shark" is a calque of its traditional Japanese name , a being a Japanese mythical creature often depicted with a long nose and red face. Another name for this species is elfin shark. | Goblin shark | Wikipedia | 479 | 318069 | https://en.wikipedia.org/wiki/Goblin%20shark | Biology and health sciences | Sharks | Animals |
Soon after Jordan's description was published, several scientists noted the similarity between Mitsukurina and the extinct Mesozoic shark Scapanorhynchus. For a time, the prevailing opinion was to treat Mitsukurina as a junior synonym of Scapanorhynchus. Eventually, more complete fossils revealed many anatomical differences between Scapanorhynchus and Mitsukurina, causing modern authors to again regard them as distinct genera. Several goblin shark specimens were described as separate species from 1904 to 1937, none of which are now considered valid. This taxonomic confusion began because the specimens' jaws were fixed at varying degrees of protrusion during preservation, giving the appearance of proportional differences among the heads.
Phylogeny and evolution
Phylogenetic studies based on morphology have classified the goblin shark as the most basal member of the order Lamniformes, known as mackerel sharks. Studies using genetic data have also confirmed a basal classification for this species. The family Mitsukurinidae, represented by Mitsukurina, Scapanorhynchus, and Anomotodon, dates back to the Aptian age of the Cretaceous period (c. 125–113 Ma). Mitsukurina itself first appears in the fossil record during the period Middle Eocene (c. 49–37 Ma); extinct species include M. lineata and M. maslinensis. Striatolamia macrota, which lived in warm shallow waters during the Paleogene period (c. 66–23 Ma), may also be a Mitsukurina species. As the last member of an ancient lineage, and one that retains several "primitive" traits, the goblin shark has been described as a "living fossil".
Description | Goblin shark | Wikipedia | 356 | 318069 | https://en.wikipedia.org/wiki/Goblin%20shark | Biology and health sciences | Sharks | Animals |
The goblin shark has a distinctively long and flat snout, resembling a blade. The proportional length of the snout decreases with age. The eyes are small and lack protective nictitating membranes; behind the eyes are spiracles. The large mouth is parabolic in shape. The jaws are very protrusible and can be extended almost to the end of the snout, though normally they are held flush against the underside of the head. It has 35–53 upper and 31–62 lower tooth rows. The teeth in the main part of the jaws are long and narrow, particularly those near the symphysis (jaw midpoint), and are finely grooved lengthwise. The rear teeth near the corners of the jaw are small and have a flattened shape for crushing. Much individual variation of tooth length and width occurs, as for whether the teeth have a smaller cusplet on each side of the main cusp, and regarding the presence of toothless gaps at the symphysis or between the main and rear teeth. The five pairs of gill slits are short, with the gill filaments inside partly exposed; the fifth pair is above the origin of the pectoral fins. | Goblin shark | Wikipedia | 243 | 318069 | https://en.wikipedia.org/wiki/Goblin%20shark | Biology and health sciences | Sharks | Animals |
The body is fairly slender and flabby. The two dorsal fins are similar in size and shape, both being small and rounded. The pectoral fins are also rather small and rounded. The pelvic and anal fins have long bases and are larger than the dorsal fins. The caudal peduncle is flattened from side-to-side and lacks keels or notches. The asymmetric caudal fin has a long upper lobe with a shallow ventral notch near the tip, and an indistinct lower lobe. The soft, semi-translucent skin has a rough texture from a covering of dermal denticles, each shaped like a short upright spine with lengthwise ridges. Living sharks of this species are pink or tan due to visible blood vessels beneath the skin; the color deepens with age, and young sharks may be almost white. The fins' margins are translucent gray or blue, and the eyes are black with bluish streaks in the irises. After death, the coloration fades quickly to dull gray or brown. Adult sharks usually measure between long. However, the capture of an enormous female estimated at long during 2000 showed this species can grow far larger than suspected previously. A 2019 study suggested that it would have reached in maximum length. Until 2022, the maximum weight recorded was for a shark of 3.8 m (12.5 ft) in length. In 2023, a heavily pregnant, individual weighing , was landed in Taiwan. The enormous individual sparked criticism of the fishing method of bottom trawling which was used to catch it. | Goblin shark | Wikipedia | 320 | 318069 | https://en.wikipedia.org/wiki/Goblin%20shark | Biology and health sciences | Sharks | Animals |
Distribution and habitat
