Miscellany

Jai Ganesh · 2024-04-21 00:06:32

2128) Talk show

Gist

A talk show is a chat show, especially one in which listeners, viewers, or the studio audience are invited to participate in the discussion.

Summary

Talk show, radio or television program in which a well-known personality interviews celebrities and other guests. The late-night television programs hosted by Johnny Carson, Jay Leno, David Letterman, and Conan O’Brien, for example, emphasized entertainment, incorporating interludes of music or comedy. Other talk shows focused on politics (see David Susskind), controversial social issues or sensationalistic topics (Phil Donahue), and emotional therapy (Oprah Winfrey).

Details

A talk show (sometimes chat show in British English) is a television programming, radio programming or Podcast genre structured around the act of spontaneous conversation. A talk show is distinguished from other television programs by certain common attributes. In a talk show, one person (or group of people or guests) discusses various topics put forth by a talk show host. This discussion can be in the form of an interview or a simple conversation about important social, political or religious issues and events. The personality of the host shapes the tone and style of the show. A common feature or unwritten rule of talk shows is to be based on "fresh talk", which is talk that is spontaneous or has the appearance of spontaneity.

The history of the talk show spans back from the 1950s to the present.

Talk shows can also have several different subgenres, which all have unique material and can air at different times of the day via different avenues.

Attributes

Beyond the inclusion of a host, a guest(s), and a studio or call-in audience, specific attributes of talk shows may be identified:

* Talk shows focus on the viewers—including the participants calling in, sitting in a studio or viewing from online or on TV.
* Talk shows center around the interaction of guests with opposing opinions and/or differing levels of expertise, which include both experts and non-experts.
* Although talk shows include guests of various expertise levels, they often cater to the credibility of one's life experiences as opposed to educational expertise.
* Talk shows involve a host responsible for furthering the agenda of the show by mediating, instigating and directing the conversation to ensure the purpose is fulfilled. The purpose of talk shows is to either address or bring awareness to conflicts, to provide information, or to entertain.
* Talk shows consist of evolving episodes that focus on differing perspectives in respect to important issues in society, politics, religion or other popular areas.
* Talk shows are produced at low cost and are typically not aired during prime time.
* Talks shows are either aired live or are recorded live with limited post-production editing.

Subgenres

There are several major formats of talk shows. Generally, each subgenre predominates during a specific programming block during the broadcast day.

* Breakfast chat or early morning shows that generally alternate between news summaries, political coverage, feature stories, celebrity interviews, and musical performances.
* Late morning chat shows that feature two or more hosts or a celebrity panel and focus on entertainment and lifestyle features.
* Daytime tabloid talk shows that generally feature a host, a guest or a panel of guests, and a live audience that interacts extensively with the host and guests. These shows may feature celebrities, political commentators, or "ordinary" people who present unusual or controversial topics.
* "Lifestyle" or self-help programs that generally feature a host or hosts of medical practitioners, therapists, or counselors and guests who seek intervention, describe medical or psychological problems, or offer advice. An example of this type of subgenre is The Oprah Winfrey Show, although it can easily fit into other categories as well.
* Evening panel discussion shows that focus on news, politics, or popular culture (such as the former UK series After Dark which was broadcast "late-night").
* Late-night talk shows that focus primarily on topical comedy and variety entertainment. Most traditionally open with a monologue by the host, with jokes relating to current events. Other segments typically include interviews with celebrity guests, recurring comedy sketches, as well as performances by musicians or other stand-up comics.
* Sunday morning talk shows are a staple of network programming in North America, and generally focus on political news and interviews with elected political figures and candidates for office, commentators, and journalists.
* Aftershows that feature in-depth discussion about a program on the same network that aired just before (for example, Talking Dead).
* Spoof talk shows, such as Space Ghost Coast to Coast, Tim and Eric Nite Live, Comedy Bang! Bang!, and The Eric Andre Show, that feature interviews that are mostly scripted, shown in a humorous and satirical way, or engages in subverting the norms of the format (particularly that of late-night talk shows).

These formats are not absolute; some afternoon programs have similar structures to late-night talk shows. These formats may vary across different countries or markets. Late night talk shows are especially significant in the United States. Breakfast television is a staple of British television. The daytime talk format has become popular in Latin America as well as the United States.

These genres also do not represent "generic" talk show genres. "Generic" genres are categorized based on the audiences' social views of talks shows derived through their cultural identities, fondness, preferences and character judgements of the talk shows in question. The subgenres listed above are based on television programming and broadly defined based on the TV guide rather than on the more specific categorizations of talk show viewers. However, there is a lack of research on "generic" genres, making it difficult to list them here. According to Mittell, "generic" genres is of significant importance in further identifying talk show genres because with such differentiation in cultural preferences within the subgenres, a further distinction of genres would better represent and target the audience.

Talk-radio host Howard Stern also hosted a talk show that was syndicated nationally in the US, then moved to satellite radio's Sirius. The tabloid talk show genre, pioneered by Phil Donahue in 1967 but popularized by Oprah Winfrey, was extremely popular during the last two decades of the 20th century.

Politics are hardly the only subject of American talk shows, however. Other radio talk show subjects include Car Talk hosted by NPR and Coast to Coast AM hosted by Art Bell and George Noory which discusses topics of the paranormal, conspiracy theories, and fringe science. Sports talk shows are also very popular ranging from high-budget shows like The Best darn Sports Show Period to Max Kellerman's original public-access television cable TV show Max on Boxing.

History

Talk shows have been broadcast on television since the earliest days of the medium. Joe Franklin, an American radio and television personality, hosted the first television talk show. The show began in 1951 on WJZ-TV (later WABC-TV) and moved to WOR-TV (later WWOR-TV) from 1962 to 1993.

NBC's The Tonight Show is the world's longest-running talk show; having debuted in 1954, it continues to this day. The show underwent some minor title changes until settling on its current title in 1962, and despite a brief foray into a more news-style program in 1957 and then reverting that same year, it has remained a talk show. Ireland's The Late Late Show is the second-longest running talk show in television history, and the longest running talk show in Europe, having debuted in 1962.

Steve Allen was the first host of The Tonight Show, which began as a local New York show, being picked up by the NBC network in 1954. It in turn had evolved from his late-night radio talk show in Los Angeles. Allen pioneered the format of late night network TV talk shows, originating such talk show staples as an opening monologue, celebrity interviews, audience participation, and comedy bits in which cameras were taken outside the studio, as well as music, although the series' popularity was cemented by second host Jack Paar, who took over after Allen had left and the show had ceased to exist.

TV news pioneer Edward R. Murrow hosted a talk show entitled Small World in the late 1950s and since then, political TV talk shows have predominantly aired on Sunday mornings.

Syndicated daily talk shows began to gain more popularity during the mid-1970s and reached their height of popularity with the rise of the tabloid talk show. Morning talk shows gradually replaced earlier forms of programming — there were a plethora of morning game shows during the 1960s and early to mid-1970s, and some stations formerly showed a morning movie in the time slot that many talk shows now occupy.

Current late night talk shows such as The Tonight Show Starring Jimmy Fallon, Conan and The Late Show with Stephen Colbert have aired featuring celebrity guests and comedy sketches. Syndicated daily talk shows range from tabloid talk shows, such as Jerry Springer and Maury, to celebrity interview shows, like Live with Kelly and Ryan, Tamron Hall, Sherri, Steve Wilkos, The Jennifer Hudson Show and The Kelly Clarkson Show, to industry leader The Oprah Winfrey Show, which popularized the former genre and has been evolving towards the latter. On November 10, 2010, Oprah Winfrey invited several of the most prominent American talk show hosts - Phil Donahue, Sally Jessy Raphael, Geraldo Rivera, Ricki Lake, and Montel Williams - to join her as guests on her show. The 1990s in particular saw a spike in the number of "tabloid" talk shows, most of which were short-lived and are now replaced by a more universally appealing "interview" or "lifestyle TV" format.

Talk shows have more recently started to appear on Internet radio. Also, several Internet blogs are in talk show format including the Baugh Experience.

The current world record for the longest talk show is held by Rabi Lamichhane from Nepal by staying on air for 62 hours from April 11 to 13, 2013 breaking the previous record set by two Ukrainians by airing the show for 52 hours in 2011.

In 2020, the fear of the spread of the coronavirus led to large changes in the operation of talk shows, with many being filmed without live audiences to ensure adherence to the rules of social distancing. The inclusion of a live, participating audience is one of the attributes that contribute to the defining characteristics of talk shows. Operating without the interaction of viewers created difficult moments and awkward silences to hosts who usually used audience responses to transition conversations.

Jai Ganesh · 2024-04-22 00:06:25

2129) Technocracy

Gist

a) a proponent, adherent, or supporter of technocracy.
b) a technological expert, especially one concerned with management or administration.

Summary

Technocracy, government by technicians who are guided solely by the imperatives of their technology. The concept developed in the United States early in the 20th century as an expression of the Progressive movement and became a subject of considerable public interest in the 1930s during the Great Depression. The origins of the technocracy movement may be traced to Frederick W. Taylor’s introduction of the concept of scientific management. Writers such as Henry L. Gannt, Thorstein Veblen, and Howard Scott suggested that businessmen were incapable of reforming their industries in the public interest and that control of industry should thus be given to engineers.

The much-publicized Committee on Technocracy, headed by Walter Rautenstrauch and dominated by Scott, was organized in 1932 in New York City. Scott proclaimed the invalidation, by technologically produced abundance, of all prior economic concepts based on scarcity; he predicted the imminent collapse of the price system and its replacement by a bountiful technocracy. Scott’s academic qualifications, however, were discredited in the press, some of the group’s data were questioned, and there were disagreements among members regarding social policy. The committee broke up within a year and was succeeded by the Continental Committee on Technocracy, which faded by 1936, and Technocracy, Inc., headed by Scott. Technocratic organizations sprang up across the United States and western Canada, but the technocracy movement was weakened by its failure to develop politically viable programs for change, and support was lost to the New Deal and third-party movements. There were also fears of authoritarian social engineering. Scott’s organization declined after 1940 but still survived in the late 20th century.

Details

What Is Technocracy?

A technocracy is a model of governance wherein decision-makers are chosen for office based on their technical expertise and background. A technocracy differs from a traditional democracy in that individuals selected to a leadership role are chosen through a process that emphasizes their relevant skills and proven performance, as opposed to whether or not they fit the majority interests of a popular vote.

The individuals that occupy such positions in a technocracy are known as "technocrats." An example of a technocrat could be a central banker who is a trained economist and follows a set of rules that apply to empirical data.

KEY TAKEAWAYS

* A technocracy is a form of governance whereby government officials or policymakers, known as technocrats, are chosen by some higher authority due to their technical skills or expertise in a specific domain.
* Decisions made by technocrats are supposed to be based on information derived from data and objective methodology, rather than opinion or self-interest.
* Critics complain that technocracy is undemocratic and disregards the will of the people.

How Technocracy Works

A technocracy is a political entity ruled by experts (technocrats) that are selected or appointed by some higher authority. Technocrats are, supposedly, selected specifically for their expertise in the area over which they are delegated authority to govern. In practice, because technocrats must always be appointed by some higher authority, the political structure and incentives that influence that higher authority will always also play some role in the selection of technocrats.

