Pythagoreanism: Two Pythagorean sects: The acousmatics devoted themselves to the observance of rituals and rules and to the interpretation of the sayings of the master; the “mathematics” were concerned with the scientific aspects of Pythagoreanism. Philolaus, who was rather a mathematic, probably published a summary of Pythagorean philosophy and science…

sound: Sound absorption: In addition to the geometric decrease in intensity caused by the inverse square law, a small part of a sound wave is lost to the air or other medium through various physical processes. One important process is the direct conduction of the vibration…

human ear: Audiometry: …obtained by means of the acoustic bridge—a device that enables the examiner to listen simultaneously to a sound reflected from the tympanic membrane of the subject and a sound of equal intensity reflected in an artificial cavity, with the volume being adjusted to equal that of the external canal of…

sonar: …category of sonar devices is acoustic communication systems, which require a projector and receiver at both ends of the acoustic path.

ultrasonics: Materials testing: …to stress and looking for acoustic emissions as the materials are stressed. Acoustic emission, the general name for this type of nondestructive study, has developed as a distinct field of acoustics.

sound: Acoustic filtration: Filtration of sound plays an important part in the design of air-handling systems. In order to attenuate the level of sound from blower motors and other sources of vibration, regions of larger or smaller cross-sectional area are inserted into air ducts, as illustrated in…

gas meter: Acoustic gas meters measure the rate of gas flow by comparing the frequency shifts of two initially identical signals (one sent upstream, the other downstream) after they are reflected.

guitar, plucked stringed musical instrument that probably originated in Spain early in the 16th century, deriving from the guitarra latina, a late-medieval instrument with a waisted body and four strings. The early guitar was narrower and deeper than the modern guitar, with a less pronounced waist.

acoustic impedance, absorption of sound in a medium, equal to the ratio of the sound pressure at a boundary surface to the sound flux (flow velocity of the particles or volume velocity, times area) through the surface. In analogy to electrical circuit theory, pressure corresponds to voltage, volume

sound intensity, amount of energy flowing per unit time through a unit area that is perpendicular to the direction in which the sound waves are travelling. Sound intensity may be measured in units of energy or work—e.g., microjoules (10-6 joule) per second per square centimetre—or in units of

acoustic interferometer, device for measuring the velocity and absorption of sound waves in a gas or liquid. A vibrating crystal creates the waves that are radiated continuously into the fluid medium, striking a movable reflector placed accurately parallel to the crystal source. The waves are then

senses: Mechanical senses: …of hair cells known as maculae. Within each maculae, the stereocilia are embedded in a gelatinous mass known as the otolithic membrane, which contains small stonelike calcium carbonate particles called otoconia. The otolithic membrane and otoconia bend the hairs in the direction of gravity, providing the animal with a vertical…

external auditory canal, passageway that leads from the outside of the head to the tympanic membrane, or eardrum membrane, of each ear. The structure of the external auditory canal is the same in all mammals. In appearance it is a slightly curved tube that extends inward from the floor of the

acoustic microscope, instrument that uses sound waves to produce an enlarged image of a small object. In the early 1940s Soviet physicist Sergey Y. Sokolov proposed the use of ultrasound in a microscope and showed that sound waves with a frequency of 3,000 megahertz (MHz) would have a resolution

mine: Submarine mine: Acoustic mines once depended on hydrophones to pick up the sound made by a ship’s propellers when the ship came within range. They had limited lifetimes owing to deterioration of their components, but techniques related to sonar and microelectronics technology have made acoustic mines more…

vestibulocochlear nerve, nerve in the human ear, serving the organs of equilibrium and of hearing. It consists of two anatomically and functionally distinct parts: the cochlear nerve, distributed to the hearing organ, and the vestibular nerve, distributed to the organ of equilibrium. The cochlear

acoustic neuroma, benign tumour occurring anywhere along the vestibulocochlear nerve (also called acoustic nerve), which originates in the ear and serves the organs of equilibrium and hearing. The tumour arises from an overproduction of Schwann cells, the myelin-producing cells that surround the

sound: Impedance: …per cubic metre, called an acoustic ohm, by analogy to electrical impedance.

Kwame Alexander: Acoustic Rooster and His Barnyard Band (2011) introduces jazz to young children through animals. Surf’s Up (2016) follows the adventures of two frogs, one who likes to read and the other who likes to surf. In Animal Ark: Celebrating Our Wild World in Poetry and…

scansion: …oscillograph are used by modern acoustic linguists to catch even slightly varying degrees of stress.

nervous system: Arthropods: A five-tissue strand, the acoustic sensillum, runs from the centre of the tympanic membrane across the tympanic cavity to a nearby skeletal support. This sensillum has two acoustic sensory receptors, called A cells. From the central end of each A cell, an axon passes within the sensillum to the…

electromechanical transducer: Electromagnetic speakers: …type of enclosure is the acoustic suspension system, in which the loudspeaker is mounted in an airtight box. To prevent resonances in the box of the type described by equation (36) in the article sound, the inside is generally coated with some sound-absorbent material. Because of the airtight seal, the…

electromechanical transducer: any type of device that either converts an electrical signal into sound waves (as in a loudspeaker) or converts a sound wave into an electrical signal (as in the microphone). Many of the transducers used in everyday life operate in both directions, such as the…

acoustic trauma, physiological changes in the body caused by sound waves. Sound waves cause variations in pressure, the intensity of which depends upon the range of oscillation, the force exerting the sound, and the distribution of waves. Excessive noise exposures can cause hearing loss and produce