The goblin shark has been caught in all three major oceans, indicating a wide global distribution. In the Atlantic Ocean, it has been recorded from the northern Gulf of Mexico, Suriname, French Guiana, and southern Brazil in the west, and France, Portugal, Madeira, and Senegal in the east. It has also been collected from seamounts along the Mid-Atlantic Ridge. In the Indo-Pacific and Oceania, it has been found off South Africa, Mozambique, Japan, Taiwan, Australia and New Zealand. This species has been recorded from off East Cape to Kaikōura Canyon and from the Challenger Plateau near New Zealand. A single eastern Pacific specimen is known, collected off southern California. This species is most often found over the upper continental slope at depths of . It has been caught as deep as , a tooth has been found lodged in an undersea cable at a depth of , and a live individual was filmed at a depth of in the Tonga Trench. Adults inhabit greater depths than juveniles. Immature goblin sharks frequent the submarine canyons off southern Japan at depths of , with individuals occasionally wandering into inshore waters as shallow as . Two juvenile goblin sharks were captured from the Tokyo Underwater Canyon in Tokyo Bay, filmed in the Kanaya Fishing Port, and released on 30 January 2008 and 24 January 2011. The goblin shark filmed in 2008 was caught at a depth of 150–350m (492–1,148 ft). On 19 April 2014, fishermen in Key West, Florida, while fishing in the Gulf of Mexico, caught a goblin shark in their fishing net, only the second one ever to be caught in the Gulf. The shark was photographed and released back into the water. The first shark found in the Gulf was caught by commercial fisherman on 25 July 2000 at a depth of approximately 919–1,099 m (3,016–3,606 ft) and is thought to have been about 20 ft long. During July 2014, a goblin shark was found in a fishery net in Sri Lanka, near the eastern coast of Sri Lanka. The shark was about long and weighed about . The shark was given to the NARA (National Aquatic Resource Research & Development Agency) for further research. | Goblin shark | Wikipedia | 447 | 318069 | https://en.wikipedia.org/wiki/Goblin%20shark | Biology and health sciences | Sharks | Animals |
Biology and ecology
Although observations of living goblin sharks are scant, its anatomy suggests its lifestyle is inactive and sluggish. Its skeleton is reduced and poorly calcified, the muscle blocks along its sides (myomeres) are weakly developed, and its fins are soft and small. Its long caudal fin, held at a low angle, is also typical of a slow-swimming shark. The long snout appears to have a sensory function, as it bears numerous ampullae of Lorenzini that can detect the weak electric fields produced by other animals. Due to the snout's softness, it is unlikely to be used for stirring up prey from the bottom as has been proposed. Vision seems to be less important than other senses, considering the relatively small optic tectum in the shark's brain. Yet unlike most deep-sea sharks, it can change the size of its pupils, thus probably does use its sight in some situations. Goblin sharks may be the prey of blue sharks (Prionace glauca). Parasites documented from this species include the copepod Echthrogaleus mitsukurinae, and the tapeworms Litobothrium amsichensis and Marsupiobothrium gobelinus.
Feeding
The goblin shark feeds mainly on teleost fishes such as rattails and dragonfishes. It also consumes cephalopods and crustaceans, including decapods and isopods. Garbage has been recorded from the stomachs of some specimens. Its known prey includes bottom-dwelling species such as the blackbelly rosefish (Helicolenus dactylopterus), and midwater species such as the squid Teuthowenia pellucida and the ostracod Macrocypridina castanea rotunda. Thus, the goblin shark appears to forage for food both near the sea floor and far above it. | Goblin shark | Wikipedia | 389 | 318069 | https://en.wikipedia.org/wiki/Goblin%20shark | Biology and health sciences | Sharks | Animals |
Since it is not a fast swimmer, the goblin shark may be an ambush predator. Its low-density flesh and large oily liver make it neutrally buoyant, allowing it to drift towards its prey with minimal motions so as to avoid detection. Once prey comes into range, the shark's specialized jaws can snap forward to capture it. The protrusion of the jaw is assisted by two pairs of elastic ligaments associated with the mandibular joint, which are pulled taut when the jaws are in their normal retracted position; when the shark bites, the ligaments release their tension and essentially "catapult" the jaws forward. At the same time, the well-developed basihyal (analogous to a tongue) on the floor of the mouth drops, expanding the oral cavity and sucking in water and prey. Striking and prey capture events were videotaped and recorded for the first time during 2008 and 2011 and helped to confirm the use and systematics of the protrusible jaws of goblin sharks. The video evidence suggests that while the jaws are definitely unique, goblin sharks use ram feeding, a type of prey capture that is typical of many mackerel sharks. What makes the goblin shark unique is the kinematics of their jaw when feeding. The lower