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cardiac patients. ( washington, d. c. : american psychological association ). pedersen, s. s. ; van den broek, k. c. ; van den berg, m. ; theuns, d. ( 2010 ). shock as a determinant of poor patient - centered outcomes in implantable cardioverter defibrillator patients : is there more to it than meets the eye? pacing clin electrophysiol ( in press ). molinari, e. ; compare, a. ; parati, g. ( 2006 ). clinical psychology and heart disease. springer, ny rozanski, a. ; blumenthal, j. ; davidson, k. ; saab, p. ; & kubzansky, l. ( 2005 ). the epidemiology, pathophysiology, and management of psychosocial risk factors in cardiac practice. journal of the american college of cardiology, 45, 637 β 51. rutledge, t. ; reis, v. a. ; linke, s. e. ; greenberg, b. h. & mills, p. j. ( 2006 ). depression in congestive heart failure : a meta - analytic review of prevalence, intervention effects, and associations with clinical outcomes. journal of the american college of cardiology, 48, 1527 β 37. sears, s. archived 2017 - 07 - 20 at the wayback machine ; matchett, m. ; conti, j. effective management of icd patient psychosocial issues and patient critical events. j cardiovasc electrophysiol 2009 ; 20 ( 11 ) : 1297 β 304. = = further reading = = paul pearsall, the heart's code : tapping the wisdom and power of our heart energy, broadway books, 1999, isbn 978 - 0767900959
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juvenile delinquency in the united states refers to crimes committed by children or young people, particularly those under the age of eighteen ( or seventeen in some states ). juvenile delinquency has been the focus of much attention since the 1950s from academics, policymakers and lawmakers. research is mainly focused on the causes of juvenile delinquency and which strategies have successfully diminished crime rates among the youth. though the causes are debated and controversial, much of the debate revolves around the punishment and rehabilitation of juveniles in a youth detention center or elsewhere. = = causes = = although juvenile delinquency existed throughout american history, there was an increase of attention on the issue in the 1950s. at this time, such delinquency was attributed to a breakdown in traditional family values and family structures, as well as a rise in consumerism and a distinct teenage culture. recent research has suggested that children with incarcerated parents are more likely to exhibit delinquent behavior compared to their peers. while some children may want to push the boundaries set by their parents or society, imposing strict laws and rules such as curfews may not necessarily lead to a decrease in juvenile delinquency rates. in fact, it may provide children with more incentive to break these rules. on the other hand, juvenile crimes can occur due to a lack of supervision and rules, such as when children commit crimes after school while their parents are at work or preoccupied. this is supported by statistics that show peak hours of juvenile crime rates. additionally, mental illness and substance abuse have been shown to be contributing factors. the former widespread use of toxic lead in gasoline and paint β and the subsequent lead poisoning of children as a result β has been hypothesized as contributed to a higher crime rate among juveniles ( i. e. the lead - crime hypothesis ). 15 β 20 % of juveniles convicted of crimes have serious mental illnesses, and the percentages increase to 30 β 90 % of convicted juveniles when the scope of mental illnesses considered widens. also, many people believe that a child's environment and family are greatly related to their juvenile delinquency record. the youth that live in lower income areas face high risk factors. thomas w. farmer's et al. study demonstrates the different types of risks young people β especially african - american young people β face. the youth can be put into three categories : single risk, multiple risks, and no risk. the risks depend on the specific traits these youth portray. farmer et al. state that multiple
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risks young people β especially african - american young people β face. the youth can be put into three categories : single risk, multiple risks, and no risk. the risks depend on the specific traits these youth portray. farmer et al. state that multiple risks are a combination of aggression, academic problems and social problems while a single risk is only one of those factors. for example, the dynamics of a family can affect a child's well - being and delinquency rate. crime rates vary due to the living situations of children. examples include a child whose parents are together, divorced, or a child with only one parent, particularly a teenaged mom. this is largely because living arrangements are directly related to increases and decreases of poverty levels. poverty level is another factor that is related to the chances a child has of becoming a juvenile delinquent. according to john m. bolland et al., the level of poverty adolescents face determine their outcome. these teenagers feel as if they do not have some type of future ahead of them, so they commit crimes, dropout of school or increase the teenaged pregnancy rates. statistics on living arrangements, poverty level and other influential factors can be found in a later section. others believe that the environment and external factors are not at play when it comes to crime. they suggest that criminals are faced with rational choice decisions in which they chose to follow the irrational path. finally, another cause could be the relationships a child develops in school or outside of school. a positive or negative friendship can have a great influence on the chances of children becoming delinquents. peer pressure plays a role as well. relationships and friendships can lead to involvement with gangs, which are major contributors of violent crimes among teenagers. = = demographics = = the juvenile violent crime rate index decreased for the second consecutive year in 2010. additionally, the children's defense fund communicates that boys are five times more likely than girls to become juvenile delinquents. also on the children defense fund website are statistics pertaining to black and latino boys and their juvenile delinquency rates. 1 of every 3 black boys is at risk of incarceration, as well as 1 of every 6 latino boys. the office of juvenile justice and delinquency prevention website also says that in 2008, juveniles were the offenders in 908 cases of murder, which constitutes 9 % of all murders committed that year. in the 1980s, 25 % of the murders that involved juvenile delinquents as the offenders also involved an adult offender. this
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2008, juveniles were the offenders in 908 cases of murder, which constitutes 9 % of all murders committed that year. in the 1980s, 25 % of the murders that involved juvenile delinquents as the offenders also involved an adult offender. this percentage rose to 31 % in the 1990s, and averaged at 37 % between 2000 and 2008. the time of day juvenile delinquents commit their crimes are the times they are not in school. on school days, juvenile crimes peak after school is let out and declines throughout the rest of the afternoon and evening on average. on non - school days it increases in the afternoon through evening, peaking from 7 pm to 9 pm local time ( usually night time ) after dark. curfews have been used to curb juvenile crime, typically the hours of 10 pm to 6 am, but only 15 % of such crimes occur during curfew hours, while most ( 63 % ) juvenile crime occurs on school days. in recent years, the opportunity for after - school activities for children have decreased as public schools have deteriorated, at the same time city parks and recreational facilities have suffered funding cutbacks, both factors have left high - risk environments for kids during those hours. this suggests that funding of after - school programs and activities for juveniles would be substantially more effective at combating juvenile crime than curfews. = = = gender = = = a large majority of juvenile delinquents are boys. boys are five times more likely than girls to become juvenile delinquents. moreover, there are many suggested explanations as to why it is that boys commit more crimes than girls. one comes from theorists who believe boys are naturally more aggressive than girls. another theory argues that boys commit more crimes because of societal pressures to be masculine and aggressive. a third theory suggests that the manner in which boys are treated by their families calls for more criminal action. = = = changes in statistics = = = changes in these statistics can be attributed to many factors. negative changes in the economy greatly affect all crime rates because people are more likely to find themselves in pressing situation like unemployment. changes in population affect juvenile delinquency rates as well because changes in population translate into more or less juveniles. shifts in population could also mean more general societal shift, like a wave of immigration. an influx of new people who are unfamiliar with the legal system could negatively affect the juvenile crime rates. other social changes, such as educational or health reforms, could have a large impact on juvenile crime rates if they create a larger population of
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of immigration. an influx of new people who are unfamiliar with the legal system could negatively affect the juvenile crime rates. other social changes, such as educational or health reforms, could have a large impact on juvenile crime rates if they create a larger population of at - risk children. = = cradle - to - prison pipeline = = this term refers to the population of boys and girls who live in conditions that cause them to be channeled into prison from birth. the pipeline suggests that there are factors such as a lack of parental supervision, poverty, and education that makes these people helpless and unable to change their situations. though this idea might not be appealing to those that believe crime is solely the failure of a rational choice decision, this phenomenon has caught the attention of many americans. this pipeline disproportionately affects minority children living in under - served community, such as black and latino children. according to the children's defense fund, 1 out of every 3 black boys and 1 out of every 3 hispanic boys are at risk of becoming delinquents in their lifetime, and therefore at risk of being sucked into this pipeline in which prison is the only option at the end of the tunnel. of course some people that are affected by the pipeline commit crimes and are imprisoned when they are older. however, if the delinquency cause by the pipeline were to occur before the age of eighteen, the boys or girls would then become juvenile delinquents. the pipeline affects more boys than girls. the children's defense fund launched a campaign called the " cradle to prison pipeline campaign " in 2008 in washington, d. c., at howard university. the campaign argues that the united states federal government spends more money on incarcerated people than on each child in the public school system. their vision is that if this budgeting were reversed, the number of juvenile delinquents would greatly decrease. the ultimate goal of this campaign is to increase support for preventive measures and resources for children. some of the programs this campaign includes increasing early childhood education and guidance, as well as increasing health and mental health coverage and counseling. many states responded to this campaign by forming coalitions and holding conventions in which they formulate ideas and tactics to dismantle the pipeline. = = legal changes = = the united states federal government enacted legislation to unify the handling of juvenile delinquents, the juvenile justice and delinquency prevention act of 1974. the act created the office of juvenile justice and delinquency prevention ( ojjdp
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united states federal government enacted legislation to unify the handling of juvenile delinquents, the juvenile justice and delinquency prevention act of 1974. the act created the office of juvenile justice and delinquency prevention ( ojjdp ) within the department of justice to administer grants for juvenile crime - combating programs ( currently only about us $ 900, 000 a year ), gather national statistics on juvenile crime, fund research on youth crime and administer four anti - confinement mandates regarding juvenile custody. specifically, the act orders : deinstitutionalization : youths charged with " status " offenses that would not be crimes if committed by adults, such as truancy, running away and being caught with alcohol or tobacco, must be " deinstitutionalized ", which in this case really means that, with certain exceptions ( e. g., minor in possession of a handgun ), status offenders may not be detained by police or confined. alleged problems with this mandate are that it overrides state and local law, limits the discretion of law enforcement officers and prevents the authorities'ability to reunify an offender with their family. segregation : arrested youths must be strictly segregated from adults in custody. under this " out of sight and sound " mandate, juveniles cannot be served food by anyone who serves jailed adults nor can a juvenile walk down a corridor past a room where an adult is being interrogated. this requirement forces local authorities to either free juveniles or maintain expensive duplicate facilities and personnel. small cities, towns and rural areas are especially hard hit, drastically raising those taxpayers'criminal justice costs. supporters of the system point to lower sexual assault rates when adults and children are separated. jail and lockup removal : as a general rule, youths subject to the original jurisdiction of juvenile courts cannot be held in jails and lockups in which adults may be detained. the act provides for a six - hour exception for identification, processing, interrogation and transfer to juvenile facilities, court or detention pending release to parents. the act also provides an exception of 24 hours for rural areas only. over representation of minority youths : states must systematically try to reduce confinement of minority youths to the proportion of those groups in the population. one of the most notable causes of juvenile delinquency is fiat, i. e., the declaration that a juvenile is delinquent by the juvenile court system without any trial, and upon finding only probable cause. many states have laws that presuppose the less harsh treatment of juvenile delinquents
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, i. e., the declaration that a juvenile is delinquent by the juvenile court system without any trial, and upon finding only probable cause. many states have laws that presuppose the less harsh treatment of juvenile delinquents than adult counterparts β treatment. in return, the juvenile surrenders certain constitutional rights, such as a right to trial by jury, the right to cross - examine, and even the right to a speedy trial. notable writings by reformers such as jerome g. miller show that very few juvenile delinquents actually broke any law. most were simply rounded up by the police after some event that possibly involved criminal action. they were brought before juvenile court judges who made findings of delinquency, simply because the police action established probable cause. in 1967, the united states supreme court decided the case in re gault, that established the protection of many, but not all, procedural rights of juveniles in court proceedings, such as the right to counsel and right to refuse self - incrimination. = = preventing juvenile delinquency = = an effective way of preventing juvenile delinquency is to tackle the problem before it happens. this entails looking at the causes of crime among teenagers and making an effort to reduce or eliminate said causes. some causes, though hard to eliminate, seem plausible. an example of this is improving the environment at home, through employment opportunities for the parents, educational opportunities for the children, and counseling and rehabilitation services if need be. these changes would not only promote a more positive environment at home but would also work towards pulling at - risk families out of poverty. another possible change could be the interaction of the community these adolescents live in. the involvement of neighbors could decrease the chances of violence among these communities. in craig pinkney's tedtalk speech, " the real roots of youth violence ", he states that people do things to be heard and seen in their communities. a cause that is more difficult to eliminate is mental illness, because sometimes these illnesses are present at birth. still, counseling and rehabilitation might aid in reducing the negative effects of these illness like violent behavior. one cause that seems almost impossible to eliminate is the rational and irrational choice idea. as mentioned above, some people believe that all crime comes down to a single situation in which an individual must make a rational or irrational decision, to commit the crime, or to not. those that believe that this rational choice option is tied to the very immutable nature of the person would have a hard time
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to a single situation in which an individual must make a rational or irrational decision, to commit the crime, or to not. those that believe that this rational choice option is tied to the very immutable nature of the person would have a hard time believing that there is any way to control the choices children make and eliminate the causes of juvenile delinquency. there are many foundations and organizations around the united states that have dedicated themselves to the reduction and elimination of juvenile delinquency. office of juvenile justice and delinquency prevention ( ojjdp ) : forming part of the u. s. department of justice, this prevention agency is a governmental organization focuses on all types of research, prevention programs, and rehabilitation programs for juveniles as offenders and victims. through collaboration, this organizations aims to improve juvenile justice policies and practices and create safer communities and neighborhoods. the ojjdp helps victims of kidnapping and sexual exploitation. currently, the ojjdp is working to prevent gang involvement and crime, girl's delinquency, and the under - aged consumption of alcohol. this foundation is important because it guides real - life policy changes that pertain to juvenile justice and juvenile delinquency. the innocence project : the main goal of this organization is not to reduce juvenile delinquency, but rather, to liberate juveniles that were falsely convicted of crimes. though this foundation is not primarily focused on reducing juvenile delinquency, it has done a good job of freeing falsely convicted teens in the past. annie e. casey foundation : the goal of this foundation is to provide a brighter and safer future for children from under - served communities. its major initiatives include : child welfare strategy group, civic sites, family economic success, juvenile detention alternatives initiative ( jdai ), kids count, leadership development, and making connections. the kids count initiative collects annual data on the well - being of children all - round the united states and publishes state - specific reports as well as state comparisons. the jdai focuses on providing a bright and healthy future as adults for children involved in the juvenile justice system. national gang center ( ngc ) : a governmental project that provides anyone on the internet with information about the gang problem in the united states. there is also a list of resources on how to identify if one's city has a gang problem and how to combat this problem. this foundation helps the people within the struggling communities be the ones to solve their own gang problems. best friends organization : this organization focuses on the overall well
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on how to identify if one's city has a gang problem and how to combat this problem. this foundation helps the people within the struggling communities be the ones to solve their own gang problems. best friends organization : this organization focuses on the overall well - being of children in the united states. it focuses on physical and emotional well - being and helps children develop healthy relationships and useful skills. instead of focusing on the elimination of current juvenile delinquency, this organization works on creating healthy and happy children that will not resort to crime. reach for youth : this organization is available in indianapolis, indiana. this organization was invented to encourage teenagers to graduate and develop ways to say no to peer pressure. = = see also = = american juvenile justice system juvenile justice and delinquency prevention act juvenile justice in the united states list of juveniles executed in the united states since 1976 office of juvenile justice and delinquency prevention youth incarceration in the united states = = references = = = = external links = = office of juvenile justice and delinquency prevention the annie e. casey foundation for vulnerable youth national gang center best friends organization innocence project
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the mediterranean sea has been defined as one of the seas most affected by marine plastic pollution. it has concentrations of microplastics which are estimated to be higher than those on average found at the global level. studies conducted within the wwf mediterranean marine initiative of 2019 have estimated that 0. 57 million metric tons of plastic enter the mediterranean sea every year ; this quantity corresponds to the dumping of 33. 800 bottles made of plastic into waters every minute, representing important risks for marine ecosystems, human health, but also for the blue economy of the area, whose coastal zones are very densely populated and among the first tourist destinations worldwide. marine plastic pollution was found in mediterranean waters in amounts similar to those present in the ocean gyres ( indian ocean gyre, north atlantic gyre, north pacific gyre, south atlantic gyre, south pacific gyre ). therefore, the mediterranean sea is oftentimes being defined as the " world's sixth greatest accumulation zone " for marine plastic litter or as an invisible " sixth garbage patch ", primarily composed of microplastics. this is an invisible garbage patch as there is no trace of permanent litter accumulation areas in the mediterranean sea, primarily because of the semi - enclosed shape of its basin, the cyclonic circulation and the currents present in the region. the mediterranean sea receives waste from coastal areas and from waters, such as rivers ( like in the case of the nile river, which, as of 2017, brought around 200 tonnes of plastic waste into the mediterranean basin yearly ). a world wide fund for nature report of 2019 estimates that, considering the mediterranean countries, around 70 % of plastic pollution coming from water - based sources comes from three areas : egypt ( 41. 3 % ), turkey ( 19. 1 % ) and italy ( 7. 6 % ). plastic litter originating from land - based sources is instead estimated to be coming from, in decreasing order : turkey, morocco, israel, spain, france, syria, egypt, albania, tunisia and italy. initiatives are being implemented at various levels to reduce and end the problem of marine plastics pollution in the mediterranean sea ; however, the governance of this problem is very complex because of the nature of such plastics ( especially microplastics ), the transboundary character of this matter, the difficulties connected with the multiplicity of the actors involved, the increasing levels of production of plastics and the issues connected with responsibility at different levels. = = history of research on the problem = = studies on marine plastic pollution began in the 1970s, when plastic
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difficulties connected with the multiplicity of the actors involved, the increasing levels of production of plastics and the issues connected with responsibility at different levels. = = history of research on the problem = = studies on marine plastic pollution began in the 1970s, when plastic debris was found in gyres in the sargasso sea and the first scientific findings were published in 1972. around a decade later, in the 1980s, the first researches focusing on the problem of marine plastic pollution in the mediterranean sea were published. the first study on the mediterranean basin focused on an area 40 miles sw of malta and reported the presence of floating debris, the majority of which was constituted by plastic. this body of research focusing on the mediterranean continued growing in the 1990s, with numerous studies on the impacts, especially biological, of plastic pollution in the marine environment and with the start of interstate discussions, primarily in the form of conferences such as, among others, that of the " international symposium on plastics in mediterranean countries ". however, the real increase in the number and variety of such studies only came later, around 2010, when more pieces of information on the quantity and distribution of plastics in the mediterranean sea was made accessible, when the knowledge on microplastics was being spread and when the impacts started to be addressed through diverse investigations as a concern. recent researches, conducted at various regional, national and international levels, address the impacts of plastic pollution in the mediterranean sea from ecological, biological, economic and social points of view and the possibilities in terms of reduction efforts and governance of the problem, also while awaiting the prospective global plastic pollution treaty. = = types of plastics found in the mediterranean sea = = plastics accounts for 80 % of waste dispersed in the marine and coastal environment of the mediterranean sea. recent studies focus on the types of plastics found and primarily on the issue of microplastics, both at a global but also at a regional level, as in the case of the mediterranean sea, which was identified as a " target hotspot of the world " due to its amounts of microplastics, around four times higher than those present in the north pacific ocean. in the mediterranean sea, microplastics are found on surface waters, as well as on beaches and deep seafloor. 94 % of microplastic items present in the mediterranean sea are thought to be in the seabed, 5 % on beaches and 1 % on surface waters. = = = plastics on mediterranean beaches and surface waters = = = plastics has been identified as the primary source of litter found on
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present in the mediterranean sea are thought to be in the seabed, 5 % on beaches and 1 % on surface waters. = = = plastics on mediterranean beaches and surface waters = = = plastics has been identified as the primary source of litter found on beaches of the mediterranean sea. researches conducted between 2019 and 2023 within the framework of the common project ( " coastal management and monitoring network for tackling marine litter in the mediterranean sea ", financed by the european union through the eni cbc med programme ) show that, out of more than 90. 000 collected objects on beaches of italy, tunisia and lebanon, 17. 000 are cigarette butts and 6. 000 are cotton buds sticks, which contain plastics. earlier researches, conducted in 2016, present similar findings and show that the ten " top marine litter items " found on beaches and surface waters of the mediterranean sea were, from the most abundant : cigarette butts and filters, plastic and polystyrene pieces, plastic caps and lids and plastic rings from bottle caps and lids, cotton bud sticks, nets and pieces of nets, bottles, foam sponge, cigarette packets, plastic bags and what remains from these when they are ripped off. these items, primarily made of single - use plastics, account for more than 60 % of marine waste in the beaches and surface waters of the mediterranean sea. the surface waters of the mediterranean sea present concentrations of microplastics that, according to a 2015 study ( unep / map ), are above 100. 000 objects per km2, with more than 64. 000. 000 floating particles per km2. as of 2019, the most common types of microplastics found are polyethylene, polystyrene, polyester and polypropylene. = = = plastics in the mediterranean seafloor = = = plastic litter that accumulates in the mediterranean sea is fragmented into small particles that then tend to gather in the seabed. studies aimed at analysing plastic pollution in the sea floor of the mediterranean have shown that plastic debris can be found in every depth from 900 m to 3000 m ; plastic litter could be found in 92. 8 % of the surveys collected from the mediterranean deep - sea. particular attention is now being devoted to the presence of microplastics and nanoplastics in the mediterranean seabed and sediments, the two regions with the highest levels of microplastics in the mediterranean sea. in 2020, scientists from the university of manchester analysed sediment samples of the mediterranean sea and identified the highest concentration
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##astics in the mediterranean seabed and sediments, the two regions with the highest levels of microplastics in the mediterranean sea. in 2020, scientists from the university of manchester analysed sediment samples of the mediterranean sea and identified the highest concentration ever recorded of microplastics on sediments of the sea floor ; the scientists also discovered that such microplastics are moved by wind, storms, hurricane and currents present in the sea bed which then make them accumulate in specific areas. once these items are deposited, their degradation is minimal because of a lack of oxygen or light and therefore the microplastics, once they come to the seafloor, remain preserved. another study from 2020 has led to the discovery of two types of plastic debris in the mediterranean seabed for the first time, on giglio island, italy : plasticrust and pyroplastics. plasticrust had been found for the first time in the atlantic ocean. this discovery revealed that the contamination by plastic debris may be more widespread than previously expected. = = = plastics in marine protected areas = = = researches on the sediment of the cabrera archipelago national maritime - terrestrial park marine protected area has found that the majority of plastic debris in these waters is microplastics, probably transported by wave currents and winds ; the study also showed that higher amounts of microplastics were found in the marine protected area rather than on other samples taken from different sites, thus opening the debate regarding the protection and conservation of these areas. other studies on the presence of plastic debris in marine protected areas have been conducted, among others, in the waters of the natural park of telascica bay in croatia and on the eu site of community interest in the north - west adriatic ; both areas present marine litter, primarily in the form of microplastics and mesoplastics. = = sources of plastic litter in the mediterranean sea = = the mediterranean sea is considered as a hotspot for plastic pollution and one of the most impacted regions of the world by this problem. as of 2019, of the estimated 10. 000 tons of plastic input per year in the mediterranean sea, half of this litter had land - based origins ( from coastal zones ) whereas the other half originated from rivers and maritime routing. this is the case for example of the nile river which, as of 2017, brought around 200 tonnes of plastic waste into the mediterranean basin yearly. once plastic waste reaches mediterranean waters, it hardly gets out : the peculiar shape of the mediterranean sea and its currents mean
