slip, in engineering and physics, sliding displacement along a plane of one part of a crystal relative to the rest of the crystal under the action of shearing forces—that is, forces acting parallel to that plane. Much of the permanent, or plastic, deformation of materials under stress is the result

spectroscopy: Basic atomic structure: The emission and absorption spectra of the elements depend on the electronic structure of the atom. An atom consists of a number of negatively charged electrons bound to a nucleus containing an equal number of positively charged protons. The nucleus

atom, the basic building block of all matter and chemistry. Atoms can combine with other atoms to form molecules but cannot be divided into smaller parts by ordinary chemical processes. Most of the atom is empty space. The rest consists of three basic types of subatomic particles: protons,

atomic theory, ancient philosophical speculation that all things can be accounted for by innumerable combinations of hard, small, indivisible particles (called atoms) of various sizes but of the same basic material; or the modern scientific theory of matter according to which the chemical elements

atomic time, timescale generated by atomic clocks, which furnish time more accurately than was possible with previous astronomical means (measurements of the rotation of the Earth and its revolution about the Sun). International Atomic Time (TAI) is based on a system consisting of about 270

isotope: Photochemical enrichment methods: In atomic vapour laser isotope separation (AVLIS), the starting material is the element itself; in molecular laser isotope separation (MLIS), the starting material is a chemical compound containing the element. Ordinary light sources are not suitable for isotope separation because they emit a broad range of…

doomsday machine: …in the event of a nuclear attack on the country maintaining the device. The former type of device might automatically launch a large number of ICBMs (intercontinental ballistic missiles) when it detected a nuclear explosion or an imminent nuclear attack, whereas the latter might detonate several very large thermonuclear bombs…

nuclear weapon, device designed to release energy in an explosive manner as a result of nuclear fission, nuclear fusion, or a combination of the two processes. Fission weapons are commonly referred to as atomic bombs. Fusion weapons are also referred to as thermonuclear bombs or, more commonly,

atomic weight, ratio of the average mass of a chemical element’s atoms to some standard. Since 1961 the standard unit of atomic mass has been one-twelfth the mass of an atom of the isotope carbon-12. An isotope is one of two or more species of atoms of the same chemical element that have different

Niklas Zennström: Joost: …2006 Zennström and Friis founded Atomico Ventures, an investment fund that sought out European technology companies that had the potential to be successful in the global market. Niklas and his wife, Catherine, established Zennström Philanthropies in 2007 to support and engage with organizations in efforts to stop climate change and…

Michel Houellebecq: Writing career and books: …the United Kingdom and as The Elementary Particles in the United States. In it he presented two half brothers who were abandoned by their parents in childhood. Bruno is driven by an insatiable sexual appetite, while Michel, a scientist, avoids the issue of any attachment whatsoever by focusing his attention…

atomism, any doctrine that explains complex phenomena in terms of aggregates of fixed particles or units. This philosophy has found its most successful application in natural science: according to the atomistic view, the material universe is composed of minute particles, which are considered to be

Logical Atomism, theory, developed primarily by the British logician Bertrand Russell and the Austrian-born philosopher Ludwig Wittgenstein, proposing that language, like other phenomena, can be analyzed in terms of aggregates of fixed, irreducible units or elements. Logical Atomism supposes that a

monopoly and competition: Concentration of sellers: …competing seller, economists speak of atomistic competition. A more common situation is that of oligopoly, in which the number of sellers is so few that the market share of each is large enough for even a modest change in price or output by one seller to have a perceptible effect…

Atomium, atomic model structure in Brussels that was designed by engineer André Waterkeyn and architects André and Jean Polak. It was built in 1958 for the World Exhibition, which was held in Belgium’s capital city. The Atomium’s construction dates from when Brussels was rebuilt after World War II,

spectroscopy: RIS atomization methods: Because the RIS technique is limited to the study of free atoms or molecules in the gas phase, the analysis of solids and liquids requires a means for releasing atoms from the bulk material. A simple and effective system atomizes samples…

metallurgy: Processes: In other atomization processes, centrifugal force is used. The metal can be poured onto a spinning disk that breaks up the stream, or a spinning rod can be melted by an electric arc so that it throws off particles as it spins.

e-cigarette: …in the cartridge, and the atomizer vaporizes the liquid, emitting it as a mist that the user inhales. Hence, e-cigarette use is commonly described as vaping, a term also used in reference to the use of similar devices, including vape pens and e-hookas.

attention-deficit/hyperactivity disorder: Treatment: …as bupropion or atomoxetine (Strattera®). Such drugs work by inhibiting the reuptake of norepinephrine from nerve terminals, thereby increasing the amount of the neurotransmitter available in the brain.