jaw seems to undergo more complex movements and is important in capturing the prey. The measured protrusions of the upper and lower jaw combined put the goblin shark jaws at 2.1–9.5 times more protrusible than other sharks. The lower jaw has a velocity about two times greater than the upper jaw because it not only protrudes forward, but also swings upward to capture the prey, and the maximum velocity of the jaws is 3.14 m/s. The goblin shark has a re-opening and re-closing pattern during the strike, a behavior that has never been seen in other sharks before and could be related to the extent with which the goblin shark protrudes its jaws. | Goblin shark | Wikipedia | 401 | 318069 | https://en.wikipedia.org/wiki/Goblin%20shark | Biology and health sciences | Sharks | Animals |
Growth and reproduction
The reproductive behaviors of the goblin shark are poorly understood. Mating has never been observed between two goblin sharks, and a pregnant female has yet to be captured. It likely shares the reproductive characteristics of other mackerel sharks, which are viviparous with small litter sizes and embryos that grow during gestation by eating undeveloped eggs (oophagy). The birth size is probably close to , the length of the smallest known specimen. Males mature sexually at about long, while female maturation size is unknown. No data is available concerning growth and aging. Some researchers have estimated, based on their own research and prior findings, that male goblin sharks mature at approximately 16 years old and can live up to 60 years. | Goblin shark | Wikipedia | 148 | 318069 | https://en.wikipedia.org/wiki/Goblin%20shark | Biology and health sciences | Sharks | Animals |
Human interactions
Given the depths at which it lives, the goblin shark poses little danger to humans. The first known findings pertaining to the goblin shark were published in 1910. "The new shark is certainly grotesque, [...] the most remarkable feature is the curiously elongated nose." A few specimens have been collected alive and brought to public aquariums, though they only survived briefly. One was kept at Tokai University and lived for a week, while another was kept at Tokyo Sea Life Park and lived for two days. Its economic significance is minimal; the meat may be dried and salted, while the jaws fetch high prices from collectors. At one time, the Japanese also used it for liver oil and fertilizer. This shark is not targeted by any fisheries, but is occasionally found as bycatch in bottom gillnets and trawls, hooked on longlines, or entangled in fishing gear. Most captures are isolated incidents; one of the few areas where it is caught regularly is off southern Japan, where around 30 individuals (mostly juveniles) are taken each year. A black scabbardfish (Aphanopus carbo) fishery off Madeira also takes two or three goblin sharks annually. During April 2003, more than a hundred goblin sharks were caught off northwestern Taiwan; the cause of the event was unknown, though observers noted it was preceded by a major earthquake. The species had never been recorded in the area before, nor has it been found in such numbers since. The International Union for Conservation of Nature (IUCN) has categorized the goblin shark as Least Concern. In addition to its wide range, most of its population is thought to reside in unfished environments because few adults are caught. Therefore, it is not believed to be threatened by human activity. However, during June 2018 the New Zealand Department of Conservation classified the goblin shark as "At Risk – Naturally Uncommon" with the qualifiers "Data Poor" and "Secure Overseas" using the New Zealand Threat Classification System. | Goblin shark | Wikipedia | 400 | 318069 | https://en.wikipedia.org/wiki/Goblin%20shark | Biology and health sciences | Sharks | Animals |
The Giraffidae are a family of ruminant artiodactyl mammals that share a recent common ancestor with deer and bovids. This family, once a diverse group spread throughout Eurasia and Africa, presently comprises only two extant genera, the giraffe (between one and eight, usually four, species of Giraffa, depending on taxonomic interpretation) and the okapi (the only known species of Okapia). Both are confined to sub-Saharan Africa: the giraffe to the open savannas, and the okapi to the dense rainforest of the Congo. The two genera look very different on first sight, but share a number of common features, including a long, dark-coloured tongue, lobed canine teeth, and horns covered in skin, called ossicones.
Taxonomy
Evolutionary background
The giraffids are ruminants of the clade Pecora. Other extant pecorans are the families Antilocapridae (pronghorns), Cervidae (deer), Moschidae (musk deer), and Bovidae (cattle, goats and sheep, wildebeests and allies, and antelopes). The exact interrelationships among the pecorans have been debated, mainly focusing on the placement of Giraffidae, but a recent large-scale ruminant genome sequencing study suggests Antilocapridae are the sister taxon to Giraffidae, as shown in the cladogram below.
