• acid lead (alloy)

    lead processing: The metal and its alloys: Acid lead, made by adding copper to fully refined lead, differs from chemical lead primarily in its higher bismuth content.

  • acid maltase deficiency (pathology)

    Pompe’s disease, hereditary defect in the body’s ability to metabolize glycogen, resulting in a muscle disorder that is usually fatal during the first year of life. The defect responsible, absence of the enzyme alpha-1,4-glucosidase, is extremely rare, occurring in fewer than one in every 150,000

  • acid phosphatase (enzyme)

    enzyme analysis: …hepatitis and obstructive jaundice; (4) acid phosphatase, an enzyme found in most body tissue but in unusually high concentration in the adult prostate gland; it is released into the circulation in metastatic cancer of the prostate; (5) peptidases, a group of enzyme-digesting proteins found in greater concentrations in the serum…

  • acid precipitation (pollution)

    acid rain, precipitation possessing a pH of about 5.2 or below primarily produced from the emission of sulfur dioxide (SO2) and nitrogen oxides (NOx; the combination of NO and NO2) from human activities, mostly the combustion of fossil fuels. In acid-sensitive landscapes, acid deposition can reduce

  • acid rain (pollution)

    acid rain, precipitation possessing a pH of about 5.2 or below primarily produced from the emission of sulfur dioxide (SO2) and nitrogen oxides (NOx; the combination of NO and NO2) from human activities, mostly the combustion of fossil fuels. In acid-sensitive landscapes, acid deposition can reduce

  • Acid Rain Program (United States government program)

    emissions trading: Acid rain and greenhouse gases: …large-scale practical application in the Acid Rain Program run by the U.S. Environmental Protection Agency in the 1990s. In 1990, amendments to the U.S. Clean Air Act of 1970 called for a halving of emissions of sulfur dioxide (SO2) within two decades, along with a parallel ambitious reduction in emissions…

  • acid rock (igneous rock)

    felsic and mafic rocks, division of igneous rocks on the basis of their silica content. Chemical analyses of the most abundant components in rocks usually are presented as oxides of the elements; igneous rocks typically consist of approximately 12 major oxides totaling over 99 percent of the rock.

  • acid-base catalysis (chemistry)

    acid-base catalysis, acceleration of a chemical reaction by the addition of an acid or a base, the acid or base itself not being consumed in the reaction. The catalytic reaction may be acid-specific (acid catalysis), as in the case of decomposition of the sugar sucrose into glucose and fructose in

  • acid-base equilibrium (chemical reaction)

    acid–base reaction: Acid–base equilibria: Certain general principles apply to any solvent with both acidic and basic properties—for example, water, alcohols, ammonia, amines, and acetic acid. Denoting the solvent molecule by SH, proton transfer can give rise to the ions SH2+ and S−, sometimes called lyonium and lyate…

  • acid–base reaction (chemistry)

    acid–base reaction, a type of chemical process typified by the exchange of one or more hydrogen ions, H+, between species that may be neutral (molecules, such as water, H2O; or acetic acid, CH3CO2H) or electrically charged (ions, such as ammonium, NH4+; hydroxide, OH−; or carbonate, CO32−). It also

  • acid-base titration (chemical process)

    titration: …the sample and titrant, include: acid-base titrations, precipitation titrations, complex-formation titrations, and oxidation-reduction (redox) titrations. In acid-base titration (i.e., the titration of an acid with a base, or vice versa), the indicator is a substance that can exist in two forms, an acid form and a basic form, which differ…

  • acid-copper lead (alloy)

    lead processing: The metal and its alloys: Acid lead, made by adding copper to fully refined lead, differs from chemical lead primarily in its higher bismuth content.

  • Acidalia Planitia (region, Mars)

    Mars: Sparsely cratered plains: These include Chryse Planitia and Acidalia Planitia (centered on 30° W longitude), Amazonis Planitia (160° W), and Utopia Planitia (250° W). The only significant relief in this huge area is a large ancient impact basin, informally called the Utopia basin (40° N, 250° W).