Radiohead: …sang for the electronic-influenced group Atoms for Peace, which in 2013 released the intricately textured Amok. He later composed the film soundtrack for Suspiria (2018). Jonny Greenwood also recorded soundtracks, among them Phantom Thread and You Were Never Really Here (both 2017). Radiohead was inducted into the Rock and Roll…

Atoms for Peace speech, speech delivered to the United Nations by U.S. Pres. Dwight D. Eisenhower on December 8, 1953 (see primary source document: Atoms for Peace). In this address, Eisenhower spelled out the necessity of repurposing existing nuclear weapons technology to peaceful ends, stating

Aton, in ancient Egyptian religion, a sun god, depicted as the solar disk emitting rays terminating in human hands, whose worship briefly was the state religion. The pharaoh Akhenaton (reigned 1353–36 bce) returned to supremacy of the sun god, with the startling innovation that the Aton was to be

Aton Hymn, the most important surviving text relating to the singular worship of the Aton, a new religious ideology espoused by the ancient Egyptian king Akhenaton of the 18th dynasty. During his reign Akhenaton returned to the supremacy of the sun god, with the startling innovation that the Aton

atonality, in music, the absence of functional harmony as a primary structural element. The reemergence of purely melodic-rhythmic forces as major determinants of musical form in the Expressionist works of Arnold Schoenberg and his school prior to World War I was a logical, perhaps inevitable

atonement, the process by which people remove obstacles to their reconciliation with God. It is a recurring theme in the history of religion and theology. Rituals of expiation and satisfaction appear in most religions as the means by which religious people reestablish or strengthen their relation

Atonement: An Academy Award-winning film version of the story appeared in 2007.

Atonement, novel by Ian McEwan, published in 2001. An Academy Award-winning film version of the story appeared in 2007. Begun as a science fiction story but then abandoned, Atonement took mature form as a work of literary fiction composed of three distinct stories. The first part of the novel

Yom Kippur, most solemn of Jewish religious holidays, observed on the 10th day of the lunar month of Tishri (in the course of September and October), when Jews seek to expiate their sins and achieve reconciliation with God. Yom Kippur concludes the “10 days of repentance” that begin with Rosh

Atoni, predominant people of Timor, easternmost of the Lesser Sunda Islands, Indonesia. They inhabit the central and western plains and mountains of the island and number about 530,000. Of Proto-Malay and Melanoid stock, they speak a Malayo-Polynesian dialect called Timorese. Atoni legend claims

atopic dermatitis, a type of dermatitis

atopy, type of hypersensitivity characterized by an immediate physiological reaction, with movement of fluid from the blood vessels into the tissues, upon exposure to an allergen. Atopy occurs mainly in persons with a familial tendency to allergic diseases; reaginic antibodies are found in the skin

Cuba: Plant and animal life: Solenodons (Atopogale cubana), which are nearly extinct ratlike insectivores, are found only in the remotest eastern regions. Other mammals include hutias (edible rodents) and manatees, or sea cows, which inhabit river mouths. Several types of bats prey on mosquitoes and insects harmful to agriculture, and in…

atopy, type of hypersensitivity characterized by an immediate physiological reaction, with movement of fluid from the blood vessels into the tissues, upon exposure to an allergen. Atopy occurs mainly in persons with a familial tendency to allergic diseases; reaginic antibodies are found in the skin

Cyrus the Great: Cyrus’s conquests: …had at least one daughter, Atossa (who married her brother Cambyses), and possibly two others, but they played no role in history.