The ancestors of pronghorn diverged from the giraffids in the Early Miocene. This was in part of a relatively late mammal diversification following a climate change that transformed subtropical woodlands into open savannah grasslands. | Giraffidae | Wikipedia | 352 | 318200 | https://en.wikipedia.org/wiki/Giraffidae | Biology and health sciences | Giraffidae | Animals |
The fossil record of giraffids and their stem-relatives is quite intensive, with fossil of these taxa include Gelocidae, Palaeomerycidae, Prolibytheridae, and Climacoceratidae. It is thought that the palaeomerycids, prolibytherids, climacoceratids and the giraffids all form a clade of pecorans known as Giraffomorpha. The relationship between the climacoceratids and giraffids is supported by the presence of a bilobed canine, and have been postulated into two hypotheses. One is the climacoceratids were the ancestors of the sivatheres, as both groups were large, deer-like giraffoids with branching antler-like ossicones, while an extinct basal group of giraffoids, canthumerycines, evolved into the ancestors of Giraffidae. Another more commonly supported hypothesis is climacoceratids were merely the sister clade to giraffids, with sivatheres being either basal giraffids or descended from a lineage that also includes the okapi. While the current range of giraffids today is in Africa, the fossil record of the group has shown this family was once widespread throughout of Eurasia.
Below is the phylogenetic relationships of giraffomorphs after Solounias (2007), Sánchez et al. (2015) and Ríos et al. (2017):
Classification
Below is the total taxonomy of valid extant and fossil taxa (as well as junior synonyms which are listed in the brackets). | Giraffidae | Wikipedia | 346 | 318200 | https://en.wikipedia.org/wiki/Giraffidae | Biology and health sciences | Giraffidae | Animals |
Family Giraffidae J.E.Gray, 1821
Basal extinct giraffids
†Csakvarotherium Kretzoi, 1930
†Csakvarotherium hungaricum Kretzoi, 1930
†Injanatherium Heintz, Brunet & Sen, 1981
†Injanatherium arabicum Morales, Soria & Thomas, 1987
†Injanatherium hazimi Heintz, Brunet & Sen, 1981
†Propalaeomeryx Lydekker, 1883 [Progiraffa Pilgrim, 1908]
†Propalaeomeryx sivalensis Lydekker, 1883 [Progiraffa exigua Pilgrim, 1908]
†Shansitherium Killgus, 1922 [Schansitherium [sic]]
†Shansitherium quadricornis (Bohlin, 1926) [Palaeotragus quadricornis Bohlin, 1926]
†Shansitherium tafeli Killgus, 1922
†Umbrotherium Abbazzi, Delfino, Gallai, Trebini & Rook, 2008
†Umbrotherium azzarolii Abbazzi, Delfino, Gallai, Trebini & Rook, 2008
Subfamily †Canthumerycinae Hamilton, 1978
†Georgiomeryx Paraskevaidis, 1940
†Georgiomeryx georgalasi Paraskevaidis, 1940
†Canthumeryx Hamilton 1973 [Zarafa Hamilton, 1973]
†Canthumeryx sirtensis Hamilton 1973 [Zarafa zelteni Hamilton, 1973]
Subfamily Giraffinae J.E.Gray, 1821
Tribe Giraffini J.E.Gray, 1821
Subtribe Giraffina J.E.Gray, 1821
Giraffa Brisson, 1762 [Camelopardalis von Schreber, 1784 and Orasius Oken, 1816]
Giraffa camelopardalis super-complex (Linnaeus, 1758)
Giraffa giraffa complex (von Schreber, 1784)
Giraffa angolensis Lydekker, 1903 – Angolan giraffe
Giraffa giraffa (von Schreber, 1784) – South African giraffe
Giraffa tippelskirchii complex Matschie, 1898
Giraffa thornicrofti Lydekker, 1911 – Rhodesian giraffe | Giraffidae | Wikipedia | 497 | 318200 | https://en.wikipedia.org/wiki/Giraffidae | Biology and health sciences | Giraffidae | Animals |
Giraffa tippelskirchii Matschie, 1898 – Masai giraffe
Giraffa reticulata de Winton, 1899 – Reticulated giraffe
Giraffa camelopardalis complex (Linnaeus, 1758)
Giraffa peralta Thomas, 1898 – West African giraffe
Giraffa antiquorum Jardine & Swainson, 1835 – Kordofan giraffe
Giraffa camelopardalis (Linnaeus, 1758) – Northern giraffe