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the case for example of the nile river which, as of 2017, brought around 200 tonnes of plastic waste into the mediterranean basin yearly. once plastic waste reaches mediterranean waters, it hardly gets out : the peculiar shape of the mediterranean sea and its currents mean that the outflow circulation of waters is limited and, therefore, that the waste that enters from the coastlines remains inside the mediterranean, accumulating within it. researchers identify some main causes of the large presence of plastic pollution in this sea : namely its semi - enclosed shape, its densely populated coasts, tourism activities, fishing, shipping, waste disposal problems, increase of the use of plastic and unsustainable consumption patterns. = = = land - based sources of plastic litter in the mediterranean sea = = = the primary land - based sources of plastic pollution in the mediterranean sea are tourism activities, vast population on the coasts, inefficient management of waste, unsustainable consumption patterns and increase on the use of plastics. according to a unep report, inhabitants and tourists of the mediterranean region produce 24 million metric tons of plastic waste ( of which less than 6 % is recycled ) each year ; this figure normally grows during the summer because of tourism presence and activities. mediterranean countries are the world's number one tourism destination ( considering both international and domestic visitors ) and waste management facilities frequently experience overload. most of the waste produced is dumped into unprotected landfills and gets into the mediterranean sea through stormwater runoffs, wind currents, rivers, wastewater streams. to this extent, considering the fact that wastewater is a pathway for waste disposal in open waters, a key challenge is also constituted by the fact that only small percentages of wastewater in the mediterranean area undergo basic and tertiary treatment. = = = ocean - based sources of plastic litter in the mediterranean sea = = = ocean - based sources of plastic litter are connected with some important economic sectors in the mediterranean : fisheries, shipping and acquaculture, which generate diverse types of debris that ends up in waters. the shipping sector in the mediterranean sea is very important as about 15 % of global shipping passes through this region. cruise - liners, military fleets, oil and gas stations, drilling activities are other ocean - based sources of plastic litter : the debris produced is then fragmented into microplastics present at all levels of the mediterranean basin. = = impacts and costs of plastic pollution in the mediterranean sea = = as the mediterranean sea is characterised by a rich biodiversity, ecological value and intense presence of economic activities, the
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fragmented into microplastics present at all levels of the mediterranean basin. = = impacts and costs of plastic pollution in the mediterranean sea = = as the mediterranean sea is characterised by a rich biodiversity, ecological value and intense presence of economic activities, the current and future impacts of marine plastic pollution in this area are particularly high. the mediterranean sea in fact hosts between 4 % and 18 % of all marine exemplars, and tourism on the coastal zones, aquaculture, the fishing industry and maritime transport represent substantial sources of income for the mediterranean countries. research shows that marine plastic pollution has impacts on marine ecosystems and economic activities at various levels, but further studies are currently being conducted to thoroughly investigate the size of such impacts in the mediterranean area, both on marine biota and on human health. = = = biological and ecological impacts = = = a study conducted by legambiente on 700 individuals of 6 different fish species discovered that one out of three fish had ingested plastic items and that more than half of the sea turtles that were analysed presented plastic litter either inside or around the body. other studies found traces of ingested plastic debris also in the stomachs of seabirds and nanoplastic particles in mussels. these are just some of the signals of the negative impact that plastic litter has on the marine biodiversity of the mediterranean basin. marine plastic litter causes problems not only in terms of the accidental ingestion of plastic items ( which can lead to gastrointestinal blockages, diseases and mortality ), but also in terms of the toxic effects that additives used in plastics can have. moreover, studies have shown that plastic items soaks up contaminants in a more rapid and efficient way than organic items floating on sea waters. long - term exposure to such plastic items and the contaminants, in particular microplastic debris, has been shown to have topological effects on species living in regions where marine plastic pollution is intense, like in the case of the mediterranean region, whose ecosystem is in constant contact with plastics. = = = impacts on human health = = = potential impacts on human health are connected, among others, with the possibility of eating fish that had ingested plastics, of drinking waters that do not undergo treatment, or through releases of chemical substances. however, effects of plastics ( and especially microplastics ) on human health are a particularly debated topic within scholars and researchers and more studies are being conducted to assess these effects. = = = impacts and costs on marine industries = = = the dangerous
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however, effects of plastics ( and especially microplastics ) on human health are a particularly debated topic within scholars and researchers and more studies are being conducted to assess these effects. = = = impacts and costs on marine industries = = = the dangerous effect of plastic pollution has also noticeable impacts on the blue economy of the mediterranean basin, in particular on the tourism, fishing and shipping sectors. calculating the complete economic impacts of marine plastic litter in the mediterranean sea is very complicated due to the various sources, the impacts at the environmental, social and economic levels, and the number of involved sectors in different geographic locations. a 2021 report by unep tried estimating annual losses of us $ 700 million on the entire blue economy of the mediterranean sea. because of current waves, high amounts of plastic objects accumulate on beaches, thus demanding continuous clean - ups and potentially disincentivizing tourism. aquaculture and fishery are impacted as the marine ecosystem is affected and as litter can damage nets, contaminate the catches and also reduce them. for the fishing sector, researches of 2021 estimate a general annual loss of euros 61. 7 millions due to marine debris in european countries ; this figure is also comprising a loss due to the decreasing of demand of fish products due to concerns on the quality of these items. the specific loss at the mediterranean level is more complicated to calculate but scholars argue the costs are considered to be higher to the substantial concentration of marine litter. the shipping sector suffers economic pressures too, as plastic marine litter, among others, can damage motors, which then have to be repaired. assessments on the impact of plastic marine litter on the shipping sector in the mediterranean region are being conducted. = = = social and clean up costs = = = marine pollution in the mediterranean has led to an increase in the costs sustained by diverse local, regional and national authorities to clean - up the beaches and coastal areas. for example, as of 2016, nice's administration spent around euros 2 million to clean up beaches. analysis conducted within the cleansea project estimated a cost of euros 3. 800 to clean up one tonne of marine litter in european countries'beaches : euros 2. 200 have been estimated to be spent annually to clean up each tonne of floating plastic litter. other impacts have been registered at the local level with losses of income and jobs in the tourism sector, as well as losses in values of residential property. = = reduction efforts = = marine plastic pollution has been defined as a global concern by the european union, the g7 and g20, the united
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losses of income and jobs in the tourism sector, as well as losses in values of residential property. = = reduction efforts = = marine plastic pollution has been defined as a global concern by the european union, the g7 and g20, the united nations environment programme ( unep ) and various organisations and institutions at local, regional and international levels. over the last few years, marine plastic debris has started to be recognised as a relevant issue also in terms of its governance and regulatory complexities, which are also due to the fact that it is a transboundary, " multifaceted " problem, with multiple causes, sources and actors involved, and that requires integrated approaches and solutions at various levels. national, regional and international actors, along with civil society and private industries are trying to address the problem of pollution in the mediterranean sea with initiatives, policies, campaigns. the majority of these initiatives addresses marine pollution in general, while also focusing, among others, on the problem of marine plastic pollution in the mediterranean sea and region. = = = policies and conventions on the mediterranean sea = = = the barcelona convention, which was adopted in 1995, was the first regional treaty aiming at reducing pollution, and marine plastic pollution, in the mediterranean region ; the european union and all countries with a mediterranean shoreline are parties to the convention and to the protocol for the protection of the mediterranean sea against pollution from land based sources and to activities that concern plastic pollution in the mediterranean basin. the barcelona convention and its protocols were established within the regional cooperation platform " mediterranean action plan of the united nations environment programme " ( unep / map ), the first regional action plan of the unep regional seas programme, which was instrumental in the adoption of the convention itself. the unep / map - barcelona convention system has been playing a role for responding to environmental challenges threatening marine and coastal ecosystems in the mediterranean region. it collects data for marine debris, litter in waters and on coastlines, amounts of plastic litter ingested by marine species. the first ever legal binding instrument with the purpose of preventing and limiting marine plastic pollution and of cleaning up marine litter already affecting the area of the mediterranean sea is the " regional plan on marine litter management " ( rpml ) in the mediterranean, which was adopted, among others, in the framework of the barcelona convention in 2013. the plan is further supported by the eu funded " marine litter med ii project " ( 2020 - 2023 ), which is focused on countries of the southern mediterranean ( algeria, egypt, libya, morocco, tunisia, israel and
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barcelona convention in 2013. the plan is further supported by the eu funded " marine litter med ii project " ( 2020 - 2023 ), which is focused on countries of the southern mediterranean ( algeria, egypt, libya, morocco, tunisia, israel and lebanon ) and is built on the results of the marine litter med project, carried out between 2016 and 2019. scholars have argued that an international agreement among countries with shorelines on the mediterranean sea could be pursued, with actions focused on eliminating plastic waste in nature, on creating plans for the prevention, control and removal of plastic litter from marine ecosystems, on banning specific types of plastic products and prevent their dumping into waters, and on establishing international committees. the prospective global plastic pollution treaty is awaited. = = = marine protected areas = = = marine protected areas represent a policy instrument which can be helpful in reducing plastic pollution in seas and its impacts on marine ecosystems, as they ban or limit fisheries, some tourism activities, dumping of materials, mining and building of harbours and offshore wind farms. nevertheless, high levels of plastic pollution, especially microplastics, have been recorded in marine protected areas in the mediterranean sea. initiatives focusing specifically on marine protected areas and plastic pollution in the mediterranean region are awaited. = = = other actors, initiatives and programmes = = = programmes and strategies at the eu level address the problem of plastic pollution in europe's seas, therefore also the mediterranean sea. key policies are the eu green deal and the zero pollution action plan, of which an important goal is that of reducing waste, marine plastic pollution and the dispersal of microplastics. among the relevant strategies, some are the water framework directive, the industrial emissions directive, the environmental liability directive, the environmental crimes directive, the waste framework directive, the waste shipment regulation, the packaging and packaging waste directive, the single - use plastics directive. the marine strategy framework directive constitutes the eu legal framework for the safeguard and preservation of the european seas, also from marine plastic litter ; the directive addresses the importance of identifying the sources of marine litter and its impacts to deploy efficient and comprehensive measures. among various actions, there is the european union's ban on diverse kinds of single - use plastics. the eu has invited mediterranean countries to implement legal, administrative and financial actions to create sustainable waste management systems to limit the problem of plastic pollution in the mediterranean sea. some of the other actors carrying out activities to raise awareness and build knowledge on the topic of plastic pollution in the mediterranean sea involve : the union for the mediterranean ; the international union for
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management systems to limit the problem of plastic pollution in the mediterranean sea. some of the other actors carrying out activities to raise awareness and build knowledge on the topic of plastic pollution in the mediterranean sea involve : the union for the mediterranean ; the international union for the conservation of nature and iucn - med, which conducts researches on macro, micro and nano plastics in the mediterranean sea and builds partnerships and alliances for the implementation of projects in the region ; wwf with different analyses and projects, such as the wwf mediterranean marine initiative ; the mediterranean information office for environment, culture and sustainable development ( mio - ecsde ) and the marlisco project ; mediterranean experts on climate and environmental change. states and civil societies actors are also operating and creating partnerships ( like in the case of the coastal management and monitoring network for tackling marine litter in the mediterranean sea ) in awareness - raising initiatives and in clean - up activities on the coastlines of the mediterranean sea, like in the case of ogyre and enaleia, who are directly cooperating with fishermen in cleaning various seas, including the mediterranean sea. other clean - up activities comprise the " mediterranean cleanup " ( mcu ), " clean up the med " by legambiente and spontaneous initiatives at various levels. the day of the mediterranean is celebrated each year on 28 november to commemorate the foundation of the barcelona convention and to raise awareness on various issues of the mediterranean basin, among which that of plastic pollution. = = references = =
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in economics, a market is a composition of systems, institutions, procedures, social relations or infrastructures whereby parties engage in exchange. while parties may exchange goods and services by barter, most markets rely on sellers offering their goods or services ( including labour power ) to buyers in exchange for money. it can be said that a market is the process by which the value of goods and services are established. markets facilitate trade and enable the distribution and allocation of resources in a society. markets allow any tradeable item to be evaluated and priced. a market emerges more or less spontaneously or may be constructed deliberately by human interaction in order to enable the exchange of rights ( cf. ownership ) of services and goods. markets generally supplant gift economies and are often held in place through rules and customs, such as a booth fee, competitive pricing, and source of goods for sale ( local produce or stock registration ). markets can differ by products ( goods, services ) or factors ( labour and capital ) sold, product differentiation, place in which exchanges are carried, buyers targeted, duration, selling process, government regulation, taxes, subsidies, minimum wages, price ceilings, legality of exchange, liquidity, intensity of speculation, size, concentration, exchange asymmetry, relative prices, volatility and geographic extension. the geographic boundaries of a market may vary considerably, for example the food market in a single building, the real estate market in a local city, the consumer market in an entire country, or the economy of an international trade bloc where the same rules apply throughout. markets can also be worldwide, see for example the global diamond trade. national economies can also be classified as developed markets or developing markets. in mainstream economics, the concept of a market is any structure that allows buyers and sellers to exchange any type of goods, services and information. the exchange of goods or services, with or without money, is a transaction. market participants or economic agents consist of all the buyers and sellers of a good who influence its price, which is a major topic of study of economics and has given rise to several theories and models concerning the basic market forces of supply and demand. a major topic of debate is how much a given market can be considered to be a " free market ", that is free from government intervention. microeconomics traditionally focuses on the study of market structure and the efficiency of market equilibrium ; when the latter ( if it exists ) is not efficient, then economists say that a market failure has occurred. however, it is not always clear how
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intervention. microeconomics traditionally focuses on the study of market structure and the efficiency of market equilibrium ; when the latter ( if it exists ) is not efficient, then economists say that a market failure has occurred. however, it is not always clear how the allocation of resources can be improved since there is always the possibility of government failure. = = definition = = in economics, a market is a coordinating mechanism that uses prices to convey information among economic entities ( such as firms, households and individuals ) to regulate production and distribution. in his seminal 1937 article " the nature of the firm ", ronald coase wrote : " an economist thinks of the economic system as being coordinated by the price mechanism.... in economic theory, we find that the allocation of factors of production between different uses is determined by the price mechanism ". thus the usage of the price mechanism to convey information is the defining feature of the market. this is in contrast to a firm, which as coase put it, " the distinguishing mark of the firm is the super - session of the price mechanism ". thus, firms and markets are two opposite forms of organizing production ; coase wrote : outside the firm, price movements direct production, which is co - ordinated through a series of exchange transactions on the market. within a firm, these market transactions are eliminated and in place of the complicated market structure with exchange transactions is substituted the entrepreneur - co - ordinator, who directs production. there are also other hybrid forms of coordinating mechanisms, in between the hierarchical firm and price - coordinating market ( e. g. global value chains, business ventures, joint venture, and strategic alliances ). the reasons for the existence of firms or other forms of co - ordinating mechanisms of production and distribution alongside the market are studied in " the theory of the firm " literature, with various complete and incomplete contract theories trying to explain the existence of the firm. incomplete contract theories that are explicitly based on bounded rationality lead to the costs of writing complete contracts. such theories include : transaction cost economies by oliver williamson and residual rights theory by groomsman, hart, and moore. the market / firm distinction can be contrasted with the relationship between the agents transacting. while in a market, the relationship is short term and restricted to the contract. in the case of firms and other co - ordinating mechanisms, it is for a longer duration. in the modern world, much economic activity takes place through fiat and not the market. lafontaine and slade ( 2007 ) estimates
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contract. in the case of firms and other co - ordinating mechanisms, it is for a longer duration. in the modern world, much economic activity takes place through fiat and not the market. lafontaine and slade ( 2007 ) estimates, in the us, that the total value added in transactions inside the firms equal the total value added of all market transactions. similarly, 80 % of all world trade is conducted under global value chains ( 2012 estimate ), while 33 % ( 1996 estimate ) is intra - firm trade. nearly 50 % of us imports and 30 % of exports take place within firms. while rajan and zingales ( 1998 ) have found that in 43 countries two - thirds of the growth in value added between 1980 and 1990 came from increase in firm size. = = types = = a market is one of the many varieties of systems, institutions, procedures, social relations and infrastructures whereby parties engage in exchange. while parties may exchange goods and services by barter, most markets rely on sellers offering their goods or services ( including labour ) in exchange for money from buyers. it can be said that a market is the process by which the prices of goods and services are established. markets facilitate trade and enable the distribution and allocation of resources in a society. markets allow any trade - able item to be evaluated and priced. a market sometimes emerges more or less spontaneously or may be constructed deliberately by human interaction in order to enable the exchange of rights ( cf. ownership ) of services and goods. markets of varying types can spontaneously arise whenever a party has interest in a good or service that some other party can provide. hence there can be a market for cigarettes in correctional facilities, another for chewing gum in a playground, and yet another for contracts for the future delivery of a commodity. there can be black markets, where a good is exchanged illegally, for example markets for goods under a command economy despite pressure to repress them and virtual markets, such as ebay, in which buyers and sellers do not physically interact during negotiation. a market can be organized as an auction, as a private electronic market, as a commodity wholesale market, as a shopping center, as complex institutions such as international markets and as an informal discussion between two individuals. markets vary in form, scale ( volume and geographic reach ), location and types of participants as well as the types of goods and services traded. the following is a non exhaustive list : = = = physical consumer markets = = = food retail markets : farmers'markets, fish markets, wet
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geographic reach ), location and types of participants as well as the types of goods and services traded. the following is a non exhaustive list : = = = physical consumer markets = = = food retail markets : farmers'markets, fish markets, wet markets and grocery stores retail marketplaces : public markets, market squares, main streets, high streets, bazaars, souqs, night markets, shopping strip malls and shopping malls big - box stores : supermarkets, hypermarkets and discount stores ad hoc auction markets : process of buying and selling goods or services by offering them up for bid, taking bids and then selling the item to the highest bidder used goods markets such as flea markets temporary markets such as fairs real estate markets = = = physical business markets = = = physical wholesale markets : sale of goods or merchandise to retailers ; to industrial, commercial, institutional, or other professional business users or to other wholesalers and related subordinated services markets for intermediate goods used in production of other goods and services labour markets : where people sell their labour to businesses in exchange for a wage online auctions and ad hoc auction markets : process of buying and selling goods or services by offering them up for bid, taking bids and then selling the item to the highest bidder temporary business markets such as trade fairs energy markets = = = non - physical markets = = = media markets ( broadcast market ) : is a region where the population can receive the same ( or similar ) television and radio station offerings and may also include other types of media including newspapers and internet content internet markets ( electronic commerce ) : trading in products or services using computer networks, such as the internet artificial markets created by regulation to exchange rights for derivatives that have been designed to ameliorate externalities, such as pollution permits ( see carbon trading ) = = = financial markets = = = financial markets facilitate the exchange of liquid assets. most investors prefer investing in two markets : the stock markets, for the exchange of shares in corporations ( nyse, amex and the nasdaq are the most common stock markets in the united states ) the bond markets there are also : currency markets are used to trade one currency for another, and are often used for speculation on currency exchange rates the money market is the name for the global market for lending and borrowing futures markets, where contracts are exchanged regarding the future delivery of goods insurance markets debt markets = = = unauthorized and illegal markets = = = grey markets ( parallel markets ) : is the trade of a commodity through distribution channels which, while legal, are unofficial
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futures markets, where contracts are exchanged regarding the future delivery of goods insurance markets debt markets = = = unauthorized and illegal markets = = = grey markets ( parallel markets ) : is the trade of a commodity through distribution channels which, while legal, are unofficial, unauthorized, or unintended by the original manufacturer markets in illegal goods such as the market for illicit drugs, illegal arms, infringing products, cigarettes sold to minors or untaxed cigarettes ( in some jurisdictions ), or the private sale of unpasteurized goat milk = = mechanisms = = in economics, a market that runs under laissez - faire policies is called a free market : it is " free " from the government, in the sense that the government makes no attempt to intervene through taxes, subsidies, minimum wages, price ceilings and so on. however, market prices may be distorted by a seller or sellers with monopoly power, or a buyer with monopsony power. such price distortions can have an adverse effect on market participant's welfare and reduce the efficiency of market outcomes. the relative level of organization and negotiating power of buyers and sellers also markedly affects the functioning of the market. markets are a system and systems have structure. the structure of a well - functioning market is defined by the theory of perfect competition. well - functioning markets of the real world are never perfect, but basic structural characteristics can be approximated for real world markets, for example : many small buyers and sellers buyers and sellers have equal access to information products are comparable markets where price negotiations meet equilibrium, but the equilibrium is not efficient are said to experience market failure. market failures are often associated with time - inconsistent preferences, information asymmetries, non - perfectly competitive markets, principal β agent problems, externalities, or public goods. among the major negative externalities which can occur as a side effect of production and market exchange, are air pollution ( side - effect of manufacturing and logistics ) and environmental degradation ( side - effect of farming and urbanization ). there exists a popular thought, especially among economists, that free markets would have a structure of a perfect competition. the logic behind this thought is that market failure is thought to be caused by other exogenic systems, and after eliminating external influences or interventions, often referred to as " exogenic systems, " the markets were allowed to operate independently, adhering to the principles of free - market economics. this approach assumes that by removing regulatory barriers, subsidies, or other external controls, the market can function more efficiently. the underlying belief is
