Tuesday, May 16, 2023

05-15-2023-2240 - Energy Price, Mine, Transformer, etc. (draft)

Energy price

From Wikipedia, the free encyclopedia

The present disambiguation page holds the title of a primary topic, and an article needs to be written about it. It is believed to qualify as a broad-concept article. It may be written directly at this page or drafted elsewhere and then moved over here. Related titles should be described in Energy price, while unrelated titles should be moved to Energy price (disambiguation).

The following articles relate to the price of energy:

This disambiguation page lists articles associated with the title Energy price.
If an internal link led you here, you may wish to change the link to point directly to the intended article.

Category:

Disambiguation pages

https://en.wikipedia.org/wiki/Energy_price

dia

Look up Mine or mine in Wiktionary, the free dictionary.

Mine, mines, miners or mining may refer to:

Extraction or digging

Miner, a person engaged in mining or digging
Mining, extraction of mineral resources from the ground through a mine

Grammar

Mine, a first-person English possessive pronoun

Military

Anti-tank mine, a land mine made for use against armored vehicles
Antipersonnel mine, a land mine targeting people walking around, either with explosives or poison gas
Bangalore mine, colloquial name for the Bangalore torpedo, a man-portable explosive device for clearing a path through wire obstacles and land mines
Cluster bomb, an aerial bomb which releases many small submunitions, which often act as mines
Land mine, explosive mines placed under or on the ground
Mining (military), digging under a fortified military position to penetrate its defenses
Naval mine, or sea mine, a mine at sea, either floating or on the sea bed, often dropped via parachute from aircraft, or otherwise lain by surface ships or submarines
Parachute mine, an air-dropped "sea mine" falling gently under a parachute, used as a high-capacity cheaply-cased large bomb against ground targets

Places

The Mine, Queensland, a locality in the Rockhampton Region, Australia
Mine, Saga, a Japanese town
Mine, Yamaguchi, a Japanese city
- Mine District, Yamaguchi, a former district in the area of the city

People

Given name

Mine Ercan (born 1978), Turkish women's wheelchair basketball player
Mine Guri, Albanian communist politician
Miné Okubo (1912–2001), American artist and writer

Nickname

Mine Boy, nickname of Alex Levinsky (1910–1990), NHL hockey player

Surname

Kazuki Mine (born 1993), Japanese football player
George Ralph Mines (born 1886), English cardiac electrophysiologist

Arts, entertainment, and media

Films

Mine (1985 film), a Turkish film
Mine (2009 film), an American documentary film
Mine (2016 film), an Italian-American film
Abandoned Mine or The Mine, a 2013 horror film
The Mine (1978 film), Turkish film

Literature

Mine (novel), a 1990 novel by Robert R. McCammon
The Mine (novel), 2012 novel by Arnab Ray

Music

Albums

Mine (Kim Jaejoong EP), 2013
Mine (Dolly Parton album), 1973
Mine (Phoebe Ryan EP), 2015
Mine (Li Yuchun album), 2007
Mines (album), a 2010 album by indie rock band Menomena
Mine!, a 1994 album released by musical duo Trout Fishing in America

Songs

"Mine" (The 1975 song), 2018
"Mine" (Bazzi song), 2017
"Mine" (Beyoncé song), 2013
"Mine" (Kelly Clarkson song), 2023
"Mine" (Alice Glass song), 2018
"Mine" (Taylor Swift song), 2010
"Mine", a song from the 1933 Broadway musical Let 'Em Eat Cake
"Mine", a song by Bebe Rexha from the album Expectations
"Mine", a song by Dolly Parton from In the Good Old Days (When Times Were Bad)
"Mine", a song by Everything but the Girl from Everything but the Girl
"Mine", a song by Ghinzu from Blow
"Mine", a song by Jason Webley from Only Just Beginning
"Mine", a song by Krezip from Days Like This
"Mine", a song by Mustasch from Mustasch
"Mine", a song by Savage Garden from Savage Garden
"Mine", a song by Sepultura from Roots
"Mine", a song by Taproot from Welcome
"Mine", a song by Christina Perri from lovestrong
"Mine", a song by Disturbed from The Lost Children
"Mine", a song by M.I from the album The Chairman
"#Mine", a song by Lil' Kim from Lil Kim Season
"Mine, Mine, Mine", a song from the soundtrack for the 1995 Disney film Pocahontas

Television

Mine (2021 TV series), a South Korean television series

Organizations and enterprises

MINE, a design office in San Francisco, US, of which Christopher Simmons is principal creative director
Colorado School of Mines or "Mines", a university in Golden, Colorado, US
Mine's, a Japanese auto tuning company
South Dakota School of Mines and Technology, a university in Rapid City, South Dakota, US

Science and technology

MINE (chemotherapy), a chemotherapy regimen
Mine or star mine, a type of fireworks
MinE, a bacterial protein
Data mining, the computational process of discovering patterns in large data sets
Leaf mine, a space in a leaf
Mina (unit), or mine, an ancient Greek unit of mass

Part of a series on
Evolutionary biology
Darwin's finches by John Gould
Index Introduction Main Outline Glossary Evidence History

Terminology

Transmutation was one of the names commonly used for evolutionary ideas in the 19th century before Charles Darwin published On The Origin of Species (1859). Transmutation had previously been used as a term in alchemy to describe the transformation of base metals into gold. Other names for evolutionary ideas used in this period include the development hypothesis (one of the terms used by Darwin) and the theory of regular gradation, used by William Chilton in the periodical press such as The Oracle of Reason.^[2] Transformation is another word used quite as often as transmutation in this context. These early 19th century evolutionary ideas played an important role in the history of evolutionary thought.

The proto-evolutionary thinkers of the 18th and early 19th century had to invent terms to label their ideas, but it was first Joseph Gottlieb Kölreuter who used the term "transmutation" to refer to species who have had biological changes through hybridization.^[3]

The terminology did not settle down until some time after the publication of the Origin of Species. The word evolved in a modern sense was first used in 1826 in an anonymous paper published in Robert Jameson's journal and evolution was a relative late-comer which can be seen in Herbert Spencer's Social Statics of 1851,^[a] and at least one earlier example, but was not in general use until about 1865–70.

Historical development

In the 10th and 11th centuries, Ibn Miskawayh's Al-Fawz al-Kabir (الفوز الأكبر), and the Brethren of Purity's Encyclopedia of the Brethren of Purity (رسائل إخوان الصفا‎) developed ideas about changes in biological species.^[5] In 1993, Muhammad Hamidullah described the ideas in lectures:

[These books] state that God first created matter and invested it with energy for development. Matter, therefore, adopted the form of vapour which assumed the shape of water in due time. The next stage of development was mineral life. Different kinds of stones developed in course of time. Their highest form being mirjan (coral). It is a stone which has in it branches like those of a tree. After mineral life evolves vegetation. The evolution of vegetation culminates with a tree which bears the qualities of an animal. This is the date-palm. It has male and female genders. It does not wither if all its branches are chopped but it dies when the head is cut off. The date-palm is therefore considered the highest among the trees and resembles the lowest among animals. Then is born the lowest of animals. It evolves into an ape. This is not the statement of Darwin. This is what Ibn Maskawayh states and this is precisely what is written in the Epistles of Ikhwan al-Safa. The Muslim thinkers state that ape then evolved into a lower kind of a barbarian man. He then became a superior human being. Man becomes a saint, a prophet. He evolves into a higher stage and becomes an angel. The one higher to angels is indeed none but God. Everything begins from Him and everything returns to Him.^[6]

In the 14th century, Ibn Khaldun further developed these ideas. According to some commentators,^[who?] statements in his 1377 work, the Muqaddimah anticipate the biological theory of evolution.^[7]

Robert Hooke proposed in a speech to the Royal Society in the late 17th century that species vary, change, and especially become extinct. His “Discourse of Earthquakes” was based on comparisons made between fossils, especially the modern pearly nautilus and the curled shells of ammonites.^[8]

In the 18th century, Jacques-Antoine des Bureaux claimed a “genealogical ascent of species”. He argued that through crossbreeding and hybridization in reproduction, “progressive organization” occurred, allowing organisms to change and more complex species to develop.^[9]

Simultaneously, Retif de la Bretonne wrote La decouverte australe par un homme-volant (1781) and La philosophie de monsieur Nicolas (1796), which encapsulated his view that more complex species, such as mankind, had developed step-by-step from “less perfect” animals. De la Bretonne believed that living forms undergo constant change. Although he believed in constant change, he took a very different approach than Diderot: chance and blind combinations of atoms, in de la Bretonne’s opinion, was not the cause of transmutation. De la Bretonne argued that all species had developed from more primitive organisms, and that nature aimed to reach perfection.^[9]

Denis Diderot, chief editor of the Encyclopedia, spent his time pouring over scientific theories attempting to explain rock strata and the diversity of fossils. Geological and fossil evidence was presented to him as contributions to Encyclopedia articles, chief among them “Mammoth,” “Fossil,” and “Ivory Fossil,” all of which noted the existence of mammoth bones in Siberia. As a result of this geological and fossil evidence, Diderot believed that species were mutable. Particularly, he argued that organisms metamorphosized over millennia, resulting in species changes. In Diderot’s theory of transformationism, random chance plays a large role in allowing species to change, develop and become extinct, as well as having new species form. Specifically, Diderot believed that given randomness and an infinite number of times, all possible scenarios would manifest themselves. He proposed that this randomness was behind the development of new traits in offspring and as a result the development and extinction of species.^[8]^[10]

Diderot drew from Leonardo da Vinci’s comparison of the leg structure of a human and a horse as proof of the interconnectivity of species. He saw this experiment as demonstrating that nature could continually try out new variations. Additionally, Diderot argued that organic molecules and organic matter possessed an inherent consciousness, which allowed the smallest particles of organic matter to organize into fibers, then a network, and then organs. The idea that organic molecules have consciousness was derived from both Maupertuis and Lucretian texts. Overall, Diderot’s musings all fit together as a “composite transformist philosophy,” one dependent on the randomness inherent to nature as a transformist mechanism.^[8]^[10]

Erasmus Darwin developed a theory of universal transformation. His major works, The Botanic Garden (1792), Zoonomia (1794–96), and The Temple of Nature all touched on the transformation of organic creatures. In both The Botanic Garden and The Temple of Nature, Darwin used poetry to describe his ideas regarding species. In Zoonomia, however, Erasmus clearly articulates (as a more scientific text) his beliefs about the connections between organic life. He notes particularly that some plants and animals have “useless appendages,” which have gradually changed from their original, useful states. Additionally, Darwin relied on cosmological transformation as a crucial aspect of his theory of transformation, making a connection between William Herschel’s approach to natural historical cosmology and the changing aspects of plants and animals.^[10]^[11]^[12]

Erasmus believed that life had one origin, a common ancestor, which he referred to as the “filament” of life. He used his understanding of chemical transmutation to justify the spontaneous generation of this filament. His geological study of Derbyshire and the sea- shells and fossils which he found there helped him to come to the conclusion that complex life had developed from more primitive forms (Laniel-Musitelli). Erasmus was an early proponent of what we now refer to as “adaptations,” albeit through a different transformist mechanism – he argued that sexual reproduction could pass on acquired traits through the father’s contribution to the embryon. These changes, he believed, were mainly driven by the three great needs of life: lust, food, and security. Erasmus proposed that these acquired changes gradually altered the physical makeup of organisms as a result of the desires of plants and animals. Notably, he describes insects developing from plants, a grand example of one species transforming into another.^[10]^[11]^[12]

Erasmus Darwin relied on Lucretian philosophy to form a theory of universal change. He proposed that both organic and inorganic matter changed throughout the course of the universe, and that plants and animals could pass on acquired traits to their progeny. His view of universal transformation placed time as a driving force in the universe’s journey towards improvement. In addition, Erasmus believed that nature had some amount of agency in this inheritance. Darwin spun his own story of how nature began to develop from the ocean, and then slowly became more diverse and more complex. His transmutation theory relied heavily on the needs which drove animal competition, as well as the results of this contest between both animals and plants.^[10]^[11]^[12]

Charles Darwin acknowledged his grandfather’s contribution to the field of transmutation in his synopsis of Erasmus’ life, The Life of Erasmus Darwin. Darwin collaborated with Ernst Krause to write a forward on Krause’s Erasmus Darwin und Seine Stellung in Der Geschichte Der Descendenz-Theorie, which translates into Erasmus Darwin and His Place in the History of the Descent Theory. Krause explains Erasmus’ motivations for arguing for the theory of descent, including Darwin’s connection with and correspondence with Rousseau, which may have influenced how he saw the world.^[13]

Jean-Baptiste Lamarck proposed a hypothesis on the transmutation of species in Philosophie Zoologique (1809). Lamarck did not believe that all living things shared a common ancestor. Rather he believed that simple forms of life were created continuously by spontaneous generation. He also believed that an innate life force, which he sometimes described as a nervous fluid, drove species to become more complex over time, advancing up a linear ladder of complexity that was related to the great chain of being. Lamarck also recognized that species were adapted to their environment. He explained this observation by saying that the same nervous fluid driving increasing complexity, also caused the organs of an animal (or a plant) to change based on the use or disuse of that organ, just as muscles are affected by exercise. He argued that these changes would be inherited by the next generation and produce slow adaptation to the environment. It was this secondary mechanism of adaptation through the inheritance of acquired characteristics that became closely associated with his name and would influence discussions of evolution into the 20th century.^[14]^[15]

The German Abraham Gottlob Werner believed in geological transformism. Specifically, Werner argued that the Earth undergoes irreversible and continuous change. The Edinburgh school, a radical British school of comparative anatomy, fostered a lot of debate around natural history.^[16]^[17] Edinburgh, which included the surgeon Robert Knox and the anatomist Robert Grant, was closely in touch with Lamarck's school of French Transformationism, which contained scientists such as Étienne Geoffroy Saint-Hilaire. Grant developed Lamarck's and Erasmus Darwin's ideas of transmutation and evolutionism, investigating homology to prove common descent. As a young student Charles Darwin joined Grant in investigations of the life cycle of marine animals. He also studied geology under professor Robert Jameson whose journal published an anonymous paper in 1826 praising "Mr. Lamarck" for explaining how the higher animals had "evolved" from the "simplest worms" – this was the first use of the word "evolved" in a modern sense. Professor Jameson was a Wernerian, which allowed him to consider transformation theories and foster the interest in transformism among his students.^[16]^[17] Jameson's course closed with lectures on the "Origin of the Species of Animals".^[18]^[19]

Diagram from the 1844 book Vestiges of the Natural History of Creation by Robert Chambers shows a model of development where fishes (F), reptiles (R), and birds (B) represent branches from a path leading to mammals (M).

The computing pioneer Charles Babbage published his unofficial Ninth Bridgewater Treatise in 1837, putting forward the thesis that God had the omnipotence and foresight to create as a divine legislator, making laws (or programs) which then produced species at the appropriate times, rather than continually interfering with ad hoc miracles each time a new species was required. In 1844 the Scottish publisher Robert Chambers anonymously published an influential and extremely controversial book of popular science entitled Vestiges of the Natural History of Creation. This book proposed an evolutionary scenario for the origins of the solar system and life on earth. It claimed that the fossil record showed an ascent of animals with current animals being branches off a main line that leads progressively to humanity. It implied that the transmutations led to the unfolding of a preordained orthogenetic plan woven into the laws that governed the universe. In this sense it was less completely materialistic than the ideas of radicals like Robert Grant, but its implication that humans were just the last step in the ascent of animal life incensed many conservative thinkers. Both conservatives like Adam Sedgwick, and radical materialists like Thomas Henry Huxley, who disliked Chambers' implications of preordained progress, were able to find scientific inaccuracies in the book that they could disparage. Darwin himself openly deplored the author's "poverty of intellect", and dismissed it as a "literary curiosity." However, the high profile of the public debate over Vestiges, with its depiction of evolution as a progressive process, and its popular success, would greatly influence the perception of Darwin's theory a decade later.^[20]^[21]^[22] It also influenced some younger naturalists, including Alfred Russel Wallace, to take an interest in the idea of transmutation.^[23]

Opposition to transmutation

Ideas about the transmutation of species were strongly associated with the radical materialism of the Enlightenment and were greeted with hostility by more conservative thinkers. Cuvier attacked the ideas of Lamarck and Geoffroy Saint-Hilaire, agreeing with Aristotle that species were immutable. Cuvier believed that the individual parts of an animal were too closely correlated with one another to allow for one part of the anatomy to change in isolation from the others, and argued that the fossil record showed patterns of catastrophic extinctions followed by re-population, rather than gradual change over time. He also noted that drawings of animals and animal mummies from Egypt, which were thousands of years old, showed no signs of change when compared with modern animals. The strength of Cuvier's arguments and his reputation as a leading scientist helped keep transmutational ideas out of the scientific mainstream for decades.^[24]

In Britain, where the philosophy of natural theology remained influential, William Paley wrote the book Natural Theology with its famous watchmaker analogy, at least in part as a response to the transmutational ideas of Erasmus Darwin.^[25] Geologists influenced by natural theology, such as Buckland and Sedgwick, made a regular practice of attacking the evolutionary ideas of Lamarck and Grant, and Sedgwick wrote a famously harsh review of The Vestiges of the Natural History of Creation.^[26]^[27] Although the geologist Charles Lyell opposed scriptural geology, he also believed in the immutability of species, and in his Principles of Geology (1830–1833) he criticized and dismissed Lamarck's theories of development. Instead, he advocated a form of progressive creation, in which each species had its "centre of creation" and was designed for this particular habitat, but would go extinct when this habitat changed.^[19]

This 1847 diagram by Richard Owen shows his conceptual archetype for all vertebrates.

Another source of opposition to transmutation was a school of naturalists who were influenced by the German philosophers and naturalists associated with idealism, such as Goethe, Hegel and Lorenz Oken. Idealists such as Louis Agassiz and Richard Owen believed that each species was fixed and unchangeable because it represented an idea in the mind of the creator. They believed that relationships between species could be discerned from developmental patterns in embryology, as well as in the fossil record, but that these relationships represented an underlying pattern of divine thought, with progressive creation leading to increasing complexity and culminating in humanity. Owen developed the idea of "archetypes" in the divine mind that would produce a sequence of species related by anatomical homologies, such as vertebrate limbs. Owen was concerned by the political implications of the ideas of transmutationists like Robert Grant, and he led a public campaign by conservatives that successfully marginalized Grant in the scientific community. In his famous 1841 paper, which coined the term dinosaur for the giant reptiles discovered by Buckland and Gideon Mantell, Owen argued that these reptiles contradicted the transmutational ideas of Lamarck because they were more sophisticated than the reptiles of the modern world. Darwin would make good use of the homologies analyzed by Owen in his own theory, but the harsh treatment of Grant, along with the controversy surrounding Vestiges, would be factors in his decision to ensure that his theory was fully supported by facts and arguments before publishing his ideas.^[19]^[28]^[29]

Notes

There are three examples of the word 'evolution' in Social Statics, but none in the sense that is used today in biology.^[4]

References

Sloan, Phillip. "Evolution". In Edward N. Zalta (ed.). The Stanford Encyclopedia of Philosophy (Fall 2010 Edition).

(Secord 2000, p. 311)

Lorenzano, Pablo. "An Analysis of the Work of Joseph Gottlieb Kölreuter and its Relation to Gregor Mendel's Work" (PDF). Retrieved 2019-12-31.

Spencer, Herbert (1851). Social Statics. London: John Chapman. Retrieved 2020-01-04 – via Online Library of Liberty.

"اﻟﻤﻗﺩﻤﻪ". www.muslimphilosophy.com. Retrieved 2020-10-12.

Muhammad Hamidullah and Afzal Iqbal (I), The Emergence of Islam: Lectures on the Development of Islamic World-view, Intellectual Tradition and Polity, pp. 143–44. Islamic Research Institute, Islamabad.

"THE MUQADDIMAH, Abd Ar Rahman bin Muhammed ibn Khaldun, Translated by Franz Rosenthal". Retrieved 2020-10-12. 5. The sciences (knowledge) of the prophets

Gregory, Mary (2006-10-23). Diderot and the Metamorphosis of Species. Routledge. doi:10.4324/9780203943823. ISBN 978-1-135-91583-4.

Corsi, Pietro (28 October 2021). "Systemes de la Nature and Theories of Life: Bridging the Eighteenth and Nineteenth Centuries". Republic of Letters. 6 – via Stanford Arcade.