An official who is labeled as a technocrat may not possess the political savvy or charisma that is typically expected of an elected politician. Instead, a technocrat may demonstrate more pragmatic and data-oriented problem-solving skills in the policy arena.

Technocracy became a popular movement in the United States during the Great Depression when it was believed that technical professionals, such as engineers and scientists, would have a better understanding than politicians regarding the economy's inherent complexity.

Although democratically officials may hold seats of authority, most come to rely on the technical expertise of select professionals in order to execute their plans.

Defense measures and policies in government are often developed with considerable consultation with military personnel to provide their firsthand insight. Medical treatment decisions, meanwhile, are based heavily on the input and knowledge of physicians, and city infrastructures could not be planned, designed, or constructed without the input of engineers.

Critiques of Technocracy

Reliance on technocracy can be criticized on several grounds. The acts and decisions of technocrats can come into conflict with the will, rights, and interests of the people whom they rule over. This in turn has often led to populist opposition to both specific technocratic policy decisions and to the degree of power in general granted to technocrats. These problems and conflicts help give rise to the populist concept of the "deep state", which consists of a powerful, entrenched, unaccountable, and oligarchic technocracy which governs in its own interests.

In a democratic society, the most obvious criticism is that there is an inherent tension between technocracy and democracy. Technocrats often may not follow the will of the people because by definition they may have specialized expertise that the general population lacks. Technocrats may or may not be accountable to the will of the people for such decisions.

In a government where citizens are guaranteed certain rights, technocrats may seek to encroach upon these rights if they believe that their specialized knowledge suggests that it is appropriate or in the larger public interest. The focus on science and technical principles might also be seen as separate and disassociated from the humanity and nature of society. For instance, a technocrat might make decisions based on calculations of data rather than the impact on the populace, individuals, or groups within the population.

In any government, regardless of who appoints the technocrats or how, there is always a risk that technocrats will engage in policymaking that favors their own interests or others whom they serve over the public interest. Technocrats are necessarily placed in a position of trust, since the knowledge used to enact their decisions is to some degree inaccessible or not understandable to the general public. This creates a situation where there can be a high risk of self-dealing, collusion, corruption, and cronyism. Economic problems such as rent-seeking, rent-extraction, or regulatory capture are common in technocracy.

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Additional Information

Technocracy is a form of government in which the decision-makers are selected based on their expertise in a given area of responsibility, particularly with regard to scientific or technical knowledge. Technocracy follows largely in the tradition of other meritocracy theories and assumes full state control over political and economic issues.

This system explicitly contrasts with representative democracy, the notion that elected representatives should be the primary decision-makers in government, though it does not necessarily imply eliminating elected representatives. Decision-makers are selected based on specialized knowledge and performance rather than political affiliations, parliamentary skills, or popularity.

The term technocracy was initially used to signify the application of the scientific method to solving social problems. In its most extreme form, technocracy is an entire government running as a technical or engineering problem and is mostly hypothetical. In more practical use, technocracy is any portion of a bureaucracy run by technologists. A government in which elected officials appoint experts and professionals to administer individual government functions, and recommend legislation, can be considered technocratic. Some uses of the word refer to a form of meritocracy, where the ablest are in charge, ostensibly without the influence of special interest groups. Critics have suggested that a "technocratic divide" challenges more participatory models of democracy, describing these divides as "efficacy gaps that persist between governing bodies employing technocratic principles and members of the general public aiming to contribute to government decision making".

History of the term

The term technocracy is derived from the Greek words, tekhne meaning skill and κράτος, kratos meaning power, as in governance, or rule. William Henry Smyth, a California engineer, is usually credited with inventing the word technocracy in 1919 to describe "the rule of the people made effective through the agency of their servants, the scientists and engineers", although the word had been used before on several occasions. Smyth used the term Technocracy in his 1919 article "'Technocracy'—Ways and Means to Gain Industrial Democracy" in the journal Industrial Management. Smyth's usage referred to Industrial democracy: a movement to integrate workers into decision-making through existing firms or revolution.

In the 1930s, through the influence of Howard Scott and the technocracy movement he founded, the term technocracy came to mean 'government by technical decision making', using an energy metric of value. Scott proposed that money be replaced by energy certificates denominated in units such as ergs or joules, equivalent in total amount to an appropriate national net energy budget, and then distributed equally among the North American population, according to resource availability.

There is in common usage found the derivative term technocrat. The word technocrat can refer to someone exercising governmental authority because of their knowledge, "a member of a powerful technical elite", or "someone who advocates the supremacy of technical experts". McDonnell and Valbruzzi define a prime minister or minister as a technocrat if "at the time of their appointment to government, they: have never held public office under the banner of a political party; are not a formal member of any party; and are said to possess recognized non-party political expertise which is directly relevant to the role occupied in government". In Russia, the President of Russia has often nominated ministers based on technical expertise from outside political circles, and these have been referred to as "technocrats".

Characteristics

Technocrats are individuals with technical training and occupations who perceive many important societal problems as being solvable with the applied use of technology and related applications. The administrative scientist Gunnar K. A. Njalsson theorizes that technocrats are primarily driven by their cognitive "problem-solution mindsets" and only in part by particular occupational group interests. Their activities and the increasing success of their ideas are thought to be a crucial factor behind the modern spread of technology and the largely ideological concept of the "information society". Technocrats may be distinguished from "econocrats" and "bureaucrats" whose problem-solution mindsets differ from those of the technocrats.

Examples

The former government of the Soviet Union has been referred to as a technocracy. Soviet leaders like Leonid Brezhnev often had a technical background. In 1986, 89% of Politburo members were engineers.

Leaders of the Chinese Communist Party used to be mostly professional engineers. According to surveys of municipal governments of cities with a population of 1 million or more in China, it has been found that over 80% of government personnel had a technical education. Under the five-year plans of the People's Republic of China, projects such as the National Trunk Highway System, the China high-speed rail system, and the Three Gorges Dam have been completed. During China's 20th National Congress, a class of technocrats in finance and economics are replaced in favor of high-tech technocrats.

In 2013, a European Union library briefing on its legislative structure referred to the Commission as a "technocratic authority", holding a "legislative monopoly" over the EU lawmaking process. The briefing suggests that this system, which elevates the European Parliament to a vetoing and amending body, was "originally rooted in the mistrust of the political process in post-war Europe". This system is unusual since the Commission's sole right of legislative initiative is a power usually associated with Parliaments.

Several governments in European parliamentary democracies have been labelled 'technocratic' based on the participation of unelected experts ('technocrats') in prominent positions. Since the 1990s, Italy has had several such governments (in Italian, governo tecnico) in times of economic or political crisis, including the formation in which economist Mario Monti presided over a cabinet of unelected professionals. The term 'technocratic' has been applied to governments where a cabinet of elected professional politicians is led by an unelected prime minister, such as in the cases of the 2011-2012 Greek government led by economist Lucas Papademos and the Czech Republic's 2009–2010 caretaker government presided over by the state's chief statistician, Jan Fischer. In December 2013, in the framework of the national dialogue facilitated by the Tunisian National Dialogue Quartet, political parties in Tunisia agreed to install a technocratic government led by Mehdi Jomaa.

The article "Technocrats: Minds Like Machines" states that Singapore is perhaps the best advertisement for technocracy: the political and expert components of the governing system there seem to have merged completely. This was underlined in a 1993 article in "Wired" by Sandy Sandfort, where he describes the information technology system of the island even at that early date making it effectively intelligent.

Engineering

Following Samuel Haber, Donald Stabile argues that engineers were faced with a conflict between physical efficiency and cost efficiency in the new corporate capitalist enterprises of the late nineteenth-century United States. Because of their perceptions of market demand, the profit-conscious, non-technical managers of firms where the engineers work often impose limits on the projects that engineers desire to undertake.

The prices of all inputs vary with market forces, thereby upsetting the engineer's careful calculations. As a result, the engineer loses control over projects and must continually revise plans. To maintain control over projects, the engineer must attempt to control these outside variables and transform them into constant factors.

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Jai Ganesh · 2024-04-22 22:52:21

2130) Hairdresser

Gist

A hairdresser is a person who cuts people's hair and puts it into a style, usually working in a special shop, called a hairdresser's.

Summary

A hairdresser's job is to organise hair into a particular style or "look". They can cut hair, add colour to it or texture it. A hairdresser may be female or male. Qualified staff are usually called "stylists", who are supported by assistants. Most hairdressing businesses are unisex, that is, they serve both sexes, and have both sexes on their staff.

Male hairdressers who simply cut men's hair (and do not serve females) are often called barbers.

Qualifications for hairdressing usually mean a college course, or an apprenticeship under a senior stylist. Some aspects of the job are quite technical (such as hair dying) and require careful teaching.

Details

A hairdresser is a person whose occupation is to cut or style hair in order to change or maintain a person's image. This is achieved using a combination of hair coloring, haircutting, and hair texturing techniques. A hairdresser may also be referred to as a 'barber' or 'hairstylist'.

History:

Ancient hairdressing

Hairdressing as an occupation dates back thousands of years. Both Aristophanes and Homer, Greek writers, mention hairdressing in their writings. Many Africans believed that hair is a method to communicate with the Divine Being. It is the highest part of the body and therefore the closest to the divine. Because of this Hairdressers held a prominent role in African communities. The status of hairdressing encouraged many to develop their skills, and close relationships were built between hairdressers and their clients. Hours would be spent washing, combing, oiling, styling and ornamenting their hair. Men would work specifically on men, and women on other women. Before a master hairdresser died, they would give their combs and tools to a chosen successor during a special ceremony.

In ancient Egypt, hairdressers had specially decorated cases to hold their tools, including lotions, scissors and styling materials. Barbers also worked as hairdressers, and wealthy men often had personal barbers within their home. With the standard of wig wearing within the culture, wigmakers were also trained as hairdressers. In ancient Rome and Greece household slaves and servants took on the role of hairdressers, including dyeing and shaving. Men who did not have their own private hair or shaving services would visit the local barbershop. Women had their hair maintained and groomed at their homes. Historical documentation is lacking regarding hairstylists from the 5th century until the 14th century. Hair care service grew in demand after a papal decree in 1092 demanded that all Roman Catholic clergymen remove their facial hair.

Europe

The first appearance of the word "hairdresser" is in 17th century Europe, and hairdressing was considered a profession. Hair fashion of the period suggested that wealthy women wear large, complex and heavily adorned hairstyles, which would be maintained by their personal maids and other people, who would spend hours dressing the woman's hair. A wealthy man's hair would often be maintained by a valet. It was in France where men began styling women's hair for the first time, and many of the notable hairdressers of the time were men, a trend that would continue into contemporary times. The first famous male hairdresser was Champagne, who was born in Southern France. Upon moving to Paris, he opened his own hair salon and dressed the hair of wealthy Parisian women until his death in 1658.

Women's hair grew taller in style during the 17th century, popularized by the hairdresser Madame Martin. The hairstyle, "the tower," was the trend with wealthy English and American women, who relied on hairdressers to style their hair as tall as possible. Tall piles of curls were pomaded, powdered and decorated with ribbons, flowers, lace, feathers and jewelry. The profession of hairdressing was launched as a genuine profession when Legros de Rumigny was declared the first official hairdresser of the French court. In 1765 de Rumigny published his book Art de la Coiffure des Dames, which discussed hairdressing and included pictures of hairstyles designed by him. The book was a best seller amongst Frenchwomen, and four years later de Rumigny opened a school for hairdressers: Academie de Coiffure. At the school he taught men and women to cut hair and create his special hair designs.