  • Acidithiobacillus ferrooxidans (bacterium)

    bacteria: pH: …sulfide deposits are attacked by A. ferrooxidans to generate sulfuric acid, which lowers the pH to 2.0 or even 0.7. However, acid tolerance of A. ferrooxidans applies only to sulfuric acid, since these bacteria die when exposed to equivalent concentrations of other acids such as hydrochloric acid. Many bacteria cannot…

  • acidity (chemistry)

    buffer: …the ionization constant of acetic acid and the expressions in brackets are the concentrations of the respective substances. The hydrogen ion concentration of the buffer solution is dependent on the relative amounts of acetic acid and acetate ion (or sodium acetate) present, known as the buffer ratio. The addition of…

  • acidity exponent (chemistry)

    acid–base reaction: Acid–base equilibria: …quantity pKa, sometimes called the acidity exponent, and defined by the relation pKa = −log10Ka. Values of pKa are generally of a more convenient magnitude.

  • acidity function (chemistry)

    acid–base reaction: Concentrated aqueous acids: …is commonly measured by the acidity function, H0, a quantity measured by the effect of the solvent on a basic indicator I. It is defined by H0 + pKih+ − log10 [IH+]/[I] and becomes equal to the pH in dilute solution. The acidity function H0 frequently is found to be…

  • acidophile (biology)

    extremophile: …organisms may be described as acidophilic (optimal growth between pH 1 and pH 5); alkaliphilic (optimal growth above pH 9); halophilic (optimal growth in environments with high concentrations of salt); thermophilic (optimal growth between 60 and 80 °C [140 and 176 °F]); hyperthermophilic (optimal growth above 80 °C [176 °F]);…

  • acidophilic organism (biology)

    extremophile: …organisms may be described as acidophilic (optimal growth between pH 1 and pH 5); alkaliphilic (optimal growth above pH 9); halophilic (optimal growth in environments with high concentrations of salt); thermophilic (optimal growth between 60 and 80 °C [140 and 176 °F]); hyperthermophilic (optimal growth above 80 °C [176 °F]);…

  • acidosis (pathology)

    acidosis, abnormally high level of acidity, or low level of alkalinity, in the body fluids, including the blood. There are two primary types of acidosis: respiratory acidosis and metabolic acidosis. Respiratory acidosis results from inadequate excretion of carbon dioxide from the lungs. This may be

  • acids and bases, proton theory of (chemistry)

    Brønsted-Lowry theory, a theory, introduced independently in 1923 by the Danish chemist Johannes Nicolaus Brønsted and the English chemist Thomas Martin Lowry, stating that any compound that can transfer a proton to any other compound is an acid, and the compound that accepts the proton is a base.

  • Acier Noir (typeface)

    Cassandre: …he designed two other typefaces, Acier Noir (1935) and Piegnot (1937). In 1939 he abandoned poster art and henceforth devoted himself to designing stage sets and to painting.

  • Acier, Michel Victor (French sculptor)

    pottery: Porcelain: …by the figure modelling of Michel Victor Acier, who came to the factory to share the position of Modellmeister with Kändler in 1764. From 1774 to 1814 the Neoclassical style was increasingly used, and the designs of Sèvres and of Wedgwood (Wedgwoodarbeit) were copied.

