Aerobic respiration.

"Aerobic respiration" requires oxygen (O) in order to create ATP. Although carbohydrates, fats, and proteins are consumed as reactants, it is the preferred method of pyruvate breakdown in glycolysis and requires that pyruvate enter the mitochondria in order to be fully oxidized by the Krebs cycle. The products of this process are carbon dioxide and water, but the energy transferred is used to break bonds in ADP as the third phosphate group is added to form ATP (adenosine triphosphate), by substrate-level phosphorylation, NADH and FADH The negative ΔG indicates that the reaction can occur spontaneously.  The potential of NADH and FADH is converted to more ATP through an electron transport chain with oxygen and protons (hydrogen) as the "terminal electron acceptors". Most of the ATP produced by aerobic cellular respiration is made by oxidative phosphorylation. The energy of O released is used to create a chemiosmotic potential by pumping protons across a membrane. This potential is then used to drive ATP synthase and produce ATP from ADP and a phosphate group. Biology textbooks often state that 38 ATP molecules can be made per oxidized glucose molecule during cellular respiration (2 from glycolysis, 2 from the Krebs cycle, and about 34 from the electron transport system). However, this maximum yield is never quite reached because of losses due to leaky membranes as well as the cost of moving pyruvate and ADP into the mitochondrial matrix, and current estimates range around 29 to 30 ATP per glucose.  Aerobic metabolism is up to 15 times more efficient than anaerobic metabolism (which yields 2 molecules ATP per 1 molecule glucose) because the double bond in O is of higher energy than other double bonds or pairs of single bonds in other common molecules in the biosphere. However, some anaerobic organisms, such as methanogens are able to continue with anaerobic respiration, yielding more ATP by using other inorganic molecules (not oxygen) of high energy as final electron acceptors in the electron transport chain. They share the initial pathway of glycolysis but aerobic metabolism continues with the Krebs cycle and oxidative phosphorylation. The post-glycolytic reactions take place in the mitochondria in eukaryotic cells, and in the cytoplasm in prokaryotic cells.

Glycolysis.

Glycolysis is a metabolic pathway that takes place in the cytosol of cells in all living organisms. Glycolysis can be literally translated as "sugar splitting", which functions with or without the presence of oxygen. In humans, aerobic conditions produce pyruvate and anaerobic conditions produce lactate. In aerobic conditions, the process converts one molecule of glucose into two molecules of pyruvate (pyruvic acid), generating energy in the form of two net molecules of ATP. Four molecules of ATP per glucose are actually produced, however, two are consumed as part of the preparatory phase. The initial phosphorylation of glucose is required to increase the reactivity (decrease its stability) in order for the molecule to be cleaved into two pyruvate molecules by the enzyme aldolase. During the pay-off phase of glycolysis, four phosphate groups are transferred to ADP by substrate-level phosphorylation to make four ATP, and two NADH are produced when the pyruvate is oxidized. The overall reaction can be expressed this way:  Starting with glucose, 1 ATP is used to donate a phosphate to glucose to produce glucose 6-phosphate. Glycogen can be converted into glucose 6-phosphate as well with the help of glycogen phosphorylase. During energy metabolism, glucose 6-phosphate becomes fructose 6-phosphate. An additional ATP is used to phosphorylate fructose 6-phosphate into fructose 1,6-bisphosphate by the help of phosphofructokinase. Fructose 1,6-biphosphate then splits into two phosphorylated molecules with three carbon chains which later degrades into pyruvate.

Oxidative decarboxylation of pyruvate.

Pyruvate is oxidized to acetyl-CoA and CO by the pyruvate dehydrogenase complex (PDC). The PDC contains multiple copies of three enzymes and is located in the mitochondria of eukaryotic cells and in the cytosol of prokaryotes. In the conversion of pyruvate to acetyl-CoA, one molecule of NADH and one molecule of CO is formed.

Citric acid cycle.

This is also called the "Krebs cycle" or the "tricarboxylic acid cycle". When oxygen is present, acetyl-CoA is produced from the pyruvate molecules created from glycolysis. Once acetyl-CoA is formed, aerobic or anaerobic respiration can occur. When oxygen is present, the mitochondria will undergo aerobic respiration which leads to the Krebs cycle. However, if oxygen is not present, fermentation of the pyruvate molecule will occur. In the presence of oxygen, when acetyl-CoA is produced, the molecule then enters the citric acid cycle (Krebs cycle) inside the mitochondrial matrix, and is oxidized to CO while at the same time reducing NAD to NADH. NADH can be used by the electron transport chain to create further ATP as part of oxidative phosphorylation. To fully oxidize the equivalent of one glucose molecule, two acetyl-CoA must be metabolized by the Krebs cycle. Two low-energy waste products, HO and CO, are created during this cycle.  The citric acid cycle is an 8-step process involving 18 different enzymes and co-enzymes. During the cycle, acetyl-CoA (2 carbons) + oxaloacetate (4 carbons) yields citrate (6 carbons), which is rearranged to a more reactive form called isocitrate (6 carbons). Isocitrate is modified to become α-ketoglutarate (5 carbons), succinyl-CoA, succinate, fumarate, malate, and, finally, oxaloacetate.  The net gain from one cycle is 3 NADH and 1 FADH as hydrogen- (proton plus electron)-carrying compounds and 1 high-energy GTP, which may subsequently be used to produce ATP. Thus, the total yield from 1 glucose molecule (2 pyruvate molecules) is 6 NADH, 2 FADH, and 2 ATP.

Oxidative phosphorylation.

In eukaryotes, oxidative phosphorylation occurs in the mitochondrial cristae. It comprises the electron transport chain that establishes a proton gradient (chemiosmotic potential) across the boundary of the inner membrane by oxidizing the NADH produced from the Krebs cycle. ATP is synthesized by the ATP synthase enzyme when the chemiosmotic gradient is used to drive the phosphorylation of ADP. The electron transfer is driven by the chemical energy of exogenous oxygen and, with the addition of two protons, water is formed.

Efficiency of ATP production.

The table below describes the reactions involved when one glucose molecule is fully oxidized into carbon dioxide. It is assumed that all the reduced coenzymes are oxidized by the electron transport chain and used for oxidative phosphorylation.  Although there is a theoretical yield of 38 ATP molecules per glucose during cellular respiration, such conditions are generally not realized because of losses such as the cost of moving pyruvate (from glycolysis), phosphate, and ADP (substrates for ATP synthesis) into the mitochondria. All are actively transported using carriers that utilize the stored energy in the proton electrochemical gradient.  The outcome of these transport processes using the proton electrochemical gradient is that more than 3 H are needed to make 1 ATP. Obviously this reduces the theoretical efficiency of the whole process and the likely maximum is closer to 28–30 ATP molecules. In practice the efficiency may be even lower because the inner membrane of the mitochondria is slightly leaky to protons. Other factors may also dissipate the proton gradient creating an apparently leaky mitochondria. An uncoupling protein known as thermogenin is expressed in some cell types and is a channel that can transport protons. When this protein is active in the inner membrane it short circuits the coupling between the electron transport chain and ATP synthesis. The potential energy from the proton gradient is not used to make ATP but generates heat. This is particularly important in brown fat thermogenesis of newborn and hibernating mammals. According to some of newer sources the ATP yield during aerobic respiration is not 36–38, but only about 30–32 ATP molecules / 1 molecule of glucose, because:  So finally we have, per molecule of glucose Altogether this gives 4 + 3 (or 5) + 20 + 3 = 30 (or 32) ATP per molecule of glucose  These figures may still require further tweaking as new structural details become available. The above value of 3 H+/ATP for the synthase assumes that the synthase translocates 9 protons, and produces 3 ATP, per rotation. The number of protons depends on the number of c subunits in the Fo c-ring, and it is now known that this is 10 in yeast Fo and 8 for vertebrates. Including one H+ for the transport reactions, this means that synthesis of one ATP requires 1+10/3=4.33 protons in yeast and 1+8/3 = 3.67 in vertebrates. This would imply that in human mitochondria the 10 protons from oxidizing NADH would produce 2.72 ATP (instead of 2.5) and the 6 protons from oxidizing succinate or ubiquinol would produce 1.64 ATP (instead of 1.5). This is consistent with experimental results within the margin of error described in a recent review.  The total ATP yield in ethanol or lactic acid fermentation is only 2 molecules coming from glycolysis, because pyruvate is not transferred to the mitochondrion and finally oxidized to the carbon dioxide (CO), but reduced to ethanol or lactic acid in the cytoplasm.

Fermentation.

Without oxygen, pyruvate (pyruvic acid) is not metabolized by cellular respiration but undergoes a process of fermentation. The pyruvate is not transported into the mitochondrion, but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. This serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. Fermentation oxidizes NADH to NAD so it can be re-used in glycolysis. In the absence of oxygen, fermentation prevents the buildup of NADH in the cytoplasm and provides NAD for glycolysis. This waste product varies depending on the organism. In skeletal muscles, the waste product is lactic acid. This type of fermentation is called lactic acid fermentation. In strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by NADH. During anaerobic glycolysis, NAD regenerates when pairs of hydrogen combine with pyruvate to form lactate. Lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. Lactate can also be used as an indirect precursor for liver glycogen. During recovery, when oxygen becomes available, NAD attaches to hydrogen from lactate to form ATP. In yeast, the waste products are ethanol and carbon dioxide. This type of fermentation is known as alcoholic or ethanol fermentation. The ATP generated in this process is made by substrate-level phosphorylation, which does not require oxygen.  Fermentation is less efficient at using the energy from glucose: only 2 ATP are produced per glucose, compared to the 38 ATP per glucose nominally produced by aerobic respiration. This is because most of the energy of aerobic respiration derives from O with its relatively weak, high-energy double bond. Glycolytic ATP, however, is created more quickly. For prokaryotes to continue a rapid growth rate when they are shifted from an aerobic environment to an anaerobic environment, they must increase the rate of the glycolytic reactions. For multicellular organisms, during short bursts of strenuous activity, muscle cells use fermentation to supplement the ATP production from the slower aerobic respiration, so fermentation may be used by a cell even before the oxygen levels are depleted, as is the case in sports that do not require athletes to pace themselves, such as sprinting.

Anaerobic respiration.