(Bowler 2003, p. ^{[page needed]})

Daly, Jennifer (27 October 2021). "The Botanic Universe: Generative Nature and Erasmus Darwin's Cosmic Transformism". Republic of Letters. 6 – via Stanford Arcade.

Elliott, Paul (March 2003). "Erasmus Darwin, Herbert Spencer, and the Origins of the Evolutionary Worldview in British Provincial Scientific Culture, 1770–1850". Isis. 94 (1): 1–29. doi:10.1086/376097. ISSN 0021-1753. PMID 12725102. S2CID 25850944.

Darwin, Charles (2003). The life of Erasmus Darwin. Cambridge University Press. ISBN 0-521-81526-6. OCLC 470610252.

(Bowler 2003, pp. 86–94)

(Larson 2004, pp. 38–41)

Jenkins, Bill (2019). Evolution before Darwin: theories of the transmutation of species in Edinburgh, 1804-1834. ISBN 978-1-4744-7651-5. OCLC 1155496577.

Sánchez González, José Carlos (May 2021). "Evolution before Darwin: Theories of the Transmutation of Species in Edinburgh, 1804–1834". Centaurus. 63: 440–442.

(Desmond & Moore 1994, p. 40)

(Bowler 2003, pp. 120–134)

(Bowler 2003, pp. 134–138)

(Bowler & Morus 2005, pp. 142–143)

(Desmond & Moore 1994, p. 47)

(Bowler 2003, p. 174)

(Larson 2004, pp. 5–24)

(Bowler 2003, pp. 103–104)

(Larson 2004, pp. 37–38)

(Bowler 2003, p. 138)

(Larson 2004, pp. 42–46)

(van Wyhe 2007, pp. 181–182)

Bibliography

Bowler, Peter J. (2003). Evolution:The History of an Idea. University of California Press. ISBN 0-520-23693-9.
Desmond, Adrian; Moore, James (1994). Darwin: The Life of a Tormented Evolutionist. W. W. Norton & Company. ISBN 0-393-31150-3.
Bowler, Peter J.; Morus, Iwan Rhys (2005). Making Modern Science. The University of Chicago Press. ISBN 0-226-06861-7.
Larson, Edward J. (2004). Evolution:The Remarkable History of Scientific Theory. Modern Library. ISBN 0-679-64288-9.
Secord, James A. (2000). Victorian sensation: the extraordinary publication, reception, and secret authorship of the Vestiges of the Natural History of Creation. Chicago.
van Wyhe, John (27 March 2007). "Mind the gap: Did Darwin avoid publishing his theory for many years?" (PDF). Notes and Records of the Royal Society. 61 (2): 177–205. doi:10.1098/rsnr.2006.0171. S2CID 202574857.

External links

Categories:

https://en.wikipedia.org/wiki/Transmutation_of_species

A transborder agglomeration is an urban agglomeration or conurbation that extends into multiple sovereign states and/or dependent territories. It includes city-states that agglomerate with their neighbouring countries.

List of transborder agglomerations

This list is incomplete; you can help by adding missing items. (August 2010)

Africa

Main municipalities	Countries	Total population
Kinshasa–Brazzaville	Democratic Republic of the Congo–Republic of the Congo	19,547,463
Bukavu–Cyangugu	Democratic Republic of the Congo–Rwanda	~1.2 million^[1]^[2]
Goma–Gisenyi	Democratic Republic of the Congo–Rwanda	756,323
Lomé–Aflao	Togo–Ghana	1,544,206
N'djamena–Kousséri	Chad–Cameroon	1,694,819

Asia

Main municipalities	Countries	Total population
Astara–Astara	Iran–Azerbaijan	100,000
Basra–Khorramshahr–Abadan	Iraq–Iran	2,000,000
Blagoveshchensk–Heihe	Russia–China	400,000
Dandong–Sinuiju	China–North Korea	1,000,000
Dhahran–Jubail–Manama	Saudi Arabia–Bahrain	2,000,000
Fergana–Kyzyl-Kiya	Uzbekistan–Kyrgyzstan	300,000
Sijori Growth Triangle (Singapore–Johor Bahru–Batam–Bintan)	Singapore–Malaysia–Indonesia	9,000,000
Greater Bay Area (Guangzhou–Dongguan–Shenzhen–Hong Kong–Macau)	China–Hong Kong–Macau	71,200,000
Kara-Suu–Qorasuv	Kyrgyzstan–Uzbekistan	40,000
Lahore–Amritsar	Pakistan–India	12,000,000
Mukdahan–Savannakhet	Thailand–Laos	200,000
Padang Besar–Padang Besar	Malaysia–Thailand	20,000
Tashkent–Saryagash	Uzbekistan–Kazakhstan	3,000,000 ^[3]
Vientiane–Nong Khai	Laos–Thailand	900,000

Europe

Main municipalities	Countries	Total population^{[citation needed]}
Øresund Region (Greater Copenhagen and Malmö)	Denmark–Sweden	3,964,522
Baarle-Hertog–Baarle-Nassau	Belgium–Netherlands	9,262
Basel–Huningue–Weil am Rhein (Regio TriRhena)	Switzerland–France–Germany	2,400,000
Bourg-Madame–Puigcerdà	France–Spain
Como–Chiasso (part of Greater Milan)^[4]	Italy–Switzerland	189,000^[5]
Saarbrücken–Forbach	Germany–France	700,000
Geneva–Annemasse–Ferney-Voltaire–Nyon (France–Vaud–Geneva basin or Grand Genève)	Switzerland–France	890,000
Gorizia–Nova Gorica	Italy–Slovenia
Görlitz–Zgorzelec	Germany–Poland	85,000
Guben–Gubin	Germany–Poland	35,000
Hendaye–Irun	France–Spain
Ivangorod–Narva	Russia–Estonia	69,000
Katowice–Ostrava (the Upper Silesian metropolitan area, including directly cut Český Těšín-Cieszyn)	Poland–Czech Republic	5,300,000
Komárno–Komárom	Slovakia–Hungary	56,000
Le Perthus–Els Límits	France–Spain	700
Basque Eurocity Bayonne-San Sebastián	France–Spain	620,000
Lille–Roubaix–Tourcoing–Mouscron–Tournai–Kortrijk	France–Belgium	1,850,000
Longwy–Aubange–Pétange	France–Belgium–Luxembourg	80,000
Strasbourg–Kehl	France–Germany	700,000
Konstanz–Kreuzlingen	Germany–Switzerland	110,000
Kerkrade–Herzogenrath	Netherlands–Germany	95,000
Frankfurt (Oder)–Słubice	Germany–Poland	75,000
Haparanda–Tornio	Sweden–Finland	32,000
Pello–Pello	Sweden–Finland	4,500
Karesuando–Karesuvanto	Sweden–Finland	500
Imatra–Svetogorsk	Finland–Russia	45,000
Rousse–Giurgiu	Bulgaria–Romania	250,000
Lifford–Strabane	Ireland–Northern Ireland	18,500
Valka–Valga	Latvia–Estonia	20,000
Vienna–Bratislava	Austria–Slovakia	1,900,000
Slavonski Brod–Brod	Croatia–Bosnia and Herzegovina	110,000
Szczecin	Poland–Germany	763,321

North America

Main municipalities	Countries	Total population
Paso Canoas	Costa Rica–Panama
Metro Vancouver–Fraser Valley–Bellingham	Canada–United States	3,050,000
Detroit–Windsor	United States–Canada	5,976,595
Buffalo-Niagara Region	United States–Canada	1,614,790
Port Huron–Sarnia–Point Edward	United States–Canada	105,776
Sault Ste. Marie–Sault Ste. Marie	United States–Canada	93,944
San Diego–Tijuana	United States–Mexico	5,105,769^[6]
Mexicali–Calexico	Mexico–United States	1,143,000
San Luis Río Colorado–San Luis	Mexico–United States	227,000
Nogales–Nogales	United States–Mexico	240,000
El Paso–Juárez	United States–Mexico	2,500,000^[7]
Laredo–Nuevo Laredo	United States–Mexico	775,481^[8]
Reynosa–McAllen	Mexico–United States	1,500,000^[9]
Brownsville–Matamoros	United States–Mexico	1,136,995^[10]

South America

Main municipalities	Countries	Total population
Saint-Laurent-du-Maroni–Albina	French Guiana (France)–Suriname
Saint Georges–Oiapoque	French Guiana (France)–Brazil	32,000
Santana do Livramento–Rivera	Brazil–Uruguay	140,000
Chuí–Chuy	Brazil–Uruguay	15,592^[11]^[12]
Corumbá–Puerto Suárez	Brazil–Bolivia	124,000
Leticia–Tabatinga–Santa Rosa	Colombia–Brazil–Peru	107,000
Ponta Porã–Pedro Juan Caballero	Brazil–Paraguay	209,000
Foz do Iguaçu–Ciudad del Este–Puerto Iguazu	Brazil–Paraguay–Argentina	800,000
Bernardo de Irigoyen–Barracão–Dionísio Cerqueira	Argentina–Brazil	36,000
Uruguaiana–Paso de los Libres	Brazil–Argentina	170,000
Cúcuta–San Antonio del Táchira	Colombia–Venezuela	700,000 ^[13]

References

"Bukavu, Democratic Republic of the Congo Population (2023) - Population Stat". populationstat.com. Retrieved 2 May 2023.

"Explore Cyangugu Town". Nyungwe Forest National Park. Retrieved 2 May 2023.

"Central Asian cities are overgrown with slums". centre1.com. Retrieved 12 May 2017.

"Archived copy" (PDF). www.espon.eu. Archived from the original (PDF) on 24 September 2015. Retrieved 12 January 2022.

"San Diego - Tijuana". World Gazetteer. Archived from the original on 2007-10-01. Retrieved 1 September 2011.

"The 411 - Fascinating Facts". Guest Life: El Paso/Juarez and Southern New Mexico. Archived from the original on 28 September 2007. Retrieved 17 Feb 2010.

"Nuevo Laredo Metro area". World Gazetteer. Archived from the original on 9 February 2013. Retrieved 1 September 2011.

"McAllen Overview". McAllen Chamber of Commerce. Retrieved 26 August 2011.

"Matamoros-Brownsville". World Gazetteer. Retrieved 22 August 2011.^{[dead link]}

"IBGE Cidades (Brazil's Census 2010)".

"INE (Uruguay's Census 2011)".

http://www.lapatilla.com/site/2016/08/15/cucuta-y-san-antonio-dos-ciudades-unidas-pero-separadas-por-cierre-frontera/ "...que une ambas ciudades formando una conurbación, los 650.000 habitantes de Cúcuta y los 50.000 de San Antonio supieron que comenzaban tiempos difíciles."

v t e World's largest cities
City proper	Capitals Africa Americas (North Latin Central South) Asia (Arab world ASEAN Arabia East, South and Southeast Asia) Europe (European Union Nordic)
Metropolitan area	Americas (North South West Indies) Europe (European Union) Asia Africa Middle East Oceania
Urban area/agglomeration	Asia Africa Europe European Union Nordic North America Oceania Transborder
Historical	World Europe
Related articles	Arcology Ecumenopolis Global city Megacity Megalopolis Conurbation Satellite city population Primate city Secondary city
Cities portal • World portal

Categories:

https://en.wikipedia.org/wiki/Transborder_agglomeration

Transport Layer Security (TLS) is a cryptographic protocol designed to provide communications security over a computer network. The protocol is widely used in applications such as email, instant messaging, and voice over IP, but its use in securing HTTPS remains the most publicly visible.

The TLS protocol aims primarily to provide security, including privacy (confidentiality), integrity, and authenticity through the use of cryptography, such as the use of certificates, between two or more communicating computer applications. It runs in the presentation layer and is itself composed of two layers: the TLS record and the TLS handshake protocols.

The closely related Datagram Transport Layer Security (DTLS) is a communications protocol that provides security to datagram-based applications. In technical writing, references to "(D)TLS" are often seen when it applies to both versions.^[1]

TLS is a proposed Internet Engineering Task Force (IETF) standard, first defined in 1999, and the current version is TLS 1.3, defined in August 2018. TLS builds on the now-deprecated SSL (Secure Sockets Layer) specifications (1994, 1995, 1996) developed by Netscape Communications for adding the HTTPS protocol to their Navigator web browser.

https://en.wikipedia.org/wiki/Transport_Layer_Security

The Dynamic Host Configuration Protocol version 6 (DHCPv6) is a network protocol for configuring Internet Protocol version 6 (IPv6) hosts with IP addresses, IP prefixes, default route, local segment MTU, and other configuration data required to operate in an IPv6 network. It is not just the IPv6 equivalent of the Dynamic Host Configuration Protocol for IPv4.

IPv6 hosts may automatically generate IP addresses internally using stateless address autoconfiguration (SLAAC), or they may be assigned configuration data with DHCPv6.

IPv6 hosts that use stateless autoconfiguration may require information other than an IP address or route. DHCPv6 can be used to acquire this information, even though it is not being used to configure IP addresses. DHCPv6 is not necessary for configuring hosts with the addresses of Domain Name System (DNS) servers, because they can be configured using Neighbor Discovery Protocol, which is also the mechanism for stateless autoconfiguration.^[1]

Many IPv6 routers, such as routers for residential networks, must be configured automatically with no operator intervention. Such routers require not only an IPv6 address for use in communicating with upstream routers, but also an IPv6 prefix for use in configuring devices on the downstream side of the router. DHCPv6 prefix delegation provides a mechanism for configuring such routers.

https://en.wikipedia.org/wiki/DHCPv6

Transfer genes or tra genes (also transfer operons or tra operons), are some genes necessary for non-sexual transfer of genetic material in both gram-positive and gram-negative bacteria. The tra locus includes the pilin gene and regulatory genes, which together form pili on the cell surface, polymeric proteins that can attach themselves to the surface of F-bacteria and initiate the conjugation. The existence of the tra region of a plasmid genome was first discovered in 1979 by David H. Figurski and Donald R. Helinski^[1] In the course of their work, Figurski and Helinski also discovered a second key fact about the tra region – that it can act in trans to the mobilization marker which it affects.^[1]

This finding suggested that there were two basic aspects necessary for a plasmid to move from one cell to another:

An origin of transfer – A plasmid with no origin of transfer is non-mobilizable.^[2]
The transfer genes – Though a functioning set of tra genes is necessary for plasmid transfer, they may be located in a variety of places including the plasmid in question, another plasmid in the same host cell, or even in the bacterial genome.^[3]

The tra genes encode proteins which are useful for the propagation of the plasmid from the host cell to a compatible donor cell or maintenance of the plasmid. Not all transfer operons are the same. Some genes are only found in a few species or a single genus of bacteria while others (such as traL) are found in very similar forms in many bacterial species. Many of the transfer systems are incompatible. For example, oriT and bom are two origins of transfer which interact with different sets of transfer genes. A plasmid with a mob site (like many found in Rhodococcus species) cannot be transferred via transfer genes which normally interact with the oriT site (which is common in E. coli)^[3]

The roles of some tra-gene encoded proteins:^[4]
Pili Assembly and Production	traA, traB, traE, traC, traF, traG, traH, traK, traL, traQ, traU, traV, traW,
Inner Membrane Proteins	traB, traE, traG, traL, traP
Periplasmic Proteins	traC, traF, traH traK, traU, traW
DNA transfer	traC, traD, traI, traM, traY
Surface Exclusion Proteins	traS, traT
Mating Pair Stabilization	traN, traG

Each of the individual genes in the tra operon codes for a different protein product. These products may perform a number of tasks including interaction with one another to perform mating pair functions and regulation of different regions of the tra operon itself,^[5] or conjugative DNA metabolism and surface exclusion.^[4] Also, note that some proteins perform multiple functions or are associated closely with proteins which have non-similar functions.

References

Figurski D, Helinski D (1979). "Replication of an origin-containing derivative of plasmid RK2 dependent on a plasmid function in trans". PNAS. 76 (4): 1648–1652. doi:10.1073/pnas.76.4.1648. PMC 383447. PMID 377280.

Fu, Y H; Tsai, M M; Luo, Y N; Deonier, R C (February 1991). "Deletion analysis of the F plasmid oriT locus". Journal of Bacteriology. 173 (3): 1012–1020. doi:10.1128/jb.173.3.1012-1020.1991. ISSN 0021-9193. PMC 207219. PMID 1991706.

Simon R, Priefer U, Puhler A (1983). "A Broad Host Range Mobilization System for In Vivo Genetic Engineering: Transposon Mutagenesis in Gram Negative Bacteria". Nature Biotechnology. 1 (9): 784–791. doi:10.1038/nbt1183-784. S2CID 46140184.

Clewell D, et al. (1993). Bacterial Conjugation. Plenum Press, New York. ISBN 978-0-306-44376-3.

Grohmann E, Muth G, Espinosa M (2003). "Conjugative Plasmid Transfer in Gram-Positive Bacteria". Microbiology and Molecular Biology Reviews. 67 (2): 277–301. doi:10.1128/MMBR.67.2.277-301.2003. PMC 156469. PMID 12794193.

Category:

Genes

https://en.wikipedia.org/wiki/Transfer_gene

Pridnestrovian Moldavian Republic Приднестро́вская Молда́вская Респу́блика (Russian) Pridnestróvskaya Moldávskaya Respúblika Republica Moldovenească Nistreană (Romanian) Република Молдовеняскэ Нистрянэ (Moldovan Cyrillic) Придністро́вська Молда́вська Респу́бліка (Ukrainian) Prydnistróvska Moldávska Respúblika
Co-official flags^[a] Coat of arms
Anthem: Мы славим тебя, Приднестровье My slavim tebya, Pridnestrovie "We Sing the Praises of Transnistria"^[2] 2:25

Status	Unrecognised state
Capital and largest city	Tiraspol 46°50′25″N 29°38′36″E
Official languages	Russian Moldovan (Romanian) Ukrainian
Interethnic language	Russian^[3]^[4]^[5]
Ethnic groups (2015)	29.1% Russians 28.6% Moldovans / Romanians^[b] 22.9% Ukrainians 2.4% Bulgarians 1.1% Gagauz 0.5% Belarusians 0.2% Transnistrians 1.4% others (14% did not specify)
Demonym(s)	Transnistrian Pridnestrovian
Government	Unitary presidential republic

• President	Vadim Krasnoselsky
• Prime Minister	Aleksandr Rozenberg
• Speaker of the Supreme Council	Alexander Korshunov
Legislature	Supreme Council
Unrecognised state

• Independence from SSR of Moldova declared	2 September 1990
• Independence from Soviet Union declared	25 August 1991
• Succeeds the Pridnestrovian Moldavian Soviet Socialist Republic	5 November 1991^[6]
• Transnistria War	2 March – 1 July 1992
Area
• Total	4,163 km² (1,607 sq mi)
• Water (%)	2.35
Population
• 31 December 2022 estimate	360,938 (Moldovan estimate)^[7]
• 2015 census	475,373^[8]
• Density	73.5/km² (190.4/sq mi)
GDP (nominal)	2021 estimate
• Total	$1.201 billion^[9]
• Per capita	$2,584
Currency	Transnistrian ruble (PRB)
Time zone	UTC+2 (EET)
• Summer (DST)	UTC+3 (EEST)
Calling code	+373^[a]
^ +373 5 and +373 2.

Transnistria, officially the Pridnestrovian Moldavian Republic (PMR),^[c] is an unrecognised breakaway state that is internationally recognised as a part of Moldova. Transnistria controls most of the narrow strip of land between the Dniester river and the Moldovan–Ukrainian border, as well as some land on the other side of the river's bank. Its capital and largest city is Tiraspol. Transnistria has been recognised only by three other unrecognised or partially recognised breakaway states: Abkhazia, Artsakh and South Ossetia.^[10] Transnistria is officially designated by the Republic of Moldova as the Administrative-Territorial Units of the Left Bank of the Dniester (Romanian: Unitățile Administrativ-Teritoriale din stînga Nistrului)^[11] or as Stînga Nistrului ("Left Bank of the Dniester").^[12]^[13]^[14] In March 2022, the Parliamentary Assembly of the Council of Europe adopted a resolution that defines the territory as under military occupation by Russia.^[15]

The region's origins can be traced to the Moldavian Autonomous Soviet Socialist Republic, which was formed in 1924 within the Ukrainian SSR. During World War II, the Soviet Union took parts of the Moldavian ASSR, which was dissolved, and of the Kingdom of Romania's Bessarabia to form the Moldavian Soviet Socialist Republic in 1940. The present history of the region dates to 1990, during the dissolution of the Soviet Union, when the Pridnestrovian Moldavian Soviet Socialist Republic was established in hopes that it would remain within the Soviet Union should Moldova seek unification with Romania or independence, the latter occurring in August 1991. Shortly afterwards, a military conflict between the two parties started in March 1992 and concluded with a ceasefire in July that year.