railroad: Automated systems: A refinement, generally known as automatic train protection (ATP), has been developed since World War II to provide continuous control of train speed. It has been applied principally to busy urban commuter and rapid-transit routes and to European and Japanese intercity high-speed routes. A display in the cab reproduces either…

tennis: The open era: …female players formed guilds—the men’s Association of Tennis Professionals (ATP) and the Women’s Tennis Association (WTA), which in 1986 became the Women’s International Tennis Association (WITA). Previous player unions had been ineffective, but the ATP showed itself a potent political force when the majority of its members boycotted Wimbledon in…

adenosine triphosphate (ATP), energy-carrying molecule found in the cells of all living things. ATP captures chemical energy obtained from the breakdown of food molecules and releases it to fuel other cellular processes. Cells require chemical energy for three general types of tasks: to drive

adenosine triphosphate: …is produced by the enzyme ATP synthase, which converts ADP and phosphate to ATP. ATP synthase is located in the membrane of cellular structures called mitochondria; in plant cells, the enzyme also is found in chloroplasts. The central role of ATP in energy metabolism was discovered by Fritz Albert Lipmann…

macular degeneration: Other forms of macular degeneration: …mutations in a gene called ABCA4 (ATP-binding cassette, subfamily A, member 4). Stargardt-like macular dystrophy differs from Stargardt macular dystrophy in that it is caused by mutations in a gene called ELOVL4 (elongation of very-long-chain fatty acids-like 4). Malattia Leventinese (Doyne honeycomb) retinal dystrophy, which is characterized by a honeycomb-like…

Wilson disease: …in a gene known as ATP7B, which produces a membrane protein that regulates the transport of copper out of cells. When the ATP7B gene is mutated, the membrane protein becomes dysfunctional, resulting in inefficient cellular export of copper. This in turn results in reduced binding of copper to a protein…

cell: The sodium-potassium pump: An enzyme called sodium-potassium-activated ATPase has been shown to be the sodium-potassium pump, the protein that transports the ions across the cell membrane while splitting ATP. Widely distributed in the animal kingdom and always associated with the cell membrane, this ATPase is found at high concentration in cells that…

Mike Enzi: …pledge—created by the special-interest group Americans for Tax Reform, headed by Grover Norquist—in which politicians promised to curb taxation, especially at the federal level. Enzi continued to take a strong interest in energy issues, and he led legislative efforts to open the Arctic National Wildlife Refuge and other public lands…

Airbus: Aerospatiale Matra: …turboprop regional aircraft and formed ATR as a 50-50 joint venture to develop, market, and support regional transport aircraft. ATR developed a family of high-wing, twin-turboprop aircraft in the 40–70 seat range, the ATR 42, its first product (entered service 1985), and the later ATR 72 (1989). In 1992 Aerospatiale…

Australian funnel-web spider, (family Atracidae), any of about 35 species and three genera of spiders native to southern and eastern Australia, several of which are potentially medically significant to humans. As burrowing spiders, they are named for their funnel-shaped webs, which open wide at the

burrowing asp, (genus Atractaspis), any of 19 species of venomous, secretive snakes, also known as mole vipers and stiletto snakes, of tropical Africa and the Middle East. They belong to the family Atractaspididae, a group distinct from vipers and elapids. Atractaspidids are characterized by a

fungus: Annotated classification: Order Atractiellales Parasitic or saprotrophic; minute globuse conidia formed from tips of hyphae; example genera include Atractiella, Saccoblastia, Helicogloea, and Phleogena. Class Classiculomycetes Parasitic; uredinalian septal pores with tremelloid haustorial cells; contains 1 order.

fungus: Annotated classification: Class Atractiellomycetes Parasitic or saprotrophic; simple septate; some pycnidial members; auricularoid basidia; gastroid; contains 1 order. Order Atractiellales Parasitic or saprotrophic; minute globuse conidia formed from tips of hyphae; example genera include Atractiella, Saccoblastia, Helicogloea, and Phleogena.

gar: …American fishes of the genera Atractosteus and Lepisosteus, in the family Lepisosteidae. Gars, which are related to the bowfin in the infraclass Holostei, are confined chiefly to fresh water, though some of the species descend to brackish or even salt water.

gar: …and relatively short in the alligator gar (A. spatula) of the southern United States. The alligator gar, reaching a length of about 3 metres (10 feet), is one of the largest of all freshwater fishes. Gars are edible but are almost never eaten in the central and northern United States.…

Judaism: Myths: …Babylonian myths of Gilgamesh and Atrahasis. There, however, the hero is eventually made immortal, whereas in the Bible this detail is omitted because, to the Israelite mind, no child of woman could achieve that status. Lastly, while the story of the Tower of Babel was told originally to account for…

rocket and missile system: Matador and other programs: However, in 1954 an automatic terrain recognition and guidance (Atran) system was added (and the missile system was subsequently designated Mace). Atran, which used radar map-matching for both en-route and terminal guidance, represented a major breakthrough in accuracy, a problem long associated with cruise missiles. The low availability of…

Islamic arts: The modern period: ʿAbd al-Wahhāb, Umm Kulthūm, Farīd al-Aṭrash, Fayrouz, Rashid al-Hundarashi, Ṣadīqah al-Mulāya, and Muḥammad al-Gubanshi.