Cellular respiration is the process by which biological fuels are oxidised in the presence of a high-energy inorganic electron acceptor (such as oxygen) to produce large amounts of energy, to drive the bulk production of ATP.  Anaerobic respiration is used by some microorganisms in which neither oxygen (aerobic respiration) nor pyruvate derivatives (fermentation) is the high-energy final electron acceptor. Rather, an inorganic acceptor such as sulfate or nitrate is used. Such organisms are typically found in unusual places such as underwater caves or near hydrothermal vents at the bottom of the ocean.  In July 2019, a scientific study of Kidd Mine in Canada discovered sulfur-breathing organisms which live 7900 feet below the surface, and which breathe sulfur in order to survive. These organisms are also remarkable due to eating rocks such as pyrite as their regular food source.

Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from oxygen molecules or nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy because weak high-energy bonds, in particular in molecular oxygen, are replaced by stronger bonds in the products. Respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. The overall reaction occurs in a series of biochemical steps, some of which are redox reactions. Although cellular respiration is technically a combustion reaction, it clearly does not resemble one when it occurs in a living cell because of the slow, controlled release of energy from the series of reactions.

Buněčné dýchání (respirace) je biochemický proces, při kterém se uvolňuje chemická energie vazeb organických sloučenin (typicky sacharidů) za vzniku pohotového energetického zdroje pro buňku (ATP). Jako odpadní produkty štěpení vzniká oxid uhličitý (CO) a voda.


Definitions.

Lord John Russell (c. 1850) observed poetically that a "proverb is the wit of one, and the wisdom of many." But giving the word "proverb" the sort of definition theorists need has proven to be a difficult task, and although scholars often quote Archer Taylor's argument that formulating a scientific "definition of a proverb is too difficult to repay the undertaking... An incommunicable quality tells us this sentence is proverbial and that one is not. Hence no definition will enable us to identify positively a sentence as proverbial," many students of proverbs have attempted to itemize its essential characteristics.  More constructively, Mieder has proposed the following definition, "A proverb is a short, generally known sentence of the folk which contains wisdom, truth, morals, and traditional views in a metaphorical, fixed, and memorizable form and which is handed down from generation to generation". Norrick created a table of distinctive features to distinguish proverbs from idioms, cliches, etc. Prahlad distinguishes proverbs from some other, closely related types of sayings, "True proverbs must further be distinguished from other types of proverbial speech, e.g. proverbial

Sources.

Proverbs come from a variety of sources. Some are, indeed, the result of people pondering and crafting language, such as some by Confucius, Plato, Baltasar Gracián, etc. Others are taken from such diverse sources as poetry, stories, songs, commercials, advertisements, movies, literature, etc. A number of the well known sayings of Jesus, Shakespeare, and others have become proverbs, though they were original at the time of their creation, and many of these sayings were not seen as proverbs when they were first coined. Many proverbs are also based on stories, often the end of a story. For example, the proverb "Who will bell the cat?" is from the end of a story about the mice planning how to be safe from the cat.  Some authors have created proverbs in their writings, such as J.R.R. Tolkien, and some of these proverbs have made their way into broader society, such as the bumper sticker pictured below. Similarly, C.S. Lewis' created proverb about a lobster in a pot, from the "Chronicles of Narnia", has also gained currency. In cases like this, deliberately created proverbs for fictional societies have become proverbs in real societies. In a fictional story set in a real society, the movie "Forrest Gump" introduced "Life is like a box of chocolates"

Interpretations.

Interpreting proverbs is often complex, but is best done in a context. Interpreting proverbs from other cultures is much more difficult than interpreting proverbs in one's own culture. Even within English-speaking cultures, there is difference of opinion on how to interpret the proverb "A rolling stone gathers no moss." Some see it as condemning a person that keeps moving, seeing moss as a positive thing, such as profit; others see the proverb as praising people that keep moving and developing, seeing moss as a negative thing, such as negative habits.  Similarly, among Tajik speakers, the proverb "One hand cannot clap"

Features.

Grammatical structures.

Proverbs in various languages are found with a wide variety of grammatical structures. In English, for example, we find the following structures (in addition to others):  However, people will often quote only a fraction of a proverb to invoke an entire proverb, e.g. "All is fair" instead of "All is fair in love and war", and "A rolling

Conservative language.

Because many proverbs are both poetic and traditional, they are often passed down in fixed forms. Though spoken language may change, many proverbs are often preserved in conservative, even archaic, form. In English, for example, "betwixt" is not used by many, but a form of it is still heard (or read) in the proverb "There is many a slip 'twixt the cup and the lip." The conservative form preserves the meter and the rhyme. This conservative nature of proverbs can result in archaic words and grammatical structures being preserved in individual proverbs, as has been documented in Amharic,

Borrowing and spread.

Proverbs are often and easily translated and transferred from one language into another. "There is nothing so uncertain as the derivation of proverbs, the same proverb being often found in all nations, and it is impossible to assign its paternity."  Proverbs are often borrowed across lines of language, religion, and even time. For example, a proverb of the approximate form "No flies enter a mouth that is shut" is currently found in Spain, France, Ethiopia, and many countries in between. It is embraced as a true local proverb in many places and should not be excluded in any collection of proverbs because it is shared by the neighbors. However, though it has gone through multiple languages and millennia, the proverb can be traced back to an ancient Babylonian proverb (Pritchard 1958:146). Another example of a widely spread proverb is "A drowning person clutches at [frogs] foam", found in Peshai of Afghanistan and Orma of Kenya, and presumably places in between.  Proverbs about one hand clapping are common across Asia, from Dari in Afghanistan to Japan. Some studies have been done devoted to the spread of proverbs in certain regions, such as India and her neighbors

Use.

In conversation.

Proverbs are used in conversation by adults more than children, partially because adults have learned more proverbs than children. Also, using proverbs well is a skill that is developed over years. Additionally, children have not mastered the patterns of metaphorical expression that are invoked in proverb

In literature.

Many authors have used proverbs in their writings, for a very wide variety of literary genres: epics, novels, poems, short stories.  Probably the most famous user of proverbs in novels is J. R. R. Tolkien in his "The Hobbit" and "The Lord of the Rings" series. Herman Melville is noted for creating proverbs in Moby Dick and in his poetry. Also, C. S. Lewis created a dozen proverbs in "The Horse and His Boy", and Mercedes Lackey created dozens for her invented Shin'a'in and Tale'edras cultures; Lackey's proverbs are notable in that they are reminiscent to those of Ancient Asia - e.g. "Just because you feel certain an enemy is lurking behind every bush, it doesn't follow that you are wrong" is like to "Before telling secrets on the road, look in the bushes." These authors are notable for not only using proverbs as integral to the development of the characters and the story line, but also for creating proverbs.  Among medieval literary texts, Geoffrey Chaucer's Troilus and Criseyde plays a special role because Chaucer's usage seems to challenge the truth value of proverbs by exposing their epistemological unreliability. Rabelais used proverbs to write an entire chapter of Gargantua.  The patterns of using proverbs in literature can change

In drama and film.

Similarly to other forms of literature, proverbs have also been used as important units of language in drama and films. This is true from the days of classical Greek works to old French to Shakespeare, to 19th Century Spanish, to today. The use of proverbs in drama and film today is still found in languages around the world, including Yorùbá and Igbo of Nigeria.  A film that makes rich use of proverbs is "Forrest Gump", known for both using and creating proverbs. Other studies of the use of proverbs in film include work by Kevin McKenna on the Russian film "Aleksandr Nevsky", Haase's study of an adaptation of Little Red Riding Hood, Elias Dominguez Barajas on the film "Viva Zapata!", and Aboneh Ashagrie on "The Athlete" (a movie in Amharic about Abebe Bikila).  Television programs have also been named with reference to proverbs, usually shortened, such Birds of a Feather and Diff'rent Strokes.  In the case of "Forrest Gump", the screenplay by Eric Roth had more proverbs than the novel by Winston Groom, but for "The Harder

In music.

Proverbs are often poetic in and of themselves, making them ideally suited for adapting into songs. Proverbs have been used in music from opera to country to hip-hop. Proverbs have also been used in music in many languages, such as the Akan language the Igede language, and Spanish. In English the proverb (or rather the beginning of the proverb), If the shoe fits has been used as a title for three albums and five songs. Other English examples of using proverbs in music include Elvis Presley's "Easy come, easy go", Harold Robe's "Never swap horses when you're crossing a stream", Arthur Gillespie's "Absence makes the heart grow fonder", Bob Dylan's "Like a rolling stone", Cher's "Apples don't fall far from the tree". Lynn Anderson made famous a song full of proverbs, "I never promised you a rose garden" (written by Joe South). In choral music, we find Michael Torke's "Proverbs" for female voice and ensemble. A number of Blues musicians have also used proverbs extensively. The frequent use of proverbs in Country music has led to published studies of proverbs in this genre. The Reggae artist

In visual form.

From ancient times, people around the world have recorded proverbs in visual form. This has been done in two ways. First, proverbs have been "written" to be displayed, often in a decorative manner, such as on pottery, cross-stitch, murals, kangas (East African women's wraps), quilts, a stained glass window, and graffiti.  Secondly, proverbs have often been visually depicted in a variety of media, including paintings, etchings, and sculpture. Jakob Jordaens painted a plaque with a proverb about drunkenness above a drunk man wearing a crown, titled "The King Drinks". Probably the most famous examples of depicting proverbs are the different versions of the paintings "Netherlandish Proverbs" by the father and son Pieter Bruegel the Elder and Pieter Brueghel the Younger, the proverbial meanings of these paintings being the subject of a 2004 conference, which led to a published volume of studies (Mieder 2004a). The same father and son also painted versions of The Blind Leading the Blind, a Biblical proverb. These and similar paintings inspired another famous painting depicting some proverbs and also idioms (leading to a series of additional paintings), such as "Proverbidioms" by T. E. Breitenbach. Another painting inspired by Bruegel's work is by the Chinese artist,

In cartoons.