Giraffa camelopardalis rothschildi Lydekker, 1903 – Rothschild's giraffe
Giraffa camelopardalis camelopardalis (Linnaeus, 1758) – Nubian giraffe
†Giraffa jumae Leakey, 1967
†Giraffa priscilla Pilgrim, 1911
†Giraffa punjabiensis Pilgrim, 1911
†Giraffa pygmaea Harris, 1976
†Giraffa sivalensis (Falconer & Cautley, 1843) [Camelopardalis sivalensis Falconer & Cautley, 1843 and Camelopardalis affinis Falconer & Cautley, 1843]
†Giraffa stillei (Dietrich, 1942) [Okapia stillei Dietrich, 1942 and Giraffa gracilis Arambourg, 1947]
Subtribe †Bohlinina Solounias, 2007
†Bohlinia Matthew, 1929
†Bohlinia adoumi Likius, Vignaud & Brunet, 2007
†Bohlinia attica (Gaudry & Lartet, 1856) [Giraffa attica (Gaudry & Lartet, 1856) and Orasius attica (Gaudry & Lartet, 1856)]
†Bohlinia nikitiae Kostopoulos, Koliadimou & Koufos, 1996
†Honanotherium Bohlin, 1927
†Honanotherium bernori Solounias & Danowitz, 2016
†Honanotherium schlosseri (Pilgrim, 1911) [Giraffa schlosseri Pilgrim, 1911]
Tribe Palaeotragini Pilgrim, 1910
Subtribe †Palaeotragina Pilgrim, 1910
†Giraffokeryx Pilgrim, 1910
†Giraffokeryx anatoliensis Geraads & Aslan, 2003 | Giraffidae | Wikipedia | 481 | 318200 | https://en.wikipedia.org/wiki/Giraffidae | Biology and health sciences | Giraffidae | Animals |
†Giraffokeryx primaevus (Churcher, 1970) [Palaeotragus primaevus Churcher, 1970; Samotherium africanum Churcher, 1970 and Amotherium africanum [sic]]
†Giraffokeryx punjabiensis Pilgrim, 1910
†Mitilanotherium
†Mitilanotherium inexpectatum
†Palaeogiraffa Bonis & Bouvrain, 2003
†Palaeogiraffa macedoniae (Geraads, 1989) [Decennatherium macedoniae Geraads, 1989]
†Palaeogiraffa major Bonis & Bouvrain, 2003
†Palaeogiraffa pamiri (Ozansoy, 1965) [Samotherium pamiri Ozansoy, 1965]
†Palaeotragus Gaudry, 1861 [Achtiaria Borissiak, 1914; Macedonitherium Sickenberg, 1967; Mitilanotherium Samson & Radulesco, 1966 and Sogdianotherium Sharapov, 1974]
†Palaeotragus coelophrys (Rodler & Weithofer, 1890) [Alcicephalus coelophrys Rodler & Weithofer, 1890]
†Palaeotragus germaini Arambourg, 1959
†Palaeotragus inexspectatus (Samson & Radulesco, 1966) [Macedonitherium martinii Sickenberg, 1967; Mitilanotherium inexpectatum Samson & Radulesco, 1966; Mitilanotherium kuruksaense (Sharapov, 1974); Mitilanotherium martinii (Sickenberg, 1967); Palaeotragus priasovicus Godina & Bajgusheva, 1985 and Sogdianotherium kuruksaense Sharapov, 1974]
†Palaeotragus lavocanti Heintz, 1976
†Palaeotragus robinsoni Crusafont-Pairó, 1979
†Palaeotragus rouenii Gaudry, 1861 [Palaeotragus microdon Koken, 1885]
†Palaeotragus tungurensis Colbert, 1936
†Praepalaeotragus Godina, Vislobokova & Abdrachmanova, 1993 | Giraffidae | Wikipedia | 493 | 318200 | https://en.wikipedia.org/wiki/Giraffidae | Biology and health sciences | Giraffidae | Animals |
†Praepalaeotragus actaensis Godina, Vislobokova & Abdrachmanova, 1993
†Samotherium Forsyth Major, 1888 [Alcicephalus Rodler & Weithofer, 1890; Chersenotherium Alexajew, 1916 and Amotherium [sic]]
†Samotherium boissieri Forsyth Major, 1888
†Samotherium eminens (Alexajew, 1916) [Chersenotherium eminens Alexajew, 1916]
†Samotherium major Bohlin, 1926
†Samotherium neumayri (Rodler & Weithofer, 1890) [Alcicephalus neumayri Rodler & Weithofer, 1890]
†Samotherium sinense (Schlosser, 1903) [Alcicephalus sinense Schlosser, 1903]
Subtribe Okapiina Bohlin, 1926
†Afrikanokeryx Harris, Solounias & Geraads, 2010
†Afrikanokeryx leakeyi Harris, Solounias & Geraads, 2010
Okapia Lankester, 1901
Okapia johnstoni (P. L. Sclater, 1901) – Okapi
†Subfamily Sivatheriinae Bonaparte, 1850
†Birgerbohlinia Crusafont Pairó, 1952
†Birgerbohlinia schaubi Crusafont Pairó, 1952
†Bramatherium Falconer, 1845 [Hydaspitherium Lydekker, 1876]
†Bramatherium giganteus Khan & Sarwar, 2002