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##ogenic systems, " the markets were allowed to operate independently, adhering to the principles of free - market economics. this approach assumes that by removing regulatory barriers, subsidies, or other external controls, the market can function more efficiently. the underlying belief is that such " freed " markets, driven by the forces of supply and demand, can self - regulate and allocate resources optimally, thus preventing or minimizing occurrences of market failures. however, this perspective remains a topic of debate among economists and policymakers, as concepts like the world market return policy, along with issues such as monopolies, externalities, and information asymmetries, highlight the complexities of market dynamics.. for a market to be competitive, there must be more than a single buyer or seller. it has been suggested that two people may trade, but it takes at least three persons to have a market so that there is competition in at least one of its two sides. however, competitive markets β as understood in formal economic theory β rely on much larger numbers of both buyers and sellers. a market with a single seller and multiple buyers is a monopoly. a market with a single buyer and multiple sellers is a monopsony. these are " the polar opposites of perfect competition ". as an argument against such logic, there is a second view that suggests that the source of market failures is inside the market system itself, therefore the removal of other interfering systems would not result in markets with a structure of perfect competition. as an analogy, such an argument may suggest that capitalists do not want to enhance the structure of markets, just like a coach of a football team would influence the referees or would break the rules if he could while he is pursuing his target of winning the game. thus, according to this view, capitalists are not enhancing the balance of their team versus the team of consumer - workers, so the market system needs a " referee " from outside that balances the game. in this second framework, the role of a " referee " of the market system is usually to be given to a democratic government. = = research = = disciplines such as sociology, economic history, economic geography and marketing developed novel understandings of markets studying actual existing markets made up of persons interacting in diverse ways in contrast to an abstract and all - encompassing concepts of " the market ". the term " the market " is generally used in two ways : " the market " denotes the abstract mechanisms whereby supply and demand confront each other and deals are made ; in its place,
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an abstract and all - encompassing concepts of " the market ". the term " the market " is generally used in two ways : " the market " denotes the abstract mechanisms whereby supply and demand confront each other and deals are made ; in its place, reference to markets reflects ordinary experience and the places, processes and institutions in which exchanges occurs " the market " signifies an integrated, all - encompassing and cohesive capitalist world economy. = = = economics = = = = = = = political economy = = = = economics used to be called political economy, as adam smith defined it in the wealth of nations : political economy, considered as a branch of the science of a statesman or legislator, proposes two distinct objects ; first, to provide a plentiful revenue or subsistence for the people, or, more properly, to enable them to provide such a revenue or subsistence for themselves ; and, secondly, to supply the state or commonwealth with a revenue sufficient for the public services. it proposes to enrich both the people and the sovereign. the earliest works of political economy are usually attributed to united kingdom scholars adam smith, thomas malthus, and david ricardo, although they were preceded by the work of the french physiocrats, such as francois quesnay ( 1694 β 1774 ) and anne - robert - jacques turgot ( 1727 β 1781 ). smith describes how exchange of goods arose : " as it is by treaty, by barter, and by purchase, that we obtain from one another the greater part of those mutual good offices which we stand in need of, so it is this same trucking disposition which originally gives occasion to the division of labour. in a tribe of hunters or shepherds, a particular person makes bows and arrows, for example, with more readiness and dexterity than any other. he frequently exchanges them for cattle or for venison, with his companions ; and he finds at last that he can, in this manner, get more cattle and venison, than if he himself went to the field to catch them. from a regard to his own interest, therefore, the making of bows and arrows grows to be his chief business, and he becomes a sort of armourer. another excels in making the frames and covers of their little huts or moveable houses. he is accustomed to be of use in this way to his neighbours, who reward him in the same manner with cattle and with venison, till at last he finds it his interest to dedicate himself entirely to this employment, and to become
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. he is accustomed to be of use in this way to his neighbours, who reward him in the same manner with cattle and with venison, till at last he finds it his interest to dedicate himself entirely to this employment, and to become a sort of house - carpenter. in the same manner a third becomes a smith or a brazier ; a fourth, a tanner or dresser of hides or skins, the principal part of the clothing of savages. and thus the certainty of being able to exchange all that surplus part of the produce of his own labour, which is over and above his own consumption, for such parts of the produce of other men's labour as he may have occasion for, encourages every man to apply himself to a particular occupation, and to cultivate and bring to perfection whatever talent of genius he may possess for that particular species of business. " and explains how exchanged mediated by money came to dominate the market : " but when barter ceases, and money has become the common instrument of commerce, every particular commodity is more frequently exchanged for money than for any other commodity. the butcher seldom carries his beef or his mutton to the baker or the brewer, in order to exchange them for bread or for beer ; but he carries them to the market, where he exchanges them for money, and afterwards exchanges that money for bread and for beer. the quantity of money which he gets for them regulates, too, the quantity of bread and beer which he can afterwards purchase. it is more natural and obvious to him, therefore, to estimate their value by the quantity of money, the commodity for which he immediately exchanges them, than by that of bread and beer, the commodities for which he can exchange them only by the intervention of another commodity ; and rather to say that his butcher's meat is worth three - pence or fourpence a - pound, than that it is worth three or four pounds of bread, or three or four quarts of small beer. hence it comes to pass, that the exchangeable value of every commodity is more frequently estimated by the quantity of money, than by the quantity either of labour or of any other commodity which can be had in exchange for it. " = = = = microeconomics = = = = microeconomics ( from greek prefix mikro - meaning " small " and economics ) is a branch of economics that studies the behavior of individuals and small impacting organizations in making decisions on the allocation of limited resources ( see scarcity ). on the other hand,
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from greek prefix mikro - meaning " small " and economics ) is a branch of economics that studies the behavior of individuals and small impacting organizations in making decisions on the allocation of limited resources ( see scarcity ). on the other hand, macroeconomics ( from the greek prefix makro - meaning " large " and economics ) is a branch of economics dealing with the performance, structure, behavior and decision - making of an economy as a whole, rather than individual markets. = = = = = marginal revolution = = = = = the modern field of microeconomics arose as an effort of neoclassical economics school of thought to put economic ideas into mathematical mode. it began in the 19th century debates surrounding the works of antoine augustin cournot, william stanley jevons, carl menger and leon walras β this period is usually denominated as the marginal revolution. a recurring theme of these debates was the contrast between the labor theory of value and the subjective theory of value, the former being associated with classical economists such as adam smith, david ricardo and karl marx ( marx was a contemporary of the marginalists ). a labour theory of value can be understood as a theory that argues that economic value is determined by the amount of socially necessary labour time while a subjective theory of value derives economic value from subjective preferences, usually by specifying a utility function in accordance with utilitarian philosophy. in his principles of economics ( 1890 ), alfred marshall presented a possible solution to this problem, using the supply and demand model. marshall's idea of solving the controversy was that the demand curve could be derived by aggregating individual consumer demand curves, which were themselves based on the consumer problem of maximizing utility. the supply curve could be derived by superimposing a representative firm supply curves for the factors of production and then market equilibrium ( economic equivalent of mechanical equilibrium ) would be given by the intersection of demand and supply curves. he also introduced the notion of different market periods : mainly long run and short run. this set of ideas gave way to what economists call perfect competition β now found in the standard microeconomics texts, even though marshall himself was highly skeptical it could be used as general model of all markets. = = = = = market structure = = = = = opposed to the model of perfect competition, some models of imperfect competition were proposed : the monopoly model, already considered by marginalist economists, describes a profit maximizing capitalist facing a market demand curve with no competitors, who may practice price discrimination. oligopol
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to the model of perfect competition, some models of imperfect competition were proposed : the monopoly model, already considered by marginalist economists, describes a profit maximizing capitalist facing a market demand curve with no competitors, who may practice price discrimination. oligopoly is a market form in which a market or industry is dominated by a small number of sellers. the oldest model was the spring water duopoly of cournot ( 1838 ) in which equilibrium is determined by the duopolists reactions functions. it was criticized by harold hotelling for its instability, by joseph bertrand for lacking equilibrium for prices as independent variables. monopolistic competition is a type of imperfect competition such that many producers sell products that are differentiated from one another ( e. g., by branding or quality ) and hence are not perfect substitutes. in monopolistic competition, a firm takes the prices charged by its rivals as given and ignores the impact of its own prices on the prices of other firms. the " founding father " of the theory of monopolistic competition is edward hastings chamberlin, who wrote a pioneering book on the subject, theory of monopolistic competition ( 1933 ). joan robinson published a book called the economics of imperfect competition with a comparable theme of distinguishing perfect from imperfect competition. chamberlin defined monopolistic competition as " challenge to traditional viewpoint of economics that competition and monopoly are alternatives and that individual prices are to be explained in terms of one or the other ". he continues : " by contrast it is held that most economic situations are composite of both competition and monopoly, and that, wherever this is the case, a false view is given by neglecting either one of the two forces and regarding the situation as made up entirely of the other ". hotelling built a model of market located over a line with two sellers in each extreme of the line, in this case maximizing profit for both sellers leads to a stable equilibrium. from this model also follows that if a seller is to choose the location of his store so as to maximize his profit, he will place his store the closest to his competitor as " the sharper competition with his rival is offset by the greater number of buyers he has an advantage ". he also argues that clustering of stores is wasteful from the point of view of transportation costs and that public interest would dictate more spatial dispersion. william baumol provided in his 1977 paper the current formal definition of a natural monopoly where " an industry in which multifirm production is more costly than production by a monopoly ".
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and that public interest would dictate more spatial dispersion. william baumol provided in his 1977 paper the current formal definition of a natural monopoly where " an industry in which multifirm production is more costly than production by a monopoly ". baumol defined a contestable market in his 1982 paper as a market where " entry is absolutely free and exit absolutely costless ", freedom of entry in stigler sense : the incumbent has no cost discrimination against entrants. he states that a contestable market will never have an economic profit greater than zero when in equilibrium and the equilibrium will also be efficient. according to baumol, this equilibrium emerges endogenously due to the nature of contestable markets ; that is, the only industry structure that survives in the long run is the one which minimizes total costs. this is in contrast to the older theory of industry structure since not only is industry structure not exogenously given, but equilibrium is reached without an ad hoc hypothesis on the behavior of firms, say using reaction functions in a duopoly. he concludes the paper commenting that regulators that seek to impede entry and / or exit of firms would do better to not interfere if the market in question resembles a contestable market. = = = = = market failure = = = = = around the 1970s the study of market failures came into focus with the study of information asymmetry. in particular, three authors emerged from this period : akerlof, spence and stiglitz. akerlof considered the problem of bad quality cars driving good quality cars out of the market in his classic " the market for lemons " ( 1970 ) because of the presence of asymmetrical information between buyers and sellers. michael spence explained that signaling was fundamental in the labour market since employers cannot know beforehand which candidate is the most productive, a college degree becomes a signaling device that a firm uses to select new personnel. stiglitz provided some general conditions under which market equilibrium is not efficient : presence of externalities, imperfect information and incomplete markets. = = = = = state interference = = = = = gyorgy lukacs, a founder of western marxism wrote about the essence of commodity - structure :. before tackling the problem itself we must be quite clear in our minds that commodity fetishism is a specific problem of our age, the age of modern capitalism. commodity exchange and the corresponding subjective and objective commodity relations existed, as we know, when society was still very primitive. what is at issue here
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in our minds that commodity fetishism is a specific problem of our age, the age of modern capitalism. commodity exchange and the corresponding subjective and objective commodity relations existed, as we know, when society was still very primitive. what is at issue here, however, is the question : how far is commodity exchange together with its structural consequences able to influence the total outer and inner life of society? thus the extent to which such exchange is the dominant form of metabolic change in a society cannot simply be treated in quantitative terms β as would harmonize with the modern modes of thought already eroded by the reifying effects of the dominant commodity form. the distinction between a society where this form is dominant, permeating every expression of life, and a society where it only makes an episodic appearance is essentially one of quality. for depending on which is the case, all the subjective phenomena in the societies concerned are objectified in qualitatively different ways. human labour is abstracted and incorporated in commodities : objectively : is so far as the commodity form facilitates the equal exchange of qualitatively different things subjectively : human labour is both the common factor to which all commodities are reduced ( in the abstract ) and the principle governing the actual production of commodities ( in reality ) the ultimate problem for the thought of the bourgeoisie is the crisis : the qualitative existence of the'things'misunderstood as use - values become the decisive factor. the failure is characteristic of classical economics and bourgeoisie economics, inadequate at explaining the true movement of economic activity in toto. the state has a system of law corresponding to capitalist needs : bureaucracy, formal standardization of justice and civil service. c. b. macpherson identifies an underlying model of the market underlying anglo - american liberal democratic political economy and philosophy in the seventeenth and eighteenth centuries : persons are cast as self - interested individuals, who enter into contractual relations with other such individuals, concerning the exchange of goods or personal capacities cast as commodities, with the motive of maximizing pecuniary interest. the state and its governance systems are cast as outside of this framework. this model came to dominant economic thinking in the later nineteenth century, as so called liberal economists such as ricardo, mill, jevons, walras and later neo - classical economics shifted from reference to geographically located marketplaces to an abstract " market ". this tradition is continued in contemporary neoliberalism epitomised by the mont pelerin society which gathered frederick hayek, ludwig von mises, milton friedman and karl
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from reference to geographically located marketplaces to an abstract " market ". this tradition is continued in contemporary neoliberalism epitomised by the mont pelerin society which gathered frederick hayek, ludwig von mises, milton friedman and karl popper, where the market is held up as optimal for wealth creation and human freedom and the states'role imagined as minimal, reduced to that of upholding and keeping stable property rights, contract and money supply. according to david harvey, this allowed for boilerplate economic and institutional restructuring under structural adjustment and post - communist reconstruction. similar formalism occurs in a wide variety of social democratic and marxist discourses that situate political action as antagonistic to the market. a central theme of empirical analyses is the variation and proliferation of types of markets since the rise of capitalism and global scale economies. the regulation school stresses the ways in which developed capitalist countries have implemented varying degrees and types of environmental, economic and social regulation, taxation and public spending, fiscal policy and government provisioning of goods, all of which have transformed markets in uneven and geographical varied ways and created a variety of mixed economies. = = = = economic coordination = = = = drawing on concepts of institutional variance and path dependence, varieties of capitalism theorists ( such as peter hall and david soskice ) identify two dominant modes of economic ordering in the developed capitalist countries : coordinated market economies ( such as germany and japan ) based on relational or incomplete contracting, network monitoring based on the exchange of private information inside networks, and more reliance on collaborative, as opposed to competitive, relationships to build the competencies of the firm anglo - american liberal market economies : firms coordinate their activities primarily via hierarchies and competitive market arrangements. however, such approaches imply that the anglo - american liberal market economies in fact operate in a matter close to the abstract notion of " the market ". while anglo - american countries have seen increasing introduction of neo - liberal forms of economic ordering, this has not led to simple convergence, but rather a variety of hybrid institutional orderings. rather, a variety of new markets have emerged, such as for carbon trading or rights to pollute. in some cases, such as emerging markets for water in england and wales, different forms of neoliberalism have been tried : moving from the state hydraulic model associated with concepts of universal provision and public service to market environmentalism associated with pricing of environmental externalities to reduce environmental degradation and efficient allocation of water resources. in this case liberalization has multiple meanings : privatization : change of ownership from state
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state hydraulic model associated with concepts of universal provision and public service to market environmentalism associated with pricing of environmental externalities to reduce environmental degradation and efficient allocation of water resources. in this case liberalization has multiple meanings : privatization : change of ownership from state monopoly to private hands commercialization : pursuing efficiency, cost - benefit analysis and profit maximization by introducing prices in comparison with the bill system proportional to property value commodification : standardization, pricing to address water scarcity according to the dublin principles and the hague declaration in a period of fiscal and ideological crisis, state failure is seen as the catalyst for liberalization, however the failure in assuring water quality can be seen as a driver for economic and ecological reregulation ( in this case coming from the european union ). more broadly the idea of a water market failure can be seen as the explanation for state intervention, generating a natural monopoly of hydraulic infrastructure and the regulation of externalities such as water pollution. the situation however is not that simple, as the regulator may have the duty of introducing competition, which can be : direct competition or product competition surrogate competition competition for corporate control by mergers and takeovers procurement competition franchising introduction of metering can result in both restriction and increase of consumption with lrmc pricing being the regulator ( ofwat ) preferred methodology. = = = marketing = = = = = = = market distribution = = = = paul dulaney converse and fred m. jones wrote : market distribution includes those activities which create place, time, and possession utilities. to the economist, market distribution is therefore part of production because it deals with the creation of utilities, and " distribution " refers to the distribution of wealth among the members of society. the businessman, however, thinks of distribution as selling his goods and getting them into the hands of the consumer. to the businessman, " distribution " means marketing β selling and transportation. the methods of studying marketing are : functional approach : services or functions performed, what goods they are performed upon, what middlemen perform them commodity approach : what goods are marketed, what function are performed on them, what middlemen perform these functions institutional approach : what institutions, or middlemen, are engaged in distribution, what functions they perform, what good they handle businesses market their products / services to a specific segments of consumers : the defining factors of the markets are determined by demographics, interests and age / gender. a small market is a niche market, while a big market is a mass market. a form of expansion is to enter a new market and
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specific segments of consumers : the defining factors of the markets are determined by demographics, interests and age / gender. a small market is a niche market, while a big market is a mass market. a form of expansion is to enter a new market and sell / advertise to a different set of users. = = = = marketing management = = = = the marketing management school, evolved in the late 1950s and early 1960s, is fundamentally linked with the marketing mix framework, a business tool used in marketing and by marketers. in his paper " the concept of the marketing mix ", neil h. borden reconstructed the history of the term " marketing mix ". he started teaching the term after an associate, james culliton, described the role of the marketing manager in 1948 as a " mixer of ingredients " ; one who sometimes follows recipes prepared by others, sometimes prepares his own recipe as he goes along, sometimes adapts a recipe from immediately available ingredients, and at other times invents new ingredients no one else has tried. the functions of total marketing include advertising, personal selling, packaging, pricing, channeling and warehousing. borden also identified the market forces affecting marketing mix : consumer buying behavior trade's behavior ( wholesale and retailing ) competitors position and behavior : industry structure, product choice, oversupply, pricing and innovation governmental behavior : regulations borden concludes saying that marketing is more an art than a science. the marketer e. jerome mccarthy proposed a four ps classification ( product, price, promotion, place ) in 1960, which has since been used by marketers throughout the world. koichi shimizu proposed a 7cs compass model ( corporation, commodity, cost, communication, channel, consumer, circumstances ) to provide a more complete picture of the nature of marketing in 1981. robert f. lauterborn wrote about the four p's in 1990 when jerry mccarthy and phil kotler proposed their alliterative litany β product, price, place and promotion β the marketing world was very different. roaring out of world war ii with a cranked - up production system ready to feed a lust for better living, american business linked management science to the art of mass marketing and rocketed to the moon. in the days of " father knows best, " it all seemed so simple. the advertiser developed a product, priced it to make a profit, placed it on the retail shelf and promoted it to a pliant, even eager consumer. mass media simultaneously taught consumptive culture and
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" it all seemed so simple. the advertiser developed a product, priced it to make a profit, placed it on the retail shelf and promoted it to a pliant, even eager consumer. mass media simultaneously taught consumptive culture and provided advertisers with efficient access to an audience which would behave, dr. dichter assured us, perfectly predictably, given the proper stimulation. he instead advocated a four cs classification which is a more consumer - oriented version of the four ps that attempts to better fit the movement from mass marketing to niche marketing : consumer : do not focus on product, study consumer wants and needs cost : forget price, instead understand the consumer cost to satisfy that want or need, even driving time versus time spent with family matters communication : forget promotion, instead focus on communication and create dialogue convenience : forget place, instead think about convenience to buy, know each market subsegment = = = sociology = = = = = = = economic rationality = = = = max weber defines the measure of rational economic action as the : systematic distribution of utilities between present and future systematic distribution of utilities between various potential uses systematic production of utilities by manufacture or transportation by the owner of the means of production systematic acquisition by agreement of the powers of control and disposal over utilities, mainly by establishing corporate groups or by exchange opposition of interests is typically resolved by bargaining or by competitive biding : utilities, goods and labour are at the disposal of the individual without interference from others transportation can be seen as a part of the process of production it is indifferent whether the individual is prevented from using force to interfere in the controls of others by means of a legal order, convention, custom, self - interest or moral standards competition for the means of production may exist under various conditions anything which may be transferred between individuals by compensation may be an object of exchange conditions of exchange may be traditional, conventional ( exchange of gifts ) or rational ( motivated by profit or need ) regulations may threaten the source of supply money may classified as : coined money is called " free money " or " market money " when it is coined by the mint without limit of amount it is called " limited " money or " administrative money " if the issue of coinage if subject to a corporate group it is called regulated money if the kind and amount of coinage is subject to rules weber defines : market situation : all the opportunities of exchanging a good for money that are known by the participants marketability : degree of regularity that a good tends to be an object of exchange in the market market freedom
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amount of coinage is subject to rules weber defines : market situation : all the opportunities of exchanging a good for money that are known by the participants marketability : degree of regularity that a good tends to be an object of exchange in the market market freedom : degree of autonomy enjoyed by the participants in price determination and competition market regulation : restrictions on marketability and market freedom, done by tradition, convention, law, voluntary action weber defines " formal rationality of economic action " to designate the extent of quantitative calculation or accounting and " substantive rationality " as the degree a group of persons is or could be adequately provided with good by means of oriented course of social action. a prominent entry - point for challenging the market model's applicability concerns exchange transactions and the homo economicus assumption of self - interest maximization. as of 2012, a number of streams of economic sociological analysis of markets focus on the role of the social in transactions and on the ways transactions involve social networks and relations of trust, cooperation and other bonds. economic geographers in turn draw attention to the ways exchange transactions occur against the backdrop of institutional, social and geographic processes, including class relations, uneven development and historically contingent path - dependencies. pierre bourdieu has suggested the market model is becoming self - realizing in virtue of its wide acceptance in national and international institutions through the 1990s. = = = = abstraction, market agencement and framing = = = = michel callon traces the history of how the market as a place ( fairs, flea markets, fish markets ) became an abstract concept ( market for ideas, dating market, job market ) which he calls the interface market model. this abstraction proceeds in three layers : sellers, buyers, platform goods competition institutions the interface market model thus establishes that : agents and goods are distinguable a transfer is a communication of property rights competition develops between agents a transaction consists of monetary payments the limitations of this model are : they do not take into account the material composition of market activities they bracket out the constructive process of creating supply and demand, which leads to underestimating the crucial role played by bilateral transactions and the initiation of these transactions they create unrealism through the concepts of aggregated supply and demand and bring about difficulties in comprehending the actual mechanisms for establishing prices they create a total impasse on the complex processes that result in a separation between agents and goods the hypothesis that goods are platforms precludes us from recognizing they are processes a description of agents that underestimates their diversity, heterogeneit