As part of the ceasefire agreement, a three-party (Russia, Moldova, Transnistria) Joint Control Commission supervises the security arrangements in the demilitarised zone, comprising 20 localities on both sides of the river.^{[citation needed]} Although the ceasefire has held, the territory's political status remains unresolved: Transnistria is an unrecognised but de facto independent presidential republic^[16] with its own government, parliament, military, police, postal system, currency, and vehicle registration.^[17]^[18]^[19]^[20] Its authorities have adopted a constitution, flag, national anthem, and coat of arms. After a 2005 agreement between Moldova and Ukraine, all Transnistrian companies that seek to export goods through the Ukrainian border must be registered with the Moldovan authorities.^[21] This agreement was implemented after the European Union Border Assistance Mission to Moldova and Ukraine (EUBAM) took force in 2005.^[22] Most Transnistrians have Moldovan citizenship,^[23] but many also have Russian, Romanian, or Ukrainian citizenship.^[24]^[25] The main ethnic groups are Russians, Moldovans/Romanians, and Ukrainians.

Transnistria, along with Abkhazia, South Ossetia, and Artsakh, is a post-Soviet "frozen conflict" zone.^[26] These four partially recognised or unrecognised states maintain friendly relations with each other and form the Community for Democracy and Rights of Nations.^[27]^[28]^[29]

https://en.wikipedia.org/wiki/Transnistria

The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is commonly referred to as TCP/IP. TCP provides reliable, ordered, and error-checked delivery of a stream of octets (bytes) between applications running on hosts communicating via an IP network. Major internet applications such as the World Wide Web, email, remote administration, and file transfer rely on TCP, which is part of the Transport Layer of the TCP/IP suite. SSL/TLS often runs on top of TCP.

TCP is connection-oriented, and a connection between client and server is established before data can be sent. The server must be listening (passive open) for connection requests from clients before a connection is established. Three-way handshake (active open), retransmission, and error detection adds to reliability but lengthens latency. Applications that do not require reliable data stream service may use the User Datagram Protocol (UDP) instead, which provides a connectionless datagram service that prioritizes time over reliability. TCP employs network congestion avoidance. However, there are vulnerabilities in TCP, including denial of service, connection hijacking, TCP veto, and reset attack.

https://en.wikipedia.org/wiki/Transmission_Control_Protocol

TCP reset attack, also known as a "forged TCP reset" or "spoofed TCP reset", is a way to terminate a TCP connection by sending a forged TCP reset packet. This tampering technique can be used by a firewall or abused by a malicious attacker to interrupt Internet connections.

The Great Firewall of China, and Iranian Internet censors are known to use TCP reset attacks to interfere with and block connections,^[1] as a major method to carry out Internet censorship.

https://en.wikipedia.org/wiki/TCP_reset_attack

https://en.wikipedia.org/wiki/Category:Computer_security_exploits

A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer's core, which induces a varying electromotive force (EMF) across any other coils wound around the same core. Electrical energy can be transferred between separate coils without a metallic (conductive) connection between the two circuits. Faraday's law of induction, discovered in 1831, describes the induced voltage effect in any coil due to a changing magnetic flux encircled by the coil.

Transformers are used to change AC voltage levels, such transformers being termed step-up or step-down type to increase or decrease voltage level, respectively. Transformers can also be used to provide galvanic isolation between circuits as well as to couple stages of signal-processing circuits. Since the invention of the first constant-potential transformer in 1885, transformers have become essential for the transmission, distribution, and utilization of alternating current electric power.^[1] A wide range of transformer designs is encountered in electronic and electric power applications. Transformers range in size from RF transformers less than a cubic centimeter in volume, to units weighing hundreds of tons used to interconnect the power grid.

https://en.wikipedia.org/wiki/Transformer

Principles

Ideal transformer equations

By Faraday's law of induction:

V_{P} = - N_{P} \frac{d Φ}{d t}

(Eq. 1^[a]^[2])

V_{S} = - N_{S} \frac{d Φ}{d t}

(Eq. 2)

where $V$ is the instantaneous voltage, $N$ is the number of turns in a winding, dΦ/dt is the derivative of the magnetic flux Φ through one turn of the winding over time (t), and subscripts _P and _S denotes primary and secondary.

Combining the ratio of eq. 1 & eq. 2:

Turns ratio

= \frac{V_{P}}{V_{S}} = \frac{N_{P}}{N_{S}} = a

(Eq. 3)

where for a step-up transformer a < 1 and for a step-down transformer a > 1.^[3]

By the law of conservation of energy, apparent, real and reactive power are each conserved in the input and output:

S = I_{P} V_{P} = I_{S} V_{S}

(Eq. 4)

where $S$ is apparent power and $I$ is current.

Combining Eq. 3 & Eq. 4 with this endnote^[b]^[4] gives the ideal transformer identity:

\frac{V_{P}}{V_{S}} = \frac{I_{S}}{I_{P}} = \frac{N_{P}}{N_{S}} = \sqrt{\frac{L_{P}}{L_{S}}} = a

(Eq. 5)

where $L$ is winding self-inductance.

By Ohm's law and ideal transformer identity:

Z_{L} = \frac{V_{S}}{I_{S}}

(Eq. 6)

Z_{L}^{'} = \frac{V_{P}}{I_{P}} = \frac{a V_{S}}{I_{S} / a} = a^{2} \frac{V_{S}}{I_{S}} = a^{2} Z_{L}

(Eq. 7)

where $Z_{L}$ is the load impedance of the secondary circuit & $Z_{L}^{'}$ is the apparent load or driving point impedance of the primary circuit, the superscript $^{'}$ denoting referred to the primary.

Ideal transformer

An ideal transformer is linear, lossless and perfectly coupled. Perfect coupling implies infinitely high core magnetic permeability and winding inductance and zero net magnetomotive force (i.e. i_pn_p − i_sn_s = 0).^[3]^[c]

Ideal transformer connected with source V_P on primary and load impedance Z_L on secondary, where 0 < Z_L < ∞.

Ideal transformer and induction law^[d]

A varying current in the transformer's primary winding creates a varying magnetic flux in the transformer core, which is also encircled by the secondary winding. This varying flux at the secondary winding induces a varying electromotive force or voltage in the secondary winding. This electromagnetic induction phenomenon is the basis of transformer action and, in accordance with Lenz's law, the secondary current so produced creates a flux equal and opposite to that produced by the primary winding.

The windings are wound around a core of infinitely high magnetic permeability so that all of the magnetic flux passes through both the primary and secondary windings. With a voltage source connected to the primary winding and a load connected to the secondary winding, the transformer currents flow in the indicated directions and the core magnetomotive force cancels to zero.

According to Faraday's law, since the same magnetic flux passes through both the primary and secondary windings in an ideal transformer, a voltage is induced in each winding proportional to its number of windings. The transformer winding voltage ratio is equal to the winding turns ratio.^[6]

An ideal transformer is a reasonable approximation for a typical commercial transformer, with voltage ratio and winding turns ratio both being inversely proportional to the corresponding current ratio.

The load impedance referred to the primary circuit is equal to the turns ratio squared times the secondary circuit load impedance.^[7]

Real transformer

Leakage flux of a transformer

Deviations from ideal transformer

The ideal transformer model neglects the following basic linear aspects of real transformers:

(a) Core losses, collectively called magnetizing current losses, consisting of^[8]

Hysteresis losses due to nonlinear magnetic effects in the transformer core, and
Eddy current losses due to joule heating in the core that are proportional to the square of the transformer's applied voltage.

(b) Unlike the ideal model, the windings in a real transformer have non-zero resistances and inductances associated with:

Joule losses due to resistance in the primary and secondary windings^[8]
Leakage flux that escapes from the core and passes through one winding only resulting in primary and secondary reactive impedance.

(c) similar to an inductor, parasitic capacitance and self-resonance phenomenon due to the electric field distribution. Three kinds of parasitic capacitance are usually considered and the closed-loop equations are provided^[9]

Capacitance between adjacent turns in any one layer;
Capacitance between adjacent layers;
Capacitance between the core and the layer(s) adjacent to the core;

Inclusion of capacitance into the transformer model is complicated, and is rarely attempted; the ‘real’ transformer model's equivalent circuit shown below does not include parasitic capacitance. However, the capacitance effect can be measured by comparing open-circuit inductance, i.e. the inductance of a primary winding when the secondary circuit is open, to a short-circuit inductance when the secondary winding is shorted.

Leakage flux

The ideal transformer model assumes that all flux generated by the primary winding links all the turns of every winding, including itself. In practice, some flux traverses paths that take it outside the windings.^[10] Such flux is termed leakage flux, and results in leakage inductance in series with the mutually coupled transformer windings.^[11] Leakage flux results in energy being alternately stored in and discharged from the magnetic fields with each cycle of the power supply. It is not directly a power loss, but results in inferior voltage regulation, causing the secondary voltage not to be directly proportional to the primary voltage, particularly under heavy load.^[10] Transformers are therefore normally designed to have very low leakage inductance.

In some applications increased leakage is desired, and long magnetic paths, air gaps, or magnetic bypass shunts may deliberately be introduced in a transformer design to limit the short-circuit current it will supply.^[11] Leaky transformers may be used to supply loads that exhibit negative resistance, such as electric arcs, mercury- and sodium- vapor lamps and neon signs or for safely handling loads that become periodically short-circuited such as electric arc welders.^[8]^: 485

Air gaps are also used to keep a transformer from saturating, especially audio-frequency transformers in circuits that have a DC component flowing in the windings.^[12] A saturable reactor exploits saturation of the core to control alternating current.

Knowledge of leakage inductance is also useful when transformers are operated in parallel. It can be shown that if the percent impedance ^[e] and associated winding leakage reactance-to-resistance (X/R) ratio of two transformers were the same, the transformers would share the load power in proportion to their respective ratings. However, the impedance tolerances of commercial transformers are significant. Also, the impedance and X/R ratio of different capacity transformers tends to vary.^[14]

Equivalent circuit

Referring to the diagram, a practical transformer's physical behavior may be represented by an equivalent circuit model, which can incorporate an ideal transformer.^[15]

Winding joule losses and leakage reactances are represented by the following series loop impedances of the model:

Primary winding: R_P, X_P
Secondary winding: R_S, X_S.

In normal course of circuit equivalence transformation, R_S and X_S are in practice usually referred to the primary side by multiplying these impedances by the turns ratio squared, (N_P/N_S)² = a².

Real transformer equivalent circuit

Core loss and reactance is represented by the following shunt leg impedances of the model:

Core or iron losses: R_C
Magnetizing reactance: X_M.

R_C and X_M are collectively termed the magnetizing branch of the model.

Core losses are caused mostly by hysteresis and eddy current effects in the core and are proportional to the square of the core flux for operation at a given frequency.^[8] ^{: 142–143} The finite permeability core requires a magnetizing current I_M to maintain mutual flux in the core. Magnetizing current is in phase with the flux, the relationship between the two being non-linear due to saturation effects. However, all impedances of the equivalent circuit shown are by definition linear and such non-linearity effects are not typically reflected in transformer equivalent circuits.^[8]^: 142 With sinusoidal supply, core flux lags the induced EMF by 90°. With open-circuited secondary winding, magnetizing branch current I₀ equals transformer no-load current.^[15]

Instrument transformer, with polarity dot and X1 markings on low-voltage ("LV") side terminal

The resulting model, though sometimes termed 'exact' equivalent circuit based on linearity assumptions, retains a number of approximations.^[15] Analysis may be simplified by assuming that magnetizing branch impedance is relatively high and relocating the branch to the left of the primary impedances. This introduces error but allows combination of primary and referred secondary resistances and reactances by simple summation as two series impedances.

Transformer equivalent circuit impedance and transformer ratio parameters can be derived from the following tests: open-circuit test, short-circuit test, winding resistance test, and transformer ratio test.

Transformer EMF equation

If the flux in the core is purely sinusoidal, the relationship for either winding between its rms voltage E_rms of the winding, and the supply frequency f, number of turns N, core cross-sectional area A in m² and peak magnetic flux density B_peak in Wb/m² or T (tesla) is given by the universal EMF equation:^[8]

E_{rms} = \frac{2 π f N A B_{peak}}{\sqrt{2}} \approx 4.44 f N A B_{peak}

Polarity

A dot convention is often used in transformer circuit diagrams, nameplates or terminal markings to define the relative polarity of transformer windings. Positively increasing instantaneous current entering the primary winding's ‘dot’ end induces positive polarity voltage exiting the secondary winding's ‘dot’ end. Three-phase transformers used in electric power systems will have a nameplate that indicate the phase relationships between their terminals. This may be in the form of a phasor diagram, or using an alpha-numeric code to show the type of internal connection (wye or delta) for each winding.

Effect of frequency

The EMF of a transformer at a given flux increases with frequency.^[8] By operating at higher frequencies, transformers can be physically more compact because a given core is able to transfer more power without reaching saturation and fewer turns are needed to achieve the same impedance. However, properties such as core loss and conductor skin effect also increase with frequency. Aircraft and military equipment employ 400 Hz power supplies which reduce core and winding weight.^[16] Conversely, frequencies used for some railway electrification systems were much lower (e.g. 16.7 Hz and 25 Hz) than normal utility frequencies (50–60 Hz) for historical reasons concerned mainly with the limitations of early electric traction motors. Consequently, the transformers used to step-down the high overhead line voltages were much larger and heavier for the same power rating than those required for the higher frequencies.

Power transformer overexcitation condition caused by decreased frequency; flux (green), iron core's magnetic characteristics (red) and magnetizing current (blue).

Operation of a transformer at its designed voltage but at a higher frequency than intended will lead to reduced magnetizing current. At a lower frequency, the magnetizing current will increase. Operation of a large transformer at other than its design frequency may require assessment of voltages, losses, and cooling to establish if safe operation is practical. Transformers may require protective relays to protect the transformer from overvoltage at higher than rated frequency.

One example is in traction transformers used for electric multiple unit and high-speed train service operating across regions with different electrical standards. The converter equipment and traction transformers have to accommodate different input frequencies and voltage (ranging from as high as 50 Hz down to 16.7 Hz and rated up to 25 kV).

At much higher frequencies the transformer core size required drops dramatically: a physically small transformer can handle power levels that would require a massive iron core at mains frequency. The development of switching power semiconductor devices made switch-mode power supplies viable, to generate a high frequency, then change the voltage level with a small transformer.

Transformers for higher frequency applications such as SMPS typically use core materials with much lower hysteresis and eddy-current losses than those for 50/60 Hz. Primary examples are iron-powder and ferrite cores. The lower frequency-dependant losses of these cores often is at the expense of flux density at saturation. For instance, ferrite saturation occurs at a substantially lower flux density than laminated iron.

Large power transformers are vulnerable to insulation failure due to transient voltages with high-frequency components, such as caused in switching or by lightning.

Energy losses

Transformer energy losses are dominated by winding and core losses. Transformers' efficiency tends to improve with increasing transformer capacity.^[17] The efficiency of typical distribution transformers is between about 98 and 99 percent.^[17]^[18]

As transformer losses vary with load, it is often useful to tabulate no-load loss, full-load loss, half-load loss, and so on. Hysteresis and eddy current losses are constant at all load levels and dominate at no load, while winding loss increases as load increases. The no-load loss can be significant, so that even an idle transformer constitutes a drain on the electrical supply. Designing energy efficient transformers for lower loss requires a larger core, good-quality silicon steel, or even amorphous steel for the core and thicker wire, increasing initial cost. The choice of construction represents a trade-off between initial cost and operating cost.^[19]

Transformer losses arise from:

Winding joule losses

Current flowing through a winding's conductor causes joule heating due to the resistance of the wire. As frequency increases, skin effect and proximity effect causes the winding's resistance and, hence, losses to increase.

Core losses

Hysteresis losses

Each time the magnetic field is reversed, a small amount of energy is lost due to hysteresis within the core, caused by motion of the magnetic domains within the steel. According to Steinmetz's formula, the heat energy due to hysteresis is given by

W_{h} \approx η β_{max}^{1.6},

and,

hysteresis loss is thus given by

P_{h} \approx W_{h} f \approx η f β_{max}^{1.6}

where, f is the frequency, η is the hysteresis coefficient and β_max is the maximum flux density, the empirical exponent of which varies from about 1.4 to 1.8 but is often given as 1.6 for iron.^[19] For more detailed analysis, see Magnetic core and Steinmetz's equation.

Eddy current losses

Eddy currents are induced in the conductive metal transformer core by the changing magnetic field, and this current flowing through the resistance of the iron dissipates energy as heat in the core. The eddy current loss is a complex function of the square of supply frequency and inverse square of the material thickness.^[19] Eddy current losses can be reduced by making the core of a stack of laminations (thin plates) electrically insulated from each other, rather than a solid block; all transformers operating at low frequencies use laminated or similar cores.

Magnetostriction related transformer hum: Magnetic flux in a ferromagnetic material, such as the core, causes it to physically expand and contract slightly with each cycle of the magnetic field, an effect known as magnetostriction, the frictional energy of which produces an audible noise known as mains hum or "transformer hum".^[20] This transformer hum is especially objectionable in transformers supplied at power frequencies and in high-frequency flyback transformers associated with television CRTs.
Stray losses: Leakage inductance is by itself largely lossless, since energy supplied to its magnetic fields is returned to the supply with the next half-cycle. However, any leakage flux that intercepts nearby conductive materials such as the transformer's support structure will give rise to eddy currents and be converted to heat.^[21]
Radiative: There are also radiative losses due to the oscillating magnetic field but these are usually small.
Mechanical vibration and audible noise transmission: In addition to magnetostriction, the alternating magnetic field causes fluctuating forces between the primary and secondary windings. This energy incites vibration transmission in interconnected metalwork, thus amplifying audible transformer hum.^[22]

Construction

Cores

Core form = core type; shell form = shell type

Closed-core transformers are constructed in 'core form' or 'shell form'. When windings surround the core, the transformer is core form; when windings are surrounded by the core, the transformer is shell form.^[23] Shell form design may be more prevalent than core form design for distribution transformer applications due to the relative ease in stacking the core around winding coils.^[23] Core form design tends to, as a general rule, be more economical, and therefore more prevalent, than shell form design for high voltage power transformer applications at the lower end of their voltage and power rating ranges (less than or equal to, nominally, 230 kV or 75 MVA). At higher voltage and power ratings, shell form transformers tend to be more prevalent.^[23]^[24]^[25] Shell form design tends to be preferred for extra-high voltage and higher MVA applications because, though more labor-intensive to manufacture, shell form transformers are characterized as having inherently better kVA-to-weight ratio, better short-circuit strength characteristics and higher immunity to transit damage.^[25]

Laminated steel cores

Shell type transformer with laminated core showing edges of laminations at the top of the photo

Interleaved E-I transformer laminations showing air gap and flux paths

Transformers for use at power or audio frequencies typically have cores made of high permeability silicon steel.^[26] The steel has a permeability many times that of free space and the core thus serves to greatly reduce the magnetizing current and confine the flux to a path which closely couples the windings.^[27] Early transformer developers soon realized that cores constructed from solid iron resulted in prohibitive eddy current losses, and their designs mitigated this effect with cores consisting of bundles of insulated iron wires.^[28] Later designs constructed the core by stacking layers of thin steel laminations, a principle that has remained in use. Each lamination is insulated from its neighbors by a thin non-conducting layer of insulation.^[29] The transformer universal EMF equation can be used to calculate the core cross-sectional area for a preferred level of magnetic flux.^[8]

The effect of laminations is to confine eddy currents to highly elliptical paths that enclose little flux, and so reduce their magnitude. Thinner laminations reduce losses,^[26] but are more laborious and expensive to construct.^[30] Thin laminations are generally used on high-frequency transformers, with some of very thin steel laminations able to operate up to 10 kHz.

Laminating the core greatly reduces eddy-current losses

One common design of laminated core is made from interleaved stacks of E-shaped steel sheets capped with I-shaped pieces, leading to its name of 'E-I transformer'.^[30] Such a design tends to exhibit more losses, but is very economical to manufacture. The cut-core or C-core type is made by winding a steel strip around a rectangular form and then bonding the layers together. It is then cut in two, forming two C shapes, and the core assembled by binding the two C halves together with a steel strap.^[30] They have the advantage that the flux is always oriented parallel to the metal grains, reducing reluctance.

