attention: Memory and habituation: …of a number of “two-process” theories of attention. One of the most influential was that advanced by the American psychologists Richard M. Shiffrin and Walter Schneider in 1977 on the basis of experiments involving visual search. Their theory of detection, search, and attention distinguishes between two modes of processing…

dipluran, (order Diplura), any of a group of about 800 species of small primitive wingless insects, considered by some entomologists to have features similar to ancestral insects. Diplurans have two appendages, or cerci, extending backward from the last of their abdominal segments, for which they

printing: Cylinder presses: In the two-revolution press, the cylinder never stops revolving but is raised on its bearings as the bed moves back again in order not to touch the form. In its lowered position the cylinder’s cogwheel engages a low-toothed rack incorporated in the bed; in its raised position…

Raphael Warnock: A politician’s life: …Warnock was forced into a runoff with Walker. On December 6, Warnock defeated Walker to win reelection to a six-year term.

biblical literature: The two- and four-source hypotheses: The two-source hypothesis is predicated upon the following observations: Matthew and Luke used Mark, both for its narrative material as well as for the basic structural outline of chronology of Jesus’ life. Matthew and Luke use a second source, which is called Q (from German Quelle,…

berdache, early European designation for American Indians (in Canada called First Nations peoples) who did not conform to Western gender and sexual norms. The term has been utilized in anthropology and other disciplines to define American Indian homosexuality, transgenderism, and intersexuality.

barb: Two-spot barb (B. ticto), 5–16 cm (2–6 inches) long; silvery with black spot near head and tail; dorsal fin of male reddish with black spots; no barbels.

statistics: Sample survey methods: In two-stage cluster sampling, a simple random sample of clusters is selected and then a simple random sample is selected from the units in each sampled cluster. One of the primary applications of cluster sampling is called area sampling, where the clusters are counties, townships, city…

two-state solution, proposed framework for resolving the Israeli-Palestinian conflict by establishing two states for two peoples: Israel for the Jewish people and Palestine for the Palestinian people. In 1993 the Israeli government and the Palestine Liberation Organization (PLO) agreed on a plan to

two-step, ballroom dance appearing in about 1890 in the United States. Its origins are unclear but may include the polka, galop, or waltz. The dance consists of sliding steps to the side in 24 time. It was one source of the fox-trot, which in about 1920 overtook it in popularity, and the term

two-step flow model of communication, theory of communication that proposes that interpersonal interaction has a far stronger effect on shaping public opinion than mass media outlets. The two-step flow model was formulated in 1948 by Paul Lazarsfeld, Bernard Berelson, and Hazel Gaudet in the book

thickknee: The double-striped thickknee (B. bistriatus) inhabits the American tropics. Others are the great stone curlew (Esacus recurvirostris), also called stone plover or reef thickknee, of coastal rivers of India; and the beach stone curlew (Orthorhamphus magnirostris) of Australia.

gasoline engine: Two-stroke cycle: In the original two-stroke cycle (as developed in 1878), the compression and power stroke of the four-stroke cycle are carried out without the inlet and exhaust strokes, thus requiring only one revolution of the crankshaft to complete the cycle. The fresh fuel mixture…

two-theatre war, a defense-planning model used to estimate the size and composition of U.S. forces necessary for optimal military readiness at any given time. The two-theatre war model held that the United States should be capable of simultaneously fighting two major conflicts in different parts of

France: The Directory of France: …the Convention added the “Two-thirds Decree” to the package, requiring for the sake of continuity that two-thirds of its deputies must sit by right in the new legislature regardless of voting in the départements. This outraged conservatives and royalists hoping to regain power legally, but their armed uprising in…

two-tier gold system, arrangement set up to protect international monetary reserves from the pressure of higher gold prices; under a two-tier system, monetary gold used as reserves would sell at a fixed price, and gold used as an ordinary commodity would sell at a freely fluctuating

anteater: The silky anteater: Also known as the two-toed, pygmy, or dwarf anteater, the silky anteater (Cyclopes didactylus) is the smallest and least-known member of the family. The silky anteater is found from southern Mexico southward to Bolivia and Brazil. It is not rare but is difficult…

sloth: Two-toed sloths: Both species of two-toed sloths (family Megalonychidae), also called unaus, belong to the genus Choloepus. Linnaeus’s two-toed sloth (C. didactylus) lives in northern South America east of the Andes and south to the central Amazon basin. Hoffmann’s two-toed sloth (C. hoffmanni) is