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they create a total impasse on the complex processes that result in a separation between agents and goods the hypothesis that goods are platforms precludes us from recognizing they are processes a description of agents that underestimates their diversity, heterogeneity, and plasticity callon offer the market agencements ( heterogenous assemblage ) model as an alternative, its features being : competition is the struggle to establish bilateral transactions that are never identical innovation is fundamental to commercial activity goods are processes proliferating agents, plastic identities and networking market agencements function through framing, that is action is oriented to a strategic goal ( obtaining bilateral transactions ), for example market oriented passiva ( c ) tion : detaches the good and liberates it from all those who participated in its elaboration and profiling renders it apt to provoke courses of actions and to contribute to their realization ( that is, imbues it with uses ) ensures that its behavior is at least to a certain extent controllable and predictable organizes the attribution and transfer of property rights callon identifies the activities necessary for framing : rendering goods pass ( act ) ive activating agencies capable of evaluating and transforming these goods organizing their encounter ensuring the attachment of the goods to the agencies obtaining consent to pay setting a price and compelling payment β actions that combine and interweave with one another, with possible feedback loops and iterations = = = = embeddedness = = = = alfred marshall wrote : thus it is on the one side a study of wealth ; and on the other, and more important side, a part of the study of man. for man's character has been moulded by his every - day work, and the material resources which he thereby procures, more than by any other influence unless it be that of his religious ideals ; and the two great forming agencies of the world's history have been the religious and the economic. here and there the ardour of the military or the artistic spirit has been for a while predominant : but religious and economic influences have nowhere been displaced from the front rank even for a time ; and they have nearly always been more important than all others put together. religious motives are more intense than economic, but their direct action seldom extends over so large a part of life. for the business by which a person earns his livelihood generally fills his thoughts during by far the greater part of those hours in which his mind is at its best ; during them his character is being formed
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seldom extends over so large a part of life. for the business by which a person earns his livelihood generally fills his thoughts during by far the greater part of those hours in which his mind is at its best ; during them his character is being formed by the way in which he uses his faculties in his work, by the thoughts and the feelings which i \ t suggests, and by his relations to his associates in work, his employers or his employees. according to max weber the spirit of capitalism as preached by benjamin franklin is directly connected with utilitarianism, rationalism and protestantism. luther calling was not a monastic one but involves the fulfilments of obligations imposed by one's position in the world. the pursuit of money and earthly goods was not viewed positively by protestantism, the puritans however emphasized that god blessings, like in the book of job, applied also to material life. the limitation of consumption inevitably results in capital accumulation, therefore, for weber, the puritan's idea of the calling and ascetic conduct contributed to development of capitalism : saving is an ascetic activity. embeddedness expresses the idea that the economy is not autonomous but subordinated to politics, religion, and social relations. polanyi's use of the term suggests the now familiar idea that market transactions depend on trust, mutual understanding, and legal enforcement of contracts. michel callon's concept of framing provides a useful schema : each economic act or transaction occurs against, incorporates and also re - performs a geographically and cultural specific complex of social histories, institutional arrangements, rules and connections. these network relations are simultaneously bracketed, so that persons and transactions may be disentangled from thick social bonds. the character of calculability is imposed upon agents as they come to work in markets and are " formatted " as calculative agencies. market exchanges contain a history of struggle and contestation that produced actors predisposed to exchange under certain sets of rules. therefore, for challon, market transactions can never be disembedded from social and geographic relations and there is no sense to talking of degrees of embeddedness and disembeddeness. during the 20th century two common forms of critique were made : categories of 19th century social science such as class, modernity or the west were social constructions these categories were artificial and not universal these are common themes in interpretive social science, cultural studies and post - structuralism. however, as timothy mitchell points out this mode of thought tends to put aside the real,
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##ity or the west were social constructions these categories were artificial and not universal these are common themes in interpretive social science, cultural studies and post - structuralism. however, as timothy mitchell points out this mode of thought tends to put aside the real, the natural and nonhuman : the idea that a universal processes exists such as modernity, capitalism and globalization should not be taken for granted. an emerging theme is the interrelationship, inter - penetrability and variations of concepts of persons, commodities and modes of exchange under particular market formations. this is most pronounced in recent movement towards post - structuralist theorizing that draws on michel foucault and actor network theory and stress relational aspects of person - hood, and dependence and integration into networks and practical systems. commodity network approaches further both deconstruct and show alternatives to the market models concept of commodities. = = = = social systems theory = = = = in social systems theory ( cf. niklas luhmann ), markets are also conceptualized as inner environments of the economy. as horizon of all potential investment decisions the market represents the environment of the actually realized investment decisions. however, such inner environments can also be observed in further function systems of society like in political, scientific, religious or mass media systems. = = = economic geography = = = wilhelm launhardt, a location theorist, wrote : the conditions governing the distribution and settling of the population over any area are dependent on the nature of its economic activity : and when this activity is engaged in the cultivation of the surface of the ground and in the husbandry of land and wood and on many kinds of handicrafts and small manufactures this distribution is to be assumed as uniform over the area ; although, as a matter of fact, the population usually lives collected together in small hamlets, and the number of the inhabitants per unit of area, or density of population, varies according to the local conditions. another part of the population, namely that which is engaged in wholesale commerce, the various professions of art and science, and that which consists of merchants and officials, lives collected in towns. transportation can be carried either by stone - paved roads or railways, the former not being fully developed by private capital alone. a widespread trend in economic history and sociology is skeptical of the idea that it is possible to develop a theory to capture an essence or unifying thread to markets. for economic geographers, reference to regional, local, or commodity specific markets can serve to undermine assumptions of global integration and highlight
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is skeptical of the idea that it is possible to develop a theory to capture an essence or unifying thread to markets. for economic geographers, reference to regional, local, or commodity specific markets can serve to undermine assumptions of global integration and highlight geographic variations in the structures, institutions, histories, path dependencies, forms of interaction and modes of self - understanding of agents in different spheres of market exchange. reference to actual markets can show capitalism not as a totalizing force or completely encompassing mode of economic activity, but rather as " a set of economic practices scattered over a landscape, rather than a systemic concentration of power ". problematic for market formalism is the relationship between formal capitalist economic processes and a variety of alternative forms, ranging from semi - feudal and peasant economies widely operative in many developing economies, to informal markets, barter systems, worker cooperatives, or illegal trades that occur in most developed countries. practices of incorporation of non - western peoples into global markets in the nineteenth and twentieth centuries did not merely result in the quashing of former social economic institutions. rather, various modes of articulation arose between transformed and hybridized local traditions and social practices and the emergent world economy. by their liberal nature, so called capitalist markets have almost always included a wide range of geographically situated economic practices that do not follow the market model. economies are thus hybrids of market and non - market elements. helpful here is j. k. gibson - graham's complex topology of the diversity of contemporary market economies describing different types of transactions, labour and economic agents. transactions can occur in black markets ( such as for marijuana ) or be artificially protected ( such as for patents ). they can cover the sale of public goods under privatization schemes to co - operative exchanges and occur under varying degrees of monopoly power and state regulation. likewise, there are a wide variety of economic agents, which engage in different types of transactions on different terms : one cannot assume the practices of a religious kindergarten, multinational corporation, state enterprise, or community - based cooperative can be subsumed under the same logic of calculability. this emphasis on proliferation can also be contrasted with continuing scholarly attempts to show underlying cohesive and structural similarities to different markets. gibson - graham thus read a variety of alternative markets for fair trade and organic foods or those using local exchange trading system as not only contributing to proliferation, but also forging new modes of ethical exchange and economic subjectivities. = = = anthropology = = = economic anthropology is a scholarly field that attempts to explain human economic behavior
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foods or those using local exchange trading system as not only contributing to proliferation, but also forging new modes of ethical exchange and economic subjectivities. = = = anthropology = = = economic anthropology is a scholarly field that attempts to explain human economic behavior in its widest historic, geographic and cultural scope. its origins as a sub - field of anthropology begin with the polish β british founder of anthropology, bronisΕaw malinowski, and his french compatriot, marcel mauss, on the nature of gift - giving exchange ( or reciprocity ) as an alternative to market exchange. studies in economic anthropology for the most part are focused on exchange but they a complex relationship with the discipline of economics, of which it is highly critical : for example trobianders described by malinowski deviate from rational self - interested individual. bronisΕaw malinowski's path - breaking work, argonauts of the western pacific ( 1922 ), addressed the question " why would men risk life and limb to travel across huge expanses of dangerous ocean to give away what appear to be worthless trinkets? ". he begins by describing trade in the south sea : the coastal populations of the south sea islands, with very few exceptions, are, or were before their extinction, expert navigators and traders. several of them had evolved excellent types of large sea - going canoes, and used to embark in them on distant trade expeditions or raids of war and conquest. the papuo - melanesians, who inhabit the coast and the outlying islands of new guinea, are no exception to this rule. in general they are daring sailors, industrious manufacturers, and keen traders. the manufacturing centres of important articles, such as pottery, stone implements, canoes, fine baskets, valued ornaments, are localised in several places, according to the skill of the inhabitants, their inherited tribal tradition, and special facilities offered by the district ; thence they are traded over wide areas, sometimes travelling more than hundreds of miles. definite forms of exchange along definite trade routes are to be found established between the various tribes. a most remarkable form of intertribal trade is that obtaining between the motu of port moresby and the tribes of the papuan gulf. the motu sail for hundreds of miles in heavy, unwieldy canoes, called lakatoi, which are provided with the characteristic crab - claw sails. they bring pottery and shell ornaments, in olden days, stone blades, to gulf papuans,
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for hundreds of miles in heavy, unwieldy canoes, called lakatoi, which are provided with the characteristic crab - claw sails. they bring pottery and shell ornaments, in olden days, stone blades, to gulf papuans, from whom they obtain in exchange sago and the heavy dug - outs, which are used afterwards by the motu for the construction of their lakatoi canoes. the economic situation can vary considerably depending on the tribes and islands : for example the gumawana villagers are known as efficient sailors and for their skill in pottery, they are, however, island monopolists keeping the trade in their own hands without improving it. in a series of three expeditions, malinowski carefully traced the network of exchanges of bracelets and necklaces across the trobriand islands and established that they were part of a system of inter - tribal exchange : it is known as the kula ring, a closed circuit in which necklaces of red shells go in a clockwise motion and bracelets of white shell go in anticlockwise motion. malinowski goes on to explain : thus in the introduction we called the kula a " form of trade, " and we ranged it alongside other systems of barter. this is quite correct, if we give the word " trade " a sufficiently wide interpretation, and mean by it any exchange of goods. but the word " trade " is used in current ethnography and economic literature with so many different implications that a whole lot of misleading, preconceived ideas have to be brushed aside in order to grasp the facts correctly. thus the aprioric current notion of primitive trade would be that of an exchange of indispensable or useful articles, done without much ceremony or regulation, under stress of dearth or need, in spasmodic, irregular intervals β and this done either by direct barter, everyone looking out sharply not to be done out of his due, or, if the savages were too timid and distrustful to face one another, by some customary arrangement, securing by means of heavy penalties compliance in the obligations incurred or imposed. * waiving for the present the question how far this conception is valid or not in general β in my opinion it is quite misleading β we have to realise clearly that the kula contradicts in almost every point the above definition of " savage trade. " it shows to us primitive exchange in an entirely different light. the kula is not a surreptitious and precar
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have to realise clearly that the kula contradicts in almost every point the above definition of " savage trade. " it shows to us primitive exchange in an entirely different light. the kula is not a surreptitious and precarious form of exchange. it is, quite on the contrary, rooted in myth, backed by traditional law, and surrounded with magical rites. all its main transactions are public and ceremonial, and carried out according to definite rules. it is not done on the spur of the moment, but happens periodically, at dates settled in advance, and it is carried on along definite trade routes, which must lead to fixed trysting places. sociologically, though transacted between tribes differing in language, culture, and probably even in race, it is based on a fixed and permanent status, on a partnership which binds into couples some thousands of individuals. this partnership is a lifelong relationship, it implies various mutual duties and privileges, and constitutes a type of inter - tribal relationship on an enormous scale. as to the economic mechanism of the transactions, this is based on a specific form of credit, which implies a high degree of mutual trust and commercial honour β and this refers also to the subsidiary, minor trade, which accompanies the kula proper. finally, the kula is not done under stress of any need, since its main aim is to exchange articles which are of no practical use. in the 1920s and later, malinowski's study became the subject of debate with the french anthropologist, marcel mauss, author of the gift ( essai sur le don, 1925 ). malinowski emphasized the exchange of goods between individuals and their non - altruistic motives for giving : they expected a return of equal or greater value ( colloquially referred to as " indian giving " ). in other words, reciprocity is an implicit part of gifting as no " free gift " is given without expectation of reciprocity. in contrast, mauss has emphasized that the gifts were not between individuals, but between representatives of larger collectivities. he stated that this exchange system was clearly linked to political authority. he argued these gifts were a " total prestation " as they were not simple, alienable commodities to be bought and sold, but like the " crown jewels " embodied the reputation, history and sense of identity of a " corporate kin group ", such as a line of kings. given the stakes, mauss asked " why anyone would give them away? " and his answer was
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like the " crown jewels " embodied the reputation, history and sense of identity of a " corporate kin group ", such as a line of kings. given the stakes, mauss asked " why anyone would give them away? " and his answer was an enigmatic concept, " the spirit of the gift ". a good part of the confusion ( and resulting debate ) was due to a bad translation. mauss appeared to be arguing that a return gift is given to keep the very relationship between givers alive ; a failure to return a gift ends the relationship ; and the promise of any future gifts. based on an improved translate, jonathan parry has demonstrated that mauss was arguing that the concept of a " pure gift " given altruistically only emerges in societies with a well - developed market ideology. rather than emphasize how particular kinds of objects are either gifts or commodities to be traded in restricted spheres of exchange, arjun appadurai and others began to look at how objects flowed between these spheres of exchange. they shifted attention away from the character of the human relationships formed through exchange and placed it on " the social life of things " instead. they examined the strategies by which an object could be " singularized " ( made unique, special, one - of - a - kind ) and so withdrawn from the market. a marriage ceremony that transforms a purchased ring into an irreplaceable family heirloom is one example whereas the heirloom, in turn, makes a perfect gift. = = = mathematical modeling = = = although arithmetic has been used since the beginning of civilization to set prices, it was not until the 19th century that data was systematically collected and more advanced mathematical tools began to be used to study markets in the form of social statistics. business intelligence is also dated to the 19th century, but it was with the rise of the computer that business analytics exploded. more recent techniques involve data mining and marketing engineering. = = = = size parameters = = = = market size can be given in terms of the number of buyers and sellers in a particular market or in terms of the total exchange of money in the market, generally annually ( per year ). when given in terms of money, market size is often termed " market value ", but in a sense distinct from market value of individual products. for one and the same goods, there may be different ( and generally increasing ) market values at the production level, the wholesale level and the retail level. for example, the value of the global illicit drug market for the year 2003 was
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individual products. for one and the same goods, there may be different ( and generally increasing ) market values at the production level, the wholesale level and the retail level. for example, the value of the global illicit drug market for the year 2003 was estimated by the united nations to be us $ 13 billion at the production level, $ 94 billion at the wholesale level ( taking seizures into account ) and us $ 322 billion at the retail level ( based on retail prices and taking seizures and other losses into account ). = = see also = = = = references = = = = further reading = = pindyck, robert s. and daniel l. rubinfeld, microeconomics, prentice hall 2012. frank, robert h., microeconomics and behavior, 6th ed., mcgraw - hill / irwin 2006. kotler, p. and keller, k. l., marketing management, prentice hall 2011. baker, michael j. and michael saren, marketing theory : a student text, sage 2010. online. aspers, patrik, markets, polity press 2011. online. bauer, leonard and herbert matis ( 1988 ) from moral to political economy : the genesis of social sciences, history of european ideas 9 ( 2 ), 125 β 143. nathaus, klaus and david gilgen ( eds. ), change of markets and market societies : concepts and case studies. historical social research 36 ( 3 ), special issue, 2011.
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clasp - knife response is a golgi tendon reflex with a rapid decrease in resistance when attempting to flex a joint, usually during a neurological examination. it is one of the characteristic responses of an upper motor neuron lesion. it gets its name from the resemblance between the motion of the limb and the sudden closing of a claspknife after sufficient pressure is applied. = = cause = = when a joint is passively flexed, the resisting force comes from the stretch reflex ( or sometimes called tendon reflex ) resulting from the extensor muscle being stretched. in upper motor neuron lesions, muscle tonus may increase and resistance of muscle to stretch increases. however, if sufficient force is applied, limb resistance suddenly decreases, presumably mediated by the golgi tendon reflex ( also call autogenic inhibition ). = = mechanism = = this reflex is observed in patients with upper motor neuron lesions. it was frequently attributed to the action of the golgi tendon organ, likely because of early studies showing that tendon organs are activated by strong muscle stretch and inhibit motor neurons of the stretched muscle. it was thought that this was a protective reflex, preventing application of so much force that muscles become damaged. more recent work strongly suggests that tendon organs are not involved in the clasp knife reflex, but that other sensory receptors in muscles are responsible. = = example = = passive flexion of elbow meets immediate resistance due to stretch reflex in the triceps muscle. further stretch activates inverse stretch reflex. the resistance to flexion suddenly collapses, and the elbow flexes. continued passive flexion stretches the muscle and the sequence may be repeated. as the muscle tone increases, resistance against flexion of the limb increases as well. however, when flexion is continued, further stretching of the triceps muscle activates an inverse stretch reflex that relaxes the muscle due to autogenic inhibition. = = see also = = hypertonia = = references = = = = external links = = lib. mcg. edu
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in chemistry, tetrahydroxozincate or tetrahydroxidozincate is a divalent anion ( negative ion ) with formula zn ( oh ) 2β4, with a central zinc atom in the + 2 or ( ii ) valence state coordinated to four hydroxide groups. it has sp3 hybridization. it is the most common of the zincate anions, and is often called just zincate. these names are also used for the salts containing that anion, such as sodium zincate na2zn ( oh ) 4 and calcium zincate cazn ( oh ) 4 Β· 2h2o zincate salts can be obtained by reaction of zinc oxide ( zno ) or zinc hydroxide ( zn ( oh ) 2 ) and a strong base like sodium hydroxide. it is now generally accepted that the resulting solutions contain the tetrahydroxozincate ion. earlier raman studies had been interpreted as indicating the existence of linear zno2β2 ions. = = related anions and salts = = the name " zincate " may also refer to a polymeric anion with formula approaching [ zn ( oh ) β3 ] n, which forms salts such as nazn ( oh ) 3 Β· h2o, or to mixed oxides of zinc and less electronegative elements, such as na2zno2. = = see also = = tetrachlorozincate or tetrachloridozincate, zncl2β4 tetranitratozincate, zn ( no3 ) 2β4 = = references = =
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deoxyribonucleic acid ( ; dna ) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. the polymer carries genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses. dna and ribonucleic acid ( rna ) are nucleic acids. alongside proteins, lipids and complex carbohydrates ( polysaccharides ), nucleic acids are one of the four major types of macromolecules that are essential for all known forms of life. the two dna strands are known as polynucleotides as they are composed of simpler monomeric units called nucleotides. each nucleotide is composed of one of four nitrogen - containing nucleobases ( cytosine [ c ], guanine [ g ], adenine [ a ] or thymine [ t ] ), a sugar called deoxyribose, and a phosphate group. the nucleotides are joined to one another in a chain by covalent bonds ( known as the phosphodiester linkage ) between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar - phosphate backbone. the nitrogenous bases of the two separate polynucleotide strands are bound together, according to base pairing rules ( a with t and c with g ), with hydrogen bonds to make double - stranded dna. the complementary nitrogenous bases are divided into two groups, the single - ringed pyrimidines and the double - ringed purines. in dna, the pyrimidines are thymine and cytosine ; the purines are adenine and guanine. both strands of double - stranded dna store the same biological information. this information is replicated when the two strands separate. a large part of dna ( more than 98 % for humans ) is non - coding, meaning that these sections do not serve as patterns for protein sequences. the two strands of dna run in opposite directions to each other and are thus antiparallel. attached to each sugar is one of four types of nucleobases ( or bases ). it is the sequence of these four nucleobases along the backbone that encodes genetic information. rna strands are created using dna strands as a template in a process called transcription, where dna bases are exchanged for their corresponding bases except in the case of thymine ( t
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these four nucleobases along the backbone that encodes genetic information. rna strands are created using dna strands as a template in a process called transcription, where dna bases are exchanged for their corresponding bases except in the case of thymine ( t ), for which rna substitutes uracil ( u ). under the genetic code, these rna strands specify the sequence of amino acids within proteins in a process called translation. within eukaryotic cells, dna is organized into long structures called chromosomes. before typical cell division, these chromosomes are duplicated in the process of dna replication, providing a complete set of chromosomes for each daughter cell. eukaryotic organisms ( animals, plants, fungi and protists ) store most of their dna inside the cell nucleus as nuclear dna, and some in the mitochondria as mitochondrial dna or in chloroplasts as chloroplast dna. in contrast, prokaryotes ( bacteria and archaea ) store their dna only in the cytoplasm, in circular chromosomes. within eukaryotic chromosomes, chromatin proteins, such as histones, compact and organize dna. these compacting structures guide the interactions between dna and other proteins, helping control which parts of the dna are transcribed. = = properties = = dna is a long polymer made from repeating units called nucleotides. the structure of dna is dynamic along its length, being capable of coiling into tight loops and other shapes. in all species it is composed of two helical chains, bound to each other by hydrogen bonds. both chains are coiled around the same axis, and have the same pitch of 34 angstroms ( 3. 4 nm ). the pair of chains have a radius of 10 a ( 1. 0 nm ). according to another study, when measured in a different solution, the dna chain measured 22 β 26 a ( 2. 2 β 2. 6 nm ) wide, and one nucleotide unit measured 3. 3 a ( 0. 33 nm ) long. the buoyant density of most dna is 1. 7g / cm3. dna does not usually exist as a single strand, but instead as a pair of strands that are held tightly together. these two long strands coil around each other, in the shape of a double helix. the nucleotide contains both a segment of the backbone of the molecule ( which holds the chain together ) and a nucleobase ( which interacts with the other dna strand in the helix ).