A steel core's remanence means that it retains a static magnetic field when power is removed. When power is then reapplied, the residual field will cause a high inrush current until the effect of the remaining magnetism is reduced, usually after a few cycles of the applied AC waveform.^[31] Overcurrent protection devices such as fuses must be selected to allow this harmless inrush to pass.

On transformers connected to long, overhead power transmission lines, induced currents due to geomagnetic disturbances during solar storms can cause saturation of the core and operation of transformer protection devices.^[32]

Distribution transformers can achieve low no-load losses by using cores made with low-loss high-permeability silicon steel or amorphous (non-crystalline) metal alloy. The higher initial cost of the core material is offset over the life of the transformer by its lower losses at light load.^[33]

Solid cores

Powdered iron cores are used in circuits such as switch-mode power supplies that operate above mains frequencies and up to a few tens of kilohertz. These materials combine high magnetic permeability with high bulk electrical resistivity. For frequencies extending beyond the VHF band, cores made from non-conductive magnetic ceramic materials called ferrites are common.^[30] Some radio-frequency transformers also have movable cores (sometimes called 'slugs') which allow adjustment of the coupling coefficient (and bandwidth) of tuned radio-frequency circuits.

Toroidal cores

Small toroidal core transformer

Toroidal transformers are built around a ring-shaped core, which, depending on operating frequency, is made from a long strip of silicon steel or permalloy wound into a coil, powdered iron, or ferrite.^[34] A strip construction ensures that the grain boundaries are optimally aligned, improving the transformer's efficiency by reducing the core's reluctance. The closed ring shape eliminates air gaps inherent in the construction of an E-I core.^[8] ^: 485 The cross-section of the ring is usually square or rectangular, but more expensive cores with circular cross-sections are also available. The primary and secondary coils are often wound concentrically to cover the entire surface of the core. This minimizes the length of wire needed and provides screening to minimize the core's magnetic field from generating electromagnetic interference.

Toroidal transformers are more efficient than the cheaper laminated E-I types for a similar power level. Other advantages compared to E-I types, include smaller size (about half), lower weight (about half), less mechanical hum (making them superior in audio amplifiers), lower exterior magnetic field (about one tenth), low off-load losses (making them more efficient in standby circuits), single-bolt mounting, and greater choice of shapes. The main disadvantages are higher cost and limited power capacity (see Classification parameters below). Because of the lack of a residual gap in the magnetic path, toroidal transformers also tend to exhibit higher inrush current, compared to laminated E-I types.

Ferrite toroidal cores are used at higher frequencies, typically between a few tens of kilohertz to hundreds of megahertz, to reduce losses, physical size, and weight of inductive components. A drawback of toroidal transformer construction is the higher labor cost of winding. This is because it is necessary to pass the entire length of a coil winding through the core aperture each time a single turn is added to the coil. As a consequence, toroidal transformers rated more than a few kVA are uncommon. Relatively few toroids are offered with power ratings above 10 kVA, and practically none above 25 kVA. Small distribution transformers may achieve some of the benefits of a toroidal core by splitting it and forcing it open, then inserting a bobbin containing primary and secondary windings.^[35]

Air cores

A transformer can be produced by placing the windings near each other, an arrangement termed an "air-core" transformer. An air-core transformer eliminates loss due to hysteresis in the core material.^[11] The magnetizing inductance is drastically reduced by the lack of a magnetic core, resulting in large magnetizing currents and losses if used at low frequencies. Air-core transformers are unsuitable for use in power distribution,^[11] but are frequently employed in radio-frequency applications.^[36] Air cores are also used for resonant transformers such as Tesla coils, where they can achieve reasonably low loss despite the low magnetizing inductance.

Windings

Windings are usually arranged concentrically to minimize flux leakage.

Cut view through transformer windings. Legend:
White: Air, liquid or other insulating medium
Green spiral: Grain oriented silicon steel
Black: Primary winding
Red: Secondary winding

The electrical conductor used for the windings depends upon the application, but in all cases the individual turns must be electrically insulated from each other to ensure that the current travels throughout every turn. For small transformers, in which currents are low and the potential difference between adjacent turns is small, the coils are often wound from enamelled magnet wire. Larger power transformers may be wound with copper rectangular strip conductors insulated by oil-impregnated paper and blocks of pressboard.^[37]

High-frequency transformers operating in the tens to hundreds of kilohertz often have windings made of braided Litz wire to minimize the skin-effect and proximity effect losses.^[38] Large power transformers use multiple-stranded conductors as well, since even at low power frequencies non-uniform distribution of current would otherwise exist in high-current windings.^[37] Each strand is individually insulated, and the strands are arranged so that at certain points in the winding, or throughout the whole winding, each portion occupies different relative positions in the complete conductor. The transposition equalizes the current flowing in each strand of the conductor, and reduces eddy current losses in the winding itself. The stranded conductor is also more flexible than a solid conductor of similar size, aiding manufacture.^[37]

The windings of signal transformers minimize leakage inductance and stray capacitance to improve high-frequency response. Coils are split into sections, and those sections interleaved between the sections of the other winding.

Power-frequency transformers may have taps at intermediate points on the winding, usually on the higher voltage winding side, for voltage adjustment. Taps may be manually reconnected, or a manual or automatic switch may be provided for changing taps. Automatic on-load tap changers are used in electric power transmission or distribution, on equipment such as arc furnace transformers, or for automatic voltage regulators for sensitive loads. Audio-frequency transformers, used for the distribution of audio to public address loudspeakers, have taps to allow adjustment of impedance to each speaker. A center-tapped transformer is often used in the output stage of an audio power amplifier in a push-pull circuit. Modulation transformers in AM transmitters are very similar.

Cooling

Cutaway view of liquid-immersed transformer. The conservator (reservoir) at top provides liquid-to-atmosphere isolation as coolant level and temperature changes. The walls and fins provide required heat dissipation.

It is a rule of thumb that the life expectancy of electrical insulation is halved for about every 7 °C to 10 °C increase in operating temperature (an instance of the application of the Arrhenius equation).^[39]

Small dry-type and liquid-immersed transformers are often self-cooled by natural convection and radiation heat dissipation. As power ratings increase, transformers are often cooled by forced-air cooling, forced-oil cooling, water-cooling, or combinations of these.^[40] Large transformers are filled with transformer oil that both cools and insulates the windings.^[41] Transformer oil is often a highly refined mineral oil that cools the windings and insulation by circulating within the transformer tank. The mineral oil and paper insulation system has been extensively studied and used for more than 100 years. It is estimated that 50% of power transformers will survive 50 years of use, that the average age of failure of power transformers is about 10 to 15 years, and that about 30% of power transformer failures are due to insulation and overloading failures.^[42]^[43] Prolonged operation at elevated temperature degrades insulating properties of winding insulation and dielectric coolant, which not only shortens transformer life but can ultimately lead to catastrophic transformer failure.^[39] With a great body of empirical study as a guide, transformer oil testing including dissolved gas analysis provides valuable maintenance information.

Building regulations in many jurisdictions require indoor liquid-filled transformers to either use dielectric fluids that are less flammable than oil, or be installed in fire-resistant rooms.^[17] Air-cooled dry transformers can be more economical where they eliminate the cost of a fire-resistant transformer room.

The tank of liquid-filled transformers often has radiators through which the liquid coolant circulates by natural convection or fins. Some large transformers employ electric fans for forced-air cooling, pumps for forced-liquid cooling, or have heat exchangers for water-cooling.^[41] An oil-immersed transformer may be equipped with a Buchholz relay, which, depending on severity of gas accumulation due to internal arcing, is used to either alarm or de-energize the transformer.^[31] Oil-immersed transformer installations usually include fire protection measures such as walls, oil containment, and fire-suppression sprinkler systems.

Polychlorinated biphenyls (PCBs) have properties that once favored their use as a dielectric coolant, though concerns over their environmental persistence led to a widespread ban on their use.^[44] Today, non-toxic, stable silicone-based oils, or fluorinated hydrocarbons may be used where the expense of a fire-resistant liquid offsets additional building cost for a transformer vault.^[17]^[45] However, the long life span of transformers can mean that the potential for exposure can be high long after banning.^[46]

Some transformers are gas-insulated. Their windings are enclosed in sealed, pressurized tanks and often cooled by nitrogen or sulfur hexafluoride gas.^[45]

Experimental power transformers in the 500‐to‐1,000 kVA range have been built with liquid nitrogen or helium cooled superconducting windings, which eliminates winding losses without affecting core losses.^[47]^[48]

Insulation

Substation transformer undergoing testing.

Insulation must be provided between the individual turns of the windings, between the windings, between windings and core, and at the terminals of the winding.

Inter-turn insulation of small transformers may be a layer of insulating varnish on the wire. Layer of paper or polymer films may be inserted between layers of windings, and between primary and secondary windings. A transformer may be coated or dipped in a polymer resin to improve the strength of windings and protect them from moisture or corrosion. The resin may be impregnated into the winding insulation using combinations of vacuum and pressure during the coating process, eliminating all air voids in the winding. In the limit, the entire coil may be placed in a mold, and resin cast around it as a solid block, encapsulating the windings.^[49]

Large oil-filled power transformers use windings wrapped with insulating paper, which is impregnated with oil during assembly of the transformer. Oil-filled transformers use highly refined mineral oil to insulate and cool the windings and core. Construction of oil-filled transformers requires that the insulation covering the windings be thoroughly dried of residual moisture before the oil is introduced. Drying may be done by circulating hot air around the core, by circulating externally heated transformer oil, or by vapor-phase drying (VPD) where an evaporated solvent transfers heat by condensation on the coil and core. For small transformers, resistance heating by injection of current into the windings is used.

Bushings

Larger transformers are provided with high-voltage insulated bushings made of polymers or porcelain. A large bushing can be a complex structure since it must provide careful control of the electric field gradient without letting the transformer leak oil.^[50]

Classification parameters

An electrical substation in Melbourne, Australia showing three of five 220 kV – 66 kV transformers, each with a capacity of 150 MVA

Camouflaged transformer in Langley City

Transformers can be classified in many ways, such as the following:

Power rating: From a fraction of a volt-ampere (VA) to over a thousand MVA.
Duty of a transformer: Continuous, short-time, intermittent, periodic, varying.
Frequency range: Power-frequency, audio-frequency, or radio-frequency.
Voltage class: From a few volts to hundreds of kilovolts.
Cooling type: Dry or liquid-immersed; self-cooled, forced air-cooled;forced oil-cooled, water-cooled.
Application: power supply, impedance matching, output voltage and current stabilizer, pulse, circuit isolation, power distribution, rectifier, arc furnace, amplifier output, etc..
Basic magnetic form: Core form, shell form, concentric, sandwich.
Constant-potential transformer descriptor: Step-up, step-down, isolation.
General winding configuration: By IEC vector group, two-winding combinations of the phase designations delta, wye or star, and zigzag; autotransformer, Scott-T
Rectifier phase-shift winding configuration: 2-winding, 6-pulse; 3-winding, 12-pulse; . . ., n-winding, [n − 1]·6-pulse; polygon; etc..

Applications

Transformer at the Limestone Generating Station in Manitoba, Canada

Various specific electrical application designs require a variety of transformer types. Although they all share the basic characteristic transformer principles, they are customized in construction or electrical properties for certain installation requirements or circuit conditions.

In electric power transmission, transformers allow transmission of electric power at high voltages, which reduces the loss due to heating of the wires. This allows generating plants to be located economically at a distance from electrical consumers.^[51] All but a tiny fraction of the world's electrical power has passed through a series of transformers by the time it reaches the consumer.^[21]

In many electronic devices, a transformer is used to convert voltage from the distribution wiring to convenient values for the circuit requirements, either directly at the power line frequency or through a switch mode power supply.

Signal and audio transformers are used to couple stages of amplifiers and to match devices such as microphones and record players to the input of amplifiers. Audio transformers allowed telephone circuits to carry on a two-way conversation over a single pair of wires. A balun transformer converts a signal that is referenced to ground to a signal that has balanced voltages to ground, such as between external cables and internal circuits. Isolation transformers prevent leakage of current into the secondary circuit and are used in medical equipment and at construction sites. Resonant transformers are used for coupling between stages of radio receivers, or in high-voltage Tesla coils.

Schematic of a large oil-filled power transformer 1. Tank 2. Lid 3. Conservator tank 4. Oil level indicator 5. Buchholz relay for detecting gas bubbles after an internal fault 6. Piping 7. Tap changer 8. Drive motor for tap changer 9. Drive shaft for tap changer 10. High voltage (HV) bushing 11. High voltage bushing current transformers 12. Low voltage (LV) bushing 13. Low voltage current transformers 14. Bushing voltage-transformer for metering 15. Core 16. Yoke of the core 17. Limbs connect the yokes and hold them up 18. Coils 19. Internal wiring between coils and tapchanger 20. Oil release valve 21. Vacuum valve

History

Discovery of induction

Faraday's experiment with induction between coils of wire^[52]

Electromagnetic induction, the principle of the operation of the transformer, was discovered independently by Michael Faraday in 1831 and Joseph Henry in 1832.^[53]^[54]^[55]^[56] Only Faraday furthered his experiments to the point of working out the equation describing the relationship between EMF and magnetic flux now known as Faraday's law of induction:

| E | = | \frac{d Φ_{B}}{d t} |,

where $| E |$ is the magnitude of the EMF in volts and Φ_B is the magnetic flux through the circuit in webers.^[57]

Faraday performed early experiments on induction between coils of wire, including winding a pair of coils around an iron ring, thus creating the first toroidal closed-core transformer.^[56]^[58] However he only applied individual pulses of current to his transformer, and never discovered the relation between the turns ratio and EMF in the windings.

Induction coil, 1900, Bremerhaven, Germany

Induction coils

Faraday's ring transformer

The first type of transformer to see wide use was the induction coil, invented by Rev. Nicholas Callan of Maynooth College, Ireland in 1836.^[56] He was one of the first researchers to realize the more turns the secondary winding has in relation to the primary winding, the larger the induced secondary EMF will be. Induction coils evolved from scientists' and inventors' efforts to get higher voltages from batteries. Since batteries produce direct current (DC) rather than AC, induction coils relied upon vibrating electrical contacts that regularly interrupted the current in the primary to create the flux changes necessary for induction. Between the 1830s and the 1870s, efforts to build better induction coils, mostly by trial and error, slowly revealed the basic principles of transformers.

First alternating current transformers

By the 1870s, efficient generators producing alternating current (AC) were available, and it was found AC could power an induction coil directly, without an interrupter.

In 1876, Russian engineer Pavel Yablochkov invented a lighting system based on a set of induction coils where the primary windings were connected to a source of AC. The secondary windings could be connected to several 'electric candles' (arc lamps) of his own design. The coils Yablochkov employed functioned essentially as transformers.^[59]

In 1878, the Ganz factory, Budapest, Hungary, began producing equipment for electric lighting and, by 1883, had installed over fifty systems in Austria-Hungary. Their AC systems used arc and incandescent lamps, generators, and other equipment.^[56]^[60]

Lucien Gaulard and John Dixon Gibbs first exhibited a device with an open iron core called a 'secondary generator' in London in 1882, then sold the idea to the Westinghouse company in the United States.^[28] They also exhibited the invention in Turin, Italy in 1884, where it was adopted for an electric lighting system.^[61]

Early series circuit transformer distribution

Induction coils with open magnetic circuits are inefficient at transferring power to loads. Until about 1880, the paradigm for AC power transmission from a high voltage supply to a low voltage load was a series circuit. Open-core transformers with a ratio near 1:1 were connected with their primaries in series to allow use of a high voltage for transmission while presenting a low voltage to the lamps. The inherent flaw in this method was that turning off a single lamp (or other electric device) affected the voltage supplied to all others on the same circuit. Many adjustable transformer designs were introduced to compensate for this problematic characteristic of the series circuit, including those employing methods of adjusting the core or bypassing the magnetic flux around part of a coil.^[61] Efficient, practical transformer designs did not appear until the 1880s, but within a decade, the transformer would be instrumental in the war of the currents, and in seeing AC distribution systems triumph over their DC counterparts, a position in which they have remained dominant ever since.^[62]

Shell form transformer. Sketch used by Uppenborn to describe ZBD engineers' 1885 patents and earliest articles.^[61]

Core form, front; shell form, back. Earliest specimens of ZBD-designed high-efficiency constant-potential transformers manufactured at the Ganz factory in 1885.

The ZBD team consisted of Károly Zipernowsky, Ottó Bláthy and Miksa Déri

Stanley's 1886 design for adjustable gap open-core induction coils

Closed-core transformers and parallel power distribution

In the autumn of 1884, Károly Zipernowsky, Ottó Bláthy and Miksa Déri (ZBD), three Hungarian engineers associated with the Ganz Works, had determined that open-core devices were impracticable, as they were incapable of reliably regulating voltage.^[60] In their joint 1885 patent applications for novel transformers (later called ZBD transformers), they described two designs with closed magnetic circuits where copper windings were either wound around an iron wire ring core or surrounded by an iron wire core.^[61] The two designs were the first application of the two basic transformer constructions in common use to this day, termed "core form" or "shell form" .^[63] The Ganz factory had also in the autumn of 1884 made delivery of the world's first five high-efficiency AC transformers, the first of these units having been shipped on September 16, 1884.^[64] This first unit had been manufactured to the following specifications: 1,400 W, 40 Hz, 120:72 V, 11.6:19.4 A, ratio 1.67:1, one-phase, shell form.^[64]

In both designs, the magnetic flux linking the primary and secondary windings traveled almost entirely within the confines of the iron core, with no intentional path through air (see Toroidal cores below). The new transformers were 3.4 times more efficient than the open-core bipolar devices of Gaulard and Gibbs.^[65] The ZBD patents included two other major interrelated innovations: one concerning the use of parallel connected, instead of series connected, utilization loads, the other concerning the ability to have high turns ratio transformers such that the supply network voltage could be much higher (initially 1,400 to 2,000 V) than the voltage of utilization loads (100 V initially preferred).^[66]^[67] When employed in parallel connected electric distribution systems, closed-core transformers finally made it technically and economically feasible to provide electric power for lighting in homes, businesses and public spaces. Bláthy had suggested the use of closed cores, Zipernowsky had suggested the use of parallel shunt connections, and Déri had performed the experiments;^[68] In early 1885, the three engineers also eliminated the problem of eddy current losses with the invention of the lamination of electromagnetic cores.^[69]

Transformers today are designed on the principles discovered by the three engineers. They also popularized the word 'transformer' to describe a device for altering the EMF of an electric current^[70] although the term had already been in use by 1882.^[71]^[72] In 1886, the ZBD engineers designed, and the Ganz factory supplied electrical equipment for, the world's first power station that used AC generators to power a parallel connected common electrical network, the steam-powered Rome-Cerchi power plant.^[73]

Westinghouse improvements

"E" shaped plates for transformer cores developed by Westinghouse

Although George Westinghouse had bought Gaulard and Gibbs' patents in 1885, the Edison Electric Light Company held an option on the US rights for the ZBD transformers, requiring Westinghouse to pursue alternative designs on the same principles. He assigned to William Stanley the task of developing a device for commercial use in United States.^[74] Stanley's first patented design was for induction coils with single cores of soft iron and adjustable gaps to regulate the EMF present in the secondary winding (see image). This design^[75] was first used commercially in the US in 1886^[76] but Westinghouse was intent on improving the Stanley design to make it (unlike the ZBD type) easy and cheap to produce.^[75]

Westinghouse, Stanley and associates soon developed a core that was easier to manufacture, consisting of a stack of thin 'E‑shaped' iron plates insulated by thin sheets of paper or other insulating material. Pre-wound copper coils could then be slid into place, and straight iron plates laid in to create a closed magnetic circuit. Westinghouse obtained a patent for the new low-cost design in 1887.^[68]

Other early transformer designs

In 1889, Russian-born engineer Mikhail Dolivo-Dobrovolsky developed the first three-phase transformer at the Allgemeine Elektricitäts-Gesellschaft ('General Electricity Company') in Germany.^[77]

In 1891, Nikola Tesla invented the Tesla coil, an air-cored, dual-tuned resonant transformer for producing very high voltages at high frequency.^[78]

Audio frequency transformers ("repeating coils") were used by early experimenters in the development of the telephone.^[79]

Notes

With turns of the winding oriented perpendicularly to the magnetic field lines, the flux is the product of the magnetic flux density and the core area, the magnetic field varying with time according to the excitation of the primary. The expression

d Φ / d t

, defined as the derivative of magnetic flux

Φ

with time

t

, provides a measure of rate of magnetic flux in the core and hence of EMF induced in the respective winding. The negative sign in eq. 1 & eq. 2 is consistent with Lenz's law and Faraday's law in that by convention EMF "induced by an increase of magnetic flux linkages is opposite to the direction that would be given by the right-hand rule."