Cartoonists, both editorial and pure humorists, have often used proverbs, sometimes primarily building on the text, sometimes primarily on the situation visually, the best cartoons combining both. Not surprisingly, cartoonists often twist proverbs, such as visually depicting a proverb literally or twisting the text as an anti-proverb. An example with all of these traits is a cartoon showing a waitress delivering two plates with worms on them, telling the customers, "Two early bird specials... here ya go."  The traditional Three wise monkeys were depicted in Bizarro with different labels. Instead of the negative imperatives, the one with ears covered bore the sign "See and speak evil", the one with eyes covered bore the sign "See and hear evil", etc. The caption at the bottom read "The power of positive thinking." Another cartoon showed a customer in a pharmacy telling a pharmacist, "I'll have an ounce of prevention." The comic strip The Argyle Sweater showed an Egyptian archeologist

In advertising.

Proverbs are frequently used in advertising, often in slightly modified form. Ford once advertised its Thunderbird with, "One drive is worth a thousand words" (Mieder 2004b: 84). This is doubly interesting since the underlying proverb behind this, "One picture is worth a thousand words," was originally introduced into the English proverb repertoire in an ad for televisions (Mieder 2004b: 83).  A few of the many proverbs adapted and used in advertising include:  The GEICO company has created a series of television ads that are built around proverbs, such as "A bird in the hand is worth two in the bush", and "The pen is mightier than the sword", "Pigs may fly/When pigs fly",

Variations.

Counter proverbs.

There are often proverbs that contradict each other, such as "Look before you leap" and "He who hesitates is lost", or "Many hands make light work" and "Too many cooks spoil the broth". These have been labeled "counter proverbs" or "antonymous proverbs". When there are such counter proverbs, each can be used in its own appropriate situation, and neither is intended to be a universal truth. Some pairs of proverbs are fully contradictory: “A messy desk is a sign of intelligence” and “A neat desk is a sign of a sick mind”.  The concept of "counter proverb" is more about pairs of contradictory proverbs than about the use of proverbs to counter each other in an argument. For example, from the Tafi language of Ghana, the following pair of proverbs are counter to each other but are each used in appropriate contexts, "A co-wife who is too powerful for you, you address her as your mother" and "Do not call your mother's co-wife your mother..." In Nepali, there is

Metaproverbs.

In many cultures, proverbs are so important and so prominent that there are proverbs about proverbs, that is, "metaproverbs". The most famous one is from Yoruba of Nigeria,

Applications.

There is a growing interest in deliberately using proverbs to achieve goals, usually to support and promote changes in society. Proverbs have also been used for public health promotion, such as promoting breast feeding with a shawl bearing a Swahili proverb "Mother's milk is sweet". Proverbs have also been applied for helping people manage diabetes, to combat prostitution, and for community development., to resolve conflicts, and to slow the transmission of HIV.  The most active field deliberately using proverbs is Christian ministry, where Joseph G. Healey and others have deliberately worked to catalyze the collection of proverbs from smaller languages and the application of them in a wide variety of church-related ministries, resulting in publications of collections and applications. This attention to proverbs by those in Christian ministries is not new, many pioneering proverb collections having been collected and published by Christian workers.  U.S. Navy Captain Edward Zellem pioneered the use of Afghan proverbs as a positive relationship-building tool during the war in Afghanistan, and in 2012 he published two bilingual collections of Afghan proverbs in Dari and English, part of an effort of nationbuilding, followed by a volume of Pashto proverbs in 2014.

Cultural values.

There is a longstanding debate among proverb scholars as to whether the cultural values of specific language communities are reflected (to varying degree) in their proverbs. Many claim that the proverbs of a particular culture reflect the values of that specific culture, at least to some degree. Many writers have asserted that the proverbs of their cultures reflect their culture and values; this can be seen in such titles as the following: "An introduction to Kasena society and culture through their proverbs", Prejudice, power, and poverty in Haiti: a study of a nation's culture as seen through its proverbs, Proverbiality and worldview in Maltese and Arabic proverbs, Fatalistic traits in Finnish proverbs, "Vietnamese cultural patterns and values as expressed in proverbs", "The Wisdom and Philosophy of the Gikuyu proverbs: The Kihooto worldview", "Spanish Grammar and Culture through Proverbs," and "How Russian Proverbs Present the Russian National Character". Kohistani has written a thesis

Religion.

Many proverbs from around the world address matters of ethics and expected of behavior. Therefore, it is not surprising that proverbs are often important texts in religions. The most obvious example is the Book of Proverbs in the Bible. Additional proverbs have also been coined to support religious values, such as the following from Dari of Afghanistan: "In childhood you're playful, In youth you're lustful, In old age you're feeble, So when will you before God be worshipful?"  Clearly proverbs in religion are

Psychology.

Though much proverb scholarship is done by literary scholars, those studying the human mind have used proverbs in a variety of studies. One of the earliest studies in this field

Paremiology.

The study of proverbs is called paremiology which has a variety of uses in the study of such topics as philosophy, linguistics, and folklore. There are several types and styles of proverbs which are analyzed within Paremiology as is the use and misuse of familiar expressions which are not strictly 'proverbial' in the dictionary definition of being fixed sentences

Paremiological minimum.

Grigorii Permjakov developed the concept of the core set of proverbs that full members of society know, what he called the "paremiological minimum" (1979). For example, an adult American is expected to be familiar with "Birds of a feather flock together", part of the American paremiological minimum. However, an average adult American is not expected to know "Fair in the cradle, foul in the saddle", an old English proverb that is not part of the current American paremiological

Sources for proverb study.

A seminal work in the study of proverbs is Archer Taylor's "The Proverb" (1931), later republished by Wolfgang Mieder with Taylor's Index included (1985/1934). A good introduction to the study of proverbs is Mieder's 2004 volume, "Proverbs: A Handbook". Mieder has also published a series of bibliography volumes on proverb research, as well as a large number of articles and other books in the field. Stan Nussbaum has edited a large collection on proverbs of Africa, published on a CD, including reprints of out-of-print collections, original collections, and works on analysis, bibliography, and application of proverbs to Christian ministry (1998). Paczolay

Noteworthy proverb scholars (paremiologists and paremiographers).

The study of proverbs has been built by a number of notable scholars and contributors. Earlier scholars were more concerned with collecting than analyzing. Desiderius Erasmus was a Latin scholar (1466 – 1536), whose collection of Latin proverbs, known as "Adagia", spread Latin proverbs across Europe. Juan de Mal Lara was a 16th century Spanish scholar, one of his books being 1568 "Philosophia vulgar", the first part of which contains one thousand and one sayings. Hernán Núñez published a collection of Spanish proverbs (1555).  In the 19th century, a growing number of scholars published

External links.

Websites related to the study of proverbs, and some that list regional proverbs:

A proverb (from ) is a simple, concrete, traditional saying that expresses a perceived truth based on common sense or experience. Proverbs are often metaphorical and use formulaic language. Collectively, they form a genre of folklore.

Přísloví je ustálený stylizovaný výrok, jenž obsahuje obecně platné zásady nebo zkušenosti mravoučné povahy. Tyto jsou vyjádřeny buď přímo, nebo obrazně. Pro snadnější zapamatování má často podobu rýmovaného dvojverší. Přísloví tvoří součást lidové slovesnosti a frazeologie.


History.

Origin.

The earliest known alphabetic (or "proto-alphabetic") inscriptions are the so-called Proto-Sinaitic (or Proto-Canaanite) script sporadically attested in the Sinai and in Canaan in the late Middle and Late Bronze Age. The script was not widely used until the rise of new Semitic kingdoms in the 13th and 12th centuries BC.  The Phoenician alphabet is a direct continuation of the "Proto-Canaanite" script of the Bronze Age collapse period. The so-called Ahiram epitaph, whose dating is controversial, engraved on the sarcophagus of king Ahiram in Byblos, Lebanon, one of five known Byblian royal inscriptions, shows essentially the fully developed Phoenician script, although the name "Phoenician" is by convention given to inscriptions beginning in the mid-11th century BC.

Spread and adaptations.

Beginning in the 9th century BC, adaptations of the Phoenician alphabet thrived, including Greek, Old Italic and Anatolian scripts. The alphabet's attractive innovation was its phonetic nature, in which one sound was represented by one symbol, which meant only a few dozen symbols to learn. The other scripts of the time, cuneiform and Egyptian hieroglyphs, employed many complex characters and required long professional training to achieve proficiency.  Another reason for its success was the maritime trading culture of Phoenician merchants, which spread the alphabet into parts of North Africa and Southern Europe. Phoenician inscriptions have been found in archaeological sites at a number of former Phoenician cities and colonies around the Mediterranean, such as Byblos (in present-day Lebanon) and Carthage in North Africa. Later finds indicate earlier use in Egypt.  The alphabet had long-term effects on the social structures of the civilizations that came in contact with it. Its simplicity not only allowed its easy adaptation to multiple languages, but it also allowed the common people to learn how to write. This upset the long-standing status of literacy as an exclusive achievement of royal and religious elites, scribes who used their monopoly on information to control the common population. The appearance of Phoenician disintegrated many of these class divisions, although many Middle Eastern kingdoms, such as Assyria, Babylonia and Adiabene, would continue to use cuneiform for legal and liturgical matters well into the Common Era.  According to Herodotus, the Phoenician prince Cadmus was accredited with the introduction of the Phoenician alphabet—"phoinikeia grammata", "Phoenician letters"—to the Greeks, who adapted it to form their Greek alphabet. Herodotus claims that the Greeks did not know of the Phoenician alphabet before Cadmus. He estimates that Cadmus lived sixteen hundred years before his time (while the historical adoption of the alphabet by the Greeks was barely 350 years before Herodotus).  The Phoenician alphabet was known to the Jewish sages of the Second Temple era, who called it the "Old Hebrew" (paleo-Hebrew) script.

Notable inscriptions.

The conventional date of 1050 BC for the emergence of the Phoenician script was chosen because there is a gap in the epigraphic record, there are not actually any Phoenician inscriptions securely dated to the 11th century. The oldest inscriptions are dated to the 10th century. The "Paleo-Hebrew alphabet" is a regional variant of the Phoenician alphabet; the term "Paleo-Hebrew" was chosen not because of a difference in the actual script but merely because it was deemed inappropriate to use "Phoenician" in reference to texts written in early Hebrew.

Modern rediscovery.