  • Aciéries Réunies de Burbach-Eich-Dudelange (Luxembourger company)

    Luxembourg: Manufacturing and trade: …the late 1970s ARBED (Aciéries Réunies de Burbach-Eich-Dudelange) SA was Luxembourg’s only remaining steelmaker. In 2001 ARBED merged with the Spanish company Aceralia and the French company Usinor to form Arcelor, which subsequently joined Mittal to create ArcelorMittal, the world’s largest steel company at the time of its formation…

  • Acilia Repetundarum, Lex (Roman law)

    epigraphy: Ancient Rome: …bce; pieces of the laws Lex Acilia Repetundarum (123 bce) and Lex Agraria (111 bce) were found in the 16th century on opposite sides of what was once a large bronze tablet; the local laws of the town of Bantia (on the borderlands of Lucania and Apulia in southern Italy)…

  • Acilius Glabrio (Roman consul)

    Marcus Porcius Cato: …Cato served with distinction under Manius Acilius Glabrio at Thermopylae in the war against the Seleucid king Antiochus III. Shortly thereafter he included Glabrio in his denunciation of the supporters of the Scipios. He then attacked Lucius Scipio and Scipio Africanus the Elder and broke their political influence. This success…

  • acinar cell (anatomy)

    pharmaceutical industry: Isolation of insulin: …destroyed by enzymes from the acinar cells. By this time Banting had enlisted the support of Charles H. Best, a fourth-year medical student. Together they tied off the pancreatic ducts through which acinar cells release the digestive enzymes. This insult caused the acinar cells to die. Subsequently, the remainder of…

  • Acinipo (Spain)

    Ronda, town, Málaga provincia (province), in the Andalusia comunidad autónoma (autonomous community), southern Spain. It lies in the Ronda Mountains west of Málaga city. The town is situated on two hills divided by a deep ravine (El Tajo de Ronda) containing the Grande River, which is an affluent

  • Acinonyx (mammal)

    feline: Evolution and classification: Acinonychinae Genus Acinonyx (cheetah) 1 almost exclusively African species. Assorted ReferencesAmazon Rain Forestclassification and characteristics

  • Acinonyx jubatus (mammal)

    cheetah, (Acinonyx jubatus), one of the world’s most-recognizable cats, known especially for its speed. Cheetahs’ sprints have been measured at a maximum of 114 km (71 miles) per hour, and they routinely reach velocities of 80–100 km per hour while pursuing prey. Nearly all the cheetahs remaining

  • Ačinsk (Russia)

    Achinsk, city, Krasnoyarsk kray (region), south-central Russia. It lies along the Chulym River, which is a tributary of the Ob. It was founded in 1621 and chartered in 1782. Important as a river-road transfer point until rail lines were constructed, it gained economic importance when an alumina

  • acinus (anatomy)

    respiratory disease: Morphological classification of respiratory disease: …terminal bronchiole opens into an acinus, so called because the structure resembles a cluster of grapes, and from this point onward the gas-exchanging portion of the lung is reached. The alveoli, or air sacs, which are divided into groups or lobules by fibrous partitions, or septa, are small hexagonal structures…

  • Acipenser baerii (fish)

    chondrostean: Distribution: The Baikal sturgeon (A. baerii) occurs in Lake Baikal and in nearby regions of Russia (Siberia), China, and Kazakhstan. A smaller species, the sterlet (A. ruthenus), inhabits the Black and Caspian seas. The starry

  • Acipenser fulvescens (fish)

    chondrostean: Distribution: The lake sturgeon of North America (A. fulvescens) occurs in the Mississippi River valley, in Lake Huron, and northward into Canada. The white, Oregon, or Sacramento sturgeon (A. transmontanus) inhabits the waters of the Pacific coast of North America from California to

  • Acipenser guldenstadtii (fish)

    sturgeon: Distribution: The Russian sturgeon, A. guldenstadtii, is one of the most valuable species inhabiting the rivers of Russia and occurs eastward to Lake Baikal. It is about the same size as the common sturgeon and is found particularly in the rivers feeding the Black and Caspian seas.…

  • Acipenser huso (fish)

    hausen, large species of sturgeon

  • Acipenser oxyrinchus (fish)

    chondrostean: Distribution: A closely related form (A. oxyrinchus) is found along the east coast of North America from the St. Lawrence River to the Gulf of Mexico. The Baikal sturgeon (A. baerii) occurs in Lake Baikal and in nearby regions of Russia (Siberia), China, and Kazakhstan. A