Although ideal transformer's winding inductances are each infinitely high, the square root of winding inductances' ratio is equal to the turns ratio.

This also implies the following: The net core flux is zero, the input impedance is infinite when secondary is open and zero when secondary is shorted; there is zero phase-shift through an ideal transformer; input and output power and reactive volt-ampere are each conserved; these three statements apply for any frequency above zero and periodic waveforms are conserved.^[5]

Direction of transformer currents is according to the Right-Hand Rule.

Percent impedance is the ratio of the voltage drop in the secondary from no load to full load.^[13]

References

Bedell, Frederick (1942). "History of A-C Wave Form, Its Determination and Standardization". Transactions of the American Institute of Electrical Engineers. 61 (12): 864. doi:10.1109/T-AIEE.1942.5058456. S2CID 51658522.

Skilling, Hugh Hildreth (1962). Electromechanics. John Wiley & Sons, Inc. p. 39

Brenner & Javid 1959, §18-6 The Ideal Transformer, pp. 598–600

Brenner & Javid 1959, §18-1 Symbols and Polarity of Mutual Inductance, pp.=589–590

Crosby 1958, p. 145

Paul A. Tipler, Physics, Worth Publishers, Inc., 1976 ISBN 0-87901-041-X, pp. 937-940

Flanagan, William M. (1993). Handbook of Transformer Design & Applications (2nd ed.). McGraw-Hill. ISBN 978-0-07-021291-6. pp. 2-1, 2-2

Say, M. G. (1983). Alternating Current Machines (5th ed.). London: Pitman. ISBN 978-0-273-01969-5.

L. Dalessandro, F. d. S. Cavalcante, and J. W. Kolar, "Self-Capacitance of High-Voltage Transformers," IEEE Transactions on Power Electronics, vol. 22, no. 5, pp. 2081–2092, 2007.

McLaren 1984, pp. 68–74

Calvert, James (2001). "Inside Transformers". University of Denver. Archived from the original on May 9, 2007. Retrieved May 19, 2007.

Terman, Frederick E. (1955). Electronic and Radio Engineering (4th ed.). New York: McGraw-Hill. pp. 15.

Heathcote 1998, p. 4

Knowlton, A.E., ed. (1949). Standard Handbook for Electrical Engineers (8th ed.). McGraw-Hill. p. see esp. Section 6 Transformers, etc, pp. 547–644. Nomenclature for Parallel Operation, pp. 585–586

Daniels 1985, pp. 47–49

"400 Hz Electrical Systems". Aerospaceweb.org. Retrieved May 21, 2007.

De Keulenaer et al. 2001

Kubo, T.; Sachs, H.; Nadel, S. (2001). Opportunities for New Appliance and Equipment Efficiency Standards. American Council for an Energy-Efficient Economy. p. 39, fig. 1. Retrieved June 21, 2009.

Heathcote 1998, pp. 41–42

"Understanding Transformer Noise" (PDF). FP. Archived from the original (PDF) on 10 May 2006. Retrieved 30 January 2013.

Nailen, Richard (May 2005). "Why We Must Be Concerned With Transformers". Electrical Apparatus. Archived from the original on 2009-04-29.

Pansini 1999, p. 23

Del Vecchio et al. 2002, pp. 10–11, Fig. 1.8

Hydroelectric Research and Technical Services Group. "Transformers: Basics, Maintenance, and Diagnostics" (PDF). U.S. Dept. of the Interior, Bureau of Reclamation. p. 12. Retrieved Mar 27, 2012.

US Army Corps of Engineers (1994). "EM 1110-2-3006 Engineering and Design – Hydroelectric Power Plants Electrical Design". Chapter 4 Power Transformers. p. 4-1.

Hindmarsh 1977, pp. 29–31

Gottlieb 1998, p. 4

Allan, D.J. (Jan 1991). "Power Transformers – The Second Century". Power Engineering Journal. 5 (1): 5–14. doi:10.1049/pe:19910004.

Kulkarni & Khaparde 2004, pp. 36–37

McLyman 2004, pp. 3-9 to 3-14

Harlow 2004, §2.1.7 & §2.1.6.2.1 in Section §2.1 Power Transformers by H. Jin Sim and Scott H. Digby in Chapter 2 Equipment Types

Boteler, D. H.; Pirjola, R. J.; Nevanlinna, H. (1998). "The Effects of Geomagnetic Disturbances On Electrical Systems at the Earth's Surface". Advances in Space Research. 22 (1): 17–27. Bibcode:1998AdSpR..22...17B. doi:10.1016/S0273-1177(97)01096-X.

Hasegawa, Ryusuke (June 2, 2000). "Present Status of Amorphous Soft Magnetic Alloys". Journal of Magnetism and Magnetic Materials. 215–216 (1): 240–245. Bibcode:2000JMMM..215..240H. doi:10.1016/S0304-8853(00)00126-8.

McLyman 2004, p. 3-1

"Toroidal Line Power Transformers. Power Ratings Tripled. | Magnetics Magazine". www.magneticsmagazine.com. Archived from the original on 2016-09-24. Retrieved 2016-09-23.

Lee, Reuben. "Air-Core Transformers". Electronic Transformers and Circuits. Retrieved May 22, 2007.

CEGB 1982

Dixon, Lloyd (2001). "Power Transformer Design" (PDF). Magnetics Design Handbook. Texas Instruments.

Harlow 2004, §3.4.8 in Section 3.4 Load and Thermal Performance by Robert F. Tillman in Chapter 3 Ancillary Topics

Pansini 1999, p. 32

H. Lee Willis, Power Distribution Planning Reference Book, 2004 CRC Press. ISBN 978-0-8247-4875-3, pg. 403

Hartley, William H. (2003). Analysis of Transformer Failures. 36th Annual Conference of the International Association of Engineering Insurers. p. 7 (fig. 6). Archived from the original on 20 October 2013. Retrieved 30 January 2013.

Hartley, William H. (~2011). "An Analysis of Transformer Failures, Part 1 – 1988 through 1997". The Locomotive. Archived from the original on 18 June 2018. Retrieved 30 January 2013.

"ASTDR ToxFAQs for Polychlorinated Biphenyls". 2001. Retrieved June 10, 2007.

Kulkarni & Khaparde 2004, pp. 2–3

"What silicone wristbands say about chemical exposure in Uruguayan children". www.buffalo.edu. Retrieved 2022-01-28.

Mehta, S.P.; Aversa, N.; Walker, M.S. (Jul 1997). "Transforming Transformers [Superconducting windings]" (PDF). IEEE Spectrum. 34 (7): 43–49. doi:10.1109/6.609815. Retrieved 14 November 2012.

Pansini 1999, pp. 66–67

Lane, Keith (2007) (June 2007). "The Basics of Large Dry-Type Transformers". EC&M. Retrieved 29 January 2013.

Ryan 2004, pp. 416–417

Heathcote 1998, p. 1

Poyser, Arthur William (1892). Magnetism and Electricity: A Manual for Students in Advanced Classes. London and New York: Longmans, Green, & Co. p. 285, fig. 248.

"A Brief History of Electromagnetism" (PDF).

"Electromagnetism". Smithsonian Institution Archives.

MacPherson, Ph.D., Ryan C. Joseph Henry: The Rise of an American scientist. Archived from the original on 2015-12-08. Retrieved 2015-10-28.

Guarnieri 2013, pp. 56–59

Chow, Tai L. (2006). Introduction to Electromagnetic Theory: A Modern Perspective. Sudbury, Mass.: Jones and Bartlett Publishers. p. 171. ISBN 978-0-7637-3827-3.

Faraday, Michael (1834). "Experimental Researches on Electricity, 7th Series". Philosophical Transactions of the Royal Society. 124: 77–122. doi:10.1098/rstl.1834.0008. S2CID 116224057.

"Stanley Transformer – 1886 - MagLab". Archived from the original on 2017-10-11. Retrieved 2021-07-27.

Hughes 1993, pp. 95–96

Uppenborn, F. J. (1889). History of the Transformer. London: E. & F. N. Spon. pp. 35–41.

Coltman 1988, pp. 86–95

Lucas, J.R. "Historical Development of the Transformer" (PDF). IEE Sri Lanka Centre. Retrieved Mar 1, 2012.

Halacsy & Von Fuchs 1961, pp. 121–125

Jeszenszky, Sándor. "Electrostatics and Electrodynamics at Pest University in the Mid-19th Century" (PDF). University of Pavia. Archived from the original on June 27, 2022. Retrieved Mar 3, 2012.

"Hungarian Inventors and Their Inventions". Institute for Developing Alternative Energy in Latin America. Archived from the original on 2012-03-22. Retrieved Mar 3, 2012.

"Bláthy, Ottó Titusz". Budapest University of Technology and Economics, National Technical Information Centre and Library. Retrieved Feb 29, 2012.

Smil, Vaclav (2005). Creating the Twentieth Century: Technical Innovations of 1867–1914 and Their Lasting Impact. Oxford: Oxford University Press. p. 71. ISBN 978-0-19-803774-3. ZBD transformer.

Electrical Society of Cornell University (1896). Proceedings of the Electrical Society of Cornell University. Andrus & Church. p. 39.

Nagy, Árpád Zoltán (Oct 11, 1996). "Lecture to Mark the 100th Anniversary of the Discovery of the Electron in 1897 (preliminary text)". Budapest. Archived from the original on November 25, 2012. Retrieved July 9, 2009.

Oxford English Dictionary (2nd ed.). Oxford University Press. 1989.

Hospitalier, Édouard (1882). The Modern Applications of Electricity. Translated by Julius Maier. New York: D. Appleton & Co. p. 103.

"Ottó Bláthy, Miksa Déri, Károly Zipernowsky". IEC Techline. Archived from the original on 2010-12-06. Retrieved Apr 16, 2010.

Skrabec, Quentin R. (2007). George Westinghouse: Gentle Genius. Algora Publishing. p. 102. ISBN 978-0-87586-508-9.

Coltman 2002

International Electrotechnical Commission. Otto Blathy, Miksa Déri, Károly Zipernowsky. IEC History. Archived from the original on December 6, 2010. Retrieved May 17, 2007.

Neidhöfer, Gerhard (2008). Michael von Dolivo-Dobrowolsky and Three-Phase: The Beginnings of Modern e Technology and Power Supply (in German). In collaboration with VDE "History of Electrical Engineering" Committee (2nd ed.). Berlin: VDE-Verl. ISBN 978-3-8007-3115-2.

Uth, Robert (Dec 12, 2000). "Tesla Coil". Tesla: Master of Lightning. PBS.org. Retrieved May 20, 2008.

"telephone | History, Definition, Invention, Uses, & Facts | Britannica". www.britannica.com. Retrieved 2022-07-17.

Bibliography

Beeman, Donald, ed. (1955). Industrial Power Systems Handbook. McGraw-Hill.
Calvert, James (2001). "Inside Transformers". University of Denver. Archived from the original on May 9, 2007. Retrieved May 19, 2007.
Coltman, J. W. (Jan 1988). "The Transformer". Scientific American. 258 (1): 86–95. Bibcode:1988SciAm.258a..86C. doi:10.1038/scientificamerican0188-86. OSTI 6851152.
Coltman, J. W. (Jan–Feb 2002). "The Transformer [Historical Overview]". IEEE Industry Applications Magazine. 8 (1): 8–15. doi:10.1109/2943.974352. S2CID 18160717.
Brenner, Egon; Javid, Mansour (1959). "Chapter 18–Circuits with Magnetic Coupling". Analysis of Electric Circuits. McGraw-Hill. pp. 586–622.
CEGB, (Central Electricity Generating Board) (1982). Modern Power Station Practice. Pergamon. ISBN 978-0-08-016436-6.
Crosby, D. (1958). "The Ideal Transformer". IRE Transactions on Circuit Theory. 5 (2): 145. doi:10.1109/TCT.1958.1086447.
Daniels, A. R. (1985). Introduction to Electrical Machines. Macmillan. ISBN 978-0-333-19627-4.
De Keulenaer, Hans; Chapman, David; Fassbinder, Stefan; McDermott, Mike (2001). The Scope for Energy Saving in the EU through the Use of Energy-Efficient Electricity Distribution Transformers (PDF). 16th International Conference and Exhibition on Electricity Distribution (CIRED 2001). Institution of Engineering and Technology. doi:10.1049/cp:20010853. Retrieved 10 July 2014.
Del Vecchio, Robert M.; Poulin, Bertrand; Feghali, Pierre T.M.; Shah, Dilipkumar; Ahuja, Rajendra (2002). Transformer Design Principles: With Applications to Core-Form Power Transformers. Boca Raton: CRC Press. ISBN 978-90-5699-703-8.
Fink, Donald G.; Beatty, H. Wayne, eds. (1978). Standard Handbook for Electrical Engineers (11th ed.). McGraw Hill. ISBN 978-0-07-020974-9.
Gottlieb, Irving (1998). Practical Transformer Handbook: for Electronics, Radio and Communications Engineers. Elsevier. ISBN 978-0-7506-3992-7.
Guarnieri, M. (2013). "Who Invented the Transformer?". IEEE Industrial Electronics Magazine. 7 (4): 56–59. doi:10.1109/MIE.2013.2283834. S2CID 27936000.
Halacsy, A. A.; Von Fuchs, G. H. (April 1961). "Transformer Invented 75 Years Ago". IEEE Transactions of the American Institute of Electrical Engineers. 80 (3): 121–125. doi:10.1109/AIEEPAS.1961.4500994. S2CID 51632693.
Hameyer, Kay (2004). Electrical Machines I: Basics, Design, Function, Operation (PDF). RWTH Aachen University Institute of Electrical Machines. Archived from the original (PDF) on 2013-02-10.
Hammond, John Winthrop (1941). Men and Volts: The Story of General Electric. J. B. Lippincott Company. pp. see esp. 106–107, 178, 238.
Harlow, James (2004). Electric Power Transformer Engineering (PDF). CRC Press. ISBN 0-8493-1704-5.^{[permanent dead link]}
Hughes, Thomas P. (1993). Networks of Power: Electrification in Western Society, 1880-1930. Baltimore: The Johns Hopkins University Press. p. 96. ISBN 978-0-8018-2873-7. Retrieved Sep 9, 2009.
Heathcote, Martin (1998). J & P Transformer Book (12th ed.). Newnes. ISBN 978-0-7506-1158-9.
Hindmarsh, John (1977). Electrical Machines and Their Applications (4th ed.). Exeter: Pergamon. ISBN 978-0-08-030573-8.
Kothari, D.P.; Nagrath, I.J. (2010). Electric Machines (4th ed.). Tata McGraw-Hill. ISBN 978-0-07-069967-0.
Kulkarni, S. V.; Khaparde, S. A. (2004). Transformer Engineering: Design and Practice. CRC Press. ISBN 978-0-8247-5653-6.
McLaren, Peter (1984). Elementary Electric Power and Machines. Ellis Horwood. ISBN 978-0-470-20057-5.
McLyman, Colonel William (2004). "Chapter 3". Transformer and Inductor Design Handbook. CRC. ISBN 0-8247-5393-3.
Pansini, Anthony (1999). Electrical Transformers and Power Equipment. CRC Press. ISBN 978-0-88173-311-2.
Parker, M. R; Ula, S.; Webb, W. E. (2005). "§2.5.5 'Transformers' & §10.1.3 'The Ideal Transformer'". In Whitaker, Jerry C. (ed.). The Electronics Handbook (2nd ed.). Taylor & Francis. pp. 172, 1017. ISBN 0-8493-1889-0.
Ryan, H. M. (2004). High Voltage Engineering and Testing. CRC Press. ISBN 978-0-85296-775-1.

External links

Wikimedia Commons has media related to Transformers.

The Wikibook School Science has a page on the topic of: How to make a transformer

General links:

(Video) Power transformer inrush current (damping)
(Video) Power transformer overexcitation (damping)
Three-phase transformer circuits from All About Circuits

Categories:

https://en.wikipedia.org/wiki/Transformer

By the 1870s, efficient generators producing alternating current (AC) were available, and it was found AC could power an induction coil directly, without an interrupter.

https://en.wikipedia.org/wiki/Transformer

Audio frequency transformers ("repeating coils") were used by early experimenters in the development of the telephone.^[79]

https://en.wikipedia.org/wiki/Transformer

In 1889, Russian-born engineer Mikhail Dolivo-Dobrovolsky developed the first three-phase transformer at the Allgemeine Elektricitäts-Gesellschaft ('General Electricity Company') in Germany.^[77]

In 1891, Nikola Tesla invented the Tesla coil, an air-cored, dual-tuned resonant transformer for producing very high voltages at high frequency.^[78]

https://en.wikipedia.org/wiki/Transformer

Faraday's experiment with induction between coils of wire^[52]

Electromagnetic induction, the principle of the operation of the transformer, was discovered independently by Michael Faraday in 1831 and Joseph Henry in 1832.^[53]

https://en.wikipedia.org/wiki/Transformer

Substation transformer undergoing testing.

https://en.wikipedia.org/wiki/Transformer

In electrical engineering, a load profile is a graph of the variation in the electrical load versus time. A load profile will vary according to customer type (typical examples include residential, commercial and industrial), temperature and holiday seasons. Power producers use this information to plan how much electricity they will need to make available at any given time. Teletraffic engineering uses a similar load curve.

Typical seasonal loads of electric utilities in Eastern New England Division in 1919. United States Geological Survey, 1921. Image courtesy of the National Museum of American History from Powering a Generation of Change

https://en.wikipedia.org/wiki/Load_profile

A rectiformer is a rectifier and transformer designed and built as a single entity for converting alternating current into direct current. It is piece of power systems equipment rather than an electronics component. Rectiformers are used for supplying power to different field of ESP (electrostatic precipitator). Rectiformers are also used to create dc supply for Hall process cells in the aluminium smelting industry.

Rectiformers are commonly found in electrowinning operations, where a direct current is required to convert base metal ions such as copper to a metal at the cathode. The passage of an electric current through a purified copper sulfate solution produces cathode copper. The equation is as follows:

Cu²⁺_aq+ 2e⁻ = Cu^o

Physical Characteristics

Rectiformers may be designed to output voltages from 30V to over 120KV dc and can weigh over 400 tons.^[1]

References

Rectiformer details, Aluminium smelting rectiformer project.

External links

Document describing rectiformer substation installation

This electronics-related article is a stub. You can help Wikipedia by expanding it.

Categories:

https://en.wikipedia.org/wiki/Rectiformer

The Transformation of the Ottoman Empire, also known as the Era of Transformation, constitutes a period in the history of the Ottoman Empire from c. 1550 to c. 1700, spanning roughly from the end of the reign of Suleiman the Magnificent to the Treaty of Karlowitz at the conclusion of the War of the Holy League. This period was characterized by numerous dramatic political, social, and economic changes, which resulted in the empire shifting from an expansionist, patrimonial state into a bureaucratic empire based on an ideology of upholding justice and acting as the protector of Sunni Islam.^[1] These changes were in large part prompted by a series of political and economic crises in the late 16th and early 17th centuries,^[2]^[3] resulting from inflation, warfare, and political factionalism.^[4] Yet despite these crises the empire remained strong both politically and economically,^[5] and continued to adapt to the challenges of a changing world. The 17th century was once characterized as a period of decline for the Ottomans, but since the 1980s historians of the Ottoman Empire have increasingly rejected that characterization, identifying it instead as a period of crisis, adaptation, and transformation.^[6]

^{https://en.wikipedia.org/wiki/Transformation_of_the_Ottoman_Empire}

In 20th-century discussions of Karl Marx's economics, the transformation problem is the problem of finding a general rule by which to transform the "values" of commodities (based on their socially necessary labour content, according to his labour theory of value) into the "competitive prices" of the marketplace. This problem was first introduced by Marx in chapter 9 of the draft of volume 3 of Capital, where he also sketched a solution. The essential difficulty was this: given that Marx derived profit, in the form of surplus value, from direct labour inputs, and that the ratio of direct labour input to capital input varied widely between commodities, how could he reconcile this with a tendency toward an average rate of profit on all capital invested among industries, if such a tendency (as predicted by Marx and Ricardo) exists?