Druze: The Druze in Syria: In 1925 Druze leader Sulṭān al-Aṭrash led a revolt against French rule. After local success, Syrian nationalists outside the Druze community joined the revolt, and the rebellion spread throughout the region and into Damascus before it was suppressed in 1927. Among Syrians, this revolt is remembered as the nation’s…

Atrato River, river in northwestern Colombia. It rises in the western slopes of the Cordillera Occidental of the Andes and flows generally northward to empty into the Gulf of Urabá of the Caribbean Sea. The river is only 416 miles (670 km) long, but its large discharge of no less than 175,000 cubic

Atrato River, river in northwestern Colombia. It rises in the western slopes of the Cordillera Occidental of the Andes and flows generally northward to empty into the Gulf of Urabá of the Caribbean Sea. The river is only 416 miles (670 km) long, but its large discharge of no less than 175,000 cubic

Australian funnel-web spider: Major genera and species: The northern tree-dwelling funnel-web spider (H. formidabilis; formerly Atrax formidabilis) is a medically significant member found in Queensland and New South Wales. Symptoms can occur within 15 to 20 minutes following a bite and include tachycardia, muscle spasms, nausea, vomiting, and pulmonary edema. As with the…

Australian funnel-web spider: Major genera and species: …venomous Sydney funnel-web spider (A. robustus). Several human deaths from the bites of these aggressive spiders have been recorded in the Sydney area since the 1920s. An antidote to the main toxin in their venom has been developed and is effective if administered to victims soon after they have…

Arras: …(Nemetacum or Nemetocenna) of the Atrebates, one of the last Gallic peoples to surrender to Julius Caesar. The woolen industry dates from the 4th century. The Middle Ages was a period of great material and cultural wealth, when Arras became the English word for tapestry hangings. The fortunes of the…

Turkmenistan: Drainage: Morghāb (Murgab, or Murgap), and Atrek; there are also numerous small mountain rivers. However, the geographic position of the rivers and the direction of their flow do not coincide with the location of cultivable lands; the most fertile—and still insufficiently used—lands lie chiefly in the south, northeast, and west, whereas…

atresia and stenosis, absence, usually congenital, of a normal bodily passage or cavity (atresia) or narrowing of a normal passage (stenosis). Most such malformations must be surgically corrected soon after birth. Almost any cavity or passage may be affected; some of the more important of these

Atreus, in Greek legend, the son of Pelops of Mycenae and his wife, Hippodamia. Atreus was the elder brother of Thyestes and was the king of Mycenae. The story of his family—the House of Atreus—is virtually unrivaled in antiquity for complexity and corruption. There are several different accounts

Treasury of Atreus, a beehive, or tholos, tomb built about 1350 to 1250 bc at Mycenae, Greece. This surviving architectural structure of the Mycenaean civilization is a pointed dome built up of overhanging (i.e., corbeled) blocks of conglomerate masonry cut and polished to give the impression of a

Atri, town, Abruzzi region, central Italy, northwest of Pescara, on a hill overlooking the Adriatic Sea 7.5 mi (12 km) to the east and the Gran Sasso d’Italia mountain group to the west. Atri originated as Hatria, a town of the Picenes, an ancient Italic people. In 282 bc it became the Roman colony

reptile: Hearing: …typically made up of a tympanum, a thin membrane located at the rear of the head; the stapes, a small bone running between the tympanum and the skull in the tympanic cavity (the middle ear); the inner ear; and a eustachian tube connecting the middle ear with the mouth cavity.…