In several regional British cities, the distinct late 1970s combination of economic turmoil, unemployment benefits (effectively an arts subsidy), and art school punks resulted in a generation of eccentric talent. In Coventry, the southernmost centre of Britain’s Midlands engineering belt, the

formal logic: Nonstandard versions of PC: …system is often called the two-valued propositional calculus.) This idea has been challenged on various grounds. Following a suggestion made by Aristotle, some logicians have maintained that propositions about those events in the future that may or may not come to pass are neither true nor false but “neuter” in…

cable television: …and more cable operators is two-way channel capability, which enables subscribers to communicate with programming facilities or information centres within the system. Using the cable connection, home viewers can, for example, participate in public-opinion polls or call up various kinds of written and graphic materials (e.g., citations from reference books,…

Shohei Ohtani: …himself as the sport’s greatest two-way player in a century following his Major League Baseball (MLB) debut in 2018. In 2021 he became the first player in major league history to be named an All-Star as both a pitcher and a position player. He made history again during the 2024…

Motorola, Inc.: Founding as Galvin Manufacturing: …company introduced a pair of two-way radio communications products for the police and military. The first was an AM-band police radio system adopted later that year in Bowling Green, Kentucky; the second was the Handie-Talkie, an AM-band, handheld device with a long antenna that ultimately was used by soldiers during…

telephone: From single-wire to two-wire circuits: …by the use of a two-wire, or “metallic,” circuit; the first demonstration of such a system occurred in 1881 on a telephone line between Providence, Rhode Island, and Boston.

quasicrystal: Microscopic images of quasicrystalline structures: There are also axes of twofold rotational symmetry passing through the edges and axes of threefold rotational symmetry passing through the vertices. This is also known as icosahedral symmetry because the icosahedron is the geometric dual of the pentagonal dodecahedron. At the centre of each face on an icosahedron, the…

Cy Twombly was an American painter, draftsman, and sculptor whose work reflects a lifelong consideration of the expressive possibilities of mark making. From 1948 to 1951 Twombly studied at the School of the Museum of Fine Arts in Boston, at Washington and Lee University in Lexington, Virginia, and

Cy Twombly was an American painter, draftsman, and sculptor whose work reflects a lifelong consideration of the expressive possibilities of mark making. From 1948 to 1951 Twombly studied at the School of the Museum of Fine Arts in Boston, at Washington and Lee University in Lexington, Virginia, and

Jack Tworkov was a Polish-born American painter, an exponent of Abstract Expressionism and founding member of the New York school, whose style was characterized by gestural brushwork. Tworkov immigrated to the United States in 1913. After receiving a degree in creative writing from Columbia

Jack Tworkov was a Polish-born American painter, an exponent of Abstract Expressionism and founding member of the New York school, whose style was characterized by gestural brushwork. Tworkov immigrated to the United States in 1913. After receiving a degree in creative writing from Columbia

virology: …virology began when two bacteriologists, Frederick William Twort in 1915 and Félix d’Hérelle in 1917, independently discovered the existence of bacteriophages (viruses that infect bacteria).

the Greens: …the UTG joined with the Tasmanian Wilderness Society (TWS) to quickly mobilize opposition to a hydroelectric plant that was planned for the Gordon River below its confluence with the Franklin River. When the UTG dissolved in 1979, TWS leader Bob Brown launched a nationwide “No Dams” campaign against the initiative,…

Taiwan: Finance: The Taiwan Stock Exchange (TWSE) opened in 1962 and has flourished since then as a place for private savings and investments. Originally the TWSE traded almost exclusively in stocks, but it subsequently began to also offer bonds and other forms of investments. The TWSE is among…

electron tube: Traveling-wave tubes: These are generally used to amplify microwave signals over broad bandwidths. The main elements of a traveling-wave tube (TWT) are (1) an electron gun, (2) a focusing structure that keeps the electrons in a linear path, (3) an RF circuit that causes RF…

chemical analysis: Triangular wave voltammetry: Triangular wave voltammetry (TWV) is a method in which the potential is linearly scanned to a value past the potential at which an electrochemical reaction occurs and is then immediately scanned back to its original potential. A triangular wave voltammogram usually has…

telegraph: Printing telegraphs: In 1932 AT&T inaugurated the Teletypewriter Exchange Service (TWX), a switched teleprinter network. Switching was accomplished manually until it was automated after World War II. In Europe a similar service called Telex was inaugurated in the early 1930s and was partially automated in Germany before World War II. In 1962…