^{https://en.wikipedia.org/wiki/Transformation_problem}

Transformative learning, as a theory, says that the process of "perspective transformation" has three dimensions: psychological (changes in understanding of the self), convictional (revision of belief systems), and behavioral (changes in lifestyle).^[1]

Transformative learning is the expansion of consciousness through the transformation of basic worldview and specific capacities of the self; transformative learning is facilitated through consciously directed processes such as appreciatively accessing and receiving the symbolic contents of the unconscious and critically analyzing underlying premises.^[2]

Perspective transformation, leading to transformative learning, occurs infrequently. Jack Mezirow believes that it usually results from a "disorienting dilemma" which is triggered by a life crisis or major life transition—although it may also result from an accumulation of transformations in meaning schemes over a period of time.^[3] Less dramatic predicaments, such as those created by a teacher for pedagogical effect, also promote transformation.^[4]

An important part of transformative learning is for individuals to change their frames of reference by critically reflecting on their assumptions and beliefs and consciously making and implementing plans that bring about new ways of defining their worlds. This process is fundamentally rational and analytical.^[5]^[6]

https://en.wikipedia.org/wiki/Transformative_learning

For Boyd, transformation is a "fundamental change in one's personality involving [together] the resolution of a personal dilemma and the expansion of consciousness resulting in greater personality integration".^[19] This calls upon extra-rational sources such as symbols, images, and archetypes to assist in creating a personal vision or meaning of what it means to be human.^[20]

https://en.wikipedia.org/wiki/Transformative_learning

On the surface, the two views of transformative learning presented here are contradictory. One advocates a rational approach that depends primarily on critical reflection whereas the other relies more on intuition and emotion.

https://en.wikipedia.org/wiki/Transformative_learning

In this image, a gene from one bacterial cell is moved to another bacterial cell. This process of the second bacterial cell taking up new genetic material is called transformation.

In molecular biology and genetics, transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membrane(s). For transformation to take place, the recipient bacterium must be in a state of competence, which might occur in nature as a time-limited response to environmental conditions such as starvation and cell density, and may also be induced in a laboratory.^[1]

Transformation is one of three processes that lead to horizontal gene transfer, in which exogenous genetic material passes from one bacterium to another, the other two being conjugation (transfer of genetic material between two bacterial cells in direct contact) and transduction (injection of foreign DNA by a bacteriophage virus into the host bacterium).^[1] In transformation, the genetic material passes through the intervening medium, and uptake is completely dependent on the recipient bacterium.^[1]

As of 2014 about 80 species of bacteria were known to be capable of transformation, about evenly divided between Gram-positive and Gram-negative bacteria; the number might be an overestimate since several of the reports are supported by single papers.^[1]

"Transformation" may also be used to describe the insertion of new genetic material into nonbacterial cells, including animal and plant cells; however, because "transformation" has a special meaning in relation to animal cells, indicating progression to a cancerous state, the process is usually called "transfection".^[2]

History

Transformation in bacteria was first demonstrated in 1928 by the British bacteriologist Frederick Griffith.^[3] Griffith was interested in determining whether injections of heat-killed bacteria could be used to vaccinate mice against pneumonia. However, he discovered that a non-virulent strain of Streptococcus pneumoniae could be made virulent after being exposed to heat-killed virulent strains. Griffith hypothesized that some "transforming principle" from the heat-killed strain was responsible for making the harmless strain virulent. In 1944 this "transforming principle" was identified as being genetic by Oswald Avery, Colin MacLeod, and Maclyn McCarty. They isolated DNA from a virulent strain of S. pneumoniae and using just this DNA were able to make a harmless strain virulent. They called this uptake and incorporation of DNA by bacteria "transformation" (See Avery-MacLeod-McCarty experiment)^[4] The results of Avery et al.'s experiments were at first skeptically received by the scientific community and it was not until the development of genetic markers and the discovery of other methods of genetic transfer (conjugation in 1947 and transduction in 1953) by Joshua Lederberg that Avery's experiments were accepted.^[5]

It was originally thought that Escherichia coli, a commonly used laboratory organism, was refractory to transformation. However, in 1970, Morton Mandel and Akiko Higa showed that E. coli may be induced to take up DNA from bacteriophage λ without the use of helper phage after treatment with calcium chloride solution.^[6] Two years later in 1972, Stanley Norman Cohen, Annie Chang and Leslie Hsu showed that CaCl
₂ treatment is also effective for transformation of plasmid DNA.^[7] The method of transformation by Mandel and Higa was later improved upon by Douglas Hanahan.^[8] The discovery of artificially induced competence in E. coli created an efficient and convenient procedure for transforming bacteria which allows for simpler molecular cloning methods in biotechnology and research, and it is now a routinely used laboratory procedure.

Transformation using electroporation was developed in the late 1980s, increasing the efficiency of in-vitro transformation and increasing the number of bacterial strains that could be transformed.^[9] Transformation of animal and plant cells was also investigated with the first transgenic mouse being created by injecting a gene for a rat growth hormone into a mouse embryo in 1982.^[10] In 1897 a bacterium that caused plant tumors, Agrobacterium tumefaciens, was discovered and in the early 1970s the tumor-inducing agent was found to be a DNA plasmid called the Ti plasmid.^[11] By removing the genes in the plasmid that caused the tumor and adding in novel genes, researchers were able to infect plants with A. tumefaciens and let the bacteria insert their chosen DNA into the genomes of the plants.^[12] Not all plant cells are susceptible to infection by A. tumefaciens, so other methods were developed, including electroporation and micro-injection.^[13] Particle bombardment was made possible with the invention of the Biolistic Particle Delivery System (gene gun) by John Sanford in the 1980s.^[14]^[15]^[16]

Definitions

Transformation is one of three forms of horizontal gene transfer that occur in nature among bacteria, in which DNA encoding for a trait passes from one bacterium to another and is integrated into the recipient genome by homologous recombination; the other two are transduction, carried out by means of a bacteriophage, and conjugation, in which a gene is passed through direct contact between bacteria.^[1] In transformation, the genetic material passes through the intervening medium, and uptake is completely dependent on the recipient bacterium.^[1]

Competence refers to a temporary state of being able to take up exogenous DNA from the environment; it may be induced in a laboratory.^[1]

It appears to be an ancient process inherited from a common prokaryotic ancestor that is a beneficial adaptation for promoting recombinational repair of DNA damage, especially damage acquired under stressful conditions. Natural genetic transformation appears to be an adaptation for repair of DNA damage that also generates genetic diversity.^[1]^[17]

Transformation has been studied in medically important Gram-negative bacteria species such as Helicobacter pylori, Legionella pneumophila, Neisseria meningitidis, Neisseria gonorrhoeae, Haemophilus influenzae and Vibrio cholerae.^[18] It has also been studied in Gram-negative species found in soil such as Pseudomonas stutzeri, Acinetobacter baylyi, and Gram-negative plant pathogens such as Ralstonia solanacearum and Xylella fastidiosa.^[18] Transformation among Gram-positive bacteria has been studied in medically important species such as Streptococcus pneumoniae, Streptococcus mutans, Staphylococcus aureus and Streptococcus sanguinis and in Gram-positive soil bacterium Bacillus subtilis.^[17] It has also been reported in at least 30 species of Pseudomonadota distributed in several different classes.^[19] The best studied Pseudomonadota with respect to transformation are the medically important human pathogens Neisseria gonorrhoeae, Haemophilus influenzae, and Helicobacter pylori.^[17]

Natural competence and transformation

Naturally competent bacteria carry sets of genes that provide the protein machinery to bring DNA across the cell membrane(s). The transport of the exogenous DNA into the cells may require proteins that are involved in the assembly of type IV pili and type II secretion system, as well as DNA translocase complex at the cytoplasmic membrane.^[20]

Due to the differences in structure of the cell envelope between Gram-positive and Gram-negative bacteria, there are some differences in the mechanisms of DNA uptake in these cells, however most of them share common features that involve related proteins. The DNA first binds to the surface of the competent cells on a DNA receptor, and passes through the cytoplasmic membrane via DNA translocase.^[21] Only single-stranded DNA may pass through, the other strand being degraded by nucleases in the process. The translocated single-stranded DNA may then be integrated into the bacterial chromosomes by a RecA-dependent process. In Gram-negative cells, due to the presence of an extra membrane, the DNA requires the presence of a channel formed by secretins on the outer membrane. Pilin may be required for competence, but its role is uncertain.^[22] The uptake of DNA is generally non-sequence specific, although in some species the presence of specific DNA uptake sequences may facilitate efficient DNA uptake.^[23]

Natural transformation

Natural transformation is a bacterial adaptation for DNA transfer that depends on the expression of numerous bacterial genes whose products appear to be responsible for this process.^[20]^[19] In general, transformation is a complex, energy-requiring developmental process. In order for a bacterium to bind, take up and recombine exogenous DNA into its chromosome, it must become competent, that is, enter a special physiological state. Competence development in Bacillus subtilis requires expression of about 40 genes.^[24] The DNA integrated into the host chromosome is usually (but with rare exceptions) derived from another bacterium of the same species, and is thus homologous to the resident chromosome.

In B. subtilis the length of the transferred DNA is greater than 1271 kb (more than 1 million bases).^[25] The length transferred is likely double stranded DNA and is often more than a third of the total chromosome length of 4215 kb.^[26] It appears that about 7-9% of the recipient cells take up an entire chromosome.^[27]

The capacity for natural transformation appears to occur in a number of prokaryotes, and thus far 67 prokaryotic species (in seven different phyla) are known to undergo this process.^[19]

Competence for transformation is typically induced by high cell density and/or nutritional limitation, conditions associated with the stationary phase of bacterial growth. Transformation in Haemophilus influenzae occurs most efficiently at the end of exponential growth as bacterial growth approaches stationary phase.^[28] Transformation in Streptococcus mutans, as well as in many other streptococci, occurs at high cell density and is associated with biofilm formation.^[29] Competence in B. subtilis is induced toward the end of logarithmic growth, especially under conditions of amino acid limitation.^[30] Similarly, in Micrococcus luteus (a representative of the less well studied Actinomycetota phylum), competence develops during the mid-late exponential growth phase and is also triggered by amino acids starvation.^[31]^[32]

By releasing intact host and plasmid DNA, certain bacteriophages are thought to contribute to transformation.^[33]

Transformation, as an adaptation for DNA repair

Competence is specifically induced by DNA damaging conditions. For instance, transformation is induced in Streptococcus pneumoniae by the DNA damaging agents mitomycin C (a DNA cross-linking agent) and fluoroquinolone (a topoisomerase inhibitor that causes double-strand breaks).^[34] In B. subtilis, transformation is increased by UV light, a DNA damaging agent.^[35] In Helicobacter pylori, ciprofloxacin, which interacts with DNA gyrase and introduces double-strand breaks, induces expression of competence genes, thus enhancing the frequency of transformation^[36] Using Legionella pneumophila, Charpentier et al.^[37] tested 64 toxic molecules to determine which of these induce competence. Of these, only six, all DNA damaging agents, caused strong induction. These DNA damaging agents were mitomycin C (which causes DNA inter-strand crosslinks), norfloxacin, ofloxacin and nalidixic acid (inhibitors of DNA gyrase that cause double-strand breaks^[38]), bicyclomycin (causes single- and double-strand breaks^[39]), and hydroxyurea (induces DNA base oxidation^[40]). UV light also induced competence in L. pneumophila. Charpentier et al.^[37] suggested that competence for transformation probably evolved as a DNA damage response.

Logarithmically growing bacteria differ from stationary phase bacteria with respect to the number of genome copies present in the cell, and this has implications for the capability to carry out an important DNA repair process. During logarithmic growth, two or more copies of any particular region of the chromosome may be present in a bacterial cell, as cell division is not precisely matched with chromosome replication. The process of homologous recombinational repair (HRR) is a key DNA repair process that is especially effective for repairing double-strand damages, such as double-strand breaks. This process depends on a second homologous chromosome in addition to the damaged chromosome. During logarithmic growth, a DNA damage in one chromosome may be repaired by HRR using sequence information from the other homologous chromosome. Once cells approach stationary phase, however, they typically have just one copy of the chromosome, and HRR requires input of homologous template from outside the cell by transformation.^[41]

To test whether the adaptive function of transformation is repair of DNA damages, a series of experiments were carried out using B. subtilis irradiated by UV light as the damaging agent (reviewed by Michod et al.^[42] and Bernstein et al.^[41]) The results of these experiments indicated that transforming DNA acts to repair potentially lethal DNA damages introduced by UV light in the recipient DNA. The particular process responsible for repair was likely HRR. Transformation in bacteria can be viewed as a primitive sexual process, since it involves interaction of homologous DNA from two individuals to form recombinant DNA that is passed on to succeeding generations. Bacterial transformation in prokaryotes may have been the ancestral process that gave rise to meiotic sexual reproduction in eukaryotes (see Evolution of sexual reproduction; Meiosis.)

Methods and mechanisms of transformation in laboratory

Schematic of bacterial transformation – for which artificial competence must first be induced.

Bacterial

Artificial competence can be induced in laboratory procedures that involve making the cell passively permeable to DNA by exposing it to conditions that do not normally occur in nature.^[43] Typically the cells are incubated in a solution containing divalent cations (often calcium chloride) under cold conditions, before being exposed to a heat pulse (heat shock). Calcium chloride partially disrupts the cell membrane, which allows the recombinant DNA to enter the host cell. Cells that are able to take up the DNA are called competent cells.

It has been found that growth of Gram-negative bacteria in 20 mM Mg reduces the number of protein-to-lipopolysaccharide bonds by increasing the ratio of ionic to covalent bonds, which increases membrane fluidity, facilitating transformation.^[44] The role of lipopolysaccharides here are verified from the observation that shorter O-side chains are more effectively transformed – perhaps because of improved DNA accessibility.

The surface of bacteria such as E. coli is negatively charged due to phospholipids and lipopolysaccharides on its cell surface, and the DNA is also negatively charged. One function of the divalent cation therefore would be to shield the charges by coordinating the phosphate groups and other negative charges, thereby allowing a DNA molecule to adhere to the cell surface.

DNA entry into E. coli cells is through channels known as zones of adhesion or Bayer's junction, with a typical cell carrying as many as 400 such zones. Their role was established when cobalamine (which also uses these channels) was found to competitively inhibit DNA uptake. Another type of channel implicated in DNA uptake consists of poly (HB):poly P:Ca. In this poly (HB) is envisioned to wrap around DNA (itself a polyphosphate), and is carried in a shield formed by Ca ions.^[44]

It is suggested that exposing the cells to divalent cations in cold condition may also change or weaken the cell surface structure, making it more permeable to DNA. The heat-pulse is thought to create a thermal imbalance across the cell membrane, which forces the DNA to enter the cells through either cell pores or the damaged cell wall.

Electroporation is another method of promoting competence. In this method the cells are briefly shocked with an electric field of 10-20 kV/cm, which is thought to create holes in the cell membrane through which the plasmid DNA may enter. After the electric shock, the holes are rapidly closed by the cell's membrane-repair mechanisms.

Yeast

Most species of yeast, including Saccharomyces cerevisiae, may be transformed by exogenous DNA in the environment. Several methods have been developed to facilitate this transformation at high frequency in the lab.^[45]

Yeast cells may be treated with enzymes to degrade their cell walls, yielding spheroplasts. These cells are very fragile but take up foreign DNA at a high rate.^[46]
Exposing intact yeast cells to alkali cations such as those of caesium or lithium allows the cells to take up plasmid DNA.^[47] Later protocols adapted this transformation method, using lithium acetate, polyethylene glycol, and single-stranded DNA.^[48] In these protocols, the single-stranded DNA preferentially binds to the yeast cell wall, preventing plasmid DNA from doing so and leaving it available for transformation.^[49]
Electroporation: Formation of transient holes in the cell membranes using electric shock; this allows DNA to enter as described above for bacteria.^[50]
Enzymatic digestion^[51] or agitation with glass beads^[52] may also be used to transform yeast cells.

Efficiency – Different yeast genera and species take up foreign DNA with different efficiencies.^[53] Also, most transformation protocols have been developed for baker's yeast, S. cerevisiae, and thus may not be optimal for other species. Even within one species, different strains have different transformation efficiencies, sometimes different by three orders of magnitude. For instance, when S. cerevisiae strains were transformed with 10 ug of plasmid YEp13, the strain DKD-5D-H yielded between 550 and 3115 colonies while strain OS1 yielded fewer than five colonies.^[54]

Plants

A number of methods are available to transfer DNA into plant cells. Some vector-mediated methods are:

Agrobacterium-mediated transformation is the easiest and most simple plant transformation. Plant tissue (often leaves) are cut into small pieces, e.g. 10x10mm, and soaked for ten minutes in a fluid containing suspended Agrobacterium. The bacteria will attach to many of the plant cells exposed by the cut. The plant cells secrete wound-related phenolic compounds which in turn act to upregulate the virulence operon of the Agrobacterium. The virulence operon includes many genes that encode for proteins that are part of a Type IV secretion system that exports from the bacterium proteins and DNA (delineated by specific recognition motifs called border sequences and excised as a single strand from the virulence plasmid) into the plant cell through a structure called a pilus. The transferred DNA (called T-DNA) is piloted to the plant cell nucleus by nuclear localization signals present in the Agrobacterium protein VirD2, which is covalently attached to the end of the T-DNA at the Right border (RB). Exactly how the T-DNA is integrated into the host plant genomic DNA is an active area of plant biology research. Assuming that a selection marker (such as an antibiotic resistance gene) was included in the T-DNA, the transformed plant tissue can be cultured on selective media to produce shoots. The shoots are then transferred to a different medium to promote root formation. Once roots begin to grow from the transgenic shoot, the plants can be transferred to soil to complete a normal life cycle (make seeds). The seeds from this first plant (called the T1, for first transgenic generation) can be planted on a selective (containing an antibiotic), or if an herbicide resistance gene was used, could alternatively be planted in soil, then later treated with herbicide to kill wildtype segregants. Some plants species, such as Arabidopsis thaliana can be transformed by dipping the flowers or whole plant, into a suspension of Agrobacterium tumefaciens, typically strain C58 (C=Cherry, 58=1958, the year in which this particular strain of A. tumefaciens was isolated from a cherry tree in an orchard at Cornell University in Ithaca, New York). Though many plants remain recalcitrant to transformation by this method, research is ongoing that continues to add to the list the species that have been successfully modified in this manner.
Viral transformation (transduction): Package the desired genetic material into a suitable plant virus and allow this modified virus to infect the plant. If the genetic material is DNA, it can recombine with the chromosomes to produce transformant cells. However, genomes of most plant viruses consist of single stranded RNA which replicates in the cytoplasm of infected cell. For such genomes this method is a form of transfection and not a real transformation, since the inserted genes never reach the nucleus of the cell and do not integrate into the host genome. The progeny of the infected plants is virus-free and also free of the inserted gene.

Some vector-less methods include:

Gene gun: Also referred to as particle bombardment, microprojectile bombardment, or biolistics. Particles of gold or tungsten are coated with DNA and then shot into young plant cells or plant embryos. Some genetic material will stay in the cells and transform them. This method also allows transformation of plant plastids. The transformation efficiency is lower than in Agrobacterium-mediated transformation, but most plants can be transformed with this method.
Electroporation: Formation of transient holes in cell membranes using electric pulses of high field strength; this allows DNA to enter as described above for bacteria.^[55]

Fungi

There are some methods to produce transgenic fungi most of them being analogous to those used for plants. However, fungi have to be treated differently due to some of their microscopic and biochemical traits:

A major issue is the dikaryotic state that parts of some fungi are in; dikaryotic cells contain two haploid nuclei, one of each parent fungus. If only one of these gets transformed, which is the rule, the percentage of transformed nuclei decreases after each sporulation.^[56]
Fungal cell walls are quite thick hindering DNA uptake so (partial) removal is often required;^[57] complete degradation, which is sometimes necessary,^[56] yields protoplasts.
Mycelial fungi consist of filamentous hyphae, which are, if at all, separated by internal cell walls interrupted by pores big enough to enable nutrients and organelles, sometimes even nuclei, to travel through each hypha. As a result, individual cells usually cannot be separated. This is problematic as neighbouring transformed cells may render untransformed ones immune to selection treatments, e.g. by delivering nutrients or proteins for antibiotic resistance.^[56]
Additionally, growth (and thereby mitosis) of these fungi exclusively occurs at the tip of their hyphae which can also deliver issues.^[56]

As stated earlier, an array of methods used for plant transformation do also work in fungi:

Agrobacterium is not only capable of infecting plants but also fungi, however, unlike plants, fungi do not secrete the phenolic compounds necessary to trigger Agrobacterium so that they have to be added, e.g. in the form of acetosyringone.^[56]
Thanks to development of an expression system for small RNAs in fungi the introduction of a CRISPR/CAS9-system in fungal cells became possible.^[56] In 2016 the USDA declared that it will not regulate a white button mushroom strain edited with CRISPR/CAS9 to prevent fruit body browning causing a broad discussion about placing CRISPR/CAS9-edited crops on the market.^[58]
Physical methods like electroporation, biolistics ("gene gun"), sonoporation that uses cavitation of gas bubbles produced by ultrasound to penetrate the cell membrane, etc. are also applicable to fungi.^[59]

Animals

Introduction of DNA into animal cells is usually called transfection, and is discussed in the corresponding article.