The Phoenician alphabet was deciphered in 1758 by Jean-Jacques Barthélemy, but its relation to the Phoenicians remained unknown until the 19th century. It was at first believed that the script was a direct variation of Egyptian hieroglyphs, which were deciphered in the early 19th century.  However, scholars could not find any link between the two writing systems, nor to hieratic or cuneiform. The theories of independent creation ranged from the idea of a single individual conceiving it, to the Hyksos people forming it from corrupt Egyptian. It was eventually discovered that the Proto-Sinaitic alphabet was inspired by the model of hieroglyphs.

Table of letters.

The chart shows the "graphical" evolution of Phoenician letter forms into other alphabets. The "sound" values also changed significantly, both at the initial creation of new alphabets and from gradual pronunciation changes which did not immediately lead to spelling changes. The Phoenician letter forms shown are idealized: actual Phoenician writing less uniform, with significant variations by era and region. When alphabetic writing began, with the early Greek alphabet, the letter forms were similar but not identical to Phoenician, and vowels were added to the consonant-only Phoenician letters. There were also distinct variants of the writing system in different parts of Greece, primarily in how those Phoenician characters that did not have an exact match to Greek sounds were used. The Ionic variant evolved into the standard Greek alphabet, and the Cumae variant into the Italic alphabets (including the Latin alphabet).  The Runic alphabet is derived from Italic, the Cyrillic alphabet from medieval Greek. The Hebrew, Syriac and Arabic scripts are derived from Aramaic (the latter as a medieval cursive variant of Nabataean). Ge'ez is from South Arabian.

Letter names.

Phoenician used a system of acrophony to name letters: a word was chosen with each initial consonant sound, and became the name of the letter for that sound. These names were not arbitrary: each Phoenician letter was based on an Egyptian hieroglyph representing an Egyptian word; this word was translated into Phoenician (or a closely related Semitic language), then the initial sound of the translated word became the letter's Phoenician value. For example, the second letter of the Phoenician alphabet was based on the Egyptian hieroglyph for "house" (a sketch of a house); the Semitic word for "house" was "bet"; hence the Phoenician letter was called "bet" and had the sound value "b".  According to a 1904 theory by Theodor Nöldeke, some of the letter names were changed in Phoenician from the Proto-Canaanite script. This includes:  Yigael Yadin (1963) went to great lengths to prove that there was actual battle equipment similar to some of the original letter forms named for weapons (samek, zayin).

Numerals.

The Phoenician numeral system consisted of separate symbols for 1, 10, 20, and 100. The sign for 1 was a simple vertical stroke (<unk>). Other numerals up to 9 were formed by adding the appropriate number of such strokes, arranged in groups of three. The symbol for 10 was a horizontal line or tack (). The sign for 20 (<unk>) could come in different glyph variants, one of them being a combination of two 10-tacks, approximately Z-shaped. Larger multiples of ten were formed by grouping the appropriate number of 20s and 10s. There existed several glyph variants for 100 (<unk>). The 100 symbol could be multiplied by a preceding numeral, e.g. the combination of "4" and "100" yielded 400. The system did not contain a numeral zero.

Derived alphabets.

The Paleo-Hebrew alphabet is a regional variant of the Phoenician alphabet, so called when used to write early Hebrew. The Samaritan alphabet is a development of Paleo-Hebrew, emerging in the 6th century BC. The South Arabian script may be derived from a stage of the Proto-Sinaitic script predating the mature development of the Phoenician alphabet proper. The Geʽez script developed from South Arabian.

Aramaic-derived.

The Aramaic alphabet, used to write Aramaic, is an early descendant of Phoenician. Aramaic, being the "lingua franca" of the Middle East, was widely adopted. It later split off (due to political divisions) into a number of related alphabets, including Hebrew, Syriac, and Nabataean, the latter of which, in its cursive form, became an ancestor of the Arabic alphabet. The Hebrew alphabet emerges in the Second Temple period, from around 300 BC, out of the Aramaic alphabet used in the Persian empire. There was, however, a revival of the "Paleo-Hebrew" mode of writing later in the Second Temple period, with some instances from the Qumran Caves, such as the "Paleo-Hebrew Leviticus scroll" dated to the 2nd or 1st century BC.  The Kharosthi script is an Arabic-derived alphasyllabary used in the Indo-Greek Kingdom in the 3rd century BC. The Syriac alphabet is the derived form of Aramaic used in the early Christian period. The Sogdian alphabet is derived from Syriac. It is in turn an ancestor of the Old Uyghur. The Manichaean alphabet is a further derivation from Sogdian.  The Arabic script is a medieval cursive variant of Nabataean, itself an offshoot of Aramaic.

Brahmic scripts.

It has been proposed, notably by Georg Bühler (1898), that the Brahmi script of India (and by extension the derived Indic alphabets) was ultimately derived from the Aramaic script, which would make Phoenician the ancestor of virtually every alphabetic writing system in use today.  It is certain that the Aramaic-derived Kharosthi script was present in northern India by the 4th century BC, so that the Aramaic model of alphabetic writing would have been known in the region, but the link from Kharosthi to the slightly younger Brahmi is tenuous. Bühler's suggestion is still entertained in mainstream scholarship, but it has never been proven conclusively, and no definitive scholarly consensus exists.

Greek-derived.

The Greek alphabet is derived from the Phoenician. With a different phonology, the Greeks adapted the Phoenician script to represent their own sounds, including the vowels absent in Phoenician. It was possibly more important in Greek to write out vowel sounds: Phoenician being a Semitic language, words were based on consonantal roots that permitted extensive removal of vowels without loss of meaning, a feature absent in the Indo-European Greek. However, Akkadian cuneiform, which wrote a related Semitic language, did indicate vowels, which suggests the Phoenicians simply accepted the model of the Egyptians, who never wrote vowels. In any case, the Greeks repurposed the Phoenician letters of consonant sounds not present in Greek; each such letter had its name shorn of its leading consonant, and the letter took the value of the now-leading vowel. For example, "ʾāleph", which designated a glottal stop in Phoenician, was repurposed to represent the vowel ; "he" became, "ḥet" became (a long vowel), "ʿayin" became (because the pharyngeality altered the following vowel), while the two semi-consonants "wau" and "yod" became the corresponding high vowels, and. (Some dialects of Greek, which did possess and, continued to use the Phoenician letters for those consonants as well.)  The Alphabets of Asia Minor are generally assumed to be offshoots of archaic versions of the Greek alphabet. Similarly, the early Paleohispanic scripts are either derived from archaic Greek or from the Phoenician script directly; the Greco-Iberian alphabet of the 4th century BC is directly adapted from Greek.  The Latin alphabet was derived from Old Italic (originally a form of the Greek alphabet), used for Etruscan and other languages. The origin of the Runic alphabet is disputed: the main theories are that it evolved either from the Latin alphabet itself, some early Old Italic alphabet via the Alpine scripts, or the Greek alphabet. Despite this debate, the Runic alphabet is clearly derived from one or more scripts that ultimately trace their roots back to the Phoenician alphabet.  The Coptic alphabet is mostly based on the mature Greek alphabet of the Hellenistic period, with a few additional letters for sounds not in Greek at the time. Those additional letters are based on the Demotic script.  The Cyrillic script was derived from the late (medieval) Greek alphabet. Some Cyrillic letters (generally for sounds not in medieval Greek) are based on Glagolitic forms.

Unicode.

The Phoenician alphabet was added to the Unicode Standard in July 2006 with the release of version 5.0. An alternative proposal to handle it as a font variation of Hebrew was turned down. (See PDF summary.)  The Unicode block for Phoenician is U+10900–U+1091F. It is intended for the representation of text in Palaeo-Hebrew, Archaic Phoenician, Phoenician, Early Aramaic, Late Phoenician cursive, Phoenician papyri, Siloam Hebrew, Hebrew seals, Ammonite, Moabite, and Punic.  The letters are encoded U+10900 "aleph" through to U+10915 "taw", U+10916, U+10917, U+10918 and U+10919 encode the numerals 1,10,20 and 100 respectively and U+1091F is the word separator.

History.

The following Unicode-related documents record the purpose and process of defining specific characters in the Phoenician block:

The Phoenician alphabet is an alphabet (more specifically, an abjad) consisting of 22 consonant letters only, leaving vowel sounds implicit, although certain late varieties use "matres lectionis" for some vowels.

Fénické písmo bylo ve starověku souhláskové písmo používané pro zaznamenání textů ve féničtině a později i v dalších příbuzných kanaánských jazycích. Z fénického písma se (nepřímo) vyvinulo mnoho dnes používaných písem, jak souhláskových (hebrejské, arabské), tak slabičná řecká alfabeta, z které je odvozena cyrilice i světově nejrozšířenější latinka.


Technological aspects.

Exhaust thrust in a turboprop is sacrificed in favour of shaft power, which is obtained by extracting additional power (up to that necessary to drive the compressor) from turbine expansion. Owing to the additional expansion in the turbine system, the residual energy in the exhaust jet is low. Consequently, the exhaust jet typically produces around or less than 10% of the total thrust. A higher proportion of the thrust comes from the propeller at low speeds and less at higher speeds.  Turboprops can have bypass ratios up to 50-100 although the propulsion airflow is less clearly defined for propellers than for fans.  The propeller is coupled to the turbine through a reduction gear that converts the high RPM/low torque output to low RPM/high torque. The propeller itself is normally a constant-speed (variable pitch) propeller type similar to that used with larger aircraft reciprocating engines.  Unlike the small diameter fans used in turbofan jet engines, the propeller has a large diameter that lets it accelerate a large volume of air. This permits a lower airstream velocity for a given amount of thrust. As it is more efficient at low speeds to accelerate a large amount of air by a small degree than a small amount of air by a large degree, a low disc loading (thrust per disc area) increases the aircraft's energy efficiency, and this reduces the fuel use.  Propellers lose efficiency as aircraft speed increases, so turboprops are normally not used on high-speed aircraft above 0.6–0.7 Mach. However, propfan engines, which are very similar to turboprop engines, can cruise at flight speeds approaching 0.75 Mach. To increase propeller efficiency across a wider range of airspeeds, turboprops are typically equipped with constant-speed (variable-pitch) propellers. The blades of a constant-speed propeller increase pitch as aircraft speed increases, allowing for a wider range of airspeeds than a fixed-pitch propeller. Another benefit of this type of propeller is that it can also be used to generate negative thrust while decelerating on the runway. Additionally, in the event of an engine failure, the propeller can be feathered, thus minimizing the drag of the non-functioning propeller.  While most modern turbojet and turbofan engines use axial-flow compressors, turboprop engines usually contain at least one stage of centrifugal compressor which have the advantage of being simple and lightweight, at the expense of a streamlined shape.  While the power turbine may be integral with the gas generator section, many turboprops today feature a free power turbine on a separate coaxial shaft. This enables the propeller to rotate freely, independent of compressor speed. Residual thrust on a turboshaft is avoided by further expansion in the turbine system and/or truncating and turning the exhaust 180 degrees, to produce two opposing jets. Apart from the above, there is very little difference between a turboprop and a turboshaft.