†Bramatherium grande (Lydekker, 1878) [Hydaspitherium grande Lydekker, 1878]
†Bramatherium magnum (Pilgrim, 1910) [Hydaspitherium magnum Pilgrim, 1910]
†Bramatherium megacephalum (Lydekker, 1876) [Hydaspitherium megacephalum Lydekker, 1876]
†Bramatherium perimense Falconer, 1845
†Bramatherium progressus Khan, Sarwar & Khan, 1993
†Bramatherium suchovi Godina, 1977
†Decennatherium Crusafont Pairó, 1952
†Decennatherium rex Ríos, Sánchez & Morales, 2017
†Decennatherium pachecoi Crusafont Pairó, 1952 | Giraffidae | Wikipedia | 511 | 318200 | https://en.wikipedia.org/wiki/Giraffidae | Biology and health sciences | Giraffidae | Animals |
†Helladotherium Gaudry, 1860
†Helladotherium duvernoyi (Gaudry & Lartet, 1856) [Camelopardalis duvernoyi Gaudry & Lartet, 1856]
†Sivatherium Falconer & Cautley, 1836 [Griquatherium Haughton, 1922; Indratherium Pilgrim, 1910; Libytherium Pomel, 1892 and Orangiatherium van Hoepen, 1932]
†Sivatherium giganteum Falconer & Cautley, 1836
†Sivatherium hendeyi Harris, 1976
†Sivatherium maurusium (Pomel, 1892) [Libytherium maurusium Pomel, 1892; Griquatherium cingulatum Haughton, 1922; Helladotherium olduvaiense Hopwood, 1934; Sivatherium olduvaiense (Hopwood, 1934); Libytherium olduvaiense Hopwood, 1934 and Orangiatherium vanrhyni van Hoepen, 1932]
†Vishnutherium Lydekker, 1876
†Vishnutherium iravadicum Lydekker 1876 | Giraffidae | Wikipedia | 253 | 318200 | https://en.wikipedia.org/wiki/Giraffidae | Biology and health sciences | Giraffidae | Animals |
Characteristics
The giraffe stands tall, with males taller than females. The giraffe and the okapi have characteristic long necks and long legs. Ossicones are present on males and females in the giraffe, but only on males in the okapi.
Giraffids share many common features with other ruminants. They have cloven hooves and cannon bones, much like bovids, and a complex, four-chambered stomach. They have no upper incisors or upper canines, replacing them with a tough, horny pad. An especially long diastema is seen between the front and cheek teeth. The latter are selenodont, adapted for grinding up tough plant matter. Like most other ruminants, the dental formula for giraffids is . Giraffids have prehensile tongues (specially adapted for grasping).
The extant giraffids, the forest-dwelling okapi and the savannah-living giraffe, have several features in common, including a pair of skin-covered horns, called ossicones, up to long (absent in female okapis); a long, black, prehensile tongue; lobed canine teeth; patterned coats acting as camouflage; and a back sloping towards the rear. The okapi's neck is long compared to most ruminants, but not nearly so long as the giraffe's. Male giraffes are the tallest of all mammals: their horns reach above the ground and their shoulder , whereas the okapi has a shoulder height of .
Distribution
The two extant genera are now confined to sub-Saharan Africa. The okapi is restricted to a small range in the northern rainforest of the Democratic Republic of Congo. Although the range of the giraffe is considerably larger, it once covered an area twice the present size – all parts of Africa that could offer an arid and dry landscape furnished with trees. | Giraffidae | Wikipedia | 402 | 318200 | https://en.wikipedia.org/wiki/Giraffidae | Biology and health sciences | Giraffidae | Animals |
Behavior
The social structure and behavior is markedly different in okapis and giraffes, but although little is known of the okapi's behavior in the wild, a few things are known to be present in both species:
They have an ambling gait similar to camels, with their weight supported alternately by their left and right legs, while their necks maintain balance. Giraffes can run up to this way and are documented to have covered in the Sahel during the dry season.