By 1777, approximately 1,200 hairdressers were working in Paris. During this time, barbers formed unions, and demanded that hairdressers do the same. Wigmakers also demanded that hairdressers cease taking away from their trade, and hairdressers responded that their roles were not the same, hairdressing was a service, and wigmakers made and sold a product. de Rumigny died in 1770 and other hairdressers gained in popularity, specifically three Frenchmen: Frederic, Larseueur, and Léonard. Leonard and Larseueur were the stylists for Marie Antoinette. Leonard was her favorite, and developed many hairstyles that became fashion trends within wealthy Parisian circles, including the loge d'opera, which towered five feet over the wearer's head. During the French Revolution he escaped the country hours before he was to be arrested, alongside the king, queen, and other clients. Léonard emigrated to Russia, where he worked as the premier hairdresser for Russian nobility.

19th century

Parisian hairdressers continued to develop influential styles during the early 19th century. Wealthy French women would have their favorite hairdressers style their hair from within their own homes, a trend seen in wealthy international communities. Hairdressing was primarily a service affordable only to those wealthy enough to hire professionals or to pay for servants to care for their hair. In the United States, Marie Laveau was one of the most famous hairdressers of the period. Laveau, located in New Orleans, began working as a hairdresser in the early 1820s, maintaining the hair of wealthy women of the city. She was a voodoo practitioner, called the "Voodoo Queen of New Orleans," and she used her connections to wealthy women to support her religious practice. She provided "help" to women who needed it for money, gifts and other favors.

French hairdresser Marcel Grateau developed the "Marcel wave" in the late part of the century. His wave required the use of a special hot hair iron and needed to be done by an experienced hairdresser. Fashionable women asked to have their hair "marceled." During this period, hairdressers began opening salons in cities and towns, led by Martha Matilda Harper, who developed one of the first retail chains of hair salons, the Harper Method.

20th century

Beauty salons became popularized during the 20th century, alongside men's barbershops. These spaces served as social spaces, allowing women to socialize while having their hair done and other services such as facials. Wealthy women still had hairdressers visit their home, but, the majority of women visited salons for services, including high-end salons such as Elizabeth Arden's Red Door Salon.

Major advancements in hairdressing tools took place during this period. Electricity led to the development of permanent wave machines and hair dryers. These tools allowed hairdressers to promote visits to their salons, over limited service in-home visits. New coloring processes were developed, including those by Eugène Schueller in Paris, which allowed hairdressers to perform complicated styling techniques. After World War I, the bob cut and the shingle bob became popular, alongside other short haircuts. In the 1930s complicated styles came back into fashion, alongside the return of the Marcel wave. Hairdressing was one of the few acceptable professions during this time for women, alongside teaching, nursing and clerical work.

Modern hairdressing:

Specialties

Some hairstylists specialize in particular services, such as colorists, who specialize in coloring hair.

By country:

United States

Occupationally, hairdressing is expected to grow faster than the average for all other occupations, at 20%. A state license is required for hairdressers to practice, with qualifications varying from state to state. Generally a person interested in hairdressing must have a high school diploma or GED, be at least 16 years of age, and have graduated from a state-licensed barber or cosmetology school. Full-time programs often last 9 months or more, leading to an associate degree. After students graduate from a program, they take a state licensing exam, which often consists of a written test, and a practical test of styling or an oral exam. Hairdressers must pay for licenses, and occasionally licenses must be renewed. Some states allow hairdressers to work without obtaining a new license, while others require a new license. About 44% of hairdressers are self-employed, often putting in 40-hour work weeks, and even longer among the self-employed. In 2008, 29% of hairstylists worked part-time, and 14% had variable schedules. As of 2008, people working as hairdressers totaled about 630,700, with a projected increase to 757,700 by 2018.

Occupational health hazards

Like many occupations, hairdressing is associated with potential health hazards stemming from the products workers use on the job as well as the environment they work in. Exposure risks are highly variable throughout the profession due to differences in the physical workspace, such as use of proper ventilation, as well as individual exposures to various chemicals throughout one's career. Hairdressers encounter a variety of chemicals on the job due to handling products such as shampoos, conditioners, sprays, chemical straighteners, permanent curling agents, bleaching agents, and dyes. While the U.S. Food and Drug Administration does hold certain guidelines over cosmetic products, such as proper labeling and provisions against adulteration, the FDA does not require approval of products prior to being sold to the public. This leaves opportunity for variations in product formulation, which can make occupational exposure evaluation challenging. However, there are certain chemicals that are commonly found in products used in hair salons and have been the subject of various occupational hazard studies.

Formaldehyde

Formaldehyde is a chemical used in various industries and has been classified by the International Agency for Research on Cancer or IARC as “carcinogenic to humans”. The presence of formaldehyde and methylene glycol, a formaldehyde derivative, have been found in hair smoothing products, such as the Brazilian Blowout. The liquid product is applied to the hair, which is then dried using a blow dryer. Simulation studies as well as observational studies of working salons have shown formaldehyde levels in the air that meet and exceed occupational exposure limits. Variations in observed levels are a function of ventilation used in the workplace as well as the levels of formaldehyde, and its derivatives, in the product itself.

Aromatic amines

Aromatic amines are a broad class of compounds containing an amine group attached to an aromatic ring. IARC has categorized most aromatic amines as known carcinogens. Their use spans several industries including use in pesticides, medications, and industrial dyes. Aromatic amines have also been found in oxidative (permanent) hair dyes; however due to their potential for carcinogenicity, they were removed from most hair dye formulations and their use was completely banned in the European Union.

Phthalates

Phthalates are a class of compounds that are esters of phthalic acid. Their main use has been as plasticizers, additives to plastic products to change certain physical characteristics. They have also been widely used in cosmetic products as preservatives, including shampoos and hair sprays. Phthalates have been implicated as endocrine disrupting chemicals, compounds that mimic the body's own hormones and can lead to dysregulation of the reproductive and neurologic systems as well as changes in metabolism and cell proliferation.

Health considerations:

Reproductive

Most hairdressers are women of childbearing age, which lends to additional considerations for potential workplace exposures and the risks they may pose. There have been studies linking mothers who are hairdressers with adverse birthing outcomes such as low birth weight, preterm delivery, perinatal death, and neonates who are small for gestational age. However, these studies failed to show a well-defined association between individual risk factors and adverse birthing outcomes. Other studies have also indicated a correlation between professional hairdressing and menstrual dysfunction as well as subfertility. However, subsequent studies did not show similar correlations. Due to such inconsistencies, further research is required.

Oncologic

The International Agency for Research on Cancer or IARC, has categorized occupational exposures of hairdressers and barbers to chemical agents found in the workplace as “probably carcinogenic to humans” or category 2A in their classification system. This is due in part to the presence of chemical compounds historically found in hair products that have exhibited mutagenic and carcinogenic effects in animal and in vitro studies. However, the same consistent effects have yet to be fully determined in humans. There have been studies showing a link between occupational exposure to hair dyes and increased risk of bladder in male hairdressers but not females. Other malignancies such as ovarian, breast and lung cancers have also been studied in hairdressers, but the outcomes of these studies were either inconclusive due to potential confounding or did not exhibit an increase in risk.

Respiratory

Volatile organic compounds have been shown to be the largest inhalation exposure in hair salons, with the greatest concentrations occurring while mixing hair dyes and with use of hair sprays. Other notable respiratory exposures included ethanol, ammonia, and formaldehyde. The concentration of exposure was generally found to be a function of the presence or absence of ventilation in the area in which they were working. Studies have exhibited an increased rate of respiratory symptoms experienced such as cough, wheezing, rhinitis, and shortness of breath among hairdressers when compared to other groups. Decreased lung function levels on spirometry have also been demonstrated in hairdressers when compared to unexposed reference groups.

Dermal

Contact dermatitis is a common dermatological diagnosis affecting hairdressers. Allergen sensitization has been considered the main cause for most cases of contact dermatitis in hairdressers, as products such as hair dyes and bleaches, as well as permanent curling agents contain chemicals that are known sensitizers. Hairdressers also spend a significant amount of time engaging in wet work with their hands being directly immersed in water or by handling of wet hair and tools. Overtime, this type of work has also been implicated in increased rate of irritant dermatitis among hairdressers due to damage of the skins natural protective barrier

Jai Ganesh · 2024-04-24 00:08:56

2131) Amputation

Gist

Amputation is the loss or removal of a body part such as a finger, toe, hand, foot, arm or leg. It can be a life changing experience affecting your ability to move, work, interact with others and maintain your independence.

Summary

Amputation is the removal of a limb by trauma, medical illness, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on individuals as a preventive surgery for such problems. A special case is that of congenital amputation, a congenital disorder, where fetal limbs have been cut off by constrictive bands. In some countries, judicial amputation is currently used to punish people who commit crimes. Amputation has also been used as a tactic in war and acts of terrorism; it may also occur as a war injury. In some cultures and religions, minor amputations or mutilations are considered a ritual accomplishment. When done by a person, the person executing the amputation is an amputator. The oldest evidence of this practice comes from a skeleton found buried in Liang Tebo cave, East Kalimantan, Indonesian Borneo dating back to at least 31,000 years ago, where it was done when the amputee was a young child.

Details

Amputation is the surgical removal of all or part of a limb or extremity such as an arm, leg, foot, hand, toe, or finger.

About 1.8 million Americans are living with amputations. Amputation of the leg -- either above or below the knee -- is the most common amputation surgery.

Reasons for Amputation

There are many reasons an amputation may be necessary. The most common is poor circulation because of damage or narrowing of the arteries, called peripheral arterial disease. Without adequate blood flow, the body's cells cannot get oxygen and nutrients they need from the bloodstream. As a result, the affected tissue begins to die and infection may set in.

Other causes for amputation may include:

* Severe injury (from a vehicle accident or serious burn, for example)
* Cancerous tumor in the bone or muscle of the limb
* Serious infection that does not get better with antibiotics or other treatment
* Thickening of nerve tissue, called a neuroma
* Frostbite

The Amputation Procedure

An amputation usually requires a hospital stay of five to 14 days or more, depending on the surgery and complications. The procedure itself may vary, depending on the limb or extremity being amputated and the patient's general health.

Amputation may be done under general anesthesia (meaning the patient is asleep) or with spinal anesthesia, which numbs the body from the waist down.

When performing an amputation, the surgeon removes all damaged tissue while leaving as much healthy tissue as possible.

A doctor may use several methods to determine where to cut and how much tissue to remove. These include:

* Checking for a pulse close to where the surgeon is planning to cut
* Comparing skin temperatures of the affected limb with those of a healthy limb
* Looking for areas of reddened skin
* Checking to see if the skin near the site where the surgeon is planning to cut is still sensitive to touch

During the procedure itself, the surgeon will:

* Remove the diseased tissue and any crushed bone
* Smooth uneven areas of bone
* Seal off blood vessels and nerves
* Cut and shape muscles so that the stump, or end of the limb, will be able to have an artificial limb (prosthesis) attached to it

The surgeon may choose to close the wound right away by sewing the skin flaps (called a closed amputation). Or the surgeon may leave the site open for several days in case there's a need to remove additional tissue.