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, in the shape of a double helix. the nucleotide contains both a segment of the backbone of the molecule ( which holds the chain together ) and a nucleobase ( which interacts with the other dna strand in the helix ). a nucleobase linked to a sugar is called a nucleoside, and a base linked to a sugar and to one or more phosphate groups is called a nucleotide. a biopolymer comprising multiple linked nucleotides ( as in dna ) is called a polynucleotide. the backbone of the dna strand is made from alternating phosphate and sugar groups. the sugar in dna is 2 - deoxyribose, which is a pentose ( five - carbon ) sugar. the sugars are joined by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings. these are known as the 3 β² - end ( three prime end ), and 5 β² - end ( five prime end ) carbons, the prime symbol being used to distinguish these carbon atoms from those of the base to which the deoxyribose forms a glycosidic bond. therefore, any dna strand normally has one end at which there is a phosphate group attached to the 5 β² carbon of a ribose ( the 5 β² phosphoryl ) and another end at which there is a free hydroxyl group attached to the 3 β² carbon of a ribose ( the 3 β² hydroxyl ). the orientation of the 3 β² and 5 β² carbons along the sugar - phosphate backbone confers directionality ( sometimes called polarity ) to each dna strand. in a nucleic acid double helix, the direction of the nucleotides in one strand is opposite to their direction in the other strand : the strands are antiparallel. the asymmetric ends of dna strands are said to have a directionality of five prime end ( 5 β² ), and three prime end ( 3 β² ), with the 5 β² end having a terminal phosphate group and the 3 β² end a terminal hydroxyl group. one major difference between dna and rna is the sugar, with the 2 - deoxyribose in dna being replaced by the related pentose sugar ribose in rna. the dna double helix is stabilized primarily by two forces : hydrogen bonds between nucleotides and base - stacking interactions among aromatic nucleobases. the four bases found in dna are adenine ( a )
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sugar ribose in rna. the dna double helix is stabilized primarily by two forces : hydrogen bonds between nucleotides and base - stacking interactions among aromatic nucleobases. the four bases found in dna are adenine ( a ), cytosine ( c ), guanine ( g ) and thymine ( t ). these four bases are attached to the sugar - phosphate to form the complete nucleotide, as shown for adenosine monophosphate. adenine pairs with thymine and guanine pairs with cytosine, forming a - t and g - c base pairs. = = = nucleobase classification = = = the nucleobases are classified into two types : the purines, a and g, which are fused five - and six - membered heterocyclic compounds, and the pyrimidines, the six - membered rings c and t. a fifth pyrimidine nucleobase, uracil ( u ), usually takes the place of thymine in rna and differs from thymine by lacking a methyl group on its ring. in addition to rna and dna, many artificial nucleic acid analogues have been created to study the properties of nucleic acids, or for use in biotechnology. = = = non - canonical bases = = = modified bases occur in dna. the first of these recognized was 5 - methylcytosine, which was found in the genome of mycobacterium tuberculosis in 1925. the reason for the presence of these noncanonical bases in bacterial viruses ( bacteriophages ) is to avoid the restriction enzymes present in bacteria. this enzyme system acts at least in part as a molecular immune system protecting bacteria from infection by viruses. modifications of the bases cytosine and adenine, the more common and modified dna bases, play vital roles in the epigenetic control of gene expression in plants and animals. a number of noncanonical bases are known to occur in dna. most of these are modifications of the canonical bases plus uracil. modified adenine n6 - carbamoyl - methyladenine n6 - methyadenine modified guanine 7 - deazaguanine 7 - methylguanine modified cytosine n4 - methylcytosine 5 - carboxylcytosine 5 - formylcytosine 5 - glycosylhydroxymethylcytosine 5 - hydroxycytosine 5 -
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##nine modified cytosine n4 - methylcytosine 5 - carboxylcytosine 5 - formylcytosine 5 - glycosylhydroxymethylcytosine 5 - hydroxycytosine 5 - methylcytosine modified thymidine Ξ± - glutamythymidine Ξ± - putrescinylthymine uracil and modifications base j uracil 5 - dihydroxypentauracil 5 - hydroxymethyldeoxyuracil others deoxyarchaeosine 2, 6 - diaminopurine ( 2 - aminoadenine ) = = = grooves = = = twin helical strands form the dna backbone. another double helix may be found tracing the spaces, or grooves, between the strands. these voids are adjacent to the base pairs and may provide a binding site. as the strands are not symmetrically located with respect to each other, the grooves are unequally sized. the major groove is 22 angstroms ( 2. 2 nm ) wide, while the minor groove is 12 a ( 1. 2 nm ) in width. due to the larger width of the major groove, the edges of the bases are more accessible in the major groove than in the minor groove. as a result, proteins such as transcription factors that can bind to specific sequences in double - stranded dna usually make contact with the sides of the bases exposed in the major groove. this situation varies in unusual conformations of dna within the cell ( see below ), but the major and minor grooves are always named to reflect the differences in width that would be seen if the dna was twisted back into the ordinary b form. = = = base pairing = = = in a dna double helix, each type of nucleobase on one strand bonds with just one type of nucleobase on the other strand. this is called complementary base pairing. purines form hydrogen bonds to pyrimidines, with adenine bonding only to thymine in two hydrogen bonds, and cytosine bonding only to guanine in three hydrogen bonds. this arrangement of two nucleotides binding together across the double helix ( from six - carbon ring to six - carbon ring ) is called a watson - crick base pair. dna with high gc - content is more stable than dna with low gc - content. a hoogsteen base pair ( hydrogen bonding the 6 - carbon ring to the 5 - carbon ring ) is a
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watson - crick base pair. dna with high gc - content is more stable than dna with low gc - content. a hoogsteen base pair ( hydrogen bonding the 6 - carbon ring to the 5 - carbon ring ) is a rare variation of base - pairing. as hydrogen bonds are not covalent, they can be broken and rejoined relatively easily. the two strands of dna in a double helix can thus be pulled apart like a zipper, either by a mechanical force or high temperature. as a result of this base pair complementarity, all the information in the double - stranded sequence of a dna helix is duplicated on each strand, which is vital in dna replication. this reversible and specific interaction between complementary base pairs is critical for all the functions of dna in organisms. = = = = ssdna vs. dsdna = = = = most dna molecules are actually two polymer strands, bound together in a helical fashion by noncovalent bonds ; this double - stranded ( dsdna ) structure is maintained largely by the intrastrand base stacking interactions, which are strongest for g, c stacks. the two strands can come apart β a process known as melting β to form two single - stranded dna ( ssdna ) molecules. melting occurs at high temperatures, low salt and high ph ( low ph also melts dna, but since dna is unstable due to acid depurination, low ph is rarely used ). the stability of the dsdna form depends not only on the gc - content ( % g, c basepairs ) but also on sequence ( since stacking is sequence specific ) and also length ( longer molecules are more stable ). the stability can be measured in various ways ; a common way is the melting temperature ( also called tm value ), which is the temperature at which 50 % of the double - strand molecules are converted to single - strand molecules ; melting temperature is dependent on ionic strength and the concentration of dna. as a result, it is both the percentage of gc base pairs and the overall length of a dna double helix that determines the strength of the association between the two strands of dna. long dna helices with a high gc - content have more strongly interacting strands, while short helices with high at content have more weakly interacting strands. in biology, parts of the dna double helix that need to separate easily, such as the tataat pribnow box in some promoters, tend to have a high at content, making the strands easier to pull apart.
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have more weakly interacting strands. in biology, parts of the dna double helix that need to separate easily, such as the tataat pribnow box in some promoters, tend to have a high at content, making the strands easier to pull apart. in the laboratory, the strength of this interaction can be measured by finding the melting temperature tm necessary to break half of the hydrogen bonds. when all the base pairs in a dna double helix melt, the strands separate and exist in solution as two entirely independent molecules. these single - stranded dna molecules have no single common shape, but some conformations are more stable than others. = = = amount = = = in humans, the total female diploid nuclear genome per cell extends for 6. 37 gigabase pairs ( gbp ), is 208. 23 cm long and weighs 6. 51 picograms ( pg ). male values are 6. 27 gbp, 205. 00 cm, 6. 41 pg. each dna polymer can contain hundreds of millions of nucleotides, such as in chromosome 1. chromosome 1 is the largest human chromosome with approximately 220 million base pairs, and would be 85 mm long if straightened. in eukaryotes, in addition to nuclear dna, there is also mitochondrial dna ( mtdna ) which encodes certain proteins used by the mitochondria. the mtdna is usually relatively small in comparison to the nuclear dna. for example, the human mitochondrial dna forms closed circular molecules, each of which contains 16, 569 dna base pairs, with each such molecule normally containing a full set of the mitochondrial genes. each human mitochondrion contains, on average, approximately 5 such mtdna molecules. each human cell contains approximately 100 mitochondria, giving a total number of mtdna molecules per human cell of approximately 500. however, the amount of mitochondria per cell also varies by cell type, and an egg cell can contain 100, 000 mitochondria, corresponding to up to 1, 500, 000 copies of the mitochondrial genome ( constituting up to 90 % of the dna of the cell ). = = = sense and antisense = = = a dna sequence is called a " sense " sequence if it is the same as that of a messenger rna copy that is translated into protein. the sequence on the opposite strand is called the " antisense " sequence. both sense and antisense sequences can exist on different parts of the same strand of dna ( i. e. both strands can contain both
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that is translated into protein. the sequence on the opposite strand is called the " antisense " sequence. both sense and antisense sequences can exist on different parts of the same strand of dna ( i. e. both strands can contain both sense and antisense sequences ). in both prokaryotes and eukaryotes, antisense rna sequences are produced, but the functions of these rnas are not entirely clear. one proposal is that antisense rnas are involved in regulating gene expression through rna - rna base pairing. a few dna sequences in prokaryotes and eukaryotes, and more in plasmids and viruses, blur the distinction between sense and antisense strands by having overlapping genes. in these cases, some dna sequences do double duty, encoding one protein when read along one strand, and a second protein when read in the opposite direction along the other strand. in bacteria, this overlap may be involved in the regulation of gene transcription, while in viruses, overlapping genes increase the amount of information that can be encoded within the small viral genome. = = = supercoiling = = = dna can be twisted like a rope in a process called dna supercoiling. with dna in its " relaxed " state, a strand usually circles the axis of the double helix once every 10. 4 base pairs, but if the dna is twisted the strands become more tightly or more loosely wound. if the dna is twisted in the direction of the helix, this is positive supercoiling, and the bases are held more tightly together. if they are twisted in the opposite direction, this is negative supercoiling, and the bases come apart more easily. in nature, most dna has slight negative supercoiling that is introduced by enzymes called topoisomerases. these enzymes are also needed to relieve the twisting stresses introduced into dna strands during processes such as transcription and dna replication. = = = alternative dna structures = = = dna exists in many possible conformations that include a - dna, b - dna, and z - dna forms, although only b - dna and z - dna have been directly observed in functional organisms. the conformation that dna adopts depends on the hydration level, dna sequence, the amount and direction of supercoiling, chemical modifications of the bases, the type and concentration of metal ions, and the presence of polyamines in solution. the first published reports of a - dna x - ray diffraction patterns β and also b - dna β used analyses
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##iling, chemical modifications of the bases, the type and concentration of metal ions, and the presence of polyamines in solution. the first published reports of a - dna x - ray diffraction patterns β and also b - dna β used analyses based on patterson functions that provided only a limited amount of structural information for oriented fibers of dna. an alternative analysis was proposed by wilkins et al. in 1953 for the in vivo b - dna x - ray diffraction - scattering patterns of highly hydrated dna fibers in terms of squares of bessel functions. in the same journal, james watson and francis crick presented their molecular modeling analysis of the dna x - ray diffraction patterns to suggest that the structure was a double helix. although the b - dna form is most common under the conditions found in cells, it is not a well - defined conformation but a family of related dna conformations that occur at the high hydration levels present in cells. their corresponding x - ray diffraction and scattering patterns are characteristic of molecular paracrystals with a significant degree of disorder. compared to b - dna, the a - dna form is a wider right - handed spiral, with a shallow, wide minor groove and a narrower, deeper major groove. the a form occurs under non - physiological conditions in partly dehydrated samples of dna, while in the cell it may be produced in hybrid pairings of dna and rna strands, and in enzyme - dna complexes. segments of dna where the bases have been chemically modified by methylation may undergo a larger change in conformation and adopt the z form. here, the strands turn about the helical axis in a left - handed spiral, the opposite of the more common b form. these unusual structures can be recognized by specific z - dna binding proteins and may be involved in the regulation of transcription. = = = alternative dna chemistry = = = for many years, exobiologists have proposed the existence of a shadow biosphere, a postulated microbial biosphere of earth that uses radically different biochemical and molecular processes than currently known life. one of the proposals was the existence of lifeforms that use arsenic instead of phosphorus in dna. a report in 2010 of the possibility in the bacterium gfaj - 1 was announced, though the research was disputed, and evidence suggests the bacterium actively prevents the incorporation of arsenic into the dna backbone and other biomolecules. = = = quadruplex structures = = = at the ends of the linear chromosomes are specialized
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, though the research was disputed, and evidence suggests the bacterium actively prevents the incorporation of arsenic into the dna backbone and other biomolecules. = = = quadruplex structures = = = at the ends of the linear chromosomes are specialized regions of dna called telomeres. the main function of these regions is to allow the cell to replicate chromosome ends using the enzyme telomerase, as the enzymes that normally replicate dna cannot copy the extreme 3 β² ends of chromosomes. these specialized chromosome caps also help protect the dna ends, and stop the dna repair systems in the cell from treating them as damage to be corrected. in human cells, telomeres are usually lengths of single - stranded dna containing several thousand repeats of a simple ttaggg sequence. these guanine - rich sequences may stabilize chromosome ends by forming structures of stacked sets of four - base units, rather than the usual base pairs found in other dna molecules. here, four guanine bases, known as a guanine tetrad, form a flat plate. these flat four - base units then stack on top of each other to form a stable g - quadruplex structure. these structures are stabilized by hydrogen bonding between the edges of the bases and chelation of a metal ion in the centre of each four - base unit. other structures can also be formed, with the central set of four bases coming from either a single strand folded around the bases, or several different parallel strands, each contributing one base to the central structure. in addition to these stacked structures, telomeres also form large loop structures called telomere loops, or t - loops. here, the single - stranded dna curls around in a long circle stabilized by telomere - binding proteins. at the very end of the t - loop, the single - stranded telomere dna is held onto a region of double - stranded dna by the telomere strand disrupting the double - helical dna and base pairing to one of the two strands. this triple - stranded structure is called a displacement loop or d - loop. = = = branched dna = = = in dna, fraying occurs when non - complementary regions exist at the end of an otherwise complementary double - strand of dna. however, branched dna can occur if a third strand of dna is introduced and contains adjoining regions able to hybridize with the frayed regions of the pre - existing double - strand. although the simplest example of branched dna involves only three strands of dna, complexes involving additional strands and multiple branches
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a third strand of dna is introduced and contains adjoining regions able to hybridize with the frayed regions of the pre - existing double - strand. although the simplest example of branched dna involves only three strands of dna, complexes involving additional strands and multiple branches are also possible. branched dna can be used in nanotechnology to construct geometric shapes, see the section on uses in technology below. = = = artificial bases = = = several artificial nucleobases have been synthesized, and successfully incorporated in the eight - base dna analogue named hachimoji dna. dubbed s, b, p, and z, these artificial bases are capable of bonding with each other in a predictable way ( s β b and p β z ), maintain the double helix structure of dna, and be transcribed to rna. their existence could be seen as an indication that there is nothing special about the four natural nucleobases that evolved on earth. on the other hand, dna is tightly related to rna which does not only act as a transcript of dna but also performs as molecular machines many tasks in cells. for this purpose it has to fold into a structure. it has been shown that to allow to create all possible structures at least four bases are required for the corresponding rna, while a higher number is also possible but this would be against the natural principle of least effort. = = = acidity = = = the phosphate groups of dna give it similar acidic properties to phosphoric acid and it can be considered as a strong acid. it will be fully ionized at a normal cellular ph, releasing protons which leave behind negative charges on the phosphate groups. these negative charges protect dna from breakdown by hydrolysis by repelling nucleophiles which could hydrolyze it. = = = macroscopic appearance = = = pure dna extracted from cells forms white, stringy clumps. = = chemical modifications and altered dna packaging = = = = = base modifications and dna packaging = = = the expression of genes is influenced by how the dna is packaged in chromosomes, in a structure called chromatin. base modifications can be involved in packaging, with regions that have low or no gene expression usually containing high levels of methylation of cytosine bases. dna packaging and its influence on gene expression can also occur by covalent modifications of the histone protein core around which dna is wrapped in the chromatin structure or else by remodeling carried out by chromatin remodeling complexes ( see chromatin remodel
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can also occur by covalent modifications of the histone protein core around which dna is wrapped in the chromatin structure or else by remodeling carried out by chromatin remodeling complexes ( see chromatin remodeling ). there is, further, crosstalk between dna methylation and histone modification, so they can coordinately affect chromatin and gene expression. for one example, cytosine methylation produces 5 - methylcytosine, which is important for x - inactivation of chromosomes. the average level of methylation varies between organisms β the worm caenorhabditis elegans lacks cytosine methylation, while vertebrates have higher levels, with up to 1 % of their dna containing 5 - methylcytosine. despite the importance of 5 - methylcytosine, it can deaminate to leave a thymine base, so methylated cytosines are particularly prone to mutations. other base modifications include adenine methylation in bacteria, the presence of 5 - hydroxymethylcytosine in the brain, and the glycosylation of uracil to produce the " j - base " in kinetoplastids. = = = damage = = = dna can be damaged by many sorts of mutagens, which change the dna sequence. mutagens include oxidizing agents, alkylating agents and also high - energy electromagnetic radiation such as ultraviolet light and x - rays. the type of dna damage produced depends on the type of mutagen. for example, uv light can damage dna by producing thymine dimers, which are cross - links between pyrimidine bases. on the other hand, oxidants such as free radicals or hydrogen peroxide produce multiple forms of damage, including base modifications, particularly of guanosine, and double - strand breaks. a typical human cell contains about 150, 000 bases that have suffered oxidative damage. of these oxidative lesions, the most dangerous are double - strand breaks, as these are difficult to repair and can produce point mutations, insertions, deletions from the dna sequence, and chromosomal translocations. these mutations can cause cancer. because of inherent limits in the dna repair mechanisms, if humans lived long enough, they would all eventually develop cancer. dna damages that are naturally occurring, due to normal cellular processes that produce reactive oxygen species, the hydrolytic activities of cellular water, etc., also occur
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the dna repair mechanisms, if humans lived long enough, they would all eventually develop cancer. dna damages that are naturally occurring, due to normal cellular processes that produce reactive oxygen species, the hydrolytic activities of cellular water, etc., also occur frequently. although most of these damages are repaired, in any cell some dna damage may remain despite the action of repair processes. these remaining dna damages accumulate with age in mammalian postmitotic tissues. this accumulation appears to be an important underlying cause of aging. many mutagens fit into the space between two adjacent base pairs, this is called intercalation. most intercalators are aromatic and planar molecules ; examples include ethidium bromide, acridines, daunomycin, and doxorubicin. for an intercalator to fit between base pairs, the bases must separate, distorting the dna strands by unwinding of the double helix. this inhibits both transcription and dna replication, causing toxicity and mutations. as a result, dna intercalators may be carcinogens, and in the case of thalidomide, a teratogen. others such as benzo [ a ] pyrene diol epoxide and aflatoxin form dna adducts that induce errors in replication. nevertheless, due to their ability to inhibit dna transcription and replication, other similar toxins are also used in chemotherapy to inhibit rapidly growing cancer cells. = = biological functions = = dna usually occurs as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell makes up its genome ; the human genome has approximately 3 billion base pairs of dna arranged into 46 chromosomes. the information carried by dna is held in the sequence of pieces of dna called genes. transmission of genetic information in genes is achieved via complementary base pairing. for example, in transcription, when a cell uses the information in a gene, the dna sequence is copied into a complementary rna sequence through the attraction between the dna and the correct rna nucleotides. usually, this rna copy is then used to make a matching protein sequence in a process called translation, which depends on the same interaction between rna nucleotides. in an alternative fashion, a cell may copy its genetic information in a process called dna replication. the details of these functions are covered in other articles ; here the focus is on the interactions between dna and other molecules that mediate the function of the genome. = = = genes and genomes = = = gen
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in a process called dna replication. the details of these functions are covered in other articles ; here the focus is on the interactions between dna and other molecules that mediate the function of the genome. = = = genes and genomes = = = genomic dna is tightly and orderly packed in the process called dna condensation, to fit the small available volumes of the cell. in eukaryotes, dna is located in the cell nucleus, with small amounts in mitochondria and chloroplasts. in prokaryotes, the dna is held within an irregularly shaped body in the cytoplasm called the nucleoid. the genetic information in a genome is held within genes, and the complete set of this information in an organism is called its genotype. a gene is a unit of heredity and is a region of dna that influences a particular characteristic in an organism. genes contain an open reading frame that can be transcribed, and regulatory sequences such as promoters and enhancers, which control transcription of the open reading frame. in many species, only a small fraction of the total sequence of the genome encodes protein. for example, only about 1. 5 % of the human genome consists of protein - coding exons, with over 50 % of human dna consisting of non - coding repetitive sequences. the reasons for the presence of so much noncoding dna in eukaryotic genomes and the extraordinary differences in genome size, or c - value, among species, represent a long - standing puzzle known as the " c - value enigma ". however, some dna sequences that do not code protein may still encode functional non - coding rna molecules, which are involved in the regulation of gene expression. some noncoding dna sequences play structural roles in chromosomes. telomeres and centromeres typically contain few genes but are important for the function and stability of chromosomes. an abundant form of noncoding dna in humans are pseudogenes, which are copies of genes that have been disabled by mutation. these sequences are usually just molecular fossils, although they can occasionally serve as raw genetic material for the creation of new genes through the process of gene duplication and divergence. = = = transcription and translation = = = a gene is a sequence of dna that contains genetic information and can influence the phenotype of an organism. within a gene, the sequence of bases along a dna strand defines a messenger rna sequence, which then defines one or more protein sequences. the relationship between the nucleotide sequences of
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contains genetic information and can influence the phenotype of an organism. within a gene, the sequence of bases along a dna strand defines a messenger rna sequence, which then defines one or more protein sequences. the relationship between the nucleotide sequences of genes and the amino - acid sequences of proteins is determined by the rules of translation, known collectively as the genetic code. the genetic code consists of three - letter'words'called codons formed from a sequence of three nucleotides ( e. g. act, cag, ttt ). in transcription, the codons of a gene are copied into messenger rna by rna polymerase. this rna copy is then decoded by a ribosome that reads the rna sequence by base - pairing the messenger rna to transfer rna, which carries amino acids. since there are 4 bases in 3 - letter combinations, there are 64 possible codons ( 43 combinations ). these encode the twenty standard amino acids, giving most amino acids more than one possible codon. there are also three'stop'or'nonsense'codons signifying the end of the coding region ; these are the tag, taa, and tga codons, ( uag, uaa, and uga on the mrna ). = = = replication = = = cell division is essential for an organism to grow, but, when a cell divides, it must replicate the dna in its genome so that the two daughter cells have the same genetic information as their parent. the double - stranded structure of dna provides a simple mechanism for dna replication. here, the two strands are separated and then each strand's complementary dna sequence is recreated by an enzyme called dna polymerase. this enzyme makes the complementary strand by finding the correct base through complementary base pairing and bonding it onto the original strand. as dna polymerases can only extend a dna strand in a 5 β² to 3 β² direction, different mechanisms are used to copy the antiparallel strands of the double helix. in this way, the base on the old strand dictates which base appears on the new strand, and the cell ends up with a perfect copy of its dna. = = = extracellular nucleic acids = = = naked extracellular dna ( edna ), most of it released by cell death, is nearly ubiquitous in the environment. its concentration in soil may be as high as 2 ΞΌg / l, and its concentration in natural aquatic environments may be as high at 88 ΞΌg / l. various possible functions have been proposed
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by cell death, is nearly ubiquitous in the environment. its concentration in soil may be as high as 2 ΞΌg / l, and its concentration in natural aquatic environments may be as high at 88 ΞΌg / l. various possible functions have been proposed for edna : it may be involved in horizontal gene transfer ; it may provide nutrients ; and it may act as a buffer to recruit or titrate ions or antibiotics. extracellular dna acts as a functional extracellular matrix component in the biofilms of several bacterial species. it may act as a recognition factor to regulate the attachment and dispersal of specific cell types in the biofilm ; it may contribute to biofilm formation ; and it may contribute to the biofilm's physical strength and resistance to biological stress. cell - free fetal dna is found in the blood of the mother, and can be sequenced to determine a great deal of information about the developing fetus. under the name of environmental dna edna has seen increased use in the natural sciences as a survey tool for ecology, monitoring the movements and presence of species in water, air, or on land, and assessing an area's biodiversity. = = = neutrophil extracellular traps = = = neutrophil extracellular traps ( nets ) are networks of extracellular fibers, primarily composed of dna, which allow neutrophils, a type of white blood cell, to kill extracellular pathogens while minimizing damage to the host cells. = = interactions with proteins = = all the functions of dna depend on interactions with proteins. these protein interactions can be non - specific, or the protein can bind specifically to a single dna sequence. enzymes can also bind to dna and of these, the polymerases that copy the dna base sequence in transcription and dna replication are particularly important. = = = dna - binding proteins = = = structural proteins that bind dna are well - understood examples of non - specific dna - protein interactions. within chromosomes, dna is held in complexes with structural proteins. these proteins organize the dna into a compact structure called chromatin. in eukaryotes, this structure involves dna binding to a complex of small basic proteins called histones, while in prokaryotes multiple types of proteins are involved. the histones form a disk - shaped complex called a nucleosome, which contains two complete turns of double - stranded dna wrapped around its surface. these non - specific interactions are formed through basic residues in the histones, making ionic bonds to the acidic sugar - phosphate backbone of
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shaped complex called a nucleosome, which contains two complete turns of double - stranded dna wrapped around its surface. these non - specific interactions are formed through basic residues in the histones, making ionic bonds to the acidic sugar - phosphate backbone of the dna, and are thus largely independent of the base sequence. chemical modifications of these basic amino acid residues include methylation, phosphorylation, and acetylation. these chemical changes alter the strength of the interaction between the dna and the histones, making the dna more or less accessible to transcription factors and changing the rate of transcription. other non - specific dna - binding proteins in chromatin include the high - mobility group proteins, which bind to bent or distorted dna. these proteins are important in bending arrays of nucleosomes and arranging them into the larger structures that make up chromosomes. a distinct group of dna - binding proteins is the dna - binding proteins that specifically bind single - stranded dna. in humans, replication protein a is the best - understood member of this family and is used in processes where the double helix is separated, including dna replication, recombination, and dna repair. these binding proteins seem to stabilize single - stranded dna and protect it from forming stem - loops or being degraded by nucleases. in contrast, other proteins have evolved to bind to particular dna sequences. the most intensively studied of these are the various transcription factors, which are proteins that regulate transcription. each transcription factor binds to one particular set of dna sequences and activates or inhibits the transcription of genes that have these sequences close to their promoters. the transcription factors do this in two ways. firstly, they can bind the rna polymerase responsible for transcription, either directly or through other mediator proteins ; this locates the polymerase at the promoter and allows it to begin transcription. alternatively, transcription factors can bind enzymes that modify the histones at the promoter. this changes the accessibility of the dna template to the polymerase. as these dna targets can occur throughout an organism's genome, changes in the activity of one type of transcription factor can affect thousands of genes. consequently, these proteins are often the targets of the signal transduction processes that control responses to environmental changes or cellular differentiation and development. the specificity of these transcription factors'interactions with dna come from the proteins making multiple contacts to the edges of the dna bases, allowing them to " read " the dna sequence. most of these base - interactions are made in the major groove, where the bases are most accessible.