  • Acipenser ruthenus (fish)

    caviar: …the golden eggs of the sterlet, was formerly reserved for the table of the tsar; more recently it found its way to the tables of Soviet dignitaries and that of the shah of Iran. Lesser grades of caviar, made from broken or immature eggs, are more heavily salted and compressed.…

  • Acipenser sinensis (fish)

    sturgeon: Conservation status: The Chinese sturgeon is thought to be the species most at risk, because its population declined nearly 98 percent between 1973 and 2010. The species decline has been associated with water pollution in the Yangtze and dam construction that has blocked access to or changed the…

  • Acipenser stellatus (fish)

    chondrostean: Distribution: The starry sturgeon (A. stellatus) occurs in rivers leading to the Black Sea, the Sea of Azov, and the Caspian Sea. The lake sturgeon of North America (A. fulvescens) occurs in the Mississippi River valley, in Lake Huron, and northward into Canada. The white, Oregon, or…

  • Acipenser sturio (fish)

    chondrostean: Distribution: The common sturgeon (Acipenser sturio; also known as the Atlantic, or Baltic, sturgeon) is found along the European coast from Norway to the Mediterranean Sea. A closely related form (A. oxyrinchus) is found along the east coast of North America from the St. Lawrence River to…

  • Acipenser transmontanus (fish)

    chondrostean: Distribution: …Oregon, or Sacramento sturgeon (A. transmontanus) inhabits the waters of the Pacific coast of North America from California to Alaska. The shovelnose sturgeons (genus Scaphirhynchus) occur in the Mississippi drainage system of North America. The Aral Sea shovelnose sturgeons (Pseudoscaphirhynchus) are found in rivers that drain into the

  • Acipenseridae (fish)

    sturgeon, (family Acipenseridae), any of about 29 species of fishes of the family Acipenseridae (subclass Chondrostei), native to temperate waters of the Northern Hemisphere. Most species live in the ocean and ascend rivers (possibly once in several years) to spawn in spring or summer; a few others

  • Acipenseriformes (fish order)

    fish: Annotated classification: Order Acipenseriformes (sturgeons and paddlefishes) Almost no internal ossification; scales as large scutes in isolated rows (Acipenseridae); snout enlarged and tactile (Polyodontidae); median fins chondrostean in having more fin rays than basal elements; tail heterocercal. Length (sturgeons) up to 6 metres (roughly 20 feet), weight to…

  • Acireale (Italy)

    Acireale, town and episcopal see, eastern Sicily, Italy, on terraces above the Ionian Sea at the foot of Mount Etna, 7 miles (11 km) northeast of Catania. Known as Aquilia by the Romans, the town was called Reale by Philip IV of Spain in 1642. The first part of its name is derived from the ancient

  • Acis (Greek mythology)

    Acis, in the Greek mythology of Ovid, the son of Faunus (Pan) and the nymph Symaethis. He was a beautiful shepherd of Sicily, the lover of the Nereid Galatea. His rival, Polyphemus the Cyclops, surprised them together and crushed him to pieces with a rock. His blood, gushing forth from beneath, was

  • Acis and Galatea (serenata by Handel)

    serenata: …genre is Handel’s pastoral serenata Acis and Galatea (c. 1718).

  • Acis et Galatée (ballet by Fokine)

    Michel Fokine: …performance by his pupils, was Acis et Galatée, based on an ancient Sicilian legend. Fokine’s enthusiasm for antiquity owed nothing in origin to the “free dance” ideas of the American dancer Isadora Duncan, although her appearance in Russia in 1905 greatly consolidated his own views. In 1905 he also composed…

  • Acis in Oxford (work by Finch)

    Robert Finch: …as did a later work, Acis in Oxford (1961), a series of meditations inspired by a performance of G.F. Handel’s dramatic oratorio Acis and Galatea. Dover Beach Revisited (1961), treating the World War II evacuation of Dunkirk and issues of faith, contains 11 variations on Matthew Arnold’s poem. In another…

  • Acisoma attenboroughi (dragonfly)

    10 Organisms Named for David Attenborough: Attenborough’s pintail: • What: striking blue and black dragonfly with intricately veined wings. An agile flier, the insect is common in rice paddies and near bodies of fresh water in its native range.