The surgical team then places a sterile dressing on the wound and may place a stocking over the stump to hold drainage tubes or bandages. The doctor may place the limb in traction, in which a device holds it in position, or may use a splint.

Recovery From Amputation

Recovery from amputation depends on the type of procedure and anesthesia used.

In the hospital, the staff changes the dressings on the wound or teaches the patient to change them. The doctor monitors wound healing and any conditions that might interfere with healing, such as diabetes or hardening of the arteries. The doctor prescribes medications to ease pain and help prevent infection.

If the patient has problems with phantom pain (a sense of pain in the amputated limb) or grief over the lost limb, the doctor will prescribe medication and/or counseling, as necessary.

Physical therapy, beginning with gentle, stretching exercises, often begins soon after surgery. Practice with the artificial limb may begin as soon as 10 to 14 days after surgery.

Ideally, the wound should fully heal in about four to eight weeks. But the physical and emotional adjustment to losing a limb can be a long process. Long-term recovery and rehabilitation will include:

* Exercises to improve muscle strength and control
* Activities to help restore the ability to carry out daily activities and promote independence
* Use of artificial limbs and assistive devices
* Emotional support, including counseling, to help with grief over the loss of the limb and adjustment to the new body image

Additional Information:

Prevention

Methods in preventing amputation, limb-sparing techniques, depend on the problems that might cause amputations to be necessary. Chronic infections, often caused by diabetes or decubitus ulcers in bedridden patients, are common causes of infections that lead to gangrene, which, when widespread, necessitates amputation.

There are two key challenges: first, many patients have impaired circulation in their extremities, and second, they have difficulty curing infections in limbs with poor blood circulation.

Crush injuries where there is extensive tissue damage and poor circulation also benefit from hyperbaric oxygen therapy (HBOT). The high level of oxygenation and revascularization speed up recovery times and prevent infections.

A study found that the patented method called Circulator Boot achieved significant results in prevention of amputation in patients with diabetes and arteriosclerosis. Another study found it also effective for healing limb ulcers caused by peripheral vascular disease. The boot checks the heart rhythm and compresses the limb between heartbeats; the compression helps cure the wounds in the walls of veins and arteries, and helps to push the blood back to the heart.

For victims of trauma, advances in microsurgery in the 1970s have made replantations of severed body parts possible.

The establishment of laws, rules, and guidelines, and employment of modern equipment help protect people from traumatic amputations.

Prognosis

The individual may experience psychological trauma and emotional discomfort. The stump will remain an area of reduced mechanical stability. Limb loss can present significant or even drastic practical limitations.

A large proportion of amputees (50–80%) experience the phenomenon of phantom limbs; they feel body parts that are no longer there. These limbs can itch, ache, burn, feel tense, dry or wet, locked in or trapped or they can feel as if they are moving. Some scientists believe it has to do with a kind of neural map that the brain has of the body, which sends information to the rest of the brain about limbs regardless of their existence. Phantom sensations and phantom pain may also occur after the removal of body parts other than the limbs, e.g. after amputation of the breast, extraction of a tooth (phantom tooth pain) or removal of an eye (phantom eye syndrome).

A similar phenomenon is unexplained sensation in a body part unrelated to the amputated limb. It has been hypothesized that the portion of the brain responsible for processing stimulation from amputated limbs, being deprived of input, expands into the surrounding brain, such that an individual who has had an arm amputated will experience unexplained pressure or movement on his face or head.

In many cases, the phantom limb aids in adaptation to a prosthesis, as it permits the person to experience proprioception of the prosthetic limb. To support improved resistance or usability, comfort or healing, some type of stump socks may be worn instead of or as part of wearing a prosthesis.

Another side effect can be heterotopic ossification, especially when a bone injury is combined with a head injury. The brain signals the bone to grow instead of scar tissue to form, and nodules and other growth can interfere with prosthetics and sometimes require further operations. This type of injury has been especially common among soldiers wounded by improvised explosive devices in the Iraq War.

Due to technological advances in prosthetics, many amputees live active lives with little restriction. Organizations such as the Challenged Athletes Foundation have been developed to give amputees the opportunity to be involved in athletics and adaptive sports such as amputee soccer.

Nearly half of the individuals who have an amputation due to vascular disease will die within 5 years, usually secondary to the extensive co-morbidities rather than due to direct consequences of amputation. This is higher than the five year mortality rates for breast cancer, colon cancer, and prostate cancer. Of persons with diabetes who have a lower extremity amputation, up to 55% will require amputation of the second leg within two to three years.

Amputation is surgery to remove all or part of a limb or extremity (outer limbs). Common types of amputation involve:

* Above-knee amputation, removing part of the thigh, knee, shin, foot and toes.
* Below-knee amputation, removing the lower leg, foot and toes.
* Arm amputation.
* Hand amputation.
* Finger amputation.
* Foot amputation, removing part of the foot.
* Toe amputation.

Why are amputations done?

Amputation can be necessary to keep an infection from spreading through your limbs and to manage pain. The most common reason for an amputation is a wound that does not heal. Often this can be from not having enough blood flow to that limb.

After a severe injury, such as a crushing injury, amputation may be necessary if the surgeon cannot repair your limb.

You also may need an amputation if you have:

* Cancerous tumors in the limb.
* Frostbite.
* Gangrene (tissue death).
* Neuroma, or thickening of nerve tissue.
* Peripheral arterial disease (PAD), or blockage of the arteries.
* Severe injury, such as from a car accident.
* Diabetes that leads to nonhealing or infected wounds or tissue death.

Jai Ganesh · 2024-04-25 00:10:52

2132) Chemistry

Gist

Chemistry is a branch of natural science that deals principally with the properties of substances, the changes they undergo, and the natural laws that describe these changes.

Summary

Chemistry, the science that deals with the properties, composition, and structure of substances (defined as elements and compounds), the transformations they undergo, and the energy that is released or absorbed during these processes. Every substance, whether naturally occurring or artificially produced, consists of one or more of the hundred-odd species of atoms that have been identified as elements. Although these atoms, in turn, are composed of more elementary particles, they are the basic building blocks of chemical substances; there is no quantity of oxygen, mercury, or gold, for example, smaller than an atom of that substance. Chemistry, therefore, is concerned not with the subatomic domain but with the properties of atoms and the laws governing their combinations and how the knowledge of these properties can be used to achieve specific purposes.

The great challenge in chemistry is the development of a coherent explanation of the complex behaviour of materials, why they appear as they do, what gives them their enduring properties, and how interactions among different substances can bring about the formation of new substances and the destruction of old ones. From the earliest attempts to understand the material world in rational terms, chemists have struggled to develop theories of matter that satisfactorily explain both permanence and change. The ordered assembly of indestructible atoms into small and large molecules, or extended networks of intermingled atoms, is generally accepted as the basis of permanence, while the reorganization of atoms or molecules into different arrangements lies behind theories of change. Thus chemistry involves the study of the atomic composition and structural architecture of substances, as well as the varied interactions among substances that can lead to sudden, often violent reactions.

Chemistry also is concerned with the utilization of natural substances and the creation of artificial ones. Cooking, fermentation, glass making, and metallurgy are all chemical processes that date from the beginnings of civilization. Today, vinyl, Teflon, liquid crystals, semiconductors, and superconductors represent the fruits of chemical technology. The 20th century saw dramatic advances in the comprehension of the marvelous and complex chemistry of living organisms, and a molecular interpretation of health and disease holds great promise. Modern chemistry, aided by increasingly sophisticated instruments, studies materials as small as single atoms and as large and complex as DNA (deoxyribonucleic acid), which contains millions of atoms. New substances can even be designed to bear desired characteristics and then synthesized. The rate at which chemical knowledge continues to accumulate is remarkable. Over time more than 8,000,000 different chemical substances, both natural and artificial, have been characterized and produced. The number was less than 500,000 as recently as 1965.

Intimately interconnected with the intellectual challenges of chemistry are those associated with industry. In the mid-19th century the German chemist Justus von Liebig commented that the wealth of a nation could be gauged by the amount of sulfuric acid it produced. This acid, essential to many manufacturing processes, remains today the leading chemical product of industrialized countries. As Liebig recognized, a country that produces large amounts of sulfuric acid is one with a strong chemical industry and a strong economy as a whole. The production, distribution, and utilization of a wide range of chemical products is common to all highly developed nations. In fact, one can say that the “iron age” of civilization is being replaced by a “polymer age,” for in some countries the total volume of polymers now produced exceeds that of iron.

Details

Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during reactions with other substances. Chemistry also addresses the nature of chemical bonds in chemical compounds.

In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant growth (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties of the soil on the Moon (cosmochemistry), how medications work (pharmacology), and how to collect DNA evidence at a crime scene (forensics).

Chemistry has existed under various names since ancient times. It has evolved, and now chemistry encompasses various areas of specialisation, or subdisciplines, that continue to increase in number and interrelate to create further interdisciplinary fields of study. The applications of various fields of chemistry are used frequently for economic purposes in the chemical industry.

Etymology

The word chemistry comes from a modification during the Renaissance of the word alchemy, which referred to an earlier set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism, and medicine. Alchemy is often associated with the quest to turn lead or other base metals into gold, though alchemists were also interested in many of the questions of modern chemistry.

The modern word alchemy in turn is derived from the Arabic word al-kīmīā. This may have Egyptian origins since al-kīmīā is derived from the Ancient Greek, which is in turn derived from the word Kemet, which is the ancient name of Egypt in the Egyptian language. Alternately, al-kīmīā may derive from 'cast together'.

Modern principles

The current model of atomic structure is the quantum mechanical model. Traditional chemistry starts with the study of elementary particles, atoms, molecules, substances, metals, crystals and other aggregates of matter. Matter can be studied in solid, liquid, gas and plasma states, in isolation or in combination. The interactions, reactions and transformations that are studied in chemistry are usually the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together. Such behaviors are studied in a chemistry laboratory.

The chemistry laboratory stereotypically uses various forms of laboratory glassware. However glassware is not central to chemistry, and a great deal of experimental (as well as applied/industrial) chemistry is done without it.

A chemical reaction is a transformation of some substances into one or more different substances. The basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. It can be symbolically depicted through a chemical equation, which usually involves atoms as subjects. The number of atoms on the left and the right in the equation for a chemical transformation is equal. (When the number of atoms on either side is unequal, the transformation is referred to as a nuclear reaction or radioactive decay.) The type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.

Energy and entropy considerations are invariably important in almost all chemical studies. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions. They can be analyzed using the tools of chemical analysis, e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists. Most chemists specialize in one or more sub-disciplines. Several concepts are essential for the study of chemistry; some of them are:

Matter

In chemistry, matter is defined as anything that has rest mass and volume (it takes up space) and is made up of particles. The particles that make up matter have rest mass as well – not all particles have rest mass, such as the photon. Matter can be a pure chemical substance or a mixture of substances.

Atom

The atom is the basic unit of chemistry. It consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. The nucleus is made up of positively charged protons and uncharged neutrons (together called nucleons), while the electron cloud consists of negatively charged electrons which orbit the nucleus. In a neutral atom, the negatively charged electrons balance out the positive charge of the protons. The nucleus is dense; the mass of a nucleon is approximately 1,836 times that of an electron, yet the radius of an atom is about 10,000 times that of its nucleus.

The atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state(s), coordination number, and preferred types of bonds to form (e.g., metallic, ionic, covalent).

Element

A chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol Z. The mass number is the sum of the number of protons and neutrons in a nucleus. Although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number; atoms of an element which have different mass numbers are known as isotopes. For example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13.

The standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. The periodic table is arranged in groups, or columns, and periods, or rows. The periodic table is useful in identifying periodic trends.

Compound

A compound is a pure chemical substance composed of more than one element. The properties of a compound bear little similarity to those of its elements. The standard nomenclature of compounds is set by the International Union of Pure and Applied Chemistry (IUPAC). Organic compounds are named according to the organic nomenclature system. The names for inorganic compounds are created according to the inorganic nomenclature system. When a compound has more than one component, then they are divided into two classes, the electropositive and the electronegative components. In addition the Chemical Abstracts Service has devised a method to index chemical substances. In this scheme each chemical substance is identifiable by a number known as its CAS registry number.

Molecule

A molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. However, this definition only works well for substances that are composed of molecules, which is not true of many substances (see below). Molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs.

Thus, molecules exist as electrically neutral units, unlike ions. When this rule is broken, giving the "molecule" a charge, the result is sometimes named a molecular ion or a polyatomic ion. However, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well-separated form, such as a directed beam in a vacuum in a mass spectrometer. Charged polyatomic collections residing in solids (for example, common sulfate or nitrate ions) are generally not considered "molecules" in chemistry. Some molecules contain one or more unpaired electrons, creating radicals. Most radicals are comparatively reactive, but some, such as nitric oxide (NO) can be stable.

The "inert" or noble gas elements (helium, neon, argon, krypton, xenon and radon) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. Identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals.

However, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the Earth are chemical compounds without molecules. These other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. Instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. Examples of such substances are mineral salts (such as table salt), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite.

One of the main characteristics of a molecule is its geometry often called its structure. While the structure of diatomic, triatomic or tetra-atomic molecules may be trivial, (linear, angular pyramidal etc.) the structure of polyatomic molecules, that are constituted of more than six atoms (of several elements) can be crucial for its chemical nature.

Substance and mixture

A chemical substance is a kind of matter with a definite composition and set of properties. A collection of substances is called a mixture. Examples of mixtures are air and alloys.

Mole and amount of substance

The mole is a unit of measurement that denotes an amount of substance (also called chemical amount). One mole is defined to contain exactly 6.02214076×{10}^{23} particles (atoms, molecules, ions, or electrons), where the number of particles per mole is known as the Avogadro constant. Molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol/{dm}^3.

Additional Information

Chemistry is the scientific study of matter, its properties, composition, and interactions. It is often referred to as the central science because it connects and bridges the physical sciences, such as physics and biology. Understanding chemistry is crucial for comprehending the world around us, from the air we breathe to the food we eat and the materials we use in everyday life.

Chemistry has many sub-disciplines such as analytical chemistry, physical chemistry, biochemistry, and more. Chemistry plays a crucial role in various industries, including pharmaceuticals, materials science, environmental science, and energy production, making it a cornerstone of modern science and technology

The area of science devoted to studying nature and also composition, properties, elements, and compounds that form matter as well as looking into their reactions forming new substances is chemistry. Chemistry has also been categorized further based on the particular areas of study.

Jai Ganesh · 2024-04-26 00:08:30

2133) Metallurgy

Gist

Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys.

Summary

Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys.

Metallurgy encompasses both the science and the technology of metals, including the production of metals and the engineering of metal components used in products for both consumers and manufacturers. Metallurgy is distinct from the craft of metalworking. Metalworking relies on metallurgy in a similar manner to how medicine relies on medical science for technical advancement. A specialist practitioner of metallurgy is known as a metallurgist.

The science of metallurgy is further subdivided into two broad categories: chemical metallurgy and physical metallurgy. Chemical metallurgy is chiefly concerned with the reduction and oxidation of metals, and the chemical performance of metals. Subjects of study in chemical metallurgy include mineral processing, the extraction of metals, thermodynamics, electrochemistry, and chemical degradation (corrosion). In contrast, physical metallurgy focuses on the mechanical properties of metals, the physical properties of metals, and the physical performance of metals. Topics studied in physical metallurgy include crystallography, material characterization, mechanical metallurgy, phase transformations, and failure mechanisms.

Historically, metallurgy has predominately focused on the production of metals. Metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. Metal alloys are often a blend of at least two different metallic elements. However, non-metallic elements are often added to alloys in order to achieve properties suitable for an application. The study of metal production is subdivided into ferrous metallurgy (also known as black metallurgy) and non-ferrous metallurgy, also known as colored metallurgy.

Ferrous metallurgy involves processes and alloys based on iron, while non-ferrous metallurgy involves processes and alloys based on other metals. The production of ferrous metals accounts for 95% of world metal production.

Modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. Some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals (including welding, brazing, and soldering). Emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials (semiconductors) and surface engineering. Many applications, practices, and devices associated or involved in metallurgy were established in ancient India and China, such as the innovation of the wootz steel , bronze, blast furnace, cast iron, hydraulic-powered trip hammers, and double acting piston bellows.

Details

Metallurgy is the art and science of extracting metals from their ores and modifying the metals for use. Metallurgy customarily refers to commercial as opposed to laboratory methods. It also concerns the chemical, physical, and atomic properties and structures of metals and the principles whereby metals are combined to form alloys.

History of metallurgy

The present-day use of metals is the culmination of a long path of development extending over approximately 6,500 years. It is generally agreed that the first known metals were gold, silver, and copper, which occurred in the native or metallic state, of which the earliest were in all probability nuggets of gold found in the sands and gravels of riverbeds. Such native metals became known and were appreciated for their ornamental and utilitarian values during the latter part of the Stone Age.

Earliest development

Gold can be agglomerated into larger pieces by cold hammering, but native copper cannot, and an essential step toward the Metal Age was the discovery that metals such as copper could be fashioned into shapes by melting and casting in molds; among the earliest known products of this type are copper axes cast in the Balkans in the 4th millennium BCE. Another step was the discovery that metals could be recovered from metal-bearing minerals. These had been collected and could be distinguished on the basis of colour, texture, weight, and flame colour and smell when heated. The notably greater yield obtained by heating native copper with associated oxide minerals may have led to the smelting process, since these oxides are easily reduced to metal in a charcoal bed at temperatures in excess of 700 °C (1,300 °F), as the reductant, carbon monoxide, becomes increasingly stable. In order to effect the agglomeration and separation of melted or smelted copper from its associated minerals, it was necessary to introduce iron oxide as a flux. This further step forward can be attributed to the presence of iron oxide gossan minerals in the weathered upper zones of copper sulfide deposits.

Bronze

In many regions, copper-math alloys, of superior properties to copper in both cast and wrought form, were produced in the next period. This may have been accidental at first, owing to the similarity in colour and flame colour between the bright green copper carbonate mineral malachite and the weathered products of such copper-math sulfide minerals as enargite, and it may have been followed later by the purposeful selection of math compounds based on their garlic odour when heated.

Element As contents varied from 1 to 7 percent, with up to 3 percent tin. Essentially As-free copper alloys with higher tin content—in other words, true bronze—seem to have appeared between 3000 and 2500 BCE, beginning in the Tigris-Euphrates delta. The discovery of the value of tin may have occurred through the use of stannite, a mixed sulfide of copper, iron, and tin, although this mineral is not as widely available as the principal tin mineral, cassiterite, which must have been the eventual source of the metal. Cassiterite is strikingly dense and occurs as pebbles in alluvial deposits together with math and gold; it also occurs to a degree in the iron oxide gossans mentioned above.

While there may have been some independent development of bronze in varying localities, it is most likely that the bronze culture spread through trade and the migration of peoples from the Middle East to Egypt, Europe, and possibly China. In many civilizations the production of copper, math copper, and tin bronze continued together for some time. The eventual disappearance of copper-math As is difficult to explain. Production may have been based on minerals that were not widely available and became scarce, but the relative scarcity of tin minerals did not prevent a substantial trade in that metal over considerable distances. It may be that tin bronzes were eventually preferred owing to the chance of contracting As poisoning from fumes produced by the oxidation of math-containing minerals.

As the weathered copper ores in given localities were worked out, the harder sulfide ores beneath were mined and smelted. The minerals involved, such as chalcopyrite, a copper-iron sulfide, needed an oxidizing roast to remove sulfur as sulfur dioxide and yield copper oxide. This not only required greater metallurgical skill but also oxidized the intimately associated iron, which, combined with the use of iron oxide fluxes and the stronger reducing conditions produced by improved smelting furnaces, led to higher iron contents in the bronze.

Iron

It is not possible to mark a sharp division between the Bronze Age and the Iron Age. Small pieces of iron would have been produced in copper smelting furnaces as iron oxide fluxes and iron-bearing copper sulfide ores were used. In addition, higher furnace temperatures would have created more strongly reducing conditions (that is to say, a higher carbon monoxide content in the furnace gases). An early piece of iron from a trackway in the province of Drenthe, Netherlands, has been dated to 1350 BCE, a date normally taken as the Middle Bronze Age for this area. In Anatolia, on the other hand, iron was in use as early as 2000 BCE. There are also occasional references to iron in even earlier periods, but this material was of meteoric origin.

Once a relationship had been established between the new metal found in copper smelts and the ore added as flux, the operation of furnaces for the production of iron alone naturally followed. Certainly, by 1400 BCE in Anatolia, iron was assuming considerable importance, and by 1200–1000 BCE it was being fashioned on quite a large scale into weapons, initially dagger blades. For this reason, 1200 BCE has been taken as the beginning of the Iron Age. Evidence from excavations indicates that the art of iron making originated in the mountainous country to the south of the Black Sea, an area dominated by the Hittites. Later the art apparently spread to the Philistines, for crude furnaces dating from 1200 BCE have been unearthed at Gerar, together with a number of iron objects.

Smelting of iron oxide with charcoal demanded a high temperature, and, since the melting temperature of iron at 1,540 °C (2,800 °F) was not attainable then, the product was merely a spongy mass of pasty globules of metal intermingled with a semiliquid slag. This product, later known as bloom, was hardly usable as it stood, but repeated reheating and hot hammering eliminated much of the slag, creating wrought iron, a much better product.

The properties of iron are much affected by the presence of small amounts of carbon, with large increases in strength associated with contents of less than 0.5 percent. At the temperatures then attainable—about 1,200 °C (2,200 °F)—reduction by charcoal produced an almost pure iron, which was soft and of limited use for weapons and tools, but when the ratio of fuel to ore was increased and furnace drafting improved with the invention of better bellows, more carbon was absorbed by the iron. This resulted in blooms and iron products with a range of carbon contents, making it difficult to determine the period in which iron may have been purposely strengthened by carburizing, or reheating the metal in contact with excess charcoal.

Carbon-containing iron had the further great advantage that, unlike bronze and carbon-free iron, it could be made still harder by quenching—i.e., rapid cooling by immersion in water. There is no evidence for the use of this hardening process during the early Iron Age, so that it must have been either unknown then or not considered advantageous, in that quenching renders iron very brittle and has to be followed by tempering, or reheating at a lower temperature, to restore toughness. What seems to have been established early on was a practice of repeated cold forging and annealing at 600–700 °C (1,100–1,300 °F), a temperature naturally achieved in a simple fire. This practice is common in parts of Africa even today.