Practical aspects of transformation in molecular biology

The discovery of artificially induced competence in bacteria allow bacteria such as Escherichia coli to be used as a convenient host for the manipulation of DNA as well as expressing proteins. Typically plasmids are used for transformation in E. coli. In order to be stably maintained in the cell, a plasmid DNA molecule must contain an origin of replication, which allows it to be replicated in the cell independently of the replication of the cell's own chromosome.

The efficiency with which a competent culture can take up exogenous DNA and express its genes is known as transformation efficiency and is measured in colony forming unit (cfu) per μg DNA used. A transformation efficiency of 1×10⁸ cfu/μg for a small plasmid like pUC19 is roughly equivalent to 1 in 2000 molecules of the plasmid used being transformed.

In calcium chloride transformation, the cells are prepared by chilling cells in the presence of Ca²⁺
(in CaCl
₂ solution), making the cell become permeable to plasmid DNA. The cells are incubated on ice with the DNA, and then briefly heat-shocked (e.g., at 42 °C for 30–120 seconds). This method works very well for circular plasmid DNA. Non-commercial preparations should normally give 10⁶ to 10⁷ transformants per microgram of plasmid; a poor preparation will be about 10⁴/μg or less, but a good preparation of competent cells can give up to ~10⁸ colonies per microgram of plasmid.^[60] Protocols, however, exist for making supercompetent cells that may yield a transformation efficiency of over 10⁹.^[61] The chemical method, however, usually does not work well for linear DNA, such as fragments of chromosomal DNA, probably because the cell's native exonuclease enzymes rapidly degrade linear DNA. In contrast, cells that are naturally competent are usually transformed more efficiently with linear DNA than with plasmid DNA.

The transformation efficiency using the CaCl
₂ method decreases with plasmid size, and electroporation therefore may be a more effective method for the uptake of large plasmid DNA.^[62] Cells used in electroporation should be prepared first by washing in cold double-distilled water to remove charged particles that may create sparks during the electroporation process.

Selection and screening in plasmid transformation

Because transformation usually produces a mixture of relatively few transformed cells and an abundance of non-transformed cells, a method is necessary to select for the cells that have acquired the plasmid.^[63] The plasmid therefore requires a selectable marker such that those cells without the plasmid may be killed or have their growth arrested. Antibiotic resistance is the most commonly used marker for prokaryotes. The transforming plasmid contains a gene that confers resistance to an antibiotic that the bacteria are otherwise sensitive to. The mixture of treated cells is cultured on media that contain the antibiotic so that only transformed cells are able to grow. Another method of selection is the use of certain auxotrophic markers that can compensate for an inability to metabolise certain amino acids, nucleotides, or sugars. This method requires the use of suitably mutated strains that are deficient in the synthesis or utility of a particular biomolecule, and the transformed cells are cultured in a medium that allows only cells containing the plasmid to grow.

In a cloning experiment, a gene may be inserted into a plasmid used for transformation. However, in such experiment, not all the plasmids may contain a successfully inserted gene. Additional techniques may therefore be employed further to screen for transformed cells that contain plasmid with the insert. Reporter genes can be used as markers, such as the lacZ gene which codes for β-galactosidase used in blue-white screening. This method of screening relies on the principle of α-complementation, where a fragment of the lacZ gene (lacZα) in the plasmid can complement another mutant lacZ gene (lacZΔM15) in the cell. Both genes by themselves produce non-functional peptides, however, when expressed together, as when a plasmid containing lacZ-α is transformed into a lacZΔM15 cells, they form a functional β-galactosidase. The presence of an active β-galactosidase may be detected when cells are grown in plates containing X-gal, forming characteristic blue colonies. However, the multiple cloning site, where a gene of interest may be ligated into the plasmid vector, is located within the lacZα gene. Successful ligation therefore disrupts the lacZα gene, and no functional β-galactosidase can form, resulting in white colonies. Cells containing successfully ligated insert can then be easily identified by its white coloration from the unsuccessful blue ones.

Other commonly used reporter genes are green fluorescent protein (GFP), which produces cells that glow green under blue light, and the enzyme luciferase, which catalyzes a reaction with luciferin to emit light. The recombinant DNA may also be detected using other methods such as nucleic acid hybridization with radioactive RNA probe, while cells that expressed the desired protein from the plasmid may also be detected using immunological methods.

References

Johnston C, Martin B, Fichant G, Polard P, Claverys JP (March 2014). "Bacterial transformation: distribution, shared mechanisms and divergent control". Nature Reviews. Microbiology. 12 (3): 181–96. doi:10.1038/nrmicro3199. PMID 24509783. S2CID 23559881.

Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002). Molecular Biology of the Cell. New York: Garland Science. p. G:35. ISBN 978-0-8153-4072-0.

Griffith F (1928). "The Significance of Pneumococcal Types". The Journal of Hygiene. 27 (2): 113–59. doi:10.1017/s0022172400031879. PMC 2167760. PMID 20474956.

Case, Christine; Funke, Berdell; Tortora, Gerard. Microbiology An Introduction(tenth edition)

Lederberg, Joshua (1994). "The Transformation of Genetics by DNA: An Anniversary Celebration of AVERY, MACLEOD and MCCARTY(1944) in Anecdotal, Historical and Critical Commentaries on Genetics". Genetics. 136 (2): 423–6. doi:10.1093/genetics/136.2.423. PMC 1205797. PMID 8150273.

Mandel M, Higa A (October 1970). "Calcium-dependent bacteriophage DNA infection". Journal of Molecular Biology. 53 (1): 159–62. doi:10.1016/0022-2836(70)90051-3. PMID 4922220.

Cohen SN, Chang AC, Hsu L (August 1972). "Nonchromosomal antibiotic resistance in bacteria: genetic transformation of Escherichia coli by R-factor DNA". Proceedings of the National Academy of Sciences of the United States of America. 69 (8): 2110–4. Bibcode:1972PNAS...69.2110C. doi:10.1073/pnas.69.8.2110. PMC 426879. PMID 4559594.

Hanahan D (June 1983). "Studies on transformation of Escherichia coli with plasmids". Journal of Molecular Biology. 166 (4): 557–80. CiteSeerX 10.1.1.460.2021. doi:10.1016/S0022-2836(83)80284-8. PMID 6345791.

Wirth R, Friesenegger A, Fiedler S (March 1989). "Transformation of various species of gram-negative bacteria belonging to 11 different genera by electroporation". Molecular & General Genetics. 216 (1): 175–7. doi:10.1007/BF00332248. PMID 2659971. S2CID 25214157.

Palmiter RD, Brinster RL, Hammer RE, Trumbauer ME, Rosenfeld MG, Birnberg NC, Evans RM (December 1982). "Dramatic growth of mice that develop from eggs microinjected with metallothionein-growth hormone fusion genes". Nature. 300 (5893): 611–5. Bibcode:1982Natur.300..611P. doi:10.1038/300611a0. PMC 4881848. PMID 6958982.

Nester, Eugene. "Agrobacterium: The Natural Genetic Engineer (100 Years Later)". APS. The American Phytopathological Society. Retrieved 14 January 2011.

Zambryski P, Joos H, Genetello C, Leemans J, Montagu MV, Schell J (1983). "Ti plasmid vector for the introduction of DNA into plant cells without alteration of their normal regeneration capacity". The EMBO Journal. 2 (12): 2143–50. doi:10.1002/j.1460-2075.1983.tb01715.x. PMC 555426. PMID 16453482.

Peters, Pamela. "Transforming Plants - Basic Genetic Engineering Techniques". Access Excellence. Retrieved 28 January 2010.

"Biologists invent gun for shooting cells with DNA" (PDF). Cornell Chronicle. 14 May 1987. p. 3.

Sanford JC, Klein TM, Wolf ED, Allen N (1987). "Delivery of substances into cells and tissues using a particle bombardment process". Journal of Particulate Science and Technology. 5: 27–37. doi:10.1080/02726358708904533.

Klein RM, Wolf ED, Wu R, Sanford JC (1992). "High-velocity microprojectiles for delivering nucleic acids into living cells. 1987". Biotechnology (Reading, Mass.). 24: 384–6. PMID 1422046.

Michod RE, Bernstein H, Nedelcu AM (May 2008). "Adaptive value of sex in microbial pathogens". Infection, Genetics and Evolution. 8 (3): 267–85. doi:10.1016/j.meegid.2008.01.002. PMID 18295550.

Seitz P, Blokesch M (May 2013). "Cues and regulatory pathways involved in natural competence and transformation in pathogenic and environmental Gram-negative bacteria" (PDF). FEMS Microbiology Reviews. 37 (3): 336–63. doi:10.1111/j.1574-6976.2012.00353.x. PMID 22928673.

Johnsborg O, Eldholm V, Håvarstein LS (December 2007). "Natural genetic transformation: prevalence, mechanisms and function". Research in Microbiology. 158 (10): 767–78. doi:10.1016/j.resmic.2007.09.004. PMID 17997281.

Chen I, Dubnau D (March 2004). "DNA uptake during bacterial transformation". Nature Reviews. Microbiology. 2 (3): 241–9. doi:10.1038/nrmicro844. PMID 15083159. S2CID 205499369.

Lacks S, Greenberg B, Neuberger M (June 1974). "Role of a deoxyribonuclease in the genetic transformation of Diplococcus pneumoniae". Proceedings of the National Academy of Sciences of the United States of America. 71 (6): 2305–9. Bibcode:1974PNAS...71.2305L. doi:10.1073/pnas.71.6.2305. PMC 388441. PMID 4152205.

Long CD, Tobiason DM, Lazio MP, Kline KA, Seifert HS (November 2003). "Low-level pilin expression allows for substantial DNA transformation competence in Neisseria gonorrhoeae". Infection and Immunity. 71 (11): 6279–91. doi:10.1128/iai.71.11.6279-6291.2003. PMC 219589. PMID 14573647.

Sisco KL, Smith HO (February 1979). "Sequence-specific DNA uptake in Haemophilus transformation". Proceedings of the National Academy of Sciences of the United States of America. 76 (2): 972–6. Bibcode:1979PNAS...76..972S. doi:10.1073/pnas.76.2.972. PMC 383110. PMID 311478.

Solomon JM, Grossman AD (April 1996). "Who's competent and when: regulation of natural genetic competence in bacteria". Trends in Genetics. 12 (4): 150–5. doi:10.1016/0168-9525(96)10014-7. PMID 8901420.

Saito Y, Taguchi H, Akamatsu T (March 2006). "Fate of transforming bacterial genome following incorporation into competent cells of Bacillus subtilis: a continuous length of incorporated DNA". Journal of Bioscience and Bioengineering. 101 (3): 257–62. doi:10.1263/jbb.101.257. PMID 16716928.

Saito Y, Taguchi H, Akamatsu T (April 2006). "DNA taken into Bacillus subtilis competent cells by lysed-protoplast transformation is not ssDNA but dsDNA". Journal of Bioscience and Bioengineering. 101 (4): 334–9. doi:10.1263/jbb.101.334. PMID 16716942.

Akamatsu T, Taguchi H (April 2001). "Incorporation of the whole chromosomal DNA in protoplast lysates into competent cells of Bacillus subtilis". Bioscience, Biotechnology, and Biochemistry. 65 (4): 823–9. doi:10.1271/bbb.65.823. PMID 11388459. S2CID 30118947.

Goodgal SH, Herriott RM (July 1961). "Studies on transformations of Hemophilus influenzae. I. Competence". The Journal of General Physiology. 44 (6): 1201–27. doi:10.1085/jgp.44.6.1201. PMC 2195138. PMID 13707010.

Aspiras MB, Ellen RP, Cvitkovitch DG (September 2004). "ComX activity of Streptococcus mutans growing in biofilms". FEMS Microbiology Letters. 238 (1): 167–74. doi:10.1016/j.femsle.2004.07.032. PMID 15336418.

Anagnostopoulos C, Spizizen J (May 1961). "Requirements for Transformation in Bacillus Subtilis". Journal of Bacteriology. 81 (5): 741–6. doi:10.1128/JB.81.5.741-746.1961. PMC 279084. PMID 16561900.

Angelov, Angel; Bergen, Paul; Nadler, Florian; Hornburg, Philipp; Lichev, Antoni; Ãœbelacker, Maria; Pachl, Fiona; Kuster, Bernhard; Liebl, Wolfgang (10 February 2015). "Novel Flp pilus biogenesis-dependent natural transformation". Frontiers in Microbiology. 6: 84. doi:10.3389/fmicb.2015.00084. PMC 4322843. PMID 25713572.

Lichev, Antoni; Angelov, Angel; Cucurull, Inigo; Liebl, Wolfgang (30 July 2019). "Amino acids as nutritional factors and (p)ppGpp as an alarmone of the stringent response regulate natural transformation in Micrococcus luteus". Scientific Reports. 9 (1): 11030. Bibcode:2019NatSR...911030L. doi:10.1038/s41598-019-47423-x. PMC 6667448. PMID 31363120.

Keen EC, Bliskovsky VV, Malagon F, Baker JD, Prince JS, Klaus JS, Adhya SL (January 2017). "Novel "Superspreader" Bacteriophages Promote Horizontal Gene Transfer by Transformation". mBio. 8 (1): e02115–16. doi:10.1128/mBio.02115-16. PMC 5241400. PMID 28096488.

Claverys JP, Prudhomme M, Martin B (2006). "Induction of competence regulons as a general response to stress in gram-positive bacteria". Annual Review of Microbiology. 60: 451–75. doi:10.1146/annurev.micro.60.080805.142139. PMID 16771651.

Michod RE, Wojciechowski MF, Hoelzer MA (January 1988). "DNA repair and the evolution of transformation in the bacterium Bacillus subtilis". Genetics. 118 (1): 31–9. doi:10.1093/genetics/118.1.31. PMC 1203263. PMID 8608929.

Dorer MS, Fero J, Salama NR (July 2010). Blanke SR (ed.). "DNA damage triggers genetic exchange in Helicobacter pylori". PLOS Pathogens. 6 (7): e1001026. doi:10.1371/journal.ppat.1001026. PMC 2912397. PMID 20686662.

Charpentier X, Kay E, Schneider D, Shuman HA (March 2011). "Antibiotics and UV radiation induce competence for natural transformation in Legionella pneumophila". Journal of Bacteriology. 193 (5): 1114–21. doi:10.1128/JB.01146-10. PMC 3067580. PMID 21169481.

Albertini S, Chételat AA, Miller B, Muster W, Pujadas E, Strobel R, Gocke E (July 1995). "Genotoxicity of 17 gyrase- and four mammalian topoisomerase II-poisons in prokaryotic and eukaryotic test systems". Mutagenesis. 10 (4): 343–51. doi:10.1093/mutage/10.4.343. PMID 7476271.

Washburn RS, Gottesman ME (January 2011). "Transcription termination maintains chromosome integrity". Proceedings of the National Academy of Sciences of the United States of America. 108 (2): 792–7. Bibcode:2011PNAS..108..792W. doi:10.1073/pnas.1009564108. PMC 3021005. PMID 21183718.

Sakano K, Oikawa S, Hasegawa K, Kawanishi S (November 2001). "Hydroxyurea induces site-specific DNA damage via formation of hydrogen peroxide and nitric oxide". Japanese Journal of Cancer Research. 92 (11): 1166–74. doi:10.1111/j.1349-7006.2001.tb02136.x. PMC 5926660. PMID 11714440.

Bernstein H, Bernstein C, Michod RE (2012). "Chapter 1: DNA repair as the primary adaptive function of sex in bacteria and eukaryotes". In Kimura S, Shimizu S (eds.). DNA Repair: New Research. Nova Sci. Publ., Hauppauge, N.Y. pp. 1–49. ISBN 978-1-62100-808-8.

Michod RE, Bernstein H, Nedelcu AM (May 2008). "Adaptive value of sex in microbial pathogens" (PDF). Infection, Genetics and Evolution. 8 (3): 267–85. doi:10.1016/j.meegid.2008.01.002. PMID 18295550.

Donahue RA, Bloom FR (July 1998). "Large-volume transformation with high-throughput efficiency chemically competent cells" (PDF). Focus. Vol. 20, no. 2. pp. 54–56. OCLC 12352630. Archived from the original (PDF) on 2013-03-06 – via Invitrogen.^{[unreliable source?]}

Srivastava S (2013). Genetics of Bacteria (PDF). India: Springer-Verlag. doi:10.1007/978-81-322-1090-0. ISBN 978-81-322-1089-4. S2CID 35917467.

Kawai S, Hashimoto W, Murata K (1 November 2010). "Transformation of Saccharomyces cerevisiae and other fungi: methods and possible underlying mechanism". Bioengineered Bugs. 1 (6): 395–403. doi:10.4161/bbug.1.6.13257. PMC 3056089. PMID 21468206.

Hinnen A, Hicks JB, Fink GR (April 1978). "Transformation of yeast". Proceedings of the National Academy of Sciences of the United States of America. 75 (4): 1929–33. Bibcode:1978PNAS...75.1929H. doi:10.1073/pnas.75.4.1929. PMC 392455. PMID 347451.

Ito H, Fukuda Y, Murata K, Kimura A (January 1983). "Transformation of intact yeast cells treated with alkali cations". Journal of Bacteriology. 153 (1): 163–8. doi:10.1128/JB.153.1.163-168.1983. PMC 217353. PMID 6336730.

Gietz RD, Woods RA (2002). "Transformation of yeast by lithium acetate/single-stranded carrier DNA/polyethylene glycol method". Guide to Yeast Genetics and Molecular and Cell Biology - Part B. Methods in Enzymology. Vol. 350. pp. 87–96. doi:10.1016/S0076-6879(02)50957-5. ISBN 9780121822538. PMID 12073338.

Gietz RD, Schiestl RH, Willems AR, Woods RA (April 1995). "Studies on the transformation of intact yeast cells by the LiAc/SS-DNA/PEG procedure". Yeast. 11 (4): 355–60. doi:10.1002/yea.320110408. PMID 7785336. S2CID 22611810.

Schiestl, Robert H.; Manivasakam, P.; Woods, Robin A.; Gietzt, R.Daniel (1 August 1993). "Introducing DNA into Yeast by Transformation". Methods. 5 (2): 79–85. doi:10.1006/meth.1993.1011.

Spencer, F.; Ketner, G.; Connelly, C.; Hieter, P. (1 August 1993). "Targeted Recombination-Based Cloning and Manipulation of Large DNA Segments in Yeast". Methods. 5 (2): 161–175. doi:10.1006/meth.1993.1021.

Costanzo MC, Fox TD (November 1988). "Transformation of yeast by agitation with glass beads". Genetics. 120 (3): 667–70. doi:10.1093/genetics/120.3.667. PMC 1203545. PMID 3066683.

Dohmen RJ, Strasser AW, Höner CB, Hollenberg CP (October 1991). "An efficient transformation procedure enabling long-term storage of competent cells of various yeast genera". Yeast. 7 (7): 691–2. doi:10.1002/yea.320070704. PMID 1776359. S2CID 7108750.

Hayama Y, Fukuda Y, Kawai S, Hashimoto W, Murata K (2002). "Extremely simple, rapid and highly efficient transformation method for the yeast Saccharomyces cerevisiae using glutathione and early log phase cells". Journal of Bioscience and Bioengineering. 94 (2): 166–71. doi:10.1016/s1389-1723(02)80138-4. PMID 16233287.

V.Singh and D.K.Jain (2014). "Applications of recombinant DNA". ISC BIOLOGY. Nageen Prakashan. p. 840.