  • aCJD

    Creutzfeldt-Jakob disease: Types: acquired (aCJD). Both sCJD and aCJD may be further divided into subtypes. The most common sCJD subtype is sCJDMM1. Subtypes of aCJD include iatrogenic (iCJD) and variant (vCJD) forms of the disease (kuru is sometimes considered a third subtype of aCJD).

  • AcK (isotope)

    francium: …an isotope of francium (francium-223) that was formerly called actinium K (AcK) and is a member of the actinium decay series. Though it is the longest-lived isotope of francium, francium-223 has a half-life of only 22 minutes. Thirty-four isotopes of francium with masses between 199 and 232 have been…

  • Ack libertas, tu ädla tingh (work by Wivallius)

    Lars Wivallius: …1632 and translates as “Ah, Liberty, Thou Noble Thing”) and love of nature (most notably the majestic “Klagovisa över denna torra och kalla vår” [1642; “Dirge over This Dry and Cold Spring”], in which the poet laments the season that he encountered upon his release from Kajaneborg).

  • ackee (plant)

    ackee, (Blighia sapida), tree of the soapberry family (Sapindaceae) native to West Africa, widely cultivated throughout tropical and subtropical regions for its edible fruit. Ackee and salt fish is a popular dish in the Caribbean and is the national dish of Jamaica. Taken to the Caribbean area with

  • Acker, Kathy (American author)

    Kathy Acker was an American novelist whose writing style and subject matter reflect the so-called punk sensibility that emerged in the 1970s. Acker’s novels combine autobiography and fiction that she deliberately plagiarized from other writers in an effort to dismantle concepts of identity and

  • Ackerley, J.R. (British writer and editor)

    J.R. Ackerley was a British novelist, dramatist, poet, and magazine editor known for his eccentricity. Ackerley’s education was interrupted by his service in World War I, during which he was captured and imprisoned for eight months in Germany. He graduated from Magdalen College, Cambridge, in 1921.

  • Ackerley, Joe Randolph (British writer and editor)

    J.R. Ackerley was a British novelist, dramatist, poet, and magazine editor known for his eccentricity. Ackerley’s education was interrupted by his service in World War I, during which he was captured and imprisoned for eight months in Germany. He graduated from Magdalen College, Cambridge, in 1921.

  • Ackerman, Diane (American author)

    Diane Ackerman is an American writer whose works often reflect her interest in natural science. Ackerman was educated at Pennsylvania State University (B.A., 1970) and Cornell University, Ithaca, N.Y. (M.F.A., 1973; M.A., 1976; Ph.D., 1978). From 1980 to 1983 she taught English at the University of

  • Ackerman, Edward A. (American geographer)

    geography: Geography as a science: a new research agenda: …well to the war effort: Edward A. Ackerman, a professor of geography at the University of Chicago from 1948 to 1955 (and later head of the Carnegie Foundation), claimed that those working in the U.S. government’s intelligence service had only a weak understanding of their material and portrayed them as…

  • Ackermann aus Böhmen, Der (work by Johannes von Tepl)

    Johannes von Tepl: 1400; Death and the Ploughman), the first important prose work in the German language.

  • Ackermann system (mechanics)

    truck: Steering: Steering is always by the Ackermann system, which provides a kingpin for each front wheel. Maximum cramp angle of the front wheels is about 35 degrees. The minimum turning radius is dependent on the wheelbase. A few vehicles have been built with two steering axles in the front.