By 1000 BCE iron was beginning to be known in central Europe. Its use spread slowly westward. Iron making was fairly widespread in Great Britain at the time of the Roman invasion in 55 BCE. In Asia iron was also known in ancient times, in China by about 700 BCE.

Brass

While some zinc appears in bronzes dating from the Bronze Age, this was almost certainly an accidental inclusion, although it may foreshadow the complex ternary alloys of the early Iron Age, in which substantial amounts of zinc as well as tin may be found. Brass, as an alloy of copper and zinc without tin, did not appear in Egypt until about 30 BCE, but after this it was rapidly adopted throughout the Roman world, for example, for currency. It was made by the calamine process, in which zinc carbonate or zinc oxide were added to copper and melted under a charcoal cover in order to produce reducing conditions. The general establishment of a brass industry was one of the important metallurgical contributions made by the Romans.

Precious metals

Bronze, iron, and brass were, then, the metallic materials on which successive peoples built their civilizations and of which they made their implements for both war and peace. In addition, by 500 BCE, rich lead-bearing silver mines had opened in Greece. Reaching depths of several hundred metres, these mines were vented by drafts provided by fires lit at the bottom of the shafts. Ores were hand-sorted, crushed, and washed with streams of water to separate valuable minerals from the barren, lighter materials. Because these minerals were principally sulfides, they were roasted to form oxides and were then smelted to recover a lead-silver alloy.

Lead was removed from the silver by cupellation, a process of great antiquity in which the alloy was melted in a shallow porous clay or bone-ash receptacle called a cupel. A stream of air over the molten mass preferentially oxidized the lead. Its oxide was removed partially by skimming the molten surface; the remainder was absorbed into the porous cupel. Silver metal and any gold were retained on the cupel. The lead from the skimmings and discarded cupels was recovered as metal upon heating with charcoal.

Native gold itself often contained quite considerable quantities of silver. These silver-gold alloys, known as electrum, may be separated in a number of ways, but presumably the earliest was by heating in a crucible with common salt. In time and with repetitive treatments, the silver was converted into silver chloride, which passed into the molten slag, leaving a purified gold. Cupellation was also employed to remove from the gold such contaminates as copper, tin, and lead. Gold, silver, and lead were used for artistic and religious purposes, personal adornment, household utensils, and equipment for the chase.

From 500 BCE to 1500 CE

In the thousand years between 500 BCE and 500 CE, a vast number of discoveries of significance to the growth of metallurgy were made. The Greek mathematician and inventor Archimedes, for example, demonstrated that the purity of gold could be measured by determining its weight and the quantity of water displaced upon immersion—that is, by determining its density. In the pre-Christian portion of the period, the first important steel production was started in India, using a process already known to ancient Egyptians. Wootz steel, as it was called, was prepared as sponge (porous) iron in a unit not unlike a bloomery. The product was hammered while hot to expel slag, broken up, then sealed with wood chips in clay containers and heated until the pieces of iron absorbed carbon and melted, converting it to steel of homogeneous composition containing 1 to 1.6 percent carbon. The steel pieces could then be heated and forged to bars for later use in fashioning articles, such as the famous Damascus swords made by medieval Arab armourers.

As, zinc, antimony, and nickel may well have been known from an early date but only in the alloy state. By 100 BCE mercury was known and was produced by heating the sulfide mineral cinnabar and condensing the vapours. Its property of amalgamating (mixing or alloying) with various metals was employed for their recovery and refining. Lead was beaten into sheets and pipes, the pipes being used in early water systems. The metal tin was available and Romans had learned to use it to line food containers. Although the Romans made no extraordinary metallurgical discoveries, they were responsible for, in addition to the establishment of the brass industry, contributing toward improved organization and efficient administration in mining.

Beginning about the 6th century, and for the next thousand years, the most meaningful developments in metallurgy centred on iron making. Great Britain, where iron ore was plentiful, was an important iron-making region. Iron weapons, agricultural implements, domestic articles, and even personal adornments were made. Fine-quality cutlery was made near Sheffield. Monasteries were often centres of learning of the arts of metalworking. Monks became well known for their iron making and bell founding, the products made either being utilized in the monasteries, disposed of locally, or sold to merchants for shipment to more distant markets. In 1408 the bishop of Durham established the first water-powered bloomery in Britain, with the power apparently operating the bellows. Once power of this sort became available, it could be applied to a range of operations and enable the hammering of larger blooms.

In Spain, another iron-making region, the Catalan forge had been invented, and its use later spread to other areas. A hearth type of furnace, it was built of stone and was charged with iron ore, flux, and charcoal. The charcoal was kept ignited with air from a bellows blown through a bottom nozzle, or tuyere (see figure). The bloom that slowly collected at the bottom was removed and upon frequent reheating and forging was hammered into useful shapes. By the 14th century the furnace was greatly enlarged in height and capacity.

If the fuel-to-ore ratio in such a furnace was kept high, and if the furnace reached temperatures sufficiently hot for substantial amounts of carbon to be absorbed into the iron, then the melting point of the metal would be lowered and the bloom would melt. This would dissolve even more carbon, producing a liquid cast iron of up to 4 percent carbon and with a relatively low melting temperature of 1,150 °C (2,100 °F). The cast iron would collect in the base of the furnace, which technically would be a blast furnace rather than a bloomery in that the iron would be withdrawn as a liquid rather than a solid lump.

While the Iron Age peoples of Anatolia and Europe on occasion may have accidently made cast iron, which is chemically the same as blast-furnace iron, the Chinese were the first to realize its advantages. Although brittle and lacking the strength, toughness, and workability of steel, it was useful for making cast bowls and other vessels. In fact, the Chinese, whose Iron Age began about 500 BCE, appear to have learned to oxidize the carbon from cast iron in order to produce steel or wrought iron indirectly, rather than through the direct method of starting from low-carbon iron.

After 1500

During the 16th century, metallurgical knowledge was recorded and made available. Two books were especially influential. One, by the Italian Vannoccio Biringuccio, was entitled De la pirotechnia (Eng. trans., The Pirotechnia of Vannoccio Biringuccio, 1943). The other, by the German Georgius Agricola, was entitled De re metallica. Biringuccio was essentially a metalworker, and his book dealt with smelting, refining, and assay methods (methods for determining the metal content of ores) and covered metal casting, molding, core making, and the production of such commodities as cannons and cast-iron cannonballs. His was the first methodical description of foundry practice.

Agricola, on the other hand, was a miner and an extractive metallurgist; his book considered prospecting and surveying in addition to smelting, refining, and assay methods. He also described the processes used for crushing and concentrating the ore and then, in some detail, the methods of assaying to determine whether ores were worth mining and extracting. Some of the metallurgical practices he described are retained in principle today.

Ferrous metals

From 1500 to the 20th century, metallurgical development was still largely concerned with improved technology in the manufacture of iron and steel. In England, the gradual exhaustion of timber led first to prohibitions on cutting of wood for charcoal and eventually to the introduction of coke, derived from coal, as a more efficient fuel. Thereafter, the iron industry expanded rapidly in Great Britain, which became the greatest iron producer in the world. The crucible process for making steel, introduced in England in 1740, by which bar iron and added materials were placed in clay crucibles heated by coke fires, resulted in the first reliable steel made by a melting process.

One difficulty with the bloomery process for the production of soft bar iron was that, unless the temperature was kept low (and the output therefore small), it was difficult to keep the carbon content low enough so that the metal remained ductile. This difficulty was overcome by melting high-carbon pig iron from the blast furnace in the puddling process, invented in Great Britain in 1784. In it, melting was accomplished by drawing hot gases over a charge of pig iron and iron ore held on the furnace hearth. During its manufacture the product was stirred with iron rabbles (rakes), and, as it became pasty with loss of carbon, it was worked into balls, which were subsequently forged or rolled to a useful shape. The product, which came to be known as wrought iron, was low in elements that contributed to the brittleness of pig iron and contained enmeshed slag particles that became elongated fibres when the metal was forged. Later, the use of a rolling mill equipped with grooved rolls to make wrought-iron bars was introduced.

The most important development of the 19th century was the large-scale production of cheap steel. Prior to about 1850, the production of wrought iron by puddling and of steel by crucible melting had been conducted in small-scale units without significant mechanization. The first change was the development of the open-hearth furnace by William and Friedrich Siemens in Britain and by Pierre and Émile Martin in France. Employing the regenerative principle, in which outgoing combusted gases are used to heat the next cycle of fuel gas and air, this enabled high temperatures to be achieved while saving on fuel. Pig iron could then be taken through to molten iron or low-carbon steel without solidification, scrap could be added and melted, and iron ore could be melted into the slag above the metal to give a relatively rapid oxidation of carbon and silicon—all on a much enlarged scale. Another major advance was Henry Bessemer’s process, patented in 1855 and first operated in 1856, in which air was blown through molten pig iron from tuyeres set into the bottom of a pear-shaped vessel called a converter. Heat released by the oxidation of dissolved silicon, manganese, and carbon was enough to raise the temperature above the melting point of the refined metal (which rose as the carbon content was lowered) and thereby maintain it in the liquid state. Very soon Bessemer had tilting converters producing 5 tons in a heat of one hour, compared with four to six hours for 50 kilograms (110 pounds) of crucible steel and two hours for 250 kilograms of puddled iron.

Neither the open-hearth furnace nor the Bessemer converter could remove phosphorus from the metal, so that low-phosphorus raw materials had to be used. This restricted their use from areas where phosphoric ores, such as those of the Minette range in Lorraine, were a main European source of iron. The problem was solved by Sidney Gilchrist Thomas, who demonstrated in 1876 that a basic furnace lining consisting of calcined dolomite, instead of an acidic lining of siliceous materials, made it possible to use a high-lime slag to dissolve the phosphates formed by the oxidation of phosphorus in the pig iron. This principle was eventually applied to both open-hearth furnaces and Bessemer converters.

As steel was now available at a fraction of its former cost, it saw an enormously increased use for engineering and construction. Soon after the end of the century it replaced wrought iron in virtually every field. Then, with the availability of electric power, electric-arc furnaces were introduced for making special and high-alloy steels. The next significant stage was the introduction of cheap oxygen, made possible by the invention of the Linde-Frankel cycle for the liquefaction and fractional distillation of air. The Linz-Donawitz process, invented in Austria shortly after World War II, used oxygen supplied as a gas from a tonnage oxygen plant, blowing it at supersonic velocity into the top of the molten iron in a converter vessel. As the ultimate development of the Bessemer/Thomas process, oxygen blowing became universally employed in bulk steel production.

Light metals

Another important development of the late 19th century was the separation from their ores, on a substantial scale, of aluminum and magnesium. In the earlier part of the century, several scientists had made small quantities of these light metals, but the most successful was Henri-Étienne Sainte-Claire Deville, who by 1855 had developed a method by which cryolite, a double fluoride of aluminum and sodium, was reduced by sodium metal to aluminum and sodium fluoride. The process was very expensive, but cost was greatly reduced when the American chemist Hamilton Young Castner developed an electrolytic cell for producing cheaper sodium in 1886. At the same time, however, Charles M. Hall in the United States and Paul-Louis-Toussaint Héroult in France announced their essentially identical processes for aluminum extraction, which were also based on electrolysis. Use of the Hall-Héroult process on an industrial scale depended on the replacement of storage batteries by rotary power generators; it remains essentially unchanged to this day.