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factors'interactions with dna come from the proteins making multiple contacts to the edges of the dna bases, allowing them to " read " the dna sequence. most of these base - interactions are made in the major groove, where the bases are most accessible. = = = dna - modifying enzymes = = = = = = = nucleases and ligases = = = = nucleases are enzymes that cut dna strands by catalyzing the hydrolysis of the phosphodiester bonds. nucleases that hydrolyse nucleotides from the ends of dna strands are called exonucleases, while endonucleases cut within strands. the most frequently used nucleases in molecular biology are the restriction endonucleases, which cut dna at specific sequences. for instance, the ecorv enzyme shown to the left recognizes the 6 - base sequence 5 β² - gatatc - 3 β² and makes a cut at the horizontal line. in nature, these enzymes protect bacteria against phage infection by digesting the phage dna when it enters the bacterial cell, acting as part of the restriction modification system. in technology, these sequence - specific nucleases are used in molecular cloning and dna fingerprinting. enzymes called dna ligases can rejoin cut or broken dna strands. ligases are particularly important in lagging strand dna replication, as they join the short segments of dna produced at the replication fork into a complete copy of the dna template. they are also used in dna repair and genetic recombination. = = = = topoisomerases and helicases = = = = topoisomerases are enzymes with both nuclease and ligase activity. these proteins change the amount of supercoiling in dna. some of these enzymes work by cutting the dna helix and allowing one section to rotate, thereby reducing its level of supercoiling ; the enzyme then seals the dna break. other types of these enzymes are capable of cutting one dna helix and then passing a second strand of dna through this break, before rejoining the helix. topoisomerases are required for many processes involving dna, such as dna replication and transcription. helicases are proteins that are a type of molecular motor. they use the chemical energy in nucleoside triphosphates, predominantly adenosine triphosphate ( atp ), to break hydrogen bonds between bases and unwind the dna double helix into single strands. these enzymes are essential for most processes where
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use the chemical energy in nucleoside triphosphates, predominantly adenosine triphosphate ( atp ), to break hydrogen bonds between bases and unwind the dna double helix into single strands. these enzymes are essential for most processes where enzymes need to access the dna bases. = = = = polymerases = = = = polymerases are enzymes that synthesize polynucleotide chains from nucleoside triphosphates. the sequence of their products is created based on existing polynucleotide chains β which are called templates. these enzymes function by repeatedly adding a nucleotide to the 3 β² hydroxyl group at the end of the growing polynucleotide chain. as a consequence, all polymerases work in a 5 β² to 3 β² direction. in the active site of these enzymes, the incoming nucleoside triphosphate base - pairs to the template : this allows polymerases to accurately synthesize the complementary strand of their template. polymerases are classified according to the type of template that they use. in dna replication, dna - dependent dna polymerases make copies of dna polynucleotide chains. to preserve biological information, it is essential that the sequence of bases in each copy are precisely complementary to the sequence of bases in the template strand. many dna polymerases have a proofreading activity. here, the polymerase recognizes the occasional mistakes in the synthesis reaction by the lack of base pairing between the mismatched nucleotides. if a mismatch is detected, a 3 β² to 5 β² exonuclease activity is activated and the incorrect base removed. in most organisms, dna polymerases function in a large complex called the replisome that contains multiple accessory subunits, such as the dna clamp or helicases. rna - dependent dna polymerases are a specialized class of polymerases that copy the sequence of an rna strand into dna. they include reverse transcriptase, which is a viral enzyme involved in the infection of cells by retroviruses, and telomerase, which is required for the replication of telomeres. for example, hiv reverse transcriptase is an enzyme for aids virus replication. telomerase is an unusual polymerase because it contains its own rna template as part of its structure. it synthesizes telomeres at the ends of chromosomes. telomeres prevent fusion of the ends of neighboring chromosomes and protect chromosome ends from damage. transcription is carried out by a dna
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it contains its own rna template as part of its structure. it synthesizes telomeres at the ends of chromosomes. telomeres prevent fusion of the ends of neighboring chromosomes and protect chromosome ends from damage. transcription is carried out by a dna - dependent rna polymerase that copies the sequence of a dna strand into rna. to begin transcribing a gene, the rna polymerase binds to a sequence of dna called a promoter and separates the dna strands. it then copies the gene sequence into a messenger rna transcript until it reaches a region of dna called the terminator, where it halts and detaches from the dna. as with human dna - dependent dna polymerases, rna polymerase ii, the enzyme that transcribes most of the genes in the human genome, operates as part of a large protein complex with multiple regulatory and accessory subunits. = = genetic recombination = = a dna helix usually does not interact with other segments of dna, and in human cells, the different chromosomes even occupy separate areas in the nucleus called " chromosome territories ". this physical separation of different chromosomes is important for the ability of dna to function as a stable repository for information, as one of the few times chromosomes interact is in chromosomal crossover which occurs during sexual reproduction, when genetic recombination occurs. chromosomal crossover is when two dna helices break, swap a section and then rejoin. recombination allows chromosomes to exchange genetic information and produces new combinations of genes, which increases the efficiency of natural selection and can be important in the rapid evolution of new proteins. genetic recombination can also be involved in dna repair, particularly in the cell's response to double - strand breaks. the most common form of chromosomal crossover is homologous recombination, where the two chromosomes involved share very similar sequences. non - homologous recombination can be damaging to cells, as it can produce chromosomal translocations and genetic abnormalities. the recombination reaction is catalyzed by enzymes known as recombinases, such as rad51. the first step in recombination is a double - stranded break caused by either an endonuclease or damage to the dna. a series of steps catalyzed in part by the recombinase then leads to joining of the two helices by at least one holliday junction, in which a segment of a single strand in each helix is annealed to
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. a series of steps catalyzed in part by the recombinase then leads to joining of the two helices by at least one holliday junction, in which a segment of a single strand in each helix is annealed to the complementary strand in the other helix. the holliday junction is a tetrahedral junction structure that can be moved along the pair of chromosomes, swapping one strand for another. the recombination reaction is then halted by cleavage of the junction and re - ligation of the released dna. only strands of like polarity exchange dna during recombination. there are two types of cleavage : east - west cleavage and north β south cleavage. the north β south cleavage nicks both strands of dna, while the east β west cleavage has one strand of dna intact. the formation of a holliday junction during recombination makes it possible for genetic diversity, genes to exchange on chromosomes, and expression of wild - type viral genomes. = = evolution = = dna contains the genetic information that allows all forms of life to function, grow and reproduce. however, it is unclear how long in the 4 - billion - year history of life dna has performed this function, as it has been proposed that the earliest forms of life may have used rna as their genetic material. rna may have acted as the central part of early cell metabolism as it can both transmit genetic information and carry out catalysis as part of ribozymes. this ancient rna world where nucleic acid would have been used for both catalysis and genetics may have influenced the evolution of the current genetic code based on four nucleotide bases. this would occur, since the number of different bases in such an organism is a trade - off between a small number of bases increasing replication accuracy and a large number of bases increasing the catalytic efficiency of ribozymes. however, there is no direct evidence of ancient genetic systems, as recovery of dna from most fossils is impossible because dna survives in the environment for less than one million years, and slowly degrades into short fragments in solution. claims for older dna have been made, most notably a report of the isolation of a viable bacterium from a salt crystal 250 million years old, but these claims are controversial. building blocks of dna ( adenine, guanine, and related organic molecules ) may have been formed extraterrestrially in outer space. complex dna and rna organic compounds of life, including uracil, cytosine, and thy
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building blocks of dna ( adenine, guanine, and related organic molecules ) may have been formed extraterrestrially in outer space. complex dna and rna organic compounds of life, including uracil, cytosine, and thymine, have also been formed in the laboratory under conditions mimicking those found in outer space, using starting chemicals, such as pyrimidine, found in meteorites. pyrimidine, like polycyclic aromatic hydrocarbons ( pahs ), the most carbon - rich chemical found in the universe, may have been formed in red giants or in interstellar cosmic dust and gas clouds. ancient dna has been recovered from ancient organisms at a timescale where genome evolution can be directly observed, including from extinct organisms up to millions of years old, such as the woolly mammoth. = = uses in technology = = = = = genetic engineering = = = methods have been developed to purify dna from organisms, such as phenol - chloroform extraction, and to manipulate it in the laboratory, such as restriction digests and the polymerase chain reaction. modern biology and biochemistry make intensive use of these techniques in recombinant dna technology. recombinant dna is a man - made dna sequence that has been assembled from other dna sequences. they can be transformed into organisms in the form of plasmids or in the appropriate format, by using a viral vector. the genetically modified organisms produced can be used to produce products such as recombinant proteins, used in medical research, or be grown in agriculture. = = = dna profiling = = = forensic scientists can use dna in blood, semen, skin, saliva or hair found at a crime scene to identify a matching dna of an individual, such as a perpetrator. this process is formally termed dna profiling, also called dna fingerprinting. in dna profiling, the lengths of variable sections of repetitive dna, such as short tandem repeats and minisatellites, are compared between people. this method is usually an extremely reliable technique for identifying a matching dna. however, identification can be complicated if the scene is contaminated with dna from several people. dna profiling was developed in 1984 by british geneticist sir alec jeffreys, and first used in forensic science to convict colin pitchfork in the 1988 enderby murders case. the development of forensic science and the ability to now obtain genetic matching on minute samples of blood, skin, saliva, or hair has led to
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jeffreys, and first used in forensic science to convict colin pitchfork in the 1988 enderby murders case. the development of forensic science and the ability to now obtain genetic matching on minute samples of blood, skin, saliva, or hair has led to re - examining many cases. evidence can now be uncovered that was scientifically impossible at the time of the original examination. combined with the removal of the double jeopardy law in some places, this can allow cases to be reopened where prior trials have failed to produce sufficient evidence to convince a jury. people charged with serious crimes may be required to provide a sample of dna for matching purposes. the most obvious defense to dna matches obtained forensically is to claim that cross - contamination of evidence has occurred. this has resulted in meticulous strict handling procedures with new cases of serious crime. dna profiling is also used successfully to positively identify victims of mass casualty incidents, bodies or body parts in serious accidents, and individual victims in mass war graves, via matching to family members. dna profiling is also used in dna paternity testing to determine if someone is the biological parent or grandparent of a child with the probability of parentage is typically 99. 99 % when the alleged parent is biologically related to the child. normal dna sequencing methods happen after birth, but there are new methods to test paternity while a mother is still pregnant. = = = dna enzymes or catalytic dna = = = deoxyribozymes, also called dnazymes or catalytic dna, were first discovered in 1994. they are mostly single stranded dna sequences isolated from a large pool of random dna sequences through a combinatorial approach called in vitro selection or systematic evolution of ligands by exponential enrichment ( selex ). dnazymes catalyze variety of chemical reactions including rna - dna cleavage, rna - dna ligation, amino acids phosphorylation - dephosphorylation, carbon - carbon bond formation, etc. dnazymes can enhance catalytic rate of chemical reactions up to 100, 000, 000, 000 - fold over the uncatalyzed reaction. the most extensively studied class of dnazymes is rna - cleaving types which have been used to detect different metal ions and designing therapeutic agents. several metal - specific dnazymes have been reported including the gr - 5 dnazyme ( lead - specific ), the ca1 - 3 dnazymes ( copper - specific ), the 39e dnazyme ( uranyl - specific ) and the naa
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##zymes have been reported including the gr - 5 dnazyme ( lead - specific ), the ca1 - 3 dnazymes ( copper - specific ), the 39e dnazyme ( uranyl - specific ) and the naa43 dnazyme ( sodium - specific ). the naa43 dnazyme, which is reported to be more than 10, 000 - fold selective for sodium over other metal ions, was used to make a real - time sodium sensor in cells. = = = bioinformatics = = = bioinformatics involves the development of techniques to store, data mine, search and manipulate biological data, including dna nucleic acid sequence data. these have led to widely applied advances in computer science, especially string searching algorithms, machine learning, and database theory. string searching or matching algorithms, which find an occurrence of a sequence of letters inside a larger sequence of letters, were developed to search for specific sequences of nucleotides. the dna sequence may be aligned with other dna sequences to identify homologous sequences and locate the specific mutations that make them distinct. these techniques, especially multiple sequence alignment, are used in studying phylogenetic relationships and protein function. data sets representing entire genomes'worth of dna sequences, such as those produced by the human genome project, are difficult to use without the annotations that identify the locations of genes and regulatory elements on each chromosome. regions of dna sequence that have the characteristic patterns associated with protein - or rna - coding genes can be identified by gene finding algorithms, which allow researchers to predict the presence of particular gene products and their possible functions in an organism even before they have been isolated experimentally. entire genomes may also be compared, which can shed light on the evolutionary history of particular organism and permit the examination of complex evolutionary events. = = = dna nanotechnology = = = dna nanotechnology uses the unique molecular recognition properties of dna and other nucleic acids to create self - assembling branched dna complexes with useful properties. dna is thus used as a structural material rather than as a carrier of biological information. this has led to the creation of two - dimensional periodic lattices ( both tile - based and using the dna origami method ) and three - dimensional structures in the shapes of polyhedra. nanomechanical devices and algorithmic self - assembly have also been demonstrated, and these dna structures have been used to template the arrangement of other molecules such as gold nanoparticles and streptavidin proteins. dna and
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##hedra. nanomechanical devices and algorithmic self - assembly have also been demonstrated, and these dna structures have been used to template the arrangement of other molecules such as gold nanoparticles and streptavidin proteins. dna and other nucleic acids are the basis of aptamers, synthetic oligonucleotide ligands for specific target molecules used in a range of biotechnology and biomedical applications. = = = history and anthropology = = = because dna collects mutations over time, which are then inherited, it contains historical information, and, by comparing dna sequences, geneticists can infer the evolutionary history of organisms, their phylogeny. this field of phylogenetics is a powerful tool in evolutionary biology. if dna sequences within a species are compared, population geneticists can learn the history of particular populations. this can be used in studies ranging from ecological genetics to anthropology. = = = information storage = = = dna as a storage device for information has enormous potential since it has much higher storage density compared to electronic devices. however, high costs, slow read and write times ( memory latency ), and insufficient reliability has prevented its practical use. = = history = = dna was first isolated by the swiss physician friedrich miescher who, in 1869, discovered a microscopic substance in the pus of discarded surgical bandages. as it resided in the nuclei of cells, he called it " nuclein ". in 1878, albrecht kossel isolated the non - protein component of " nuclein ", nucleic acid, and later isolated its five primary nucleobases. in 1909, phoebus levene identified the base, sugar, and phosphate nucleotide unit of rna ( then named " yeast nucleic acid " ). in 1929, levene identified deoxyribose sugar in " thymus nucleic acid " ( dna ). levene suggested that dna consisted of a string of four nucleotide units linked together through the phosphate groups ( " tetranucleotide hypothesis " ). levene thought the chain was short and the bases repeated in a fixed order. in 1927, nikolai koltsov proposed that inherited traits would be inherited via a " giant hereditary molecule " made up of " two mirror strands that would replicate in a semi - conservative fashion using each strand as a template ". in 1928, frederick griffith in his experiment discovered that traits of the " smooth " form of pneumococcus could be transferred to the " rough " form of the same bacteria by mixing killed " smooth
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fashion using each strand as a template ". in 1928, frederick griffith in his experiment discovered that traits of the " smooth " form of pneumococcus could be transferred to the " rough " form of the same bacteria by mixing killed " smooth " bacteria with the live " rough " form. this system provided the first clear suggestion that dna carries genetic information. in 1933, while studying virgin sea urchin eggs, jean brachet suggested that dna is found in the cell nucleus and that rna is present exclusively in the cytoplasm. at the time, " yeast nucleic acid " ( rna ) was thought to occur only in plants, while " thymus nucleic acid " ( dna ) only in animals. the latter was thought to be a tetramer, with the function of buffering cellular ph. in 1937, william astbury produced the first x - ray diffraction patterns that showed that dna had a regular structure. in 1943, oswald avery, along with co - workers colin macleod and maclyn mccarty, identified dna as the transforming principle, supporting griffith's suggestion ( avery β macleod β mccarty experiment ). erwin chargaff developed and published observations now known as chargaff's rules, stating that in dna from any species of any organism, the amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine. late in 1951, francis crick started working with james watson at the cavendish laboratory within the university of cambridge. dna's role in heredity was confirmed in 1952 when alfred hershey and martha chase in the hershey β chase experiment showed that dna is the genetic material of the enterobacteria phage t2. in may 1952, raymond gosling, a graduate student working under the supervision of rosalind franklin, took an x - ray diffraction image, labeled as " photo 51 ", at high hydration levels of dna. this photo was given to watson and crick by maurice wilkins and was critical to their obtaining the correct structure of dna. franklin told crick and watson that the backbones had to be on the outside. before then, linus pauling, and watson and crick, had erroneous models with the chains inside and the bases pointing outwards. franklin's identification of the space group for dna crystals revealed to crick that the two dna strands were antiparallel. in february 1953, linus pauling and robert corey proposed a model for nucleic acids
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the bases pointing outwards. franklin's identification of the space group for dna crystals revealed to crick that the two dna strands were antiparallel. in february 1953, linus pauling and robert corey proposed a model for nucleic acids containing three intertwined chains, with the phosphates near the axis, and the bases on the outside. watson and crick completed their model, which is now accepted as the first correct model of the double helix of dna. on 28 february 1953 crick interrupted patrons'lunchtime at the eagle pub in cambridge, england to announce that he and watson had " discovered the secret of life ". the 25 april 1953 issue of the journal nature published a series of five articles giving the watson and crick double - helix structure dna and evidence supporting it. the structure was reported in a letter titled " molecular structure of nucleic acids a structure for deoxyribose nucleic acid ", in which they said, " it has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material. " this letter was followed by a letter from franklin and gosling, which was the first publication of their own x - ray diffraction data and of their original analysis method. then followed a letter by wilkins and two of his colleagues, which contained an analysis of in vivo b - dna x - ray patterns, and which supported the presence in vivo of the watson and crick structure. in april 2023, scientists, based on new evidence, concluded that rosalind franklin was a contributor and " equal player " in the discovery process of dna, rather than otherwise, as may have been presented subsequently after the time of the discovery. in 1962, after franklin's death, watson, crick, and wilkins jointly received the nobel prize in physiology or medicine. nobel prizes are awarded only to living recipients. a debate continues about who should receive credit for the discovery. in an influential presentation in 1957, crick laid out the central dogma of molecular biology, which foretold the relationship between dna, rna, and proteins, and articulated the " adaptor hypothesis ". final confirmation of the replication mechanism that was implied by the double - helical structure followed in 1958 through the meselson β stahl experiment. further work by crick and co - workers showed that the genetic code was based on non - overlapping triplets of bases, called codons, allowing har gobind khorana, robert w. holley, and marshall
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##ahl experiment. further work by crick and co - workers showed that the genetic code was based on non - overlapping triplets of bases, called codons, allowing har gobind khorana, robert w. holley, and marshall warren nirenberg to decipher the genetic code. these findings represent the birth of molecular biology. in 1986, dna analysis was first used in a criminal investigation when police in the uk requested alec jeffreys of the university of leicester to prove or disprove the involvement in a particular case of a suspect who claimed innocence in the matter. although the suspect had already confessed to committing a recent rape - murder, he was denying any involvement in a similar crime committed three years earlier. yet the details of the two cases were so alike that the police concluded both crimes had been committed by the same person. however, all charges against the suspect were dropped when jeffreys'dna testing exonerated the suspect β from both the earlier murder and the one to which he'd confessed. further such dna profiling led to positive identification of another suspect who, in 1988, was found guilty of both rape - murders. = = see also = = = = references = = = = further reading = = = = external links = = dna binding site prediction on protein dna the double helix game from the official nobel prize web site dna under electron microscope dolan dna learning center double helix : 50 years of dna, nature proteopedia dna proteopedia forms _ of _ dna encode threads explorer encode home page at nature double helix 1953 β 2003 national centre for biotechnology education genetic education modules for teachers β dna from the beginning study guide pdb molecule of the month dna " clue to chemistry of heredity found ". the new york times, june 1953. first american newspaper coverage of the discovery of the dna structure dna from the beginning another dna learning center site on dna, genes, and heredity from mendel to the human genome project. the register of francis crick personal papers 1938 β 2007 at mandeville special collections library, university of california, san diego seven - page, handwritten letter that crick sent to his 12 - year - old son michael in 1953 describing the structure of dna. see crick's medal goes under the hammer, nature, 5 april 2013.