Twyfelfontein, site of rock paintings and engravings as well as archaeological remains in northwest Namibia. Locally known as /Ui-//aes (“place among rocks”), the site has one of the largest collections of rock engravings, known as petroglyphs, in Africa; more than 2,000 paintings and engravings

construction: Improvements in building services: …in England during the 1870s Thomas Twyford developed the first large one-piece ceramic lavatories as well as the ceramic washdown water closet. At first these ceramic fixtures were very expensive, but their prices declined until they became standard, and their forms remain largely unchanged today. The bathtub proved to be…

United States: Audiences: …dance troupes and museums (the Twyla Tharp dance company, despite its worldwide reputation, for instance, and a popular orientation that included several successful seasons on Broadway, was compelled to survive only by being absorbed into American Ballet Theatre) rests on hard and fixed facts about the economics of the arts,…

Jack Twyman was an American professional basketball player who was a six-time National Basketball Association (NBA) All-Star but is perhaps best remembered for the years of support he provided to teammate Maurice Stokes, who was incapacitated by an on-court injury. Twyman went from being an awkward

Jack Twyman was an American professional basketball player who was a six-time National Basketball Association (NBA) All-Star but is perhaps best remembered for the years of support he provided to teammate Maurice Stokes, who was incapacitated by an on-court injury. Twyman went from being an awkward

optical interferometer: The Twyman-Green interferometer, an adaptation of the Michelson instrument introduced in 1916 by the English electrical engineer Frank Twyman and the English chemist Arthur Green, is used for testing lenses and prisms. It uses a point source of monochromatic light at the focus of a quality…

Jack Twyman: …2013 the NBA created the Twyman-Stokes Teammate of the Year Award, which was to be given annually to the league’s “ideal teammate.”

Sir Roger Twysden was an English political pamphleteer and constitutional historian who is noted for his work on the development of English law and constitutional government. Twysden was educated at Emmanuel College, Cambridge. He was knighted in 1620 and served in Parliament in 1625 and 1626. At

Sketchpad: …that would run on the TX-2, one of the first programmable computers, at MIT’s Lincoln Laboratory. The TX-2 had twice the memory capacity of the largest commercial machines and impressive programmable capabilities. The computer possessed 320 KB (kilobytes) of memory and powered a 23-cm (9-inch) cathode-ray tube (CRT) display. Sketchpad…

numerals and numeral systems: Number bases: …left”; the endings -teen and -ty both refer to ten, and hundred comes originally from a pre-Greek term meaning “ten times [ten].”

Teyateyaneng, village, northwestern Lesotho, 19 miles (31 km) northeast of Maseru, on the country’s main north-south road. Teyateyaneng was named after the Teja-Tejane (“Quicksands”) River, which flows south of the village, and is often abbreviated as TY. The village is on a hilltop, the site of a

Tyagaraja was an Indian composer of Carnatic songs of the genre kirtana, or kriti (devotional songs), and of ragas. He is the most prominent person in the history of southern Indian classical music, and he is venerated by contemporary Carnatic musicians. Tyagaraja is said to have composed the music

Tien Shan, great mountain system of Central Asia. Its name is Chinese for “Celestial Mountains.” Stretching about 1,500 miles (2,500 km) from west-southwest to east-northeast, it mainly straddles the border between China and Kyrgyzstan and bisects the ancient territory of Turkistan. It is about 300

Anatolia: The Old Hittite Kingdom: …Edict of Telipinus are known: Tuwanuwa (classical Tyana, near modern Bor); Hupisna (classical Heraclea Cybistra; modern Ereğli); Parsuhanda (Purushkhanda; probably modern Acemhöyük); and Lusna (classical Lystra). With the exception of Landa (probably to the north), the sites are all located in the territory to the south of the Kızıl River…

Landuma: Their language, also called Landuma or Tyapi, belongs to the Atlantic branch of the Niger-Congo family and is related to Baga. The Landuma are agriculturalists—corn (maize), millet, groundnuts (peanuts), and rice being the major crops. Social organization centres in a paramount chief, with villages governed by subordinate chiefs. Marriage…