Adria, town and episcopal see in the Veneto regione of northern Italy, on the Bianco Canal just east of Rovigo. Founded by the Etruscans or the Veneti of northeastern Italy, it later became a Roman town and was a flourishing port on the Adriatic Sea (to which it gave its name) until the silting up

atrium, in vertebrates and the higher invertebrates, heart chamber that receives blood into the heart and drives it into a ventricle, or chamber, for pumping blood away from the heart. Fishes have one atrium; amphibians, reptiles, birds, and mammals, two. In humans the atria are the two upper

atrial fibrillation, irregular rhythm of contraction of the muscles of the atrium, the upper chamber of the heart. In some cases the fibrillations are not noticed by the patient, but frequently the chaotic, rapid, and shallow beats are felt as significant palpitations of the heart, often

cardiovascular disease: Supraventricular arrhythmia: Atrial flutter (rapid atrial beat) may occur suddenly and unpredictably or may be a chronic sustained arrhythmia. The heart rate in atrial flutter approximates 300 beats per minute and is difficult to treat pharmacologically. In general, only a fraction of the atrial beats (one-third to…

renal system: The role of hormones in renal function: This hormone, called atrial natriuretic peptide (ANP), exerts a vasodilator effect on the kidney and also reduces tubular reabsorption of sodium. Both actions result in increased urinary elimination of salt and water and tend to restore atrial pressure toward the normal. It is probably an important hormone controlling…

Bainbridge reflex, acceleration of the heart rate resulting from increased blood pressure in, or increased distension of, the large systemic veins and the right upper chamber of the heart. This reflex, first described by the British physiologist Francis Arthur Bainbridge in 1915, prevents the

atrial septal defect, congenital opening in the partition between the two upper chambers (atria) of the heart. The most common atrial septal defect is persistence of the foramen ovale, an opening in this partition that is normal before birth and that normally closes at birth or shortly thereafter.

scrub-bird: …western, or noisy, scrub-bird (Atrichornis clamosus), discovered in dry brushlands of Western Australia in the 1840s, was believed extinct after 1889 but was rediscovered in 1961. The 18-centimetre (7-inch) rufous scrub-bird (A. rufescens), discovered in the 1860s in wet forests of New South Wales, 2,500 miles (4,000 km) away…

scrub-bird: The 18-centimetre (7-inch) rufous scrub-bird (A. rufescens), discovered in the 1860s in wet forests of New South Wales, 2,500 miles (4,000 km) away from the other species, is now known to range to Queensland, where it is protected in Lamington National Park.

scrub-bird, either of two species of rare Australian birds comprising the family Atrichornithidae (order Passeriformes), allied to lyrebirds. Both species are brown, with a longish, pointed tail—rather like the brown thrasher of the United States. The 22-centimetre (9-inch) western, or noisy,

Gerhart Hauptmann: …work is the Atrides cycle, Die Atriden-Tetralogie (1941–48), which expresses through tragic Greek myths Hauptmann’s horror of the cruelty of his own time.

Wilhelm His: …muscle fibres (known as the bundle of His) running along the muscular partition between the left and right chambers of the heart. He found that these fibres help communicate a single rhythm of contraction to all parts of the heart.

human cardiovascular system: External surface of the heart: One, the atrioventricular groove, is along the line where the right atrium and the right ventricle meet; it contains a branch of the right coronary artery (the coronary arteries deliver blood to the heart muscle). The other, the anterior interventricular sulcus, runs along the line between the…

pacemaker: …patch of conductive tissue, the atrioventricular node, initiating a second discharge along an assembly of conductive fibres called the bundle of His, which induces the contraction of the ventricles. When electrical conduction through the atrioventricular node or bundle of His is interrupted, the condition is called heart block. An artificial…

human cardiovascular system: Origin and development: …the formation of the two atrioventricular valves (the valves between atria and ventricles), which regulate the direction of blood flow through the heart.

saltbush, (genus Atriplex), genus of about 300 species of herbs and shrubs in the amaranth family (Amaranthaceae), often found on saline soils. Saltbush plants grow throughout temperate and subtropical areas of the world. Young leaves of several species, including the garden orach (A. hortensis),

saltbush: …of western North America, especially four-wing saltbush, or chamiso (A. canescens), and spiny saltbush (A. confertifolia).

saltbush: canescens), and spiny saltbush (A. confertifolia).