History.

Alan Arnold Griffith had published a paper on turbine design in 1926. Subsequent work at the Royal Aircraft Establishment investigated axial turbine designs that could be used to supply power to a shaft and thence a propeller. From 1929, Frank Whittle began work on centrifugal turbine designs that would deliver pure jet thrust.  The world's first turboprop was designed by the Hungarian mechanical engineer György Jendrassik. Jendrassik published a turboprop idea in 1928, and on 12 March 1929 he patented his invention. In 1938, he built a small-scale (100 Hp; 74.6 kW) experimental gas turbine. The larger Jendrassik Cs-1, with a predicted output of 1,000 bhp, was produced and tested at the Ganz Works in Budapest between 1937 and 1941. It was of axial-flow design with 15 compressor and 7 turbine stages, annular combustion chamber and many other modern features. First run in 1940, combustion problems limited its output to 400 bhp. In 1941, the engine was abandoned due to war, and the factory was turned over to conventional engine production. The world's first turboprop engine that went into mass production was designed by a German engineer, Max Adolf Mueller, in 1942.  The first mention of turboprop engines in the general public press was in the February 1944 issue of the British aviation publication "Flight", which included a detailed cutaway drawing of what a possible future turboprop engine could look like. The drawing was very close to what the future Rolls-Royce Trent would look like. The first British turboprop engine was the Rolls-Royce RB.50 Trent, a converted Derwent II fitted with reduction gear and a Rotol five-bladed propeller. Two Trents were fitted to Gloster Meteor "EE227" — the sole "Trent-Meteor" — which thus became the world's first turboprop-powered aircraft, albeit a test-bed not intended for production. It first flew on 20 September 1945. From their experience with the Trent, Rolls-Royce developed the Rolls-Royce Clyde, the first turboprop engine to be fully type certificated for military and civil use, and the Dart, which became one of the most reliable turboprop engines ever built. Dart production continued for more than fifty years. The Dart-powered Vickers Viscount was the first turboprop aircraft of any kind to go into production and sold in large numbers. It was also the first four-engined turboprop. Its first flight was on 16 July 1948. The world's first single engined turboprop aircraft was the Armstrong Siddeley Mamba-powered Boulton Paul Balliol, which first flew on 24 March 1948.  The Soviet Union built on German World War II development by Junkers Motorenwerke, while BMW, Heinkel-Hirth and Daimler-Benz also developed and partially tested designs. While the Soviet Union had the technology to create the airframe for a jet-powered strategic bomber comparable to Boeing's B-52 Stratofortress, they instead produced the Tupolev Tu-95 Bear, powered with four Kuznetsov NK-12 turboprops, mated to eight contra-rotating propellers (two per nacelle) with supersonic tip speeds to achieve maximum cruise speeds in excess of 575 mph, faster than many of the first jet aircraft and comparable to jet cruising speeds for most missions. The Bear would serve as their most successful long-range combat and surveillance aircraft and symbol of Soviet power projection throughout the end of the 20th century. The USA would incorporate contra-rotating turboprop engines, such as the ill-fated twin-turbine Allison T40 — essentially a twinned up pair of Allison T38 turboprop engines driving contra-rotating propellers – into a series of experimental aircraft during the 1950s, with aircraft powered with the T40, like the Convair R3Y Tradewind flying boat never entering U.S. Navy service.  The first American turboprop engine was the General Electric XT31, first used in the experimental Consolidated Vultee XP-81. The XP-81 first flew in December 1945, the first aircraft to use a combination of turboprop and turbojet power. The technology of the Allison's earlier T38 design evolved into the Allison T56, with quartets of the T56s being used to power the Lockheed Electra airliner, its military maritime patrol derivative the P-3 Orion, and the widely produced C-130 Hercules military transport aircraft. One of the most produced turboprop engines used in civil aviation is the Pratt & Whitney Canada PT6 engine.  The first turbine-powered, shaft-driven helicopter was the Kaman K-225, a development of Charles Kaman's K-125 synchropter, which used a Boeing T50 turboshaft engine to power it on 11 December 1951.

Usage.

Compared to turbofans, turboprops are most efficient at flight speeds below 725 km/h (450 mph; 390 knots) because the jet velocity of the propeller (and exhaust) is relatively low. Modern turboprop airliners operate at nearly the same speed as small regional jet airliners but burn two-thirds of the fuel per passenger. However, compared to a turbojet (which can fly at high altitude for enhanced speed and fuel efficiency) a propeller aircraft has a lower ceiling.  Compared to piston engines, their greater power-to-weight ratio (which allows for shorter takeoffs) and reliability can offset their higher initial cost, maintenance and fuel consumption. As jet fuel can be easier to obtain than avgas in remote areas, turboprop-powered aircraft like the Cessna Caravan and Quest Kodiak are used as bush airplanes.  Turboprop engines are generally used on small subsonic aircraft, but the Tupolev Tu-114 can reach 470 kn (870 km/h, 541 mph). Large military aircraft, like the Tupolev Tu-95, and civil aircraft, such as the Lockheed L-188 Electra, were also turboprop powered. The Airbus A400M is powered by four Europrop TP400 engines, which are the second most powerful turboprop engines ever produced, after the Kuznetsov NK-12.  In 2017, the most widespread turboprop airliners in service were the ATR 42/72 (950 aircraft), Bombardier Q400 (506), De Havilland Canada Dash 8-100/200/300 (374), Beechcraft 1900 (328), de Havilland Canada DHC-6 Twin Otter (270), Saab 340 (225). Less widespread and older airliners include the BAe Jetstream 31, Embraer EMB 120 Brasilia, Fairchild Swearingen Metroliner, Dornier 328, Saab 2000, Xian MA60, MA600 and MA700, Fokker 27 and 50.  Turboprop business aircraft include the Piper Meridian, Socata TBM, Pilatus PC-12, Piaggio P.180 Avanti, Beechcraft King Air and Super King Air. In April 2017, there were 14,311 business turboprops in the worldwide fleet.

Reliability.

Between 2012 and 2016, the ATSB observed 417 events with turboprop aircraft, 83 per year, over 1.4 million flight hours: 2.2 per 10,000 hours. Three were "high risk" involving engine malfunction and unplanned landing in single‐engine Cessna 208 Caravans, four "medium risk" and 96% "low risk". Two occurrences resulted in minor injuries due to engine malfunction and terrain collision in agricultural aircraft and five accidents involved aerial work: four in agriculture and one in an air ambulance.

A turboprop engine is a turbine engine that drives an aircraft propeller. In its simplest form a turboprop consists of an intake, compressor, combustor, turbine, and a propelling nozzle. Air is drawn into the intake and compressed by the compressor. Fuel is then added to the compressed air in the combustor, where the fuel-air mixture then combusts. The hot combustion gases expand through the turbine. Some of the power generated by the turbine is used to drive the compressor. Thrust is obtained by the combusting gases, pushing toward a (vectored) surface in front of the expanding gas.

Turbovrtulový motor nebo také proudovrtulový motor či turboprop se dá považovat za hybrid vrtulového a proudového motoru - většina částí je stejná jako u proudového motoru (vstupní ústrojí, kompresor, spalovací komora, turbína, výstupní ústrojí). V podstatě to je proudový motor, jehož energie se však použije k pohonu vrtule a pouze necelých 10 % výkonu se přímo podílí tahovou silou na pohonu letadla.


Terminology.

The word "abdication" is derived from the Latin "abdicatio" meaning to disown or renounce (from "ab", away from, and "dicare", to dedicate or relinquish). In its broadest sense "abdication" is the act of renouncing and resigning from any formal office, but it is applied especially to the supreme office of state. In Roman law the term was also applied to the disowning of a family member, such as the disinheriting of a son. Today the term commonly applies to monarchs, or to those who have been formally crowned. An elected or appointed official is said to resign rather than to abdicate. A notable exception is the voluntary relinquishing of the office of Bishop of Rome (and thus Sovereign of the Vatican City State) by the Pope, called Papal resignation or Papal renunciation.

Historical examples.

In certain cultures, the abdication of a monarch was seen as a profound and shocking abandonment of royal duty. As a result, abdications usually only occurred in the most extreme circumstances of political turmoil or violence. For other cultures, abdication was a much more routine element of succession.

The Roman Empire.

Among the most notable abdications of antiquity are those of Lucius Cornelius Sulla, the Dictator, in 79 BC; Emperor Diocletian in AD 305; and Emperor Romulus Augustulus in AD 476.

The Papacy, the Papal States and Vatican City.

Due to the complex nature of the office of Pope (head of the worldwide Roman Catholic Church and sovereign of the Papal States from 754 to 1870 and of Vatican City since 1929), a papal abdication involves both the spiritual and the secular sphere. Technically, the correct term for a reigning Pope voluntarily stepping down as Bishop of Rome is renunciation or resignation, as regulated in Canon 332 §2 of the 1983 Code of Canon Law.  The debate is open about some disputed resignations in the early middle ages: the last three popes to resign were Celestine V in 1294, Gregory XII in 1415, to end the Western Schism, and Benedict XVI in 2013, who was succeeded by Francis. Benedict's resignation, that occurred 598 years after the last time a Pope did so, and 719 years after the last one who renounced entirely on his own volition, was an event unheard of for more than half a millennium, and was met with a great deal of surprise worldwide.

Britain.