  • Ackermann, Haider (French fashion designer)

    Timothée Chalamet: Red carpet fashion: …has favored such designers as Haider Ackermann, Alexander McQueen, and Stella McCartney. A few of Chalamet’s more daring looks included a Virgil Abloh sequin harness that he sported at the 2019 Golden Globe Awards and a cropped shimmering jacket from Louis Vuitton’s women’s wear line, under which he wore nothing,…

  • Ackermann, Konrad Ernst (German actor and manager)

    Konrad Ernst Ackermann was an actor-manager who was a leading figure in the development of German theatre. Conflicting accounts exist of Ackermann’s early adult years. He was probably not a trained scientist and surgeon, as has been widely reported, but was instead a soldier—and later an officer—in

  • Ackermann, Louise-Victorine (French poet)

    Louise-Victorine Ackermann was a French poet who is best-known for works characterized by a deep sense of pessimism. Educated by her father in the philosophy of the Encyclopédistes, she traveled to Berlin in 1838 to study German and there married (1843) Paul Ackermann, an Alsatian philologist. Two

  • Ackermann, Wilhelm (German logician)

    history of logic: Propositional and predicate logic: …Theoretical Logic”) by Hilbert and Wilhelm Ackermann.

  • Ackman, William Albert (American investor)

    William Albert “Bill” Ackman (born May 11, 1966, Chappaqua, New York, U.S.), is an American billionaire hedge fund manager. Ackman is the founder and chief executive officer (CEO) of Pershing Square Capital Management. Throughout his career, Ackman had a reputation as an activist investor—a

  • Ackoli (work by Holub)

    Miroslav Holub: … (1963; “The So-Called Heart”), and Ačkoli (1969; Although).

  • Ackroyd, Peter (British author, biographer, critic and scholar)

    Peter Ackroyd is a British novelist, critic, biographer, and scholar whose technically innovative novels present an unconventional view of history. Ackroyd graduated from Clare College, Cambridge (M.A., 1971), and then attended Yale University for two years. In 1973 he returned to England and

  • ACL (anatomy)

    anterior cruciate ligament (ACL), thick band of connective tissue that joins the femur to the tibia. Its primary function is to provide stability to the knee. Injuries to the anterior cruciate ligament (ACL) are among the most common types of trauma affecting the knee, being especially common among

  • Aclla Cuna (Inca religion)

    Chosen Women, in Inca religion, women who lived in temple convents under a vow of chastity. Their duties included the preparation of ritual food, the maintenance of a sacred fire, and the weaving of garments for the emperor and for ritual use. They were under the supervision of matrons called Mama

  • ACLU (ProCon debate)

    ARCHIVED TOPIC: This topic was archived on Dec. 15, 2021 and will no longer be updated. Since its creation on Jan. 19, 1920, the American Civil Liberties Union (ACLU) has often been at the center of controversy and public debate. They have taken on issues ranging from abortion, the death penalty,

  • ACLU (American organization)

    American Civil Liberties Union (ACLU), organization founded by Roger Baldwin and others in New York City in 1920 to champion constitutional liberties in the United States. The ACLU works to protect Americans’ constitutional rights and freedoms as set forth in the U.S. Constitution and its

  • ACM (international organization)

    Association for Computing Machinery (ACM), international organization for computer science and information technology professionals and, since 1960, institutions associated with the field. Since 1966 ACM has annually presented one or more individuals with the A.M. Turing Award, the most prestigious

  • Acmaeidae (gastropod family)

    gastropod: Classification: …in rocky shallow waters (Acmaeidae and Patellidae). Superfamily Trochacea Small to large spiral shells in shallow to deep ocean waters, often brightly coloured, with or without heavy shell ornamentation; Trochidae (top shells), Turbinidae (turban shells), and Phasianellidae (pheasant shells

  • Acme Colored Giants (American sports team)

    baseball: Segregation: …during 19th century were the Acme Colored Giants, who represented Celoron, New York, in the Iron and Oil Leagues in 1898.