The dominance hierarchy, which has been well-documented among giraffes, has also been seen among captive okapis. An adult giraffe head can weigh , and if necessary, male giraffes establish a hierarchy among themselves by swinging their heads at each other, horns first, a behavior known as "necking". A subordinate okapi signals submission by placing its head and neck on the ground.
Giraffes are sociable, whereas okapis live mainly solitary lives. Giraffes temporarily form herds of up to 20 individuals; these herds can be mixed or uniform groups of males and females, young and adults. Okapis are normally seen in mother-offspring pairs, although they occasionally gather around a prime food source. Giraffe are not territorial, but have ranges that can dramatically vary between – – depending on food availability, whereas okapis have individual ranges about in size.
Giraffes and okapis are normally silent, but both have a range of vocalizations, including coughing, snorting, moaning, hissing, and whistling. Giraffes have been suggested to be able to communicate using infrasonic sounds like elephants and blue whales. | Giraffidae | Wikipedia | 348 | 318200 | https://en.wikipedia.org/wiki/Giraffidae | Biology and health sciences | Giraffidae | Animals |
The African penguin (Spheniscus demersus), also known as Cape penguin or South African penguin, is a species of penguin confined to southern African waters. It is the only penguin found in the Old World. Like all penguins, it is flightless, with a streamlined body and wings stiffened and flattened into flippers for a marine habitat. Adults weigh an average of and are tall. The species has distinctive pink patches of skin above the eyes and a black facial mask. The body's upper parts are black and sharply delineated from the white underparts, which are spotted and marked with a black band.
The African penguin is a pursuit diver and feeds primarily on fish and squid. Once extremely numerous, the African penguin is now the rarest species of penguin classified as critically endangered, with its population declining rapidly due to a combination of several threats. It is a charismatic species and is popular with tourists. Other vernacular names of the species include black-footed penguin and jackass penguin, due to the species' loud, donkey-like noise (although several related species of South American penguins produce the same sound). They can be found along the coast of South Africa and Namibia.
Taxonomy
In 1747, the English naturalist George Edwards included an illustration and a description of the African penguin in the second volume of his A Natural History of Uncommon Birds. He used the English name "The Black-Footed Penguins". Edwards based his hand-coloured etching on two preserved specimens that had been brought to London. He suspected that they had been collected near the Cape of Good Hope. When in 1758 the Swedish naturalist Carl Linnaeus updated his Systema Naturae for the tenth edition, he placed the African penguin with the wandering albatross in the genus Diomedea. Linnaeus included a brief description, coined the binomial name Diomedea demersa and cited Edwards' work. The African penguin is now placed with the banded penguins in the genus Spheniscus that was introduced in 1760 by the French zoologist Mathurin Jacques Brisson. The genus name Spheniscus is from Ancient Greek word σφήν (sphēn) meaning "wedge" and is a reference to the animal's thin, wedge-shaped flippers. The specific epithet demersus is Latin meaning "plunging" (from demergere meaning "to sink"). | African penguin | Wikipedia | 482 | 318215 | https://en.wikipedia.org/wiki/African%20penguin | Biology and health sciences | Sphenisciformes | Animals |
Banded penguins are found mainly in the Southern Hemisphere with the Humboldt penguin and Magellanic penguins found in southern South America and the Galápagos penguin found in the Pacific Ocean near the equator. All are similar in shape, colour and behaviour.
Description
African penguins grow to tall and weigh between . The beak length of the African penguin varies, usually growing between . They have a black stripe and black spots on the chest, the pattern of which is unique to each penguin, like human fingerprints. The sweat glands above the eyes cool the birds' blood and as the temperature rises, increased blood flow causes the glands to get pinker. This species exhibits slight sexual dimorphism; the males are slightly larger than the females and have longer beaks. Juveniles do not possess the bold, delineated markings of the adult, but instead have dark upperparts that vary from greyish-blue to brown; the pale underparts lack both spots and the band. The beak is more pointed than that of the Humboldt penguin. The African penguin's colouring is a form of protective colouration known as countershading. The white undersides of the birds are difficult to spot by predators under the water and the penguins' black backs blend in with the water when viewed from above.
African penguins resemble and are thought to be related to the Humboldt, Magellanic and Galápagos penguins. African penguins have a very recognisable appearance, with a thick band of black that is in the shape of an upside-down horseshoe. They have black feet and black spots that vary in size and shape between individuals. Magellanic penguins share a similar bar marking that often confuses the two; the Magellanic has a double bar on the throat and chest, whereas the African has a single bar. These penguins have the nickname "jackass penguin", which comes from the loud penguin noises they make.