One of the most notable abdications in recent history is that of King Edward VIII of the United Kingdom and the Dominions. In 1936 Edward abdicated to marry American divorcée Wallis Simpson, over the objections of the British establishment, the governments of the Commonwealth, the Royal Family and the Church of England. It was the first time in history that the British or English crown was surrendered entirely voluntarily. Richard II of England, for example, was forced to abdicate after power was seized by his cousin, Henry Bolingbroke, while Richard was abroad.  During the Glorious Revolution in 1688, James II of England and VII of Scotland fled to France, dropping the Great Seal of the Realm into the Thames, and the question was discussed in Parliament whether he had forfeited the throne or had abdicated. The latter designation was agreed upon in spite of James's protest, and in a full assembly of the Lords and Commons it was resolved "that King James II having endeavoured to subvert the constitution of the kingdom, by breaking the original contract between king and people, and, by the advice of Jesuits and other wicked persons, having violated the fundamental laws, and having withdrawn himself out of this kingdom, has abdicated the government, and that the throne is thereby vacant." The Scottish parliament pronounced a decree of forfeiture and deposition.  In Scotland, Mary, Queen of Scots, was forced to abdicate in favour of her one-year-old son, James VI.  Today, because the title to the Crown depends upon statute, particularly the Act of Settlement 1701, a royal abdication can be effected only by an Act of Parliament; under the terms of the Statute of Westminster 1931, such an act must be agreed by the parliaments of all extant signatories of the Statute. To give legal effect to the abdication of King Edward VIII, His Majesty's Declaration of Abdication Act 1936 was passed.

Japan.

In Japanese history, abdication was used very often, and in fact occurred more often than death on the throne. In those days, most executive authority resided in the hands of regents (see Sesshō and Kampaku), and the Emperor's chief task was priestly, containing so many repetitive rituals that it was deemed the incumbent Emperor deserved pampered retirement as an honored retired emperor after a service of around ten years. A tradition developed that an Emperor should accede to the throne relatively young. The high-priestly duties were deemed possible for a walking child; and a dynast who had passed his toddler years was regarded as suitable and old enough; reaching the age of legal majority was not a requirement. Thus, many Japanese Emperors have acceded as children, some only 6 or 8 years old. Childhood apparently helped the monarch to endure tedious duties and to tolerate subjugation to political power-brokers, as well as sometimes to cloak the truly powerful members of the imperial dynasty. Almost all Japanese empresses and dozens of Emperors abdicated and lived the rest of their lives in pampered retirement, wielding influence behind the scenes, often with more power than they had had while on the throne (see Cloistered rule). Several Emperors abdicated while still in their teens. These traditions show in Japanese folklore, theater, literature and other forms of culture, where the Emperor is usually described or depicted as an adolescent.  Before the Meiji Restoration, Japan had eleven reigning empresses. Over half of Japanese empresses abdicated once a suitable male descendant was considered to be old enough to rule. There is also no provision for abdication in the Imperial Household Law, the Meiji Constitution, or the current 1947 Constitution of Japan.  After the defeat of Japan in World War II, many members of the Imperial Family, such as Princes Chichibu, Takamatsu and Higashikuni, pressured then-Emperor Hirohito to abdicate so that one of the Princes could serve as regent until Crown Prince Akihito came of age. On February 27, 1946, the Emperor's youngest brother, Prince Mikasa (Takahito), even stood up in the privy council and indirectly urged the Emperor to step down and accept responsibility for Japan's defeat. U.S. General Douglas MacArthur insisted that Emperor Hirohito remain on the throne. MacArthur saw the Emperor as a symbol of the continuity and cohesion of the Japanese people.  On 13 July 2016, national broadcaster NHK reported that the Emperor intended to abdicate in favor of his eldest son Crown Prince Naruhito within a few years, citing his age; an abdication within the Imperial Family has not occurred since Emperor Kōkaku abdicated in 1817. However, senior officials within the Imperial Household Agency have denied that there is any official plan for the monarch to abdicate. A potential abdication by the Emperor would require an amendment to the Imperial Household Law, which currently has no provisions for such a move. On 8 August 2016, the Emperor gave a rare televised address, where he emphasized his advanced age and declining health; this address is interpreted as an implication of his intention to abdicate. On 1 December 2017, Prime Minister Shinzo Abe announced that Emperor Akihito would step down on 30 April 2019. The announcement came after a meeting of the Imperial Household Council.  On 19 May 2017, the bill that would allow Akihito to abdicate was issued by the Japanese government's cabinet. On 8 June 2017, the National Diet passed a one-off bill allowing Akihito to abdicate, and for the government to begin arranging the process of handing over the position to Crown Prince Naruhito. The abdication officially occurred on 30 April 2019.

Other examples in recent history.

Hussein ibn Ali al-Hashimi, Sharif of Mecca abdicated the Kingdom of Hejaz in October 1924.  In recent decades, the monarchs or leaders of the Netherlands, Belgium, Luxembourg, Qatar, Cambodia, Bhutan and Japan have abdicated as a result of old age. In the Netherlands, the last three monarchs Wilhelmina, Juliana, and Beatrix have all abdicated. In all three instances, this was done to pass the throne to the heir sooner.  In June 2014, King Juan Carlos of Spain announced his intent to abdicate in favor of his son, Felipe. Felipe took the throne as King Felipe VI on June 19.  Attribution

Abdication is the act of formally relinquishing monarchical authority. Abdications have played various roles in the succession procedures of monarchies. While some cultures have viewed abdication as an extreme abandonment of duty, in other societies (such as pre-Meiji Restoration Japan), abdication was a regular event, and helped maintain stability during political succession.

Abdikace (z lat. "abdicatio" – odřeknutí) je odstoupení hlavy státu. U předsedů vlád a ministrů se používá pojmu demise. V České republice je abdikace prezidenta republiky upravena v čl. 61 Ústavy, podle kterého se prezident může vzdát svého úřadu do rukou předsedy Senátu. Do 1. října 2012 šlo o předsedu Poslanecké sněmovny.


History.

The word "catenary" is derived from the Latin word "catēna", which means "chain". The English word "catenary" is usually attributed to Thomas Jefferson, who wrote in a letter to Thomas Paine on the construction of an arch for a bridge:  It is often said that Galileo thought the curve of a hanging chain was parabolic. In his "Two New Sciences" (1638), Galileo says that a hanging cord is an approximate parabola, and he correctly observes that this approximation improves as the curvature gets smaller and is almost exact when the elevation is less than 45°. That the curve followed by a chain is not a parabola was proven by Joachim Jungius (1587–1657); this result was published posthumously in 1669.  The application of the catenary to the construction of arches is attributed to Robert Hooke, whose "true mathematical and mechanical form" in the context of the rebuilding of St Paul's Cathedral alluded to a catenary. Some much older arches approximate catenaries, an example of which is the Arch of Taq-i Kisra in Ctesiphon.  In 1671, Hooke announced to the Royal Society that he had solved the problem of the optimal shape of an arch, and in 1675 published an encrypted solution as a Latin anagram in an appendix to his "Description of Helioscopes," where he wrote that he had found "a true mathematical and mechanical form of all manner of Arches for Building." He did not publish the solution to this anagram in his lifetime, but in 1705 his executor provided it as "ut pendet continuum flexile, sic stabit contiguum rigidum inversum", meaning "As hangs a flexible cable so, inverted, stand the touching pieces of an arch."  In 1691, Gottfried Leibniz, Christiaan Huygens, and Johann Bernoulli derived the equation in response to a challenge by Jakob Bernoulli; their solutions were published in the "Acta Eruditorum" for June 1691. David Gregory wrote a treatise on the catenary in 1697 in which he provided an incorrect derivation of the correct differential equation.  Euler proved in 1744 that the catenary is the curve which, when rotated about the -axis, gives the surface of minimum surface area (the catenoid) for the given bounding circles. Nicolas Fuss gave equations describing the equilibrium of a chain under any force in 1796.

Inverted catenary arch.

Catenary arches are often used in the construction of kilns. To create the desired curve, the shape of a hanging chain of the desired dimensions is transferred to a form which is then used as a guide for the placement of bricks or other building material.  The Gateway Arch in St. Louis, Missouri, United States is sometimes said to be an (inverted) catenary, but this is incorrect. It is close to a more general curve called a flattened catenary, with equation, which is a catenary if. While a catenary is the ideal shape for a freestanding arch of constant thickness, the Gateway Arch is narrower near the top. According to the U.S. National Historic Landmark nomination for the arch, it is a "weighted catenary" instead. Its shape corresponds to the shape that a weighted chain, having lighter links in the middle, would form.

Catenary bridges.

In free-hanging chains, the force exerted is uniform with respect to length of the chain, and so the chain follows the catenary curve. The same is true of a simple suspension bridge or "catenary bridge," where the roadway follows the cable.  A stressed ribbon bridge is a more sophisticated structure with the same catenary shape.  However, in a suspension bridge with a suspended roadway, the chains or cables support the weight of the bridge, and so do not hang freely. In most cases the roadway is flat, so when the weight of the cable is negligible compared with the weight being supported, the force exerted is uniform with respect to horizontal distance, and the result is a parabola, as discussed below (although the term "catenary" is often still used, in an informal sense). If the cable is heavy then the resulting curve is between a catenary and a parabola.

Anchoring of marine objects.

The catenary produced by gravity provides an advantage to heavy anchor rodes. An anchor rode (or anchor line) usually consists of chain or cable or both. Anchor rodes are used by ships, oil rigs, docks, floating wind turbines, and other marine equipment which must be anchored to the seabed.  When the rode is slack, the catenary curve presents a lower angle of pull on the anchor or mooring device than would be the case if it were nearly straight. This enhances the performance of the anchor and raises the level of force it will resist before dragging. To maintain the catenary shape in the presence of wind, a heavy chain is needed, so that only larger ships in deeper water can rely on this effect. Smaller boats also rely on catenary to maintain maximum holding power.

Mathematical description.

Equation.

The equation of a catenary in Cartesian coordinates has the form  where is the hyperbolic cosine function, and where is measured from the lowest point. All catenary curves are similar to each other; changing the parameter is equivalent to a uniform scaling of the curve.  The Whewell equation for the catenary is  Differentiating gives  and eliminating gives the Cesàro equation  The radius of curvature is then  which is the length of the line normal to the curve between it and the -axis.

Relation to other curves.