  • Acmeist (Russian poets)

    Acmeist, member of a small group of early-20th-century Russian poets reacting against the vagueness and affectations of Symbolism. It was formed by the poets Sergey Gorodetsky and Nikolay S. Gumilyov. They reasserted the poet as craftsman and used language freshly and with intensity. Centred in St.

  • acmite (mineral)

    aegirine: In this series, the name acmite is given to crystals with the composition NaFeSi2O6 as well as to the reddish brown or greenish black pointed crystals approximating that composition. Aegirine generally is restricted to the dark green to greenish black, blunt crystals of the same composition. For detailed physical properties,…

  • ACNA

    Anglican Church in North America (ACNA), Anglican church formed in 2009 in Bedford, Texas. Its founders were theological traditionalists who had seceded from the Episcopal Church and the Anglican Church of Canada. It is not one of the 42 churches formally recognized by the Anglican Communion, the

  • acne (dermatology)

    acne, any inflammatory disease of the sebaceous, or oil, glands of the skin. There are some 50 different types of acne. In common usage, the term acne is frequently used alone to designate acne vulgaris, or common acne, probably the most prevalent of all chronic skin disorders. Acne vulgaris

  • acne vulgaris (dermatology)

    childhood disease and disorder: Disorders associated with adolescence: Acne vulgaris (common acne) is a prevalent skin condition that has its onset during adolescence. At puberty, androgenic stimulation of the skin’s sebaceous (oil) glands (which empty into the canals of the hair follicles) causes increased production of the fatty substance sebum. In susceptible individuals,…

  • ACO (international organization)

    North Atlantic Treaty Organization: Organization: …states, subsumes two strategic commands: Allied Command Operations (ACO) and Allied Command Transformation (ACT). ACO is headed by the SACEUR and located at Supreme Headquarters Allied Powers Europe (SHAPE) in Casteau, Belgium. ACT is headquartered in Norfolk, Virginia, U.S. During the alliance’s first 20 years, more than $3 billion worth…

  • Acochlidacea (gastropod order)

    gastropod: Classification: Order Acochlidacea Three families with visceral mass longer than foot; 4 species in fresh water; a few with sexes in separate animals; size minute. Order Philinoglossacea No head appendages; gill lacking; no external shell; 2 families. Order Anaspidea Shell reduced

  • Acoela (flatworm order)

    flatworm: Annotated classification: Order Acoela Exclusively marine; mouth present; pharynx simple or lacking; no intestine; without protonephridia, oviducts, yolk glands, or definitely delimited gonads; about 200 species. Order Neorhabdocoela Saclike linear intestine; protonephridia and oviducts usually present; gonads few, mostly compact; nervous system generally with 2 longitudinal

  • acoelomate (biology)

    animal: Acoelomates: Flatworms (phyla Platyhelminthes, Nemertea, and Mesozoa) lack a coelom, although nemerteans have a fluid-filled cavity at their anterior, or head, end, which is used to eject the proboscis rapidly. The lack of a fluid-filled cavity adjacent to the muscles reduces the extent to which…

  • Acoemetae (Byzantine monks)

    Acoemeti, monks at a series of 5th- to 6th-century Byzantine monasteries who were noted for their choral recitation of the divine office in constant and never interrupted relays. Their first monastery, at Constantinople, was founded in about 400 by St. Alexander Akimetes, who, after long study of

  • Acoemeti (Byzantine monks)

    Acoemeti, monks at a series of 5th- to 6th-century Byzantine monasteries who were noted for their choral recitation of the divine office in constant and never interrupted relays. Their first monastery, at Constantinople, was founded in about 400 by St. Alexander Akimetes, who, after long study of

  • Acolhua (people)