Caryophyllales: Amaranthaceae: Sea orach (A. halimus) is cultivated for its beautiful foliage and silvery gray stems; its flowers are green and rather inconspicuous. Garden orach (A. hortensis) was at one time used as a cure for gout. Another interesting ornamental genus is Bassia, which includes summer cypress…

Caryophyllales: Amaranthaceae: Garden orach (A. hortensis) was at one time used as a cure for gout. Another interesting ornamental genus is Bassia, which includes summer cypress (B. scoparia) and burning bush (B. scoparia trichophylla); the leaves of the latter turn a beautiful red in autumn.

angiosperm: Dermal tissue: , saltbush, Atriplex vesicaria; Amaranthaceae) that prevent a toxic internal accumulation of salt. In other cases, trichomes help prevent predation by insects, and many plants produce secretory (glandular) or stinging hairs (e.g., stinging nettle, Urtica dioica; Urticaceae) for chemical defense against herbivores. In insectivorous plants, trichomes have

reptile: Hearing: …typically made up of a tympanum, a thin membrane located at the rear of the head; the stapes, a small bone running between the tympanum and the skull in the tympanic cavity (the middle ear); the inner ear; and a eustachian tube connecting the middle ear with the mouth cavity.…

atrium, in vertebrates and the higher invertebrates, heart chamber that receives blood into the heart and drives it into a ventricle, or chamber, for pumping blood away from the heart. Fishes have one atrium; amphibians, reptiles, birds, and mammals, two. In humans the atria are the two upper

atrium, in architecture, an open central court originally of a Roman house and later of a Christian basilica. In domestic and commercial architecture, the concept of the atrium experienced a revival in the 20th century. In Roman times the hearth was situated in the atrium. With the developing

Esther Boise Van Deman: …published her preliminary findings in The Atrium Vestae (1909). Van Deman extended her research to other kinds of concrete and brick constructions and published “Methods of Determining the Date of Roman Concrete Monuments” in The American Journal of Archaeology in 1912. Her basic methodology, with few modifications, became standard procedure…

Michael Moorcock: Ballard that later appeared in The Atrocity Exhibition (1970); Thomas Disch’s Camp Concentration (1968), about an American military camp where political prisoners are subjected to experiments to increase their intelligence; and Brian Aldiss’s Barefoot in the Head (1969), about the aftermath of a war in which Europe had been bombarded…

belladonna, (Atropa belladonna), tall bushy herb of the nightshade family (Solanaceae), the source of the crude drug of the same name. The highly poisonous plant is a native of wooded or waste areas in central and southern Eurasia. It grows to about 1.5 metres (4–5 feet) tall and has dull green

Azerbaijan, geographic region that comprises the extreme northwestern portion of Iran. It is bounded on the north by the Aras River, which separates it from independent Azerbaijan and Armenia; on the east by the Iranian region of Gīlān and the Caspian Sea; on the south by the Iranian regions of

Media: …the north was left to Atropates, a former general of Darius III, who succeeded in founding an independent kingdom, named Atropatene, with its capital at Gazaca. In later times Atropatene came under the control of Parthia, Armenia, and Rome.

digestive system disease: Mouth and oral cavity: A bald tongue (atrophic glossitis), with a smooth surface due to complete atrophy of the papillae, is associated with malnutrition, severe iron deficiency anemia, pernicious anemia, and pellagra, a disorder of skin and mucous membranes due to niacin deficiency. The condition is endemic in underdeveloped countries in which…

vaginitis: Atrophic vaginitis occurs in postmenopausal women because the lack of estrogen stimulation causes the surface membrane of the vagina to become thin, dry, and fragile, increasing the likelihood of infection. Hormone replacement therapy restores the protective surface and eliminates vaginitis.

atrophy, decrease in size of a body part, cell, organ, or other tissue. The term implies that the atrophied part was of a size normal for the individual, considering age and circumstance, prior to the diminution. In atrophy of an organ or body part, there may be a reduction in the number or in the

atropine, poisonous crystalline substance belonging to a class of compounds known as alkaloids and used in medicine. Atropine occurs naturally in belladonna (Atropa belladonna), from which the crystalline compound was first prepared in 1831. Since then, a number of synthetic and semisynthetic

Atropos, in Greek mythology, one of the three Fates, the others being Clotho and Lachesis. Atropos’s name (meaning “unalterable” or “inflexible”) indicates her function, that of rendering the decisions of her sisters irreversible or immutable. Atropos is most frequently represented with scales, a

Atryn, trade name of recombinant human antithrombin, an anticoagulant agent used to prevent thrombosis—the formation of a clot in a blood vessel that may block or impede the flow of blood, causing a potentially life-threatening condition. Atryn was developed by U.S.-based GTC Biotherapeutics and

Atrypa, genus of extinct brachiopods, or lamp shells, that has a broad time range and occurs abundantly as fossils in marine rocks from the Silurian through the Early Carboniferous (444 million to 318 million years ago). Many species of Atrypa have been described. The genus is easily recognized by