When a parabola is rolled along a straight line, the roulette curve traced by its focus is a catenary. The envelope of the directrix of the parabola is also a catenary. The involute from the vertex, that is the roulette formed traced by a point starting at the vertex when a line is rolled on a catenary, is the tractrix.  Another roulette, formed by rolling a line on a catenary, is another line. This implies that square wheels can roll perfectly smoothly on a road made of a series of bumps in the shape of an inverted catenary curve. The wheels can be any regular polygon except a triangle, but the catenary must have parameters corresponding to the shape and dimensions of the wheels.

Geometrical properties.

Over any horizontal interval, the ratio of the area under the catenary to its length equals, independent of the interval selected. The catenary is the only plane curve other than a horizontal line with this property. Also, the geometric centroid of the area under a stretch of catenary is the midpoint of the perpendicular segment connecting the centroid of the curve itself and the -axis.

Science.

A moving charge in a uniform electric field travels along a catenary (which tends to a parabola if the charge velocity is much less than the speed of light ).  The surface of revolution with fixed radii at either end that has minimum surface area is a catenary revolved about the -axis.

Analysis.

Model of chains and arches.

In the mathematical model the chain (or cord, cable, rope, string, etc.) is idealized by assuming that it is so thin that it can be regarded as a curve and that it is so flexible any force of tension exerted by the chain is parallel to the chain. The analysis of the curve for an optimal arch is similar except that the forces of tension become forces of compression and everything is inverted. An underlying principle is that the chain may be considered a rigid body once it has attained equilibrium. Equations which define the shape of the curve and the tension of the chain at each point may be derived by a careful inspection of the various forces acting on a segment using the fact that these forces must be in balance if the chain is in static equilibrium.  Let the path followed by the chain be given parametrically by where represents arc length and is the position vector. This is the natural parameterization and has the property that  where is a unit tangent vector. A differential equation for the curve may be derived as follows. Let be the lowest point on the chain, called the vertex of the catenary. The slope of the curve is zero at C since it is a minimum point. Assume is to the right of since the other case is implied by symmetry. The forces acting on the section of the chain from c to r are the tension of the chain at, the tension of the chain at r, and the weight of the chain. The tension at is tangent to the curve at and is therefore horizontal without any vertical component and it pulls the section to the left so it may be written where is the magnitude of the force. The tension at is parallel to the curve at and pulls the section to the right. The tension at can be split into two components so it may be written, where is the magnitude of the force and is the angle between the curve at and the -axis (see tangential angle). Finally, the weight of the chain is represented by where is the mass per unit length, is the acceleration of gravity and is the length of the segment of chain between and.  The chain is in equilibrium so the sum of three forces is, therefore  and  and dividing these gives  It is convenient to write  which is the length of chain whose weight on Earth is equal in magnitude to the tension at. Then  is an equation defining the curve.  The horizontal component of the tension, is constant and the vertical component of the tension, is proportional to the length of chain between the and the vertex.

Derivation of equations for the curve.

The differential equation given above can be solved to produce equations for the curve.  From  the formula for arc length gives  Then  and  The second of these equations can be integrated to give  and by shifting the position of the -axis, can be taken to be 0. Then  The -axis thus chosen is called the "directrix" of the catenary.  It follows that the magnitude of the tension at a point is, which is proportional to the distance between the point and the directrix.  The integral of the expression for can be found using standard techniques, giving  and, again, by shifting the position of the -axis, can be taken to be 0. Then  The -axis thus chosen passes through the vertex and is called the axis of the catenary.  These results can be used to eliminate giving

Alternative derivation.

The differential equation can be solved using a different approach. From  it follows that  and  Integrating gives,  and  As before, the and -axes can be shifted so and can be taken to be 0. Then  and taking the reciprocal of both sides  Adding and subtracting the last two equations then gives the solution and

Determining parameters.

In general the parameter is the position of the axis. The equation can be determined in this case as follows: Relabel if necessary so that is to the left of and let be the horizontal and be the vertical distance from to. Translate the axes so that the vertex of the catenary lies on the -axis and its height is adjusted so the catenary satisfies the standard equation of the curve  and let the coordinates of and be and respectively. The curve passes through these points, so the difference of height is  and the length of the curve from to is  When is expanded using these expressions the result is  so  This is a transcendental equation in and must be solved numerically. It can be shown with the methods of calculus that there is at most one solution with and so there is at most one position of equilibrium.

Generalizations with vertical force.

Nonuniform chains.

If the density of the chain is variable then the analysis above can be adapted to produce equations for the curve given the density, or given the curve to find the density.  Let denote the weight per unit length of the chain, then the weight of the chain has magnitude  where the limits of integration are and. Balancing forces as in the uniform chain produces  and and therefore  Differentiation then gives  In terms of and the radius of curvature this becomes

Suspension bridge curve.

A similar analysis can be done to find the curve followed by the cable supporting a suspension bridge with a horizontal roadway. If the weight of the roadway per unit length is and the weight of the cable and the wire supporting the bridge is negligible in comparison, then the weight on the cable from to is where is the horizontal distance between and. Proceeding as before gives the differential equation  This is solved by simple integration to get  and so the cable follows a parabola. If the weight of the cable and supporting wires is not negligible then the analysis is more complex.

Catenary of equal strength.

In a catenary of equal strength, the cable is strengthened according to the magnitude of the tension at each point, so its resistance to breaking is constant along its length. Assuming that the strength of the cable is proportional to its density per unit length, the weight,, per unit length of the chain can be written, where is constant, and the analysis for nonuniform chains can be applied.  In this case the equations for tension are  Combining gives  and by differentiation  where is the radius of curvature.  The solution to this is  In this case, the curve has vertical asymptotes and this limits the span to. Other relations are  The curve was studied 1826 by Davies Gilbert and, apparently independently, by Gaspard-Gustave Coriolis in 1836.  Recently, it was shown that this type of catenary could act as a building block of electromagnetic metasurface and was known as "catenary of equal phase gradient".

Elastic catenary.

In an elastic catenary, the chain is replaced by a spring which can stretch in response to tension. The spring is assumed to stretch in accordance with Hooke's Law. Specifically, if is the natural length of a section of spring, then the length of the spring with tension applied has length  where is a constant equal to, where is the stiffness of the spring. In the catenary the value of is variable, but ratio remains valid at a local level, so The curve followed by an elastic spring can now be derived following a similar method as for the inelastic spring.  The equations for tension of the spring are  and  from which  where is the natural length of the segment from to and is the mass per unit length of the spring with no tension and is the acceleration of gravity. Write  so  Then and from which and  Integrating gives the parametric equations  Again, the and -axes can be shifted so and can be taken to be 0. So  are parametric equations for the curve. At the rigid limit where is large, the shape of the curve reduces to that of a non-elastic chain.

Other generalizations.

Chain under a general force.

With no assumptions being made regarding the force acting on the chain, the following analysis can be made.  First, let be the force of tension as a function of. The chain is flexible so it can only exert a force parallel to itself. Since tension is defined as the force that the chain exerts on itself, must be parallel to the chain. In other words,  where is the magnitude of and is the unit tangent vector.  Second, let be the external force per unit length acting on a small segment of a chain as a function of. The forces acting on the segment of the chain between and are the force of tension at one end of the segment, the nearly opposite force at the other end, and the external force acting on the segment which is approximately. These forces must balance so  Divide by and take the limit as to obtain  These equations can be used as the starting point in the analysis of a flexible chain acting under any external force. In the case of the standard catenary, where the chain has mass per unit length and is the acceleration of gravity.

In physics and geometry, a catenary (, ) is the curve that an idealized hanging chain or cable assumes under its own weight when supported only at its ends.

Řetězovka (lat. "catenaria") je křivka, kterou vytvoří řetěz (lépe řečeno homogenní dokonale pevné a ohebné vlákno), který je na svých koncích zavěšen (ne nutně ve stejné výšce) v homogenním gravitačním poli.


Scientific value.

The return of Mars samples would benefit science by allowing more extensive analysis to be undertaken of the samples than could be done by instruments painstakingly transferred to Mars. Also, the presence of the samples on Earth would allow scientific equipment to be used on stored samples, even years and decades after the sample-return mission.  In 2006, MEPAG identified 55 important future science investigations related to the exploration of Mars. In 2008, they concluded that about half of the investigations "could be addressed to one degree or another by MSR", making MSR "the single mission that would make the most progress towards the entire list" of investigations. Moreover, it was found that a significant fraction of the investigations cannot be meaningfully advanced without returned samples.  One source of Mars samples is what are thought to be Martian meteorites, which are rocks ejected from Mars that made their way to Earth. Of over 61,000 meteorites that have been found on Earth, 132 were identified as Martian. These meteorites are thought to be from Mars because they have elemental and isotopic compositions that are similar to rocks and atmosphere gases analyzed by spacecraft on Mars.  In 1996, the possibility of life on Mars was questioned again when apparent microfossils might have been found in a Mars meteorite (see ALH84001). This led to a renewed interest in a Mars sample-return, and several different architectures were considered. NASA administrator Goldin laid out three options for MSR: "paced", "accelerated", and "aggressive". It was thought that MSR could be done for less than US$100 million per year, with something similar to then-current Mars exploration budgets.

History.

For at least three decades, Western scientists have advocated the return of geological samples from Mars. One concept was studied with the Sample Collection for Investigation of Mars (SCIM) proposal, which involved sending a spacecraft in a grazing pass through Mars upper atmosphere to collect dust and air samples without landing or orbiting.  The Soviet Union considered a Mars sample-return mission, Mars 5NM, in 1975 but it was cancelled due to the repeated failures of the N1 rocket that would have been used to launch it. A double sample-return mission, Mars 5M (Mars-79) planned for 1979, was cancelled due to complexity and technical problems.  One mission concept (provisionally named simply Mars Sample-Return) was originally considered by NASA's Mars Exploration Program to return samples by 2008, but was cancelled following a review of the program. In the summer of 2001, the Jet Propulsion Laboratory (JPL) requested mission concepts and proposals from industry-led teams (specifically Boeing, Lockheed Martin, and TRW). That following winter, JPL made similar requests of certain university aerospace engineering departments (namely both MIT and the University of Michigan). A decade later, a NASA-ESA concept mission was aborted in 2012.  The United States' Mars Exploration Program, formed after "Mars Observer" failure in September 1992, supported a Mars sample-return. One example of a mission architecture was the "Groundbreaking Mars Sample-Return" by Glenn J. MacPherson in the early 2000s.  In early 2011, the National Research Council's Planetary Science Decadal Survey, which laid out mission planning priorities for the period 2013–2022 at the request of NASA and the NSF, declared a MSR campaign its highest priority Flagship Mission for that period. In particular, it endorsed the proposed Mars Astrobiology Explorer-Cacher (MAX-C) mission in a "descoped" (less ambitious) form, although this mission plan was officially cancelled in April 2011.  In September 2012, the United States' Mars Program Planning Group endorsed a sample-return after evaluating long-term Mars' plans.  The key mission requirement for the planned "Perseverance" rover is that it must help prepare NASA for its MSR campaign, which is needed before any crewed mission takes place. Such effort would require three additional vehicles: an orbiter, a fetch rover, and a Mars ascent vehicle (MAV). In April 2020, an updated version of the mission was presented.