    Texcoco: …Valley of Mexico by the Acolhuas, a pre-Columbian people of the Nahuatl-speaking group of tribes, which gained mastery of the valley after the collapse of the Toltec hegemony in the mid-12th century ad. The rulers of Texcoco were the first among Nahuatl tribal leaders to establish their rule over Anáhuac…

  • Acoli (people)

    Acholi, ethnolinguistic group of northern Uganda and South Sudan. Numbering more than one million at the turn of the 21st century, they speak a Western Nilotic language of the Eastern Sudanic branch of the Nilo-Saharan family and are culturally and historically related to their traditional enemies,

  • acolyte (religion)

    acolyte, (from Greek akolouthos, “server,” “companion,” or “follower”), in the Roman Catholic church, a person is installed in a ministry in order to assist the deacon and priest in liturgical celebrations, especially the eucharistic liturgy. The first probable reference to the office dates from

  • Acoma (pueblo, New Mexico, United States)

    Acoma, Indian pueblo, Valencia county, west-central New Mexico, U.S. The pueblo lies 55 miles (89 km) west-southwest of Albuquerque and is known as the “Sky City.” Its inhabitants live in terraced dwellings made of stone and adobe atop a precipitous sandstone butte 357 feet (109 metres) high. They

  • Acoma (people)

    Ancestral Pueblo culture: Zuni, Acoma, and Laguna. As farmers, Ancestral Pueblo peoples and their nomadic neighbours were often mutually hostile; this is the source of the term Anasazi, a Navajo word meaning “ancestors of the enemy,” which once served as the customary scientific name for this group.

  • Acominatus, Michael (Byzantine historian)

    Michael Choniates was a Byzantine humanist scholar and archbishop of Athens whose extensive Classical literary works provide the principal documentary witness to the political turbulence of 13th-century Greece after its occupation by the Western Crusaders. Having studied at Constantinople

  • Acominatus, Nicetas (Byzantine historian)

    Nicetas Choniates was a Byzantine statesman, historian, and theologian. His chronicle of Byzantium’s humiliations during the Third and Fourth Crusades (1189 and 1204) and his anthology of 12th-century theological writings constitute authoritative historical sources for this period and established

  • Acomys (rodent)

    African spiny mouse, (genus Acomys), any of more than a dozen species of small to medium-sized rodents characterized by the harsh, inflexible spiny hairs of their upperparts. African spiny mice have large eyes and ears and scaly, nearly bald tails that are shorter than or about as long as the body.

  • Acomys cahirinus (mammal)

    African spiny mouse: …golden spiny mouse and the Cairo spiny mouse (A. cahirinus).

  • Acomys cilicicus (mammal)

    African spiny mouse: The most restricted is A. cilicicus, which is known only from a single locality in southern Turkey.

  • Acomys kempi (mammal)

    African spiny mouse: …species native to East Africa, Kemp’s spiny mouse (A. kempi) and Percival’s spiny mouse (A. percivali), possess the ability to slough off patches of skin when attempting to escape capture from predators. The wounds that remain, which may be painful in appearance, may shrink dramatically within the first 24 hours…

  • Acomys percivali (mammal)

    African spiny mouse: kempi) and Percival’s spiny mouse (A. percivali), possess the ability to slough off patches of skin when attempting to escape capture from predators. The wounds that remain, which may be painful in appearance, may shrink dramatically within the first 24 hours after the injury. They are covered…

  • Acomys russatus (mammal)

    African spiny mouse: The golden spiny mouse (Acomys russatus), found from Egypt to Saudi Arabia, is one of the largest, with a body up to 25 cm (9.8 inches) long and a shorter tail of up to 7 cm. The Cape spiny mouse (A. subspinosus) of South Africa is…

  • Acomys subspinosus (mammal)

    African spiny mouse: The Cape spiny mouse (A. subspinosus) of South Africa is one of the smallest, with a body up to 10 cm long and a tail of less than 2 cm. Depending upon the species, fur covering the upperparts may be gray, grayish yellow, brownish red, or…