Distribution and habitat
The African penguin is only found on the southwestern coast of Africa, living in colonies on 24 islands between Namibia and Algoa Bay, near Port Elizabeth, South Africa. It is the only penguin species that breeds in Africa and its presence gave name to the Penguin Islands. | African penguin | Wikipedia | 437 | 318215 | https://en.wikipedia.org/wiki/African%20penguin | Biology and health sciences | Sphenisciformes | Animals |
Two colonies were established by penguins in the 1980s on the mainland near Cape Town, namely Boulders Beach near Simon's Town and Stony Point in Betty's Bay. Mainland colonies likely became possible only in recent times due to the reduction of predator numbers, although the Betty's Bay colony has been attacked by leopards. The only other mainland colony is in Namibia, but it is not known when it was established.
Boulders Beach is a tourist attraction due to the beach, swimming and the penguins. The penguins will allow people to approach them as close as a meter.
Breeding populations of African penguins are being kept in numerous zoos worldwide. No colonies are known outside the southwestern coast of Africa, although vagrants (mostly juveniles) may occasionally be sighted beyond the normal range.
Population
Roughly 4 million African penguins existed at the beginning of the 19th century. Of the 1.5 million African penguins estimated in 1910, only some 10% remained at the end of the 20th century. African penguin populations, which breed in Namibia and South Africa, have declined by 95% since pre-industrial times.
Today, their breeding is largely restricted to 24 islands from Namibia to Algoa Bay, South Africa, with the Boulders Beach colony being an exception to this rule.
The total population fell to approximately 150,000–180,000 in 2000. Of those, 56,000 belonged to the Dassen Island colony and 14,000 to the Robben Island colony. The colony at Dyer Island in South Africa fell from 46,000 in the early 1970s to 3,000 in 2008.
In 2008, 5,000 breeding pairs were estimated to live in Namibia.
In 2010, the total African penguin population was estimated at 55,000. At the rate of decline seen from 2000 to 2010, the African penguin is expected to be extinct in the wild by 2026.
In 2012, about 18,700 breeding pairs were estimated to live in South Africa, with the majority on St. Croix Island in Algoa Bay.
The total breeding population across both South Africa and Namibia fell to a historic low of about 20,850 pairs in 2019.
Behaviour | African penguin | Wikipedia | 426 | 318215 | https://en.wikipedia.org/wiki/African%20penguin | Biology and health sciences | Sphenisciformes | Animals |
Diet
African penguins forage in the open sea, where they feed on pelagic fish such as sardines (including the blue pilchard), Cape horse mackerels, red-eye round herrings and anchovies (specifically the European anchovy and the Southern African anchovy) and marine invertebrates such as squids and small crustaceans, primarily krills and shrimps. Penguins normally swim within of the shore. A penguin may consume up to of prey every day, but this may increase to over when raising older chicks.
Due to the marked decline of sardines in the waters near its habitat, African penguins' diet has shifted towards anchovies to some extent, although available sardine biomass is still a notable determinant of penguin population development and breeding success. While a diet of anchovies appears to be generally sufficient for the penguins, it is not ideal due to anchovies' lower concentrations of fat and protein. The Penguin's diet changes throughout the year; as in many seabirds, it is believed that the interaction of diet choice and breeding success helps the penguins maintain their population size. Although parent penguins are protective of their chicks, they will not incur nutritional deficits themselves if food is scarce and hunting requires a greater time or energy commitment. This may lead to higher rates of brood loss under poor food conditions.
When foraging, African penguins carry out dives that reach an average depth of and last for 69 seconds, although a maximum depth of and duration of 275 seconds has been recorded.
Breeding
The African penguin is monogamous; it breeds in colonies and pairs return to the same site each year. It has an extended breeding season, with nesting usually peaking from March to May in South Africa and November to December in Namibia. A clutch of two eggs is laid either in burrows burrowed in guano or nests in the sand under boulders or bushes. Incubation is undertaken equally by both parents for around 40 days. At least one parent guards the chicks for about one month, whereafter the chicks join a crèche with other chicks and both parents spend most of the day foraging in the sea.
Chicks fledge at 60 to 130 days, the timing depending on environmental factors such as the quality and availability of food. The fledged chicks then go to sea on their own, where they spend the next one to nearly two years. They then return to their natal colony to moult into adult plumage. | African penguin | Wikipedia | 498 | 318215 | https://en.wikipedia.org/wiki/African%20penguin | Biology and health sciences | Sphenisciformes | Animals |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.