Welding

One of the most significant changes in the technology of metals fabrication has been the introduction of fusion welding during the 20th century. Before this, the main joining processes were riveting and forge welding. Both had limitations of scale, although they could be used to erect substantial structures. In 1895 Henry-Louis Le Chatelier stated that the temperature in an oxyacetylene flame was 3,500 °C (6,300 °F), some 1,000 °C higher than the oxyhydrogen flame already in use on a small scale for brazing and welding. The first practical oxyacetylene torch, drawing acetylene from cylinders containing acetylene dissolved in acetone, was produced in 1901. With the availability of oxygen at even lower cost, oxygen cutting and oxyacetylene welding became established procedures for the fabrication of structural steel components.

The metal in a join can also be melted by an electric arc, and a process using a carbon as a negative electrode and the workpiece as a positive first became of commercial interest about 1902. Striking an arc from a coated metal electrode, which melts into the join, was introduced in 1910. Although it was not widely used until some 20 years later, in its various forms it is now responsible for the bulk of fusion welds.

Metallography

The 20th century has seen metallurgy change progressively, from an art or craft to a scientific discipline and then to part of the wider discipline of materials science. In extractive metallurgy, there has been the application of chemical thermodynamics, kinetics, and chemical engineering, which has enabled a better understanding, control, and improvement of existing processes and the generation of new ones. In physical metallurgy, the study of relationships between macrostructure, microstructure, and atomic structure on the one hand and physical and mechanical properties on the other has broadened from metals to other materials such as ceramics, polymers, and composites.

Metallurgy and mining

This greater scientific understanding has come largely from a continuous improvement in microscopic techniques for metallography, the examination of metal structure. The first true metallographer was Henry Clifton Sorby of Sheffield, England, who in the 1860s applied light microscopy to the polished surfaces of materials such as rocks and meteorites. Sorby eventually succeeded in making photomicrographic records, and by 1885 the value of metallography was appreciated throughout Europe, with particular attention being paid to the structure of steel. For example, there was eventual acceptance, based on micrographic evidence and confirmed by the introduction of X-ray diffraction by William Henry and William Lawrence Bragg in 1913, of the allotropy of iron and its relationship to the hardening of steel. During subsequent years there were advances in the atomic theory of solids; this led to the concept that, in nonplastic materials such as glass, fracture takes place by the propagation of preexisting cracklike defects and that, in metals, deformation takes place by the movement of dislocations, or defects in the atomic arrangement, through the crystalline matrix. Proof of these concepts came with the invention and development of the electron microscope; even more powerful field ion microscopes and high-resolution electron microscopes now make it possible to detect the position of individual atoms.

Another example of the development of physical metallurgy is a discovery that revolutionized the use of aluminum in the 20th century. Originally, most aluminum was used in cast alloys, but the discovery of age hardening by Alfred Wilm in Berlin about 1906 yielded a material that was twice as strong with only a small change in weight. In Wilm’s process, a solute such as magnesium or copper is trapped in supersaturated solid solution, without being allowed to precipitate out, by quenching the aluminum from a higher temperature rather than slowly cooling it. The relatively soft aluminum alloy that results can be mechanically formed, but, when left at room temperature or heated at low temperatures, it hardens and strengthens. With copper as the solute, this type of material came to be known by the trade name Duralumin. The advances in metallography described above eventually provided the understanding that age hardening is caused by the dispersion of very fine precipitates from the supersaturated solid solution; this restricts the movement of the dislocations that are essential to crystal deformation and thus raises the strength of the metal. The principles of precipitation hardening have been applied to the strengthening of a large number of alloys.

Additional Information

Metallurgy plays a pivotal role in many industries like aviation, public transportation and electronics — industries that require making things.

From the production of mighty machinery and sturdy construction materials to the creation of intricate electrical systems, metals take center stage. With their exceptional mechanical strength, remarkable thermal conductivity and impressive electrical properties, metals are the lifeblood of technological advancements.

Through skilled hands, metallurgy unlocks the potential of metals, shaping them into essential components that power our modern world. Metallurgists extract, refine and meticulously craft to meet the ever-evolving demands of industries, driving innovation and propelling us into the future.

What Is Metallurgy?

Metallurgy is the study and manipulation of metals and their properties. It is a field of science that focuses on understanding how metals behave and finding ways to improve their properties for different applications. Metallurgists work with widely used metals — like iron, aluminum, copper and steel — in various industries.

One important part of the field is extracting metals from their natural sources, such as ores. An ore is a naturally occurring rock or mineral that contains a valuable material, such as metal or gemstones, which can be extracted and processed for various industrial purposes.

Once extraction is complete, ores can be purified to remove impurities and improve their quality. Think of purification in metallurgy like filtering water. Just as you remove impurities and contaminants from water to make it clean and safe to drink, metallurgists use different methods to remove unwanted substances from metals or ores, making them pure and of higher quality for their intended use.

Metallurgists also study the structure of metals at a microscopic level. They examine how atoms are arranged in metals and how this arrangement affects their properties, like strength, hardness, and conductivity. By understanding the structure, metallurgists can modify metals through processes like heating and cooling, known as heat treatment, to improve their properties.

Metallurgists develop new alloys by combining different metals or adding other elements. Think of it as mixing different paint colors to create a vibrant masterpiece that is stronger, more durable, or corrosion-resistant. Stainless steel, for example, is an alloy that combines iron's strength with chromium's corrosion resistance, making it perfect for shiny kitchen appliances and sturdy construction materials. It's like having the best of both worlds in one metal combo!

Jai Ganesh · Yesterday 00:08:27

2134) Stoichiometry

Gist

Stoichiometry, in chemistry, is the determination of the proportions in which elements or compounds react with one another. The rules followed in the determination of stoichiometric relationships are based on the laws of conservation of mass and energy and the law of combining weights or volumes.

Summary

Stoichiometry is based on the law of conservation of mass. This states that, in a closed system (no outside forces), the mass of the products is the same as the mass of the reactants. Stoichiometry is used to balance reactions so that they obey this law. It is also used to calculate the mass of products and/or reactants.

In order for an equation to be balanced, the number of elements needs to be equal on the left (reactants) and right (products) sides of the equation. We balance equations by using stoichiometric coefficients.

* Stoichiometry is the mathematical relationship between products and reactants in a chemical reaction.

* Stoichiometric coefficients are the numbers before an element/compound which indicate the number of moles present. They show the ratio between reactants and products. They are used to balance equations.

* Stoichiometry can be used to calculate yield by utilizing the ratio between reactants and products. This same concept is used to calculate needed reactant amounts.

* The limiting reactant is the reactant that is completely consumed in the reaction. Once this reactant is fully consumed, it stops the reaction and therefore limits the product made. It can be determined by calculating the yield for all reactants.

* For gas reactions, the ideal gas law must be used to calculate yield.

* The equation for the ideal gas law is PV = nRT where P=pressure, V=volume, n=moles, R=ideal gas constant, and T=temperature.

Details

Stoichiometry is the relationship between the weights of reactants and products before, during, and following chemical reactions.

Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equals the total mass of the products, leading to the insight that the relations among quantities of reactants and products typically form a ratio of positive integers. This means that if the amounts of the separate reactants are known, then the amount of the product can be calculated. Conversely, if one reactant has a known quantity and the quantity of the products can be empirically determined, then the amount of the other reactants can also be calculated.

This is illustrated in the image here, where the balanced equation is:

CH4 + 2 O2 → CO2 + 2 H2O

Here, one molecule of methane reacts with two molecules of oxygen gas to yield one molecule of carbon dioxide and two molecules of water. This particular chemical equation is an example of complete combustion. Stoichiometry measures these quantitative relationships, and is used to determine the amount of products and reactants that are produced or needed in a given reaction. Describing the quantitative relationships among substances as they participate in chemical reactions is known as reaction stoichiometry. In the example above, reaction stoichiometry measures the relationship between the quantities of methane and oxygen that react to form carbon dioxide and water.

IUPAC definition for stoichiometry

Because of the well known relationship of moles to atomic weights, the ratios that are arrived at by stoichiometry can be used to determine quantities by weight in a reaction described by a balanced equation. This is called composition stoichiometry.

Gas stoichiometry deals with reactions involving gases, where the gases are at a known temperature, pressure, and volume and can be assumed to be ideal gases. For gases, the volume ratio is ideally the same by the ideal gas law, but the mass ratio of a single reaction has to be calculated from the molecular masses of the reactants and products. In practice, because of the existence of isotopes, molar masses are used instead in calculating the mass ratio.

Etymology

The term stoichiometry was first used by Jeremias Benjamin Richter in 1792 when the first volume of Richter's Anfangsgründe der Stöchyometrie, oder Messkunst chymischer Elemente (Fundamentals of Stoichiometry, or the Art of Measuring the Chemical Elements) was published. The term is derived from the Ancient Greek words στοιχεῖον stoicheion "element" and μέτρον metron "measure".

Definition

A stoichiometric amount or stoichiometric ratio of a reagent is the optimum amount or ratio where, assuming that the reaction proceeds to completion:

* All of the reagent is consumed
* There is no deficiency of the reagent
* There is no excess of the reagent.

Stoichiometry rests upon the very basic laws that help to understand it better, i.e., law of conservation of mass, the law of definite proportions (i.e., the law of constant composition), the law of multiple proportions and the law of reciprocal proportions. In general, chemical reactions combine in definite ratios of chemicals. Since chemical reactions can neither create nor destroy matter, nor transmute one element into another, the amount of each element must be the same throughout the overall reaction. For example, the number of atoms of a given element X on the reactant side must equal the number of atoms of that element on the product side, whether or not all of those atoms are actually involved in a reaction.

Chemical reactions, as macroscopic unit operations, consist of simply a very large number of elementary reactions, where a single molecule reacts with another molecule. As the reacting molecules (or moieties) consist of a definite set of atoms in an integer ratio, the ratio between reactants in a complete reaction is also in integer ratio. A reaction may consume more than one molecule, and the stoichiometric number counts this number, defined as positive for products (added) and negative for reactants (removed). The unsigned coefficients are generally referred to as the stoichiometric coefficients.

Each element has an atomic mass, and considering molecules as collections of atoms, compounds have a definite molar mass. By definition, the atomic mass of carbon-12 is 12 Da, giving a molar mass of 12 g/mol. The number of molecules per mole in a substance is given by the Avogadro constant, defined as 6.02214076×{10}^{23} {mol}^{-1}. Thus, to calculate the stoichiometry by mass, the number of molecules required for each reactant is expressed in moles and multiplied by the molar mass of each to give the mass of each reactant per mole of reaction. The mass ratios can be calculated by dividing each by the total in the whole reaction.

Elements in their natural state are mixtures of isotopes of differing mass; thus, atomic masses and thus molar masses are not exactly integers. For instance, instead of an exact 14:3 proportion, 17.04 g of ammonia consists of 14.01 g of nitrogen and 3 × 1.01 g of hydrogen, because natural nitrogen includes a small amount of nitrogen-15, and natural hydrogen includes hydrogen-2 (deuterium).