Poyedinok, N. L.; Blume, Ya. B. (March 2018). "Advances, Problems, and Prospects of Genetic Transformation of Fungi". Cytology and Genetics. 52 (2): 139–154. doi:10.3103/S009545271802007X. ISSN 0095-4527. S2CID 4561837.

He, Liya; Feng, Jiao; Lu, Sha; Chen, Zhiwen; Chen, Chunmei; He, Ya; Yi, Xiuwen; Xi, Liyan (2017). "Genetic transformation of fungi". The International Journal of Developmental Biology. 61 (6–7): 375–381. doi:10.1387/ijdb.160026lh. ISSN 0214-6282. PMID 27528043.

Waltz, Emily (April 2016). "Gene-edited CRISPR mushroom escapes US regulation". Nature. 532 (7599): 293. Bibcode:2016Natur.532..293W. doi:10.1038/nature.2016.19754. ISSN 0028-0836. PMID 27111611.

Rivera, Ana Leonor; Magaña-Ortíz, Denis; Gómez-Lim, Miguel; Fernández, Francisco; Loske, Achim M. (June 2014). "Physical methods for genetic transformation of fungi and yeast". Physics of Life Reviews. 11 (2): 184–203. Bibcode:2014PhLRv..11..184R. doi:10.1016/j.plrev.2014.01.007. PMID 24507729.

Bacterial Transformation Archived 2010-06-10 at the Wayback Machine

Inoue H, Nojima H, Okayama H (November 1990). "High efficiency transformation of Escherichia coli with plasmids". Gene. 96 (1): 23–8. doi:10.1016/0378-1119(90)90336-P. PMID 2265755.

Donahue RA, Bloom FR (September 1998). "Transformation efficiency of E. coli electroporated with large plasmid DNA" (PDF). Focus. 20 (3): 77–78. Archived from the original on September 3, 2011.

Birnboim HC, Doly J (November 1979). "A rapid alkaline extraction procedure for screening recombinant plasmid DNA". Nucleic Acids Research. 7 (6): 1513–23. doi:10.1093/nar/7.6.1513. PMC 342324. PMID 388356.

External links

Bacterial Transformation (a Flash Animation)
"Ready, aim, fire!" At the Max Planck Institute for Molecular Plant Physiology in Potsdam-Golm plant cells are 'bombarded' using a particle gun

Categories:

https://en.wikipedia.org/wiki/Transformation_(genetics)

In United States copyright law, transformative use or transformation is a type of fair use that builds on a copyrighted work in a different manner or for a different purpose from the original, and thus does not infringe its holder's copyright. Transformation is an important issue in deciding whether a use meets the first factor of the fair-use test, and is generally critical for determining whether a use is in fact fair, although no one factor is dispositive.

Transformativeness is a characteristic of such derivative works that makes them transcend, or place in a new light, the underlying works on which they are based. In computer- and Internet-related works, the transformative characteristic of the later work is often that it provides the public with a benefit not previously available to it, which would otherwise remain unavailable. Such transformativeness weighs heavily in a fair use analysis and may excuse what seems a clear copyright infringement from liability.

In United States patent law the term also refers to the test set in In re Bilski: that a patent-eligible invention must "transform a particular article into a different state or thing".

https://en.wikipedia.org/wiki/Transformative_use

Transformation optics is a branch of optics which applies metamaterials to produce spatial variations, derived from coordinate transformations, which can direct chosen bandwidths of electromagnetic radiation. This can allow for the construction of new composite artificial devices, which probably could not exist without metamaterials and coordinate transformation. Computing power that became available in the late 1990s enables prescribed quantitative values for the permittivity and permeability, the constitutive parameters, which produce localized spatial variations. The aggregate value of all the constitutive parameters produces an effective value, which yields the intended or desired results.

Hence, complex artificial materials, known as metamaterials, are used to produce transformations in optical space.

The mathematics underpinning transformation optics is similar to the equations that describe how gravity warps space and time, in general relativity. However, instead of space and time, these equations show how light can be directed in a chosen manner, analogous to warping space. For example, one potential application is collecting sunlight with novel solar cells by concentrating the light in one area. Hence, a wide array of conventional devices could be markedly enhanced by applying transformation optics.^[1]^[2]^[3]^[4]^[5]

Coordinate transformations

Transformation optics has its beginnings in two research endeavors, and their conclusions. They were published on May 25, 2006, in the same issue of the peer-reviewed journal Science. The two papers describe tenable theories on bending or distorting light to electromagnetically conceal an object. Both papers notably map the initial configuration of the electromagnetic fields on to a Cartesian mesh. Twisting the Cartesian mesh, in essence, transforms the coordinates of the electromagnetic fields, which in turn conceal a given object. Hence, with these two papers, transformation optics is born.^[5]

Transformation optics subscribes to the capability of bending light, or electromagnetic waves and energy, in any preferred or desired fashion, for a desired application. Maxwell's equations do not vary even though coordinates transform. Instead values of chosen parameters of materials "transform", or alter, during a certain time period. Transformation optics developed from the capability to choose which parameters for a given material, known as a metamaterial. Hence, since Maxwell's equations retain the same form, it is the successive values of permittivity and permeability that change, over time. Permittivity and permeability are in a sense responses to the electric and magnetic fields of a radiated light source respectively, among other descriptions. The precise degree of electric and magnetic response can be controlled in a metamaterial, point by point. Since so much control can be maintained over the responses of the material, this leads to an enhanced and highly flexible gradient-index material. Conventionally predetermined refractive index of ordinary materials become independent spatial gradients, that can be controlled at will. Therefore, transformation optics is a new method for creating novel and unique optical devices.^[1]^[2]^[6]^[7]

Transformation optics can go beyond cloaking (mimic celestial mechanics) because its control of the trajectory and path of light is highly effective. Transformation optics is a field of optical and material engineering and science embracing nanophotonics, plasmonics, and optical metamaterials.

Developments

Developments in this field focus on advances in research of transformation optics. Transformation optics is the foundation for exploring a diverse set of theoretical, numerical, and experimental developments, involving the perspectives of the physics and engineering communities. The multi-disciplinary perspectives for inquiry and designing of materials develop understanding of their behaviors, properties, and potential applications for this field.

If a coordinate transformation can be derived or described, a ray of light (in the optical limit) will follow lines of a constant coordinate. There are constraints on the transformations, as listed in the references. In general, however, a particular goal can be accomplished using more than one transformation. The classic cylindrical cloak (first both simulated and demonstrated experimentally) can be created with many transformations. The simplest, and most often used, is a linear coordinate mapping in the radial coordinate. There is significant ongoing research into determining advantages and disadvantages of particular types of transformations, and what attributes are desirable for realistic transformations. One example of this is the broadband carpet cloak: the transformation used was quasi-conformal. Such a transformation can yield a cloak that uses non-extreme values of permittivity and permeability, unlike the classic cylindrical cloak, which required some parameters to vary towards infinity at the inner radius of the cloak.

General coordinate transformations can be derived which compress or expand space, bend or twist space, or even change the topology (e.g. by mimicking a wormhole). Much current interest involves designing invisibility cloaks, event cloaks, field concentrators, or beam-bending waveguides.

Mimicking celestial mechanics

The interactions of light and matter with spacetime, as predicted by general relativity, can be studied using the new type of artificial optical materials that feature extraordinary abilities to bend light (which is actually electromagnetic radiation). This research creates a link between the newly emerging field of artificial optical metamaterials to that of celestial mechanics, thus opening a new possibility to investigate astronomical phenomena in a laboratory setting. The recently introduced, new class, of specially designed optical media can mimic the periodic, quasi-periodic and chaotic motions observed in celestial objects that have been subjected to gravitational fields.^[8]^[9]^[10]

Hence, a new class of metamaterials introduced with the nomenclature “continuous-index photon traps” (CIPTs). CIPTz have applications as optical cavities. As such, CIPTs can control, slow and trap light in a manner similar to celestial phenomena such as black holes, strange attractors, and gravitational lenses.^[8]^[9]

A composite of air and the dielectric Gallium Indium Arsenide Phosphide (GaInAsP), operated in the infrared spectral range and featured a high refractive index with low absorptions.^[8]^[11]

This opens an avenue to investigate light phenomena that imitates orbital motion, strange attractors and chaos in a controlled laboratory environment by merging the study of optical metamaterials with classical celestial mechanics.^[9]

If a metamaterial could be produced that did not have high intrinsic loss and a narrow frequency range of operation then it could be employed as a type of media to simulate light motion in a curved spacetime vacuum. Such a proposal is brought forward, and metamaterials become prospective media in this type of study. The classical optical-mechanical analogy renders the possibility for the study of light propagation in homogeneous media as an accurate analogy to the motion of massive bodies, and light, in gravitational potentials. A direct mapping of the celestial phenomena is accomplished by observing photon motion in a controlled laboratory environment. The materials could facilitate periodic, quasi-periodic and chaotic light motion inherent to celestial objects subjected to complex gravitational fields.^[8]

Twisting the optical metamaterial effects its "space" into new coordinates. The light that travels in real space will be curved in the twisted space, as applied in transformational optics. This effect is analogous to starlight when it moves through a closer gravitational field and experiences curved spacetime or a gravitational lensing effect. This analogue between classic electromagnetism and general relativity, shows the potential of optical metamaterials to study relativity phenomena such as the gravitational lens.^[8]^[11]

Observations of such celestial phenomena by astronomers can sometimes take a century of waiting. Chaos in dynamic systems is observed in areas as diverse as molecular motion, population dynamics and optics. In particular, a planet around a star can undergo chaotic motion if a perturbation, such as another large planet, is present. However, owing to the large spatial distances between the celestial bodies, and the long periods involved in the study of their dynamics, the direct observation of chaotic planetary motion has been a challenge. The use of the optical-mechanical analogy may enable such studies to be accomplished in a bench-top laboratory setting at any prescribed time.^[8]^[11]

The study also points toward the design of novel optical cavities and photon traps for application in microscopic devices and lasers systems.^[8]

For related information see:Chaos theory and General relativity

Producing black holes with metamaterials

Matter propagating in a curved spacetime is similar to the electromagnetic wave propagation in a curved space and in an in homogeneous metamaterial, as stated in the previous section. Hence a black hole can possibly be simulated using electromagnetic fields and metamaterials. In July 2009 a metamaterial structure forming an effective black hole was theorized, and numerical simulations showed a highly efficient light absorption.^[10]^[12]

The first experimental demonstration of electromagnetic black hole at microwave frequencies occurred in October 2009. The proposed black hole was composed of non-resonant, and resonant, metamaterial structures, which can absorb electromagnetic waves efficiently coming from all directions due to the local control of electromagnetic fields. It was constructed of a thin cylinder at 21.6 centimeters in diameter comprising 60 concentric rings of metamaterials. This structure created a gradient index of refraction, necessary for bending light in this way. However, it was characterized as being artificially inferior substitute for a real black hole. The characterization was justified by an absorption of only 80% in the microwave range, and that it has no internal source of energy. It is singularly a light absorber. The light absorption capability could be beneficial if it could be adapted to technologies such as solar cells. However, the device is limited to the microwave range.^[13]^[14]

Also in 2009, transformation optics were employed to mimic a black hole of Schwarzschild form. Similar properties of photon sphere were also found numerically for the metamaterial black hole. Several reduced versions of the black hole systems were proposed for easier implementations.^[15]

MIT computer simulations by Fung along with lab experiments are designing a metamaterial with a multilayer sawtooth structure that slows and absorbs light over a wide range of wavelength frequencies, and at a wide range of incident angles, at 95% efficiency. This has an extremely wide window for colors of light.

Multi-dimensional universe

Engineering optical space with metamaterials could be useful to reproduce an accurate laboratory model of the physical multiverse. "This ‘metamaterial landscape’ may include regions in which one or two spatial dimensions are compactified." Metamaterial models appear to be useful for non-trivial models such as 3D de Sitter space with one compactified dimension, 2D de Sitter space with two compactified dimensions, 4D de Sitter dS4, and anti-de Sitter AdS4 spaces.^[10]^[16]

Gradient index lensing

Transformation optics is employed to increase capabilities of gradient index lenses.

Conventional optical limitations

Optical elements (lenses) perform a variety of functions, ranging from image formation, to light projection or light collection. The performance of these systems is frequently limited by their optical elements, which dominate system weight and cost, and force tradeoffs between system parameters such as focal length, field of view (or acceptance angle), resolution, and range.^[17]

Conventional lenses are ultimately limited by geometry. Available design parameters are a single index of refraction (n) per lens element, variations in the element surface profile, including continuous surfaces (lens curvature) and/or discontinuous surfaces (diffractive optics). Light rays undergo refraction at the surfaces of each element, but travel in straight lines within the lens. Since the design space of conventional optics is limited to a combination of refractive index and surface structure, correcting for aberrations (for example through the use of achromatic or diffractive optics) leads to large, heavy, complex designs, and/or greater losses, lower image quality, and manufacturing difficulties.^[17]

GRIN lenses

Gradient index lenses (or GRIN lenses) as the name implies, are optical elements whose index of refraction varies within the lens. Control of the internal refraction allows the steering of light in curved trajectories through the lens. GRIN optics thus increase the design space to include the entire volume of the optical elements, providing the potential for dramatically reduced size, weight, element count, and assembly cost, as well as opening up new space to trade between performance parameters. However, past efforts to make large aperture GRIN lenses have had limited success due to restricted refractive index change, poor control over index profiles, and/or severe limitations in lens diameter.^[17]

Recent advances

Recent steps forward in material science have led to at least one method for developing large (>10 mm) GRIN lenses with 3-dimensional gradient indexes. There is a possibility of adding expanded deformation capabilities to the GRIN lenses. This translates into controlled expansion, contraction, and shear (for variable focus lenses or asymmetric optical variations). These capabilities have been demonstrated. Additionally, recent advances in transformation optics and computational power provide a unique opportunity to design, assemble and fabricate elements in order to advance the utility and availability of GRIN lenses across a wide range of optics-dependent systems, defined by needs. A possible future capability could be to further advance lens design methods and tools, which are coupled to enlarged fabrication processes.^[17]

Battlefield applications

Transformation optics has potential applications for the battlefield. The versatile properties of metamaterials can be tailored to fit almost any practical need, and transformation optics shows that space for light can be bent in almost any arbitrary way. This is perceived as providing new capabilities to soldiers in the battlefield. For battlefield scenarios benefits from metamaterials have both short term and long term impacts.^[18]

For example, determining whether a cloud in the distance is harmless or an aerosol of enemy chemical or biological warfare is very difficult to assess quickly. However, with the new metamaterials being developed, the ability exists to see things smaller than the wavelength of light – something which has yet to be achieved in the far field. Utilizing metamaterials in the creation of a new lens may allow soldiers to be able to see pathogens and viruses that are impossible to detect with any visual device.^[18]

Harnessing subwavelength capabilities then allow for other advancements which appear to be beyond the battlefield. All kinds of materials could be manufactured with nano-manufacturing, which could go into electronic and optical devices from night vision goggles to distance sensors to other kinds of sensors. Longer term views include the possibility for cloaking materials, which would provide "invisibility" by redirecting light around a cylindrical shape.^[18]

References

Pendry, J.B.; Schurig, D.; Smith, D. R. (2006). "Controlling Electromagnetic Electromagnetic Fields". Science. 312 (5514): 1780–1782. Bibcode:2006Sci...312.1780P. doi:10.1126/science.1125907. PMID 16728597. S2CID 7967675.

Leonhardt, Ulf (Jun 2006). "Optical Conformal Mapping". Science. 312 (5781): 1777–1780. Bibcode:2006Sci...312.1777L. doi:10.1126/science.1126493. PMID 16728596. S2CID 8334444.

Schurig, D.; et al. (2006). "Metamaterial Electromagnetic Cloak at Microwave Frequencies". Science. 314 (5801): 977–980. Bibcode:2006Sci...314..977S. doi:10.1126/science.1133628. PMID 17053110. S2CID 8387554. A recently published theory has suggested that a cloak of invisibility is in principle possible, at least over a narrow frequency band. We describe here the first practical realization of such a cloak.

Liu, R; Ji, C; Mock, J. J.; Chin, J. Y.; Cui, T. J.; Smith, D. R. (January 16, 2009). "Broadband Ground-Plane Cloak". Science. 323 (5912): 366–369. Bibcode:2009Sci...323..366L. doi:10.1126/science.1166949. PMID 19150842. S2CID 206516809.

"Transformation Optics May Usher in a Host of Radical Advances". Azonano. October 17, 2008. Retrieved 2010-05-24.

Pendry, Sir John (2006). "Transformation Optics". Imperial College, London. Retrieved 2010-05-24.

Schurig, David; David Smith; Steve Cummer (2008). "Transformation Optics and Cloaking". Center for Metamaterials & Integrated Plasmonics. Retrieved 2010-05-24.

Genov, Dentcho A.; Zhang, Shuang; Zhang, Xiang (2009-07-20). "Mimicking celestial mechanics in metamaterials" (PDF). Nature Physics. 5 (9): 687–692. Bibcode:2009NatPh...5..687G. doi:10.1038/nphys1338.

Yarris, Lynn; Xiang Zhang (July 20, 2009). "Testing Relativity, Black Holes, and Strange attractors in the Laboratory". Lawrence Berkeley National Laboratory. Retrieved 2010-06-05.

Leonhardt, Ulf; Philbin, Thomas G (2006). "General relativity in electrical engineering". New Journal of Physics. 8 (10): 247. arXiv:cond-mat/0607418. Bibcode:2006NJPh....8..247L. doi:10.1088/1367-2630/8/10/247. S2CID 12100599.

Genov, Dentcho A.; Zhang, Shuang; Zhang, Xiang (2009). "Mimicking celestial mechanics in metamaterials". Nature Physics. 5 (9): 687–692. Bibcode:2009NatPh...5..687G. doi:10.1038/nphys1338.

Narimanov, E. E.; Kildishev, A. V. (2009). "Optical black hole: Broadband omnidirectional light absorber". Applied Physics Letters. 95 (4): 041106. Bibcode:2009ApPhL..95d1106N. doi:10.1063/1.3184594.

Cheng, Qiang; Cui, Tie Jun; Jiang, Wei Xiang; Cai, Ben Geng (2009). "An electromagnetic black hole made of metamaterials". arXiv:0910.2159 [physics.optics].

Matson, John (2009-10-29). "Researchers Create an Electromagnetic "Black Hole" the Size of a Salad Plate". Scientific American. Retrieved 2009-04-20.

Huanyang Chen; Rong-Xin Miao; Miao Li (2010). "Transformation optics that mimics the system outside a Schwarzschild black hole". Optics Express. 15188 (14): 15183–15188. arXiv:0912.4856. Bibcode:2010OExpr..1815183C. doi:10.1364/OE.18.015183. PMID 20640003. S2CID 19634131.

Smolyaninov, Igor I (2011). "Metamaterial 'multiverse'". Journal of Optics. 13 (2): 024004. arXiv:1005.1002. Bibcode:2011JOpt...13b4004S. doi:10.1088/2040-8978/13/2/024004. S2CID 250892352.

Strategic Technology Office (February 1, 2010). "Manufacturable Gradient Index Optics (M-GRIN)". DARPA. Retrieved 2010-06-04.

Kyzer, Lindy OCPA – Media Relations Division (Aug 21, 2008). "Army research on invisibility not science fiction". U.S. Army. Retrieved 2010-06-04.

Four key forms of capital

Fig. 1. Nested hypercycles of the transformations through the parallel evolution of four forms of capital

Fig. 1 refers to the four transformations through the parallel (and overlapping) evolution of four forms of capital: Natural→Built→Human→Social. These evolved forms of capital present a minimal complex of sustainability and self-sustainability of pre-human and human systems.

Natural capital (N). The nature-produced, renewed and reproduced “resources” of land, water, air, raw materials, biomass and organisms. Natural capital is subject to both renewable and non-renewable depletion, degradation, cultivation, recycling and reuse.

Built capital (B). The man-made physical assets of infrastructures, technologies, buildings and means of transportation. This is the manufactured “hardware” of nations. This national hardware must be continually maintained, renewed and modernized to assure its continued productivity, efficiency and effectiveness.

Human capital (H). The continued investment in people's skills, knowledge, education, health & nutrition, abilities, motivation and effort. This is the “software” and “brainware” of a nation; most important form of capital for developing nations.

Social capital (S). The enabling infrastructure of institutions, civic communities, cultural and national cohesion, collective and family values, trust, traditions, respect and the sense of belonging. This is the voluntary, spontaneous “social order” which cannot be engineered, but its self-production (autopoiesis) can be nurtured, supported and cultivated.