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in topology, a branch of mathematics, an extension topology is a topology placed on the disjoint union of a topological space and another set. there are various types of extension topology, described in the sections below. = = extension topology = = let x be a topological space and p a set disjoint from x. consider in x βͺ p the topology whose open sets are of the form a βͺ q, where a is an open set of x and q is a subset of p. the closed sets of x βͺ p are of the form b βͺ q, where b is a closed set of x and q is a subset of p. for these reasons this topology is called the extension topology of x plus p, with which one extends to x βͺ p the open and the closed sets of x. as subsets of x βͺ p the subspace topology of x is the original topology of x, while the subspace topology of p is the discrete topology. as a topological space, x βͺ p is homeomorphic to the topological sum of x and p, and x is a clopen subset of x βͺ p. if y is a topological space and r is a subset of y, one might ask whether the extension topology of y β r plus r is the same as the original topology of y, and the answer is in general no. note the similarity of this extension topology construction and the alexandroff one - point compactification, in which case, having a topological space x which one wishes to compactify by adding a point β in infinity, one considers the closed sets of x βͺ { β } to be the sets of the form k, where k is a closed compact set of x, or b βͺ { β }, where b is a closed set of x. = = open extension topology = = let ( x, t ) { \ displaystyle ( x, { \ mathcal { t } } ) } be a topological space and p { \ displaystyle p } a set disjoint from x { \ displaystyle x }. the open extension topology of t { \ displaystyle { \ mathcal { t } } } plus p { \ displaystyle p } is t β = t βͺ { x βͺ a : a β p }. { \ displaystyle { \ mathcal { t } } ^ { * } = { \ mathcal { t } } \ cup \ { x \ cup a : a \ subset p \ }. } let x β = x βͺ p
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. { \ displaystyle { \ mathcal { t } } ^ { * } = { \ mathcal { t } } \ cup \ { x \ cup a : a \ subset p \ }. } let x β = x βͺ p { \ displaystyle x ^ { * } = x \ cup p }. then t β { \ displaystyle { \ mathcal { t } } ^ { * } } is a topology in x β { \ displaystyle x ^ { * } }. the subspace topology of x { \ displaystyle x } is the original topology of x { \ displaystyle x }, i. e. t β | x = t { \ displaystyle { \ mathcal { t } } ^ { * } | x = { \ mathcal { t } } }, while the subspace topology of p { \ displaystyle p } is the discrete topology, i. e. t β | p = p ( p ) { \ displaystyle { \ mathcal { t } } ^ { * } | p = { \ mathcal { p } } ( p ) }. the closed sets in x β { \ displaystyle x ^ { * } } are { b βͺ p : x β b β§ x b β t } { \ displaystyle \ { b \ cup p : x \ subset b \ land x \ setminus b \ in { \ mathcal { t } } \ } }. note that p { \ displaystyle p } is closed in x β { \ displaystyle x ^ { * } } and x { \ displaystyle x } is open and dense in x β { \ displaystyle x ^ { * } }. if y a topological space and r is a subset of y, one might ask whether the open extension topology of y β r plus r is the same as the original topology of y, and the answer is in general no. note that the open extension topology of x β { \ displaystyle x ^ { * } } is smaller than the extension topology of x β { \ displaystyle x ^ { * } }. assuming x { \ displaystyle x } and p { \ displaystyle p } are not empty to avoid trivialities, here are a few general properties of the open extension topology : x { \ displaystyle x } is dense in x β { \ displaystyle x ^ { * } }. if p { \ displaystyle p } is finite, x β { \ displaystyle x ^ {
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properties of the open extension topology : x { \ displaystyle x } is dense in x β { \ displaystyle x ^ { * } }. if p { \ displaystyle p } is finite, x β { \ displaystyle x ^ { * } } is compact. so x β { \ displaystyle x ^ { * } } is a compactification of x { \ displaystyle x } in that case. x β { \ displaystyle x ^ { * } } is connected. if p { \ displaystyle p } has a single point, x β { \ displaystyle x ^ { * } } is ultraconnected. for a set z and a point p in z, one obtains the excluded point topology construction by considering in z the discrete topology and applying the open extension topology construction to z β { p } plus p. = = closed extension topology = = let x be a topological space and p a set disjoint from x. consider in x βͺ p the topology whose closed sets are of the form x βͺ q, where q is a subset of p, or b, where b is a closed set of x. for this reason this topology is called the closed extension topology of x plus p, with which one extends to x βͺ p the closed sets of x. as subsets of x βͺ p the subspace topology of x is the original topology of x, while the subspace topology of p is the discrete topology. the open sets of x βͺ p are of the form q, where q is a subset of p, or a βͺ p, where a is an open set of x. note that p is open in x βͺ p and x is closed in x βͺ p. if y is a topological space and r is a subset of y, one might ask whether the closed extension topology of y β r plus r is the same as the original topology of y, and the answer is in general no. note that the closed extension topology of x βͺ p is smaller than the extension topology of x βͺ p. for a set z and a point p in z, one obtains the particular point topology construction by considering in z the discrete topology and applying the closed extension topology construction to z β { p } plus p. = = notes = = = = works cited = =
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in mathematics, a quasifield is an algebraic structure ( q, +, β
) { \ displaystyle ( q, +, \ cdot ) } where + { \ displaystyle + } and β
{ \ displaystyle \ cdot } are binary operations on q { \ displaystyle q }, much like a division ring, but with some weaker conditions. all division rings, and thus all fields, are quasifields. = = definition = = a quasifield ( q, +, β
) { \ displaystyle ( q, +, \ cdot ) } is a structure, where + { \ displaystyle + } and β
{ \ displaystyle \ cdot } are binary operations on q { \ displaystyle q }, satisfying these axioms : ( q, + ) { \ displaystyle ( q, + ) } is a group ( q 0, β
) { \ displaystyle ( q _ { 0 }, \ cdot ) } is a loop, where q 0 = q { 0 } { \ displaystyle q _ { 0 } = q \ setminus \ { 0 \ } \, } a β
( b + c ) = a β
b + a β
c a, b, c β q { \ displaystyle a \ cdot ( b + c ) = a \ cdot b + a \ cdot c \ quad \ forall a, b, c \ in q } ( left distributivity ) a β
x = b β
x + c { \ displaystyle a \ cdot x = b \ cdot x + c } has exactly one solution for x { \ displaystyle x }, a, b, c β q, a = b { \ displaystyle \ forall a, b, c \ in q, a \ neq b } strictly speaking, this is the definition of a left quasifield. a right quasifield is similarly defined, but satisfies right distributivity instead. a quasifield satisfying both distributive laws is called a semifield, in the sense in which the term is used in projective geometry. although not assumed, one can prove that the axioms imply that the additive group ( q, + ) { \ displaystyle ( q, + ) } is abelian. thus, when referring to an abelian quasifield, one means that ( q 0, β
) { \ displaystyle ( q _ { 0 }, \ cdot ) } is
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\ displaystyle ( q, + ) } is abelian. thus, when referring to an abelian quasifield, one means that ( q 0, β
) { \ displaystyle ( q _ { 0 }, \ cdot ) } is abelian. = = kernel = = the kernel k { \ displaystyle k } of a quasifield q { \ displaystyle q } is the set of all elements c { \ displaystyle c } such that : a β
( b β
c ) = ( a β
b ) β
c a, b β q { \ displaystyle a \ cdot ( b \ cdot c ) = ( a \ cdot b ) \ cdot c \ quad \ forall a, b \ in q } ( a + b ) β
c = ( a β
c ) + ( b β
c ) a, b β q { \ displaystyle ( a + b ) \ cdot c = ( a \ cdot c ) + ( b \ cdot c ) \ quad \ forall a, b \ in q } restricting the binary operations + { \ displaystyle + } and β
{ \ displaystyle \ cdot } to k { \ displaystyle k }, one can shown that ( k, +, β
) { \ displaystyle ( k, +, \ cdot ) } is a division ring. one can now make a vector space of q { \ displaystyle q } over k { \ displaystyle k }, with the following scalar multiplication : v β l = v β
l v β q, l β k { \ displaystyle v \ otimes l = v \ cdot l \ quad \ forall v \ in q, l \ in k } as a finite division ring is a finite field by wedderburn's theorem, the order of the kernel of a finite quasifield is a prime power. the vector space construction implies that the order of any finite quasifield must also be a prime power. = = examples = = all division rings, and thus all fields, are quasifields. a ( right ) near - field that is a ( right ) quasifield is called a " planar near - field ". the smallest quasifields are abelian and unique. they are the finite fields of orders up to and including eight. the smallest quasifields that are not division rings are the four non - abelian quasifields of order nine ; they are presented in hall ( 1959 ) and weibel ( 2007 )
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. they are the finite fields of orders up to and including eight. the smallest quasifields that are not division rings are the four non - abelian quasifields of order nine ; they are presented in hall ( 1959 ) and weibel ( 2007 ). = = projective planes = = given a quasifield q { \ displaystyle q }, we define a ternary map t : q Γ q Γ q β q { \ displaystyle t \ colon q \ times q \ times q \ to q } by t ( a, b, c ) = a β
b + c a, b, c β q { \ displaystyle t ( a, b, c ) = a \ cdot b + c \ quad \ forall a, b, c \ in q } one can then verify that ( q, t ) { \ displaystyle ( q, t ) } satisfies the axioms of a planar ternary ring. associated to ( q, t ) { \ displaystyle ( q, t ) } is its corresponding projective plane. the projective planes constructed this way are characterized as follows ; the details of this relationship are given in hall ( 1959 ). a projective plane is a translation plane with respect to the line at infinity if and only if any ( or all ) of its associated planar ternary rings are right quasifields. it is called a shear plane if any ( or all ) of its ternary rings are left quasifields. the plane does not uniquely determine the ring ; all 4 nonabelian quasifields of order 9 are ternary rings for the unique non - desarguesian translation plane of order 9. these differ in the fundamental quadrilateral used to construct the plane ( see weibel 2007 ). = = history = = quasifields were called " veblen β wedderburn systems " in the literature before 1975, since they were first studied in the 1907 paper ( veblen - wedderburn 1907 ) by o. veblen and j. wedderburn. surveys of quasifields and their applications to projective planes may be found in hall ( 1959 ) and weibel ( 2007 ). = = references = = hall, marshall jr. ( 1959 ), theory of groups, macmillan, lccn 59005035, mr 0103215. veblen, o. ; wedderburn, j. h. m. ( 1907 ), " non - desarguesian and non - pascalian geometries ", transactions
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59005035, mr 0103215. veblen, o. ; wedderburn, j. h. m. ( 1907 ), " non - desarguesian and non - pascalian geometries ", transactions of the american mathematical society, 8 ( 3 ) : 379 β 388, doi : 10. 2307 / 1988781, jstor 1988781 weibel, charles ( 2007 ), " survey of non - desarguesian planes ", notices of the ams, 54 ( 10 ) : 1294 β 1303 = = see also = = near - field semifield alternative division ring hall systems ( hall planes ) moufang plane = = external links = = quasifields by hauke klein.
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in complex analysis, the loewner energy is an invariant of a domain in the complex plane, or equivalently an invariant of the boundary of the domain, a simple closed curve. according to the uniformization theorem, every domain has a conformal mapping to one of three uniform riemann surfaces : an open unit disk, the complex plane, or the riemann sphere. in 1923 work on the bieberbach conjecture, charles loewner showed that ( a suitable normalization of ) this uniform mapping can be described as the solution to the loewner differential equation, which depends on a certain real - valued function, the driving function, defined on the boundary of the domain. the loewner energy was originally defined by yilin wang and ( independently ) by peter friz and atul shekhar as the dirichlet energy of this driving function. in later work, wang found an equivalent definition of the loewner energy as the dirichlet energy of the logarithmic derivative of the conformal mapping itself. this energy is bounded when the boundary of the domain is a weil β petersson curve, a kind of quasicircle obeying an additional smoothness condition. = = references = =
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in chemistry, intervalence charge transfer, often abbreviated ivct or even it, is a type of charge - transfer band that is associated with mixed valence compounds. it is most common for systems with two metal sites differing only in oxidation state. quite often such electron transfer reverses the oxidation states of the sites. the term is frequently extended to the case of metal - to - metal charge transfer between non - equivalent metal centres. the transition produces a characteristically intense absorption in the electromagnetic spectrum. the band is usually found in the visible or near infrared region of the spectrum and is broad. the process can be described as follows : lnm + - bridge - m'ln + hΞ½ β lnm - bridge - m'+ ln = = mixed valency and the it band = = since the energy states of valence tautomers affect the ivct band, the strength of electronic interaction between the sites, known as Ξ± ( the mixing coefficient ), can be determined by analysis of the ivct band. depending on the value of Ξ±, mixed valence complexes are classified into three groups : class i : Ξ± ~ 0, the complex has no interaction between redox sites. no ivct band is observed. the oxidation states of the two metal sites are distinct and do not readily interconvert. class ii : 0 < Ξ± < 1 / 2 { \ displaystyle \ scriptstyle 1 / { \ sqrt { 2 } } } = 0. 707, intermediate interaction between sites. an ivct band is observed. the oxidation states of the two metal sites are distinct, but they readily interconvert. this is by far the most common class of intervalence complexes. class iii : Ξ± > 1 / 2 { \ displaystyle \ scriptstyle 1 / { \ sqrt { 2 } } } = 0. 707, interaction between redox sites is very strong. it is better to consider these sites as one united site, not as two isolated sites. an ivct band is observed. the oxidation states of the two metal sites are essentially equivalent. in these situations, the two metals are often best described as having the same half integer oxidation state. = = references = =
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an rf antenna ion source ( or radio frequency antenna ion source ) is an internal multi - cusp design that can produce a particle beam of about ~ 30 to 40 ma current. it is used in high energy particle physics and in accelerator laboratories. previous rf antennas would penetrate the porcelain enamel coating on the antenna section at high rf power. this problem has been corrected in the development stage with a ten layer coating of titanium dioxide, with approximately 1 mm thick coating. with the development of the rf antenna ion source, or " non - thermionic ion source, " the ion source has an advantage over conventional cold cathodes and hot filament ion sources. the filament continuously burns out over time with a shorter lifespan, requiring venting of the ion source to atmosphere and rebuilding of the ion source. = = see also = = ion source particle accelerator = = external links = = lawrence berkley national laboratory improvement of the lifetime of radio frequency antenna
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continuous integration ( ci ) is the practice of integrating source code changes frequently and ensuring that the integrated codebase is in a workable state. typically, developers merge changes to an integration branch, and an automated system builds and tests the software system. often, the automated process runs on each commit or runs on a schedule such as once a day. grady booch first proposed the term ci in 1991, although he did not advocate integrating multiple times a day, but later, ci came to include that aspect. = = history = = the earliest known work ( 1989 ) on continuous integration was the infuse environment developed by g. e. kaiser, d. e. perry, and w. m. schell. in 1994, grady booch used the phrase continuous integration in object - oriented analysis and design with applications ( 2nd edition ) to explain how, when developing using micro processes, " internal releases represent a sort of continuous integration of the system, and exist to force closure of the micro process ". in 1997, kent beck and ron jeffries invented extreme programming ( xp ) while on the chrysler comprehensive compensation system project, including continuous integration. beck published about continuous integration in 1998, emphasising the importance of face - to - face communication over technological support. in 1999, beck elaborated more in his first full book on extreme programming. cruisecontrol, one of the first open - source ci tools, was released in 2001. in 2010, timothy fitz published an article detailing how imvu's engineering team had built and been using the first practical cd system. while his post was originally met with skepticism, it quickly caught on and found widespread adoption as part of the lean software development methodology, also based on imvu. = = practices = = the core activities of ci are developers co - locate code changes in a shared, integration area frequently and that the resulting integrated codebase is verified for correctness. the first part generally involves merging changes to a common version control branch. the second part generally involves automated processes including : building, testing and many other processes. typically, a server builds from the integration area frequently ; i. e. after each commit or periodically like once a day. the server may perform quality control checks such as running unit tests and collect software quality metrics via processes such as static analysis and performance testing. = = related practices = = this section lists best practices from practitioners for other practices that enhance ci. = = = build automation = = = build automation is a best practice. build automation tools automate building. proponents
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as static analysis and performance testing. = = related practices = = this section lists best practices from practitioners for other practices that enhance ci. = = = build automation = = = build automation is a best practice. build automation tools automate building. proponents of ci recommend that a single command should have the capability of building the system. automation often includes automating the integration, which often includes deployment into a production - like environment. in many cases, the build script not only compiles binaries but also generates documentation, website pages, statistics and distribution media ( such as debian deb, red hat rpm or windows msi files ). = = = atomic commits = = = ci requires the version control system to support atomic commits ; i. e., all of a developer's changes are handled as a single commit. = = = committing changes = = = when making a code change, a developer creates a branch that is a copy of the current codebase. as other changes are committed to the repository, this copy diverges from the latest version. the longer development continues on a branch without merging to the integration branch, the greater the risk of multiple integration conflicts and failures when the developer branch is eventually merged back. when developers submit code to the repository they must first update their code to reflect the changes in the repository since they took their copy. the more changes the repository contains, the more work developers must do before submitting their own changes. eventually, the repository may become so different from the developers'baselines that they enter what is sometimes referred to as " merge hell ", or " integration hell ", where the time it takes to integrate exceeds the time it took to make their original changes. = = = testing locally = = = proponents of ci suggest that developers should use test - driven development and to ensure that all unit tests pass locally before committing to the integration branch so that one developer's work does not break another developer's copy. incomplete features can be disabled before committing, using feature toggles. = = = continuous delivery and continuous deployment = = = continuous delivery ensures the software checked in on an integration branch is always in a state that can be deployed to users, and continuous deployment automates the deployment process. continuous delivery and continuous deployment are often performed in conjunction with ci and together form a ci / cd pipeline. = = = version control = = = proponents of ci recommend storing all files and information needed for building in version control, ( for git a repository ) ; that the system should be build
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conjunction with ci and together form a ci / cd pipeline. = = = version control = = = proponents of ci recommend storing all files and information needed for building in version control, ( for git a repository ) ; that the system should be buildable from a fresh checkout and not require additional dependencies. martin fowler recommends that all developers commit to the same integration branch. = = = commit frequently = = = developers can reduce the effort of resolving conflicting changes by synchronizing changes with each other frequently ; at least daily. checking in a week's worth of work risks conflict both in likelihood of occurrence and complexity to resolve. relatively small conflicts are significantly easier to resolve than larger ones. integrating ( committing ) changes at least once a day is considered good practice, and more often better. = = = daily build = = = building daily, if not more often, is generally recommended. = = = every commit should be built = = = the system should build commits to the current working version to verify that they integrate correctly. a common practice is to use automated continuous integration, although this may be done manually. automated continuous integration employs a continuous integration server or daemon to monitor the revision control system for changes, then automatically run the build process. = = = every bug - fix commit should come with a test case = = = when fixing a bug, it is a good practice to push a test case that reproduces the bug. this avoids the fix to be reverted, and the bug to reappear, which is known as a regression. = = = keep the build fast = = = the build needs to complete rapidly so that if there is a problem with integration, it is quickly identified. = = = test in a clone of the production environment = = = having a test environment can lead to failures in tested systems when they deploy in the production environment because the production environment may differ from the test environment in a significant way. however, building a replica of a production environment is cost - prohibitive. instead, the test environment or a separate pre - production environment ( " staging " ) should be built to be a scalable version of the production environment to alleviate costs while maintaining technology stack composition and nuances. within these test environments, service virtualisation is commonly used to obtain on - demand access to dependencies ( e. g., apis, third - party applications, services, mainframes, etc. ) that are beyond the team's control, still evolving, or too complex to configure in
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- demand access to dependencies ( e. g., apis, third - party applications, services, mainframes, etc. ) that are beyond the team's control, still evolving, or too complex to configure in a virtual test lab. = = = make it easy to get the latest deliverables = = = making builds readily available to stakeholders and testers can reduce the amount of rework necessary when rebuilding a feature that doesn't meet requirements. additionally, early testing reduces the chances that defects survive until deployment. finding errors earlier can reduce the amount of work necessary to resolve them. all programmers should start the day by updating the project from the repository. that way, they will all stay up to date. = = = everyone can see the results of the latest build = = = it should be easy to find out whether the build breaks and, if so, who made the relevant change and what that change was. = = = automate deployment = = = most ci systems allow the running of scripts after a build finishes. in most situations, it is possible to write a script to deploy the application to a live test server that everyone can look at. a further advance in this way of thinking is continuous deployment, which calls for the software to be deployed directly into production, often with additional automation to prevent defects or regressions. = = benefits = = ci benefits include : facilitates detecting bugs earlier reduces effort to find cause of bugs ; if a ci test fails then changes since last good build contain causing change ; if build after each change then exactly one change is the cause avoids the chaos of integrating many changes when a test fails or a bug is found, reverting the codebase to a good state results in fewer lost changes frequent availability of a known - good build for testing, demo, and release frequent code commit encourages modular, less complex code quick feedback on system - wide impact of code changes supports collection of software metrics such as code coverage, code complexity = = risks = = risks of ci include : build system setup requires effort writing and maintaining an automated test suite requires effort value added depends on the quality of tests high build latency ( sitting in queue ) limits value implies that incomplete code should not be integrated which is counter to some developer's preferred practice safety and mission - critical development assurance ( e. g., do - 178c, iso 26262 ) require documentation and review which may be difficult to achieve = = best practices for cloud systems = = the following practices can enhance
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s preferred practice safety and mission - critical development assurance ( e. g., do - 178c, iso 26262 ) require documentation and review which may be difficult to achieve = = best practices for cloud systems = = the following practices can enhance productivity of pipelines, especially in systems hosted in the cloud : number of pipelines : small teams can be more productive by having one repository and one pipeline. in contrast, larger organizations may have separate repositories and pipelines for each team or even separate repositories and pipelines for each service within a team. permissions : in the context of pipeline - related permissions, adhering to the principle of least privilege can be challenging due to the dynamic nature of architecture. administrators may opt for more permissive permissions while implementing compensating security controls to minimize the blast radius. = = see also = = application release automation β process of packaging and deploymentpages displaying short descriptions of redirect targets build light indicator β visual device used in agile software development to inform the team on the build progresspages displaying wikidata descriptions as a fallback comparison of continuous integration software continuous design β modular design process in which components can be freely substituted to improve the design, modify performance or change another feature at a later timepages displaying wikidata descriptions as a fallback continuous testing β process of executing automated tests as part of the software delivery pipeline to obtain immediate feedback on the business risks associated with a release candidatepages displaying wikidata descriptions as a fallback multi - stage continuous integration β software development technique rapid application development β concept of software development = = references = = = = external links = = " continuous integration " ( wiki ) ( a collegial discussion ). c2. { { cite journal } } : cite journal requires | journal = ( help ) richardson, jared. " continuous integration : the cornerstone of a great shop " ( introduction ). flowers, jay. " a recipe for build maintainability and reusability ". archived from the original on 25 june 2020. retrieved 28 may 2006. duvall, paul ( 4 december 2007 ). " developer works ". ibm. " version lifecycle ". mediawiki. june 2024.