Pontus de Tyard was a Burgundian poet and member of the literary circle known as La Pléiade who was a forthright theorist and a popularizer of Renaissance learning for the elite. Tyard was seigneur (lord) of Bissy-sur-Fley and an associate of the Lyonese poets, especially Maurice Scève. In 1551 he

Anatoly Rybakov: …II in Tyazhyoly pesok (1979; Heavy Sand), an epic novel that brought him an international audience. With the arrival of Premier Mikhail Gorbachev’s policy of glasnost, Rybakov was allowed to publish Deti Arbata (1987; Children of the Arbat), much of which had been suppressed for more than two decades. The…

pipa: …the contemporary pipa is the quxiang (“curved-neck”) pipa, which traveled from Persia by way of the Silk Road and reached western China in the 4th century ad. It had a pear-shaped wooden body with two crescent-shaped sound holes, a curved neck, four strings, and four frets. In performance it was…

Simon Of Sudbury was the archbishop of Canterbury from 1375 and chancellor of England from 1380 who lost his life in the Peasants’ Revolt of 1381. Simon served for 12 years as an auditor (judge) of the Rota at the papal Curia, and in 1359 Pope Innocent VI employed him in an attempt to persuade King

Romeo and Juliet: When Tybalt, a Capulet, seeks out Romeo in revenge for the insult of Romeo’s having dared to shower his attentions on Juliet, an ensuing scuffle ends in the death of Romeo’s dearest friend, Mercutio. Impelled by a code of honour among men, Romeo kills Tybalt and…

Tyburn, small left-bank tributary of the River Thames, England, its course now wholly within London and below ground. Before it was culverted, the river traversed London from the heights of Hampstead through Regent’s Park to the lower areas of Westminster, where it entered the marshy floodplain of

Tyche, in Greek religion, the goddess of chance, with whom the Roman Fortuna was later identified; a capricious dispenser of good and ill fortune. The Greek poet Hesiod called her the daughter of the Titan Oceanus and his consort Tethys; other writers attributed her fatherhood to Zeus, the supreme

Epicureanism: Criticism and evaluation: …century under the name of tychism by Charles Sanders Peirce, a logician and philosopher of science.

Tycho, conspicuous impact crater resulting from an impact event and lying at the centre of the most extensive system of bright rays on the near side of the Moon. The rays, which are light-coloured streaks formed of material ejected from the impact, dominate the southern highlands and extend for

Copenhagen: The contemporary city: …the 16th-century astronomer is the Tycho Brahe Planetarium, which opened in 1989.

Tycho’s Nova, one of the few recorded supernovas in the Milky Way Galaxy. The Danish astronomer Tycho Brahe first observed the “new star” on Nov. 11, 1572. Other European observers claimed to have noticed it as early as the preceding August, but Tycho’s precise measurements showed that it was not

Tychonic system, scheme for the structure of the solar system put forward in 1583 by the Danish astronomer Tycho Brahe. He retained from the ancient Ptolemaic system the idea of Earth as a fixed centre of the universe around which the Sun and Moon revolved, but he held that, as in the newer system

Tychy, city, Śląskie województwo (province), southern Poland. It lies on the Bielsko-Biała rail line on the southern edge of the Upper Silesia industrial district and is surrounded by the Pszczyna forests. Tychy was early known for its beer, its first brewery having opened in 1629, and, later, for

Ukrainian literature: …of Volodymyr Vynnychenko’s prose, while Pavlo Tychyna was the leading Symbolist poet. Neoclassicism produced the poet Mykola Zerov, and Futurism was initiated by Mykhailo Semenko.

Tyconius, one of the most important biblical theologians of 4th-century North African Latin Christianity. Although little is known of his life, his positions on the theology of the church (ecclesiology) ultimately provided his younger contemporary and the Church Father St. Augustine with crucial

Saint David’s, cathedral city, historic and present county of Pembrokeshire, southwestern Wales. It lies within Pembrokeshire Coast National Park in the River Alun valley near the tip of Saint David’s Head peninsula (the westernmost point in Wales). Situated in an area important for Celtic

Oeneus: Their son, Tydeus, was exiled for murder, and Oeneus was deposed. Tydeus died on the expedition of the Seven Against Thebes, but his son Diomedes returned and restored Oeneus to the throne. Oeneus handed Calydon over to his son-in-law Andraemon, the husband of Gorge.