A stoichiometric reactant is a reactant that is consumed in a reaction, as opposed to a catalytic reactant, which is not consumed in the overall reaction because it reacts in one step and is regenerated in another step.

Additional Information

Stoichiometry is the quantitative analysis of the reactants required or the products formed. Chemical reactions act on the chemical changes undergone by various compounds and elements.

A balanced chemical equation imparts a lot of information. The coefficients stipulate the molar ratios and the discrete number of particles participating in a specific reaction. Stoichiometry is the quantitative analysis of the reactants required or the products formed.

Although it sounds complicated while the vocabulary of the word, the concept of stoichiometry is very simple and easy to understand.

What is Stoichiometry?

The word ‘stoichiometry‘ comes from the Greek words ‘stoicheion’ (meaning element) and ‘metron’ (meaning measure). Hence, it means measurement of the element.

Stoichiometry denotes the quantitative connection between a chemical reaction’s products and the reactants. Stoichiometry is a branch of chemistry that applies the laws of definite proportions and the conservation of mass and energy to chemical activity.

A well-balanced chemical reaction and the coefficients of reactants and products of a reaction are all part of the stoichiometry of a reaction. In short, stoichiometry means is the measurement of small parts in a reaction.

Definition of Stoichiometry

The balanced chemical equation represents the stoichiometry definition for a reaction. It represents the quantities or amounts of products and reactants involved in the chemical equation.

In chemistry, stoichiometry definition is given as the quantitative connection between two or more substances, especially in chemical or physical change processes.

Stoichiometry definition can be the definite proportions in which elements or compounds react with one another. The rules followed in calculating the stoichiometric relationships are based on the laws of conservation of mass and energy and the law of combining weights or volumes.

molecular-model-illustration-545862141-57dec4f93df78c9cce4ab839.jpg

Jai Ganesh · Today 00:12:08

2135) Manicure

Gist

Manicure is a cosmetic treatment of the hands and fingernails, including trimming and polishing of the nails and removing cuticles.

Summary

A manicure is the act of beautifying one's hands or fingernails. Manicures can be done at home or by a professional in a nail salon. During a manicure, the nail is filed with a nail file; the free edge of the nail is cut, the cuticle is treated, the person's hand is massaged and nail polish is put on.

History

5000 years ago, manicures were first used. Henna was used in India for manicure. The word mehendi, another word for henna, derives from the Sanskrit mehandika. Cixi, the Dowager Empress of China, had very long naturally-grown nails.

How it is done

When you get a manicure, your fingernails get filed and shaped and possibly painted red. You might get a manicure at a spa or salon as a way to pamper yourself.

You can pay a professional to give you a manicure, or you can do a manicure at home with a nail file and a bottle of nail polish. Some people get manicures for fun and relaxation, while others don't feel well dressed without the perfect nails that a manicure provides. In French the word manicure means "care of the hands," and it comes from the Latin word for "hand," manus.

Details

A manicure is a mostly cosmetic beauty treatment for the fingernails and hands performed at home or in a nail salon. A manicure usually consists of filing and shaping the free edge of nails, pushing and clipping (with a cuticle pusher and cuticle nippers) any nonliving tissue (but limited to the cuticle and hangnails), treatments with various liquids, massage of the hand, and the application of fingernail polish. When the same is applied to the toenails and feet, the treatment is referred to as a pedicure. Together, the treatments may be known as a mani-pedi. Most nail polish can stay on nails for 2–3 days before another manicure is required for maintenance, if there is no damage done to it.

Some manicures include painting pictures or designs on the nails, applying small decals, or imitation jewels (from 2 dimension to 3 dimension). Other nail treatments may include the application of artificial gel nails, tips, or acrylics, which may be referred to as French manicures.

Nail technicians, such as manicurists and pedicurists, must be licensed in certain states and countries, and must follow government regulations. Since skin is manipulated and often times trimmed, there is a risk of spreading infection when tools are used across many people. Therefore, having improper sanitation can pose serious issues.

Etymology

The English word manicure comes from the French word manucure, meaning care of the hands, which in turn originates from the Latin words manus, for hand, and cura, for care. Similarly, the English word pedicure comes from the Latin words pes (genitive case: pedis), for foot, and cura, for care. Colloquially, the word for manicure is sometimes shortened to mani.

Types

French manicures

Jeff Pink, founder of the professional nail brand ORLY, is credited with creating the natural nail look later called the French manicure in 1976.

In the mid-1970s, Pink was tasked by a film director to come up with a universal nail look that would save screen actresses from having to spend time getting their nails redone to go along with their costume changes. Inspired by the instant brightening effect of a white pencil applied to the underside, Pink suspected that the solution was to apply that same neutralizing principle to the top of the nail. "I got one gallon of white polish for the tips, and pink, beige, or rose for the nail," he recalled in a 2014 interview with The National.

Acrylic manicure with jewel design

The Natural Nail Kit, as Pink called it then, was a hit among movie stars and studios who found the time-saving strategy indispensable. "The director commented that I should get an Oscar for saving the industry so much money," he said. Eventually Pink took the trend to the catwalk crowd in Paris, and they liked it, too. But, it still needed, as he thought, a more pleasing name. He gave it the French rebranding on the flight back home to Los Angeles.

Nails that have undergone a French manicure are characterized by a lack of artificial base color and white tips at the free edge of the nail. For this reason, they are sometimes referred to as French tips. The nail tips are painted white, while the rest of the nails are polished in a pink or a suitable nude shade. French manicures can be achieved with artificial nails. However, it is also as common to perform a French manicure on natural nails. Another technique is to whiten the underside of the nail with white pencil and paint a sheer color over the entire nail.

Hot oil manicures

A hot oil manicure is a specific type of manicure that cleans the cuticles and softens them with oil. Types of oils that can be used are mineral oil, olive oil, some lotions or commercial preparations in an electric heater.

Dip powder manicures

Dip powder manicures are an alternative to traditional acrylic nails and gel polish. Dip powders have become popular due to ease of application. They are similar to traditional silk or fiberglass enhancements, with the fiber being replaced by acrylic powder. Both methods rely on layering cyanoacrylate over the natural nail and encasing either the fiber or acrylic powder. While a single layer of fiber is typical, multiple alternating layers of powder and cyanoacrylate may be used in dip nails.

Paraffin wax treatments

Hands or feet can be covered in melted paraffin wax for softening and moisturizing. Paraffin wax is used because it can be heated to temperatures of over 95 °F (35 °C) without burning or injuring the body. The intense heat allows for deeper absorption of emollients and essential oils. The wax is usually infused with various botanical ingredients such as aloe vera, azulene, chamomile, or tea tree oil, and fruit waxes such as apple, peach, and strawberry, are often used in salons. Paraffin wax treatments are often charged as an addition to the standard manicure or pedicure. They are often not covered in general training and are a rare treatment in most nail salons.

Professional services should not include dipping clients' hands or feet into a communal paraffin bath, as the wax can be a vector for disease. Paraffin should be applied in a way that avoids contamination, often by placing a portion of the wax into a bag or mitt, which is placed on the client's hand or foot and covered with a warm towel, cotton mitt, or booty to retain warmth. The paraffin is left for a few minutes until it has cooled.

Sanitation options

In Australia, the United States, and other countries, many nail salons offer personal nail tool kits for purchase to avoid some of the sanitation issues in the salon. The kits are often kept in the salon and given to the client to take home, or are thrown away after use. They are only used when that client comes in for a treatment.

Another option is to give the client the files and wooden cuticle sticks after the manicure. Since the 1970s, the overwhelming majority of professional salons use electric nail files that are faster and yield higher quality results, particularly with acrylic nail enhancements.

Shape

There are several nail shapes: the basic shapes are almond, oval, pointed, round, square, square oval, square with rounded corners, and straight with a rounded tip. The square oval shape is sometimes known as squoval, a term coined in 1984. The squoval is considered a sturdy shape, useful for those who work with their hands.

Additional Information

A nail technician or nail stylist is a person whose occupation is to style and shape a person's nails. This is achieved using a combination of decorating nails with coloured varnish, transfers, gems or glitter.

A nail technician or nail stylist is a person whose occupation is to style and shape a person's nails. This is achieved using a combination of decorating nails with coloured varnish, transfers, gems or glitter. Basic treatments include manicures and pedicures, as well as cleaning and filing nails and applying overlays or extensions.

Using a stencil or stamping, nail stylists can also paint designs onto nails with an airbrush, by hand. A nail stylist will often complete a consultation with the client to check for any signs of skin problems, deformities or nail disease before treatment, advise clients about looking after their hands and nails, and recommend nail care products.

Training to become a nail stylist involves completing a professional course that normally takes at least a year. Courses will more than likely cover anatomy and physiology of the nails, hands, arms, feet and legs, contraindications that may arise, identifying diseases and disorders, proper sanitation and sterilizing techniques, how to perform nail services safely, gel polish application, liquid and powder enhancements and hard gel enhancements. The work itself tends to take place in a beauty salon although some nail stylists will make house calls to clients. Once licensed, many nail stylists will keep their own regular client list. The basic equipment needed to carry out Nail services can be easily obtained. Types of basic equipment can include nail drills, brushes, gel polish, and a UV lamp. Specialist equipment will be needed for specific nail applications.

Getting a manicure is an excellent way to pamper yourself after a hard week of work. There’s not much that is more relaxing than getting your hands massaged, and then beautified. We use our hands to do all the work we do, which means it’s important to take proper care of them once in a while.

Fortunately, there are a great many manicures that you can choose from at the nail salon. Let’s have a look at some of the more common ones.

Basic Manicure

Most manicures use a basic manicure as a starting point, but this can be a simple and beautiful look in its own right. This involves an oil, lotion or cream first being applied to your cuticles, and then your hands being soaked in warm water. Your cuticles will then be managed, and you can choose the shape and length you want for the nails. Your hands will then be massaged with oils. Following this, your stylist will apply a base coat, a main coat and finally a top coat of polish. Once you’re done with this basic step, you have the choice of either leaving it at that, or getting a more creative option.

French Manicure

The French manicure is probably the most classic of manicure styles, and the look that you probably associate with getting a manicure at all. It’s a clean and beautiful look, with a clear, beige or pale pink polish applied over the whole nail, and white polish at the top. Of course, there are variations in the style, with bolder colors being used for the nail and cuticle. Whatever variation you choose, you’re guaranteed a vibrant and gorgeous look that should be perfect for any occasion.

American Manicure

This style very much resembles a French manicure, but is set apart by the shape and color of the nails. Where the French styles tend to be more obvious, the American manicure seeks to create a subtler, more natural look. This involves having the tips rounded, and off white or neutral colors being used on the tips, instead of the French manicures bright whites. Again, there are variations of this styles, and it can be used in the more classic style, or given a touch of modernity through the use of uncommon colors.

Reverse French Manicure

The reverse French manicure is essentially exactly what it sounds like. The look is relatively new, but attained popularity within the mainstream fairly quickly. It basically entails the nail being painted white, and the tip painted darker. Other options include a black and white look, or a strip of color on the tip coupled with an all white nail.

Paraffin Manicure

If your hands are particularly overworked or dry, this might be the right option for you. This manicure involves using paraffin wax on the hands in order to instantaneously infuse it with moisture and make it smooth. Paraffin manicures also involve a more energetic hand massage, as well as a basic manicure look.

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