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burnishing is the plastic deformation of a surface due to sliding contact with another object. it smooths the surface and makes it shinier. burnishing may occur on any sliding surface if the contact stress locally exceeds the yield strength of the material. the phenomenon can occur both unintentionally as a failure mode, and intentionally as part of a metalworking or manufacturing process. it is a squeezing operation under cold working. = = failure mode ( unintentionally ) = = the action of a hardened ball against a softer, flat plate illustrates the process of burnishing. if the ball is pushed directly into the plate, stresses develop in both objects around the area where they contact. as this normal force increases, both the ball and the plate's surfaces deform. the deformation caused by the hardened ball increases with the magnitude of the force pressing against it. if the force on it is small, when the force is released both the ball and plate's surface will return to their original, undeformed shape. in that case, the stresses in the plate are always less than the yield strength of the material, so the deformation is purely elastic. since it was given that the flat plate is softer than the ball, the plate's surface will always deform more. if a larger force is used, there will also be plastic deformation and the plate's surface will be permanently altered. a bowl - shaped indentation will be left behind, surrounded by a ring of raised material that was displaced by the ball. the stresses between the ball and the plate are described in more detail by hertzian stress theory. dragging the ball across the plate will have a different effect than pressing. in that case, the force on the ball can be decomposed into two component forces : one normal to the plate's surface, pressing it in, and the other tangential, dragging it along. as the tangential component is increased, the ball will start to slide along the plate. at the same time, the normal force will deform both objects, just as with the static situation. if the normal force is low, the ball will rub against the plate but not permanently alter its surface. the rubbing action will create friction and heat, but it will not leave a mark on the plate. however, as the normal force increases, eventually the stresses in the plate's surface will exceed its yield strength. when this happens the ball will plow through the surface and create a trough behind it. the pl
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leave a mark on the plate. however, as the normal force increases, eventually the stresses in the plate's surface will exceed its yield strength. when this happens the ball will plow through the surface and create a trough behind it. the plowing action of the ball is burnishing. burnishing also occurs when the ball can rotate, as would happen in the above scenario if another flat plate was brought down from above to induce downwards loading, and at the same time to cause rotation and translation of the ball, as in the case of a ball bearing. burnishing also occurs on surfaces that conform to each other, such as between two flat plates, but it happens on a microscopic scale. even the smoothest of surfaces will have imperfections if viewed at a high enough magnification. the imperfections that extend above the general form of a surface are called asperities, and they can plow material on another surface just like the ball dragging along the plate. the combined effect of many of these asperities produce the smeared texture that is associated with burnishing. = = effects on sliding contact = = burnishing is normally undesirable in mechanical components for a variety of reasons, sometimes simply because its effects are unpredictable. even light burnishing will significantly alter the surface finish of a part. initially the finish will be smoother, but with repetitive sliding action, grooves will develop on the surface along the sliding direction. the plastic deformation associated with burnishing will harden the surface and generate compressive residual stresses. although these properties are usually advantageous, excessive burnishing leads to sub - surface cracks which cause spalling, a phenomenon where the upper layer of a surface flakes off of the bulk material. burnishing may also affect the performance of a machine. the plastic deformation associated with burnishing creates greater heat and friction than from rubbing alone. this reduces the efficiency of the machine and limits its speed. furthermore, plastic deformation alters the form and geometry of the part. this reduces the precision and accuracy of the machine. the combination of higher friction and degraded form often leads to a runaway situation that continually worsens until the component fails. to prevent destructive burnishing, sliding must be avoided, and in rolling situations, loads must be beneath the spalling threshold. in the areas of a machine that slide with respect to each other, roller bearings can be inserted so that the components are in rolling contact instead of sliding. if sliding cannot be avoided, then a lubricant should be added between the components. the purpose of the
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a machine that slide with respect to each other, roller bearings can be inserted so that the components are in rolling contact instead of sliding. if sliding cannot be avoided, then a lubricant should be added between the components. the purpose of the lubricant in this case is to separate the components with a lubricant film so they cannot contact. the lubricant also distributes the load over a larger area, so that the local contact forces are not as high. if there was already a lubricant, its film thickness must be increased ; usually this can be accomplished by increasing the viscosity of the lubricant. = = in manufacturing ( intentionally ) = = burnishing is not always unwanted. if it occurs in a controlled manner, it can have desirable effects. burnishing processes are used in manufacturing to improve the size, shape, surface finish, or surface hardness of a workpiece. it is essentially a forming operation that occurs on a small scale. the benefits of burnishing often include combatting fatigue failure, preventing corrosion and stress corrosion, texturing surfaces to eliminate visual defects, closing porosity, creating surface compressive residual stress. there are several forms of burnishing processes, the most common are roller burnishing and ball burnishing ( a subset of which is also referred to as ballizing ). in both cases, a burnishing tool runs against the workpiece and plastically deforms its surface. in some instances of the latter case ( and always in ballizing ), it rubs, in the former it generally rotates and rolls. the workpiece may be at ambient temperature, or heated to reduce the forces and wear on the tool. the tool is usually hardened and coated with special materials to increase its life. ball burnishing, or ballizing, is a replacement for other bore finishing operations such as grinding, honing, or polishing. a ballizing tool consists of one or more over - sized balls that are pushed through a hole. the tool is similar to a broach, but instead of cutting away material, it plows it out of the way. ball burnishing is also used as a deburring operation. it is especially useful for removing the burr in the middle of a through hole that was drilled from both sides. ball burnishing tools of another type are sometimes used in cnc milling centres to follow a ball - nosed milling operation : the hardened ball is applied along a zig - zag toolpath in a holder similar to a ball
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drilled from both sides. ball burnishing tools of another type are sometimes used in cnc milling centres to follow a ball - nosed milling operation : the hardened ball is applied along a zig - zag toolpath in a holder similar to a ball - point pen, except that the'ink'is pressurised, recycled lubricant. this combines the productivity of a machined finish which is achieved by a'semi - finishing'cut, with a better finish than obtainable with slow and time - consuming finish cuts. the feed rate for burnishing is that associated with'rapid traverse'rather than finish machining. roller burnishing, or surface rolling, is used on cylindrical, conical, or disk shaped workpieces. the tool resembles a roller bearing, but the rollers are generally very slightly tapered so that their envelope diameter can be accurately adjusted. the rollers typically rotate within a cage, as in a roller bearing. typical applications for roller burnishing include hydraulic system components, shaft fillets, and sealing surfaces. very close control of size can be exercised. burnishing also occurs to some extent in machining processes. in turning, burnishing occurs if the cutting tool is not sharp, if a large negative rake angle is used, if a very small depth of cut is used, or if the workpiece material is gummy. as a cutting tool wears, it becomes more blunt and the burnishing effect becomes more pronounced. in grinding, since the abrasive grains are randomly oriented and some are not sharp, there is always some amount of burnishing. this is one reason the grinding is less efficient and generates more heat than turning. in drilling, burnishing occurs with drills that have lands to burnish the material as it drills into it. regular twist drills or straight fluted drills have 2 lands to guide them through the hole. on burnishing drills there are 4 or more lands, similar to reamers. burnish setting, also known as flush, gypsy, or shot setting, is a setting technique used in stonesetting. a space is drilled, into which a stone is inserted such that the girdle of the stone, the point of maximum diameter, is just below the surface of the metal. a burnishing tool is used to push metal all around the stone to hold the stone and give a flush appearance, with a burnished edge around it. this type of setting has a long history but is gaining a resurgence in contemporary jewelry. = = see also = = low plasticity
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push metal all around the stone to hold the stone and give a flush appearance, with a burnished edge around it. this type of setting has a long history but is gaining a resurgence in contemporary jewelry. = = see also = = low plasticity burnishing = = references = = = = external links = = metal burnishing ( cutlery, pewter, silver ) spons'workshop
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the carryover effect is a term used in clinical chemistry to describe the transfer of unwanted material from one container or mixture to another. it describes the influence of one sample upon the following one. it may be from a specimen, or a reagent, or even the washing medium. the significance of carry over is that even a small amount can lead to erroneous results. = = carryover effect in clinical laboratory = = carryover experiments are widely used for clinical chemistry and immunochemistry analyzers to evaluate and validate carryover effects. the pipetting and washing systems in an automated analyzer are designed to continuously cycle between the aspiration of patient specimens and cleaning. an obvious concern is a potential for carryover of analyte from one patient specimen into one or more following patient specimens, which can falsely increase or decrease the measured analyte concentration. specimen carryover is typically addressed by judicious choice of probe material, probe design, and an efficient probe washing system to flush the probe of residual patient specimens or reagents retained in their bores or clinging to the probe exterior surface before they are introduced into the next patient sample, reagent container, or cuvette / reaction vessel. = = significance in carryover assessment = = the pathological range of measurement could be of several order to reference interval ( e. g., sex hormone, tumor marker, troponin... etc. ). a small portion of carryover could lead to erroneous results. = = carryover assessment = = iupac made a recommendation in 1991 for the description and measurement of carryover effects in clinical chemistry. the carryover ratio is the percentage of h3 carry to l1 constituting the carryover portion " h ". in a design of 3 high samples followed by 3 low samples, h can be calculated as ( l1 - mean of l2 & l3 ) / ( h3 - mean of l2 & l3 ) the carryover ratio's acceptance criteria depend on the measurement and the laboratory concerned. for example, 1 % carryover of plasma albumin would generally lead to a clinically insignificant effect, while 1 % carryover of cardiac high sensitivity troponin assay would be catastrophic. = = references = =
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Carryover effect
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wikipedia
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wpgma ( weighted pair group method with arithmetic mean ) is a simple agglomerative ( bottom - up ) hierarchical clustering method, generally attributed to sokal and michener. the wpgma method is similar to its unweighted variant, the upgma method. = = algorithm = = the wpgma algorithm constructs a rooted tree ( dendrogram ) that reflects the structure present in a pairwise distance matrix ( or a similarity matrix ). at each step, the nearest two clusters, say i { \ displaystyle i } and j { \ displaystyle j }, are combined into a higher - level cluster i βͺ j { \ displaystyle i \ cup j }. then, its distance to another cluster k { \ displaystyle k } is simply the arithmetic mean of the average distances between members of k { \ displaystyle k } and i { \ displaystyle i } and k { \ displaystyle k } and j { \ displaystyle j } : d ( i βͺ j ), k = d i, k + d j, k 2 { \ displaystyle d _ { ( i \ cup j ), k } = { \ frac { d _ { i, k } + d _ { j, k } } { 2 } } } the wpgma algorithm produces rooted dendrograms and requires a constant - rate assumption : it produces an ultrametric tree in which the distances from the root to every branch tip are equal. this ultrametricity assumption is called the molecular clock when the tips involve dna, rna and protein data. = = working example = = this working example is based on a jc69 genetic distance matrix computed from the 5s ribosomal rna sequence alignment of five bacteria : bacillus subtilis ( a { \ displaystyle a } ), bacillus stearothermophilus ( b { \ displaystyle b } ), lactobacillus viridescens ( c { \ displaystyle c } ), acholeplasma modicum ( d { \ displaystyle d } ), and micrococcus luteus ( e { \ displaystyle e } ). = = = first step = = = first clustering let us assume that we have five elements ( a, b, c, d, e ) { \ displaystyle ( a, b, c, d, e ) } and the following matrix d 1 { \ displaystyle d _ { 1 } } of pairwise distances
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WPGMA
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have five elements ( a, b, c, d, e ) { \ displaystyle ( a, b, c, d, e ) } and the following matrix d 1 { \ displaystyle d _ { 1 } } of pairwise distances between them : in this example, d 1 ( a, b ) = 17 { \ displaystyle d _ { 1 } ( a, b ) = 17 } is the smallest value of d 1 { \ displaystyle d _ { 1 } }, so we join elements a { \ displaystyle a } and b { \ displaystyle b }. first branch length estimation let u { \ displaystyle u } denote the node to which a { \ displaystyle a } and b { \ displaystyle b } are now connected. setting Ξ΄ ( a, u ) = Ξ΄ ( b, u ) = d 1 ( a, b ) / 2 { \ displaystyle \ delta ( a, u ) = \ delta ( b, u ) = d _ { 1 } ( a, b ) / 2 } ensures that elements a { \ displaystyle a } and b { \ displaystyle b } are equidistant from u { \ displaystyle u }. this corresponds to the expectation of the ultrametricity hypothesis. the branches joining a { \ displaystyle a } and b { \ displaystyle b } to u { \ displaystyle u } then have lengths Ξ΄ ( a, u ) = Ξ΄ ( b, u ) = 17 / 2 = 8. 5 { \ displaystyle \ delta ( a, u ) = \ delta ( b, u ) = 17 / 2 = 8. 5 } ( see the final dendrogram ) first distance matrix update we then proceed to update the initial distance matrix d 1 { \ displaystyle d _ { 1 } } into a new distance matrix d 2 { \ displaystyle d _ { 2 } } ( see below ), reduced in size by one row and one column because of the clustering of a { \ displaystyle a } with b { \ displaystyle b }. bold values in d 2 { \ displaystyle d _ { 2 } } correspond to the new distances, calculated by averaging distances between each element of the first cluster ( a, b ) { \ displaystyle ( a, b ) } and each of the remaining elements : d 2 ( ( a, b ), c ) = ( d 1 ( a, c ) + d 1 ( b, c ) ) / 2 = ( 21 +
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WPGMA
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displaystyle ( a, b ) } and each of the remaining elements : d 2 ( ( a, b ), c ) = ( d 1 ( a, c ) + d 1 ( b, c ) ) / 2 = ( 21 + 30 ) / 2 = 25. 5 { \ displaystyle d _ { 2 } ( ( a, b ), c ) = ( d _ { 1 } ( a, c ) + d _ { 1 } ( b, c ) ) / 2 = ( 21 + 30 ) / 2 = 25. 5 } d 2 ( ( a, b ), d ) = ( d 1 ( a, d ) + d 1 ( b, d ) ) / 2 = ( 31 + 34 ) / 2 = 32. 5 { \ displaystyle d _ { 2 } ( ( a, b ), d ) = ( d _ { 1 } ( a, d ) + d _ { 1 } ( b, d ) ) / 2 = ( 31 + 34 ) / 2 = 32. 5 } d 2 ( ( a, b ), e ) = ( d 1 ( a, e ) + d 1 ( b, e ) ) / 2 = ( 23 + 21 ) / 2 = 22 { \ displaystyle d _ { 2 } ( ( a, b ), e ) = ( d _ { 1 } ( a, e ) + d _ { 1 } ( b, e ) ) / 2 = ( 23 + 21 ) / 2 = 22 } italicized values in d 2 { \ displaystyle d _ { 2 } } are not affected by the matrix update as they correspond to distances between elements not involved in the first cluster. = = = second step = = = second clustering we now reiterate the three previous steps, starting from the new distance matrix d 2 { \ displaystyle d _ { 2 } } : here, d 2 ( ( a, b ), e ) = 22 { \ displaystyle d _ { 2 } ( ( a, b ), e ) = 22 } is the smallest value of d 2 { \ displaystyle d _ { 2 } }, so we join cluster ( a, b ) { \ displaystyle ( a, b ) } and element e { \ displaystyle e }. second branch length estimation let v { \ displaystyle v } denote the node to which ( a, b ) { \ displaystyle ( a, b ) } and e { \ displaystyle e }
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WPGMA
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and element e { \ displaystyle e }. second branch length estimation let v { \ displaystyle v } denote the node to which ( a, b ) { \ displaystyle ( a, b ) } and e { \ displaystyle e } are now connected. because of the ultrametricity constraint, the branches joining a { \ displaystyle a } or b { \ displaystyle b } to v { \ displaystyle v }, and e { \ displaystyle e } to v { \ displaystyle v } are equal and have the following length : Ξ΄ ( a, v ) = Ξ΄ ( b, v ) = Ξ΄ ( e, v ) = 22 / 2 = 11 { \ displaystyle \ delta ( a, v ) = \ delta ( b, v ) = \ delta ( e, v ) = 22 / 2 = 11 } we deduce the missing branch length : Ξ΄ ( u, v ) = Ξ΄ ( e, v ) β Ξ΄ ( a, u ) = Ξ΄ ( e, v ) β Ξ΄ ( b, u ) = 11 β 8. 5 = 2. 5 { \ displaystyle \ delta ( u, v ) = \ delta ( e, v ) - \ delta ( a, u ) = \ delta ( e, v ) - \ delta ( b, u ) = 11 - 8. 5 = 2. 5 } ( see the final dendrogram ) second distance matrix update we then proceed to update the d 2 { \ displaystyle d _ { 2 } } matrix into a new distance matrix d 3 { \ displaystyle d _ { 3 } } ( see below ), reduced in size by one row and one column because of the clustering of ( a, b ) { \ displaystyle ( a, b ) } with e { \ displaystyle e } : d 3 ( ( ( a, b ), e ), c ) = ( d 2 ( ( a, b ), c ) + d 2 ( e, c ) ) / 2 = ( 25. 5 + 39 ) / 2 = 32. 25 { \ displaystyle d _ { 3 } ( ( ( a, b ), e ), c ) = ( d _ { 2 } ( ( a, b ), c ) + d _ { 2 } ( e, c ) ) / 2 = ( 25. 5 + 39 ) / 2 = 32. 25 } of note, this average calculation of the new distance does not account for the larger size of the (
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WPGMA
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