Tydings-McDuffie Act, (1934), the U.S. statute that provided for Philippine independence, to take effect on July 4, 1946, after a 10-year transitional period of Commonwealth government. The bill was signed by U.S. Pres. Franklin D. Roosevelt on March 24, 1934, and was sent to the Philippine Senate

Christopher Tye was a composer, poet, and organist who was an innovator in the style of English cathedral music perfected by Thomas Tallis, William Byrd, and Orlando Gibbons. Very little is known of Tye’s early life, but the first verifiable documentation states that he earned a bachelor of music

chinook salmon, (Oncorhynchus tshawytscha) prized North Pacific food and sport fish of the family Salmonidae. It weighs up to 60 kg (130 pounds) and is silvery with round black spots. Spawning runs occur in spring, adults swimming as far as 3,200 km (2,000 miles) up the Yukon. Young chinook salmon

Lake Tyers, coastal lake in Gippsland, on the eastern coast of Victoria, Australia, near the northeastern end of Ninety Mile Beach. The lake consists of two main channels; the eastern half curves northeasterly into the interior for about 10 miles (16 km), and the western channel extends

girdle tie, in Egyptian religion, protective amulet formed like a knot and made of gold, carnelian, or red glazed ware. Most samples of the girdle tie have been found tied around the necks of mummies; the amulets were intended to protect the dead from all that was harmful in the

lighthouse: Compressed air: …later compressed-air signal was the tyfon. Employing a metal diaphragm vibrated by differential air pressure, it was more compact and efficient than its predecessors.

pottery: 17th-century slipware: …or more handles, known as tygs; and London for dishes with such pious exhortations as “Fast and Pray,” obviously inspired by the Puritans. Manufacture was also started in Staffordshire, and many surviving examples were signed by the potter in slip. The work of Thomas Toft is particularly valued. The best…

The Tyger, poem by William Blake, published in his Songs of Innocence and of Experience at the peak of his lyrical achievement. The tiger is the key image in the Songs of Experience, the embodiment of an implacable primal power. Its representation of a physicality that both attracts and terrifies

tigerware, 16th- and 17th-century German stoneware having a brown, mottled glaze, and made in the Rhenish centres of Cologne and Frechen, Ger. Tigerware was imported to England and imitated there in the different medium of delft, or tin-glazed earthenware; the imitations were also called tigerware.

Tadeusz Mazowiecki: …Mazowiecki the first editor of Tygodnik Solidarność (“Solidarity Weekly”), the new Solidarity newspaper. His ties to Wałęsa only deepened during the government’s suppression of the Solidarity movement from 1981 to 1988.

Chiwara, antelope figure of the Bambara (Bamana) people of Mali that represents the spirit that taught humans the fundamentals of agriculture. The Bambara honour Chiwara though art and dance. According to Bambara legend, Chiwara used his antlers and pointed stick to dig into the earth, making it

Tyla is a South African singer who gained international recognition when a video of a live performance of her 2023 single “Water,” featuring the bacardi, a contemporary South African dance style, went viral on social media. She dubbed her music “popiano,” a mix of pop with amapiano, the South

plant disease: Nematode diseases: The citrus nematode (Tylenchulus semipenetrans) occurs wherever citrus is grown, exacting a heavy toll in fruit quality and production. Typical symptoms are a slow decline, yellowing and dying of leaves, and dieback of twigs and branches in many groves 15 years or older. Infested nursery stock…

Tylenol, trademarked brand of acetaminophen, an aspirin-free pain reliever and fever reducer introduced in 1955 by McNeil Laboratories, Inc. (now part of the Johnson & Johnson pharmaceutical conglomerate). See

Tyler, city, seat (1846) of Smith county, northeastern Texas, U.S. It is located 100 miles (160 km) east-southeast of Dallas. Laid out in 1846 and named for President John Tyler, it was a farming centre until 1930, when the East Texas oil field was discovered. A transportation focus, Tyler became

Tyler: …its flower industry, exemplified by Tyler Municipal Rose Garden and Museum (the country’s largest rose showcase), its annual Texas Rose Festival (October), and the Azalea and Spring Flower Trail. The city is the seat of Texas College (1894), Tyler Junior College (1926), and the University of Texas at Tyler (1971);…

Tyler Perry: …to television with his sitcoms House of Payne (2006–12; 2020– ); Meet the Browns (2009–11), which evolved from a play (2004) and a film (2008); and For Better or Worse (2011–17), which centred on characters from Why Did I Get Married? and its sequel. The latter series was picked up…

mineral processing: Size analysis: …standard (now obsolete) was the Tyler Series, in which wire screens were identified by mesh size, as measured in wires or openings per inch. Modern standards now classify sieves according to the size of the aperture, as measured in millimetres or micrometres (10-6 metre).