NASA–ESA concept.

In mid-2006, the International Mars Architecture for the Return of Samples (iMARS) Working Group was chartered by the International Mars Exploration Working Group (IMEWG) to outline the scientific and engineering requirements of an internationally sponsored and executed Mars sample-return mission in the 2018–2023 time frame.  In October 2009, NASA and ESA established the Mars Exploration Joint Initiative to proceed with the ExoMars program, whose ultimate aim is "the return of samples from Mars in the 2020s". ExoMars' first mission would launch in 2018 with unspecified missions to return samples in the 2020–2022 time frame. The cancellation of the caching rover MAX-C, and later NASA withdrawal from ExoMars, pushed back a sample-return mission to an undetermined date. Due to budget limitations the MAX-C mission was canceled in 2011, and the overall cooperation in 2012. The pull-out was described as "traumatic" for the science community.  In April 2018, a letter of intent was signed by NASA and ESA that may provide a basis for a Mars sample-return mission. In July 2019, a mission architecture was proposed to return samples to Earth by 2032: In April 2020, an updated version of the mission was presented.

NASA proposals.

In September 2012, NASA announced its intention to further study several strategies of bringing a sample of Mars to Earth – including a multiple launch scenario, a single-launch scenario, and a multiple-rover scenario – for a mission beginning as early as 2018. Dozens of samples would be collected and cached by the Mars 2020 rover, and would be left on the surface of Mars for possible later retrieval. A "fetch rover" would retrieve the sample caches and deliver them to a Mars ascent vehicle (MAV). In July 2018 NASA contracted Airbus to produce a "fetch rover" concept.  The MAV would launch from Mars and enter a 500 km orbit and rendezvous with a new Mars orbiter. The sample container would be transferred to an Earth entry vehicle (EEV) which would bring it to Earth, enter the atmosphere under a parachute and hard-land for retrieval and analyses in specially designed safe laboratories.

Two-launches architecture.

In this scenario, the sample-return mission would span two launches at an interval of about four years. The first launch would be for the orbiter, the second for the lander. The lander would include the Mars Ascent Vehicle (MAV).

Three-launches architecture.

This concept would have the sample-return mission split into a total of three launches. In this scenario, the sample-collection rover (e.g. Mars 2020 rover) would be launched separately to land on Mars first, and carry out analyses and sample collection over a lifetime of at least 500 Sols (Martian days).  Some years later, a Mars orbiter would be launched, followed by a lander carrying the Mars Ascent Vehicle (MAV). The lander would bring a small and simple "fetch rover", whose sole function would be to retrieve the sample containers from the caches left on the surface or directly from the "Perseverance" rover, and return them to the lander where it would be loaded onto the MAV for delivery to the orbiter and then be sent to Earth.  This design would ease the schedule of the whole project, giving controllers time and flexibility to carry out the required operations. Furthermore, the program could rely on the successful landing system developed for the Mars Science Laboratory, avoiding the costs and risks associated with developing and testing yet another landing system from scratch.

SCIM.

SCIM (Sample Collection for Investigation of Mars) was a low-cost low-risk Mars sample-return mission design, proposed in the Mars Scout Program. SCIM would return dust and air samples without landing or orbiting, by dipping through the atmosphere as it collects Mars material. It uses heritage from the successful "Stardust" and "Genesis" sample-return missions.

Mars Future Missions.

Supports the development of the Mars Sample Return (MSR) mission that is planning to enter formulation (Phase A) as early as the summer of FY 2020. In FY 2021, MSR formulation activities include concept and technology development, and early design and studies in support of the Sample Return Lander and the Capture/Containment and Return System. It also supports a study of the facility required for the handling of returned samples. In developing concepts for a Mars Sample Return mission, the future budget supports an estimated MSR launch readiness date of 2026. Also included is funding for potential collaboration with Canada on the Mars Ice Mapper. The Mars Ice Mapper is a remote sensing mission under study intended to map and profile the near-surface (3–15 meters) water ice, particularly that which lies in the mid-latitude regions, in support of future science and exploration missions.

Additional plans.

China.

China is considering a Mars sample-return mission by 2030. The plan as of 2017 is to launch a large spacecraft that can carry out all phases of the mission, including sample collection, ascent from Mars, rendezvous in Mars orbit, and a flight back to Earth. Such a mission would require the super-heavy-lift Long March 9 rocket. The needed technologies are to be tested during the HX-1 mission launching in 2020. An alternative plan announced in 2019 involves using the 2020 HX-1 mission to cache the samples for retrieval in 2030. These samples would be retrieved by a sample collection lander with Mars ascent vehicle launched in November 2028 on a Long March 3B, and collected in Mars orbit using an Earth Return Orbiter launched on a Long March 5 also in November 2028, with return to Earth in September 2031.

France.

France has worked towards a sample-return for many years. This included concepts of an extraterrestrial sample curation facility for returned samples, and numerous proposals. They worked on the development of a Mars sample-return orbiter, which would capture and return the samples as part of a joint mission with either the United States or other European countries.

Japan.

On 9 June 2015, the Japanese Aerospace Exploration Agency (JAXA) unveiled a plan named Martian Moons Exploration (MMX) to retrieve samples from one of the moons of Mars. This mission will build on the expertise to be gained from the "Hayabusa 2" and SLIM missions. Of the two moons, Phobos's orbit is closer to Mars and its surface may have adhered particles blasted from the red planet; thus the Phobos samples collected by MMX may contain material originating from Mars itself. Japan has also shown interest in participating in an international Mars sample-return mission.

Russia.

A Russian Mars sample-return mission concept is Mars-Grunt. It is meant to use Fobos-Grunt design heritage. Plans as of 2011 envisioned a two-stage architecture with an orbiter and a lander (but no roving capability), with samples gathered from the immediate surroundings of the lander by a robotic arm.

Potential for back contamination.

Since it is currently unknown whether life forms exist on Mars, the mission could potentially transfer viable organisms resulting in back contamination—the introduction of extraterrestrial organisms into Earth's biosphere. The scientific consensus is that the potential for large-scale effects, either through pathogenesis or ecological disruption, is extremely small. Returned samples from Mars will be treated as potentially biohazardous until scientists can determine that the returned samples are safe. The goal is to reduce the probability of release of a Mars particle to less than one in a million.  The proposed NASA Mars sample-return mission will not be approved by NASA until the National Environmental Policy Act (NEPA) process has been completed. Furthermore, under the terms of Article VII of the Outer Space Treaty and probably various other legal frameworks, were a release of organisms to occur, the releasing nation or nations would be liable for any resultant damages.  Part of the sample-return mission would be to prevent contact between the Martian environment and the exterior of the sample container. In order to eliminate the risk of parachute failure, the current plan is to use the thermal protection system to cushion the capsule upon impact (at terminal velocity). The sample container will be designed to withstand the force of the impact. To receive the returned samples, NASA proposed a specially designed Biosafety Level 4 containment facility, the Mars Sample-Return Receiving facility (MSRRF). Not knowing what properties (e.g., size) any Martian organisms might exhibit is a complication in design of such a facility.  Other scientists and engineers, notably Robert Zubrin of the Mars Society, argued in the fringe "Journal of Cosmology" that contamination risk is functionally zero and there is little need to worry. They cite, among other things, lack of any verifiable incident although trillions of kilograms of material have been exchanged between Mars and Earth due to meteorite impacts.  The International Committee Against Mars Sample Return (ICAMSR) is a small advocacy group led by Barry DiGregorio, who campaigns against a Mars sample-return mission. While ICAMSR acknowledges a low probability for biohazards, it considers the proposed containment measures insufficient, and unsafe at this stage. ICAMSR is demanding more "in situ" studies on Mars first, and preliminary biohazard testing at the International Space Station before the samples are brought to Earth. DiGregorio supports the conspiracy theory of a NASA coverup regarding the discovery of microbial life by the 1976 "Viking" landers. DiGregorio also supports a fringe view that several pathogens -such as common viruses- originate in space and probably caused some of the mass extinctions, and deadly pandemics. These claims connecting terrestrial disease and extraterrestrial pathogens have been rejected by the scientific community.

NASA Sample-Return Robot Challenge.

The Sample-Return Robot Challenge, as part of NASA's Centennial Challenges program, offered a total $1.5 million to teams that can build fully autonomous robots that can find, retrieve, and return up to 10 different sample types within a large outdoor environment (80,000 m). The challenge started in 2012 and ended in 2016. Over 50 teams competed during the 5-year duration of the competition. A robot named Cataglyphis, developed by Team Mountaineers from West Virginia University completed the final challenge in 2016.

A Mars Sample-Return (MSR) mission would be a spaceflight mission to collect rock and dust samples on Mars and then return them to Earth. Sample-return would be a very powerful type of exploration, because the analysis is freed from the time, budget, and space constraints of spacecraft sensors.

Mars Sample Return (česky doprava vzorku z Marsu) je plánovaná vysoce komplexní robotická mise k planetě Mars, která by měla dopravit zpět na Zemi vzorky marsovské horniny (podobně jako programy Apollo nebo Luna dopravily horninu z Měsíce). V současné době se její přípravou zabývá Evropská kosmická agentura v rámci projektu Aurora, nicméně je předpoklad, že vzhledem ke značným finančním nákladům půjde o mezinárodní misi s účastí americké NASA.