Anne Tyler is an American novelist and short-story writer whose comedies of manners are marked by compassionate wit and precise details of domestic life. She won a Pulitzer Prize for the novel Breathing Lessons (1988). Tyler, the daughter of Quakers, spent her early years in North Carolina and in

John Tyler was the 10th president of the United States (1841–45), who took office upon the death of Pres. William Henry Harrison. A maverick Democrat who refused allegiance to the program of party leader Andrew Jackson, Tyler was rejected in office by both the Democratic Party and the Whig Party

Jailhouse Rock: Peggy Van Alden (played by Judy Tyler) is the talent agent who helps him on his way up.

Julia Tyler was an American first lady (June 26, 1844–March 4, 1845), the wife of John Tyler, 10th president of the United States. For eight months she presided over the White House with charming exuberance. Julia Gardiner, the daughter of David Gardiner, a lawyer and state senator, and Juliana

Letitia Tyler was an American first lady (1841–42), the first wife of John Tyler, 10th president of the United States. Letitia Christian was the seventh of 12 children born to Robert Christian, a planter, and Mary Brown Christian. Although few records documenting her early life exist, historians

Letitia Tyler was an American first lady (1841–42), the first wife of John Tyler, 10th president of the United States. Letitia Christian was the seventh of 12 children born to Robert Christian, a planter, and Mary Brown Christian. Although few records documenting her early life exist, historians

Stella McCartney: …the 2001 Academy Award ceremonies), Liv Tyler, and Gwyneth Paltrow, and model Kate Moss.

Moses Coit Tyler was a U.S. literary historian whose use of literary documents in the history of pre-Revolutionary American ideas was a major contribution to U.S. historiography. The descendant of an old New England family, Tyler was taken west in 1837 by his parents, who eventually settled in

Royall Tyler was a U.S. lawyer, teacher, and dramatist, known as the author of the first American comedy, The Contrast (1787). After graduating from Harvard University, Tyler served in the U.S. Army and later became a lawyer. A meeting with Thomas Wignell, the star comedian of the American Company,

Steven Tyler is an American singer-songwriter best known as the lead singer and front man for the heavy metal rock band Aerosmith. Tyler and guitarist Joe Perry were the driving force behind Aerosmith, which formed in the 1970s. The band is known for its bluesy, swaggering rock, which often was

Billie Eilish: When We All Fall Asleep, Where Do We Go? and Happier than Ever: …such as Childish Gambino and Tyler, the Creator. Her debut album, When We All Fall Asleep, Where Do We Go?, was released on March 29, 2019, and reached number one on the Billboard 200 chart. The song “Bad Guy” from the album was Eilish’s first number-one single on the Billboard…

Wat Tyler was the leader of the Peasants’ Revolt of 1381, the first great popular rebellion in English history; his leadership proved one of the chief factors in the success of protest against the harsh taxation of the poorer classes. Chosen as captain by the Kentish rebels on June 7, Tyler led

Wat Tyler was the leader of the Peasants’ Revolt of 1381, the first great popular rebellion in English history; his leadership proved one of the chief factors in the success of protest against the harsh taxation of the poorer classes. Chosen as captain by the Kentish rebels on June 7, Tyler led

Royall Tyler was a U.S. lawyer, teacher, and dramatist, known as the author of the first American comedy, The Contrast (1787). After graduating from Harvard University, Tyler served in the U.S. Army and later became a lawyer. A meeting with Thomas Wignell, the star comedian of the American Company,

callus, in dermatology, small area of thickened skin, the formation of which is caused by continued friction, pressure, or other physical or chemical irritation. Calluses form when mild but repeated injury causes the cells of the epidermis (the outermost layer of the skin) to become increasingly