theatre: Acoustics: …centred on the problem of acoustics in the ancient theatre. The difficulty in achieving audibility to an audience of thousands, disposed around three-fifths to two-thirds of a full circular orchestra in the open air, seems to have been insoluble so long as the performer remained in the orchestra. A more…

electromechanical transducer: Electromagnetic speakers: A horn enclosure uses a flared tube to obtain the best acoustic coupling between the loudspeaker cone and the outside, thereby radiating the best possible coherent wave from the speaker cone. Such a system is extremely efficient and is therefore used in public-address systems, open-air theatres,…

acoustics: Acoustic problems: Acoustic shadows, regions in which some frequency regions of sound are attenuated, can be caused by diffraction effects as the sound wave passes around large pillars and corners or underneath a low balcony. Large reflectors called clouds, suspended over the performers, can be of such…

mechanoreception: Mechanoreceptor function: …of these organs as the acoustico-lateralis system. The nerves to all the sense organs of the system arise from a common neural centre (called the acoustic tubercle in the wall of the brain’s medulla oblongata). Among amphibians such as frogs, lateral-line organs and their neural connections disappear during the metamorphosis…

acoustics, the science concerned with the production, control, transmission, reception, and effects of sound. The term is derived from the Greek akoustos, meaning “heard.” Beginning with its origins in the study of mechanical vibrations and the radiation of these vibrations through mechanical

architectural acoustics, Relationship between sound produced in a space and its listeners, of particular concern in the design of concert halls and auditoriums. Good acoustic design takes into account such issues as reverberation time; sound absorption of the finish materials; echoes; acoustic

metabolism: Fatty acids: …relatively small molecule known as acyl-carrier protein (ACP–SH); in higher organisms ACP–SH is part of a multienzyme complex called fatty acid synthetase. ACP–SH is involved in all of the reactions leading to the synthesis of a fatty acid such as palmitic acid from acetyl coenzyme A and malonyl coenzyme A.…

metabolism: Fatty acids: …relatively small molecule known as acyl-carrier protein (ACP–SH); in higher organisms ACP–SH is part of a multienzyme complex called fatty acid synthetase. ACP–SH is involved in all of the reactions leading to the synthesis of a fatty acid such as palmitic acid from acetyl coenzyme A and malonyl coenzyme A.…

Passaic, city, Passaic county, northeastern New Jersey, U.S., on the Passaic River, 9 miles (14 km) north of Newark. It was established by the Dutch in 1678 as a fur-trading post. In 1685 Hartman Michielson purchased the site, then called Acquackanonk, from the Delaware Indians. It was renamed for

date rape, a term used largely in industrialized countries to describe the forcing or coercing of a victim into unwanted sexual activity by a friend, romantic suitor, or peer through violence, verbal pressure, misuse of authority, use of incapacitating substances, or threat of violence. Although

Carlo Emilio Gadda: …del dolore (1963, revised 1970; Acquainted with Grief) is autobiographical, though its setting is transferred from modern Italy to an invented South American country.

Acquainted with the Night, novel by Heinrich Böll, published in German in 1953 as Und sagte kein einziges Wort (“And Said Not a Single Word”). One of Böll’s best-known works, the novel is set in Germany just after World War II. It examines the marriage of Fred and Käthe Bogner, who alternately

Claudio Aquaviva was the fifth and youngest general of the Society of Jesus, considered by many to have been the order’s greatest leader. The youngest son of the Duke of Atri, he joined the order in 1567. Shortly after completing his studies he was appointed provincial superior of Naples and then

personality assessment: Personality inventories: The response set called acquiescence, for example, refers to one’s tendency to respond with “true” or “yes” answers to questionnaire items regardless of what the item content is. It is conceivable that two people might be quite similar in all respects except for their tendency toward acquiescence. This difference…

acquired character, in biology, modification in structure or function acquired by an organism during its life, caused by environmental factors. With respect to higher organisms, there is no evidence that such changes are transmissible genetically—the view associated with Lamarckism—but, among

Jean-Baptiste Lamarck: The inheritance of acquired characters: In 1800 Lamarck first set forth the revolutionary notion of species mutability during a lecture to students in his invertebrate zoology class at the National Museum of Natural History. By 1802 the general outlines of his broad theory of organic transformation…

Christianity: Christian mysticism: …prayer and the distinction between acquired contemplation, for which the believer could strive with the help of grace, and infused contemplation, which was a pure and unmerited gift, framed much of this discussion. Other Roman Catholic theologians, such as Cuthbert Butler in Western Mysticism (1922) and Anselm Stolz in Theologie…

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).

AIDS, transmissible disease of the immune system caused by the human immunodeficiency virus (HIV). HIV is a lentivirus (literally meaning “slow virus”; a member of the retrovirus family) that slowly attacks and destroys the immune system, the body’s defense against infection, leaving an individual

immune system: Specific, acquired immunity: It has been known for centuries that persons who contract certain diseases and survive generally do not catch those illnesses again. Greek historian Thucydides recorded that, when the plague was raging in Athens during the 5th century bce, the sick and dying…

AIDS, transmissible disease of the immune system caused by the human immunodeficiency virus (HIV). HIV is a lentivirus (literally meaning “slow virus”; a member of the retrovirus family) that slowly attacks and destroys the immune system, the body’s defense against infection, leaving an individual

Sir Macfarlane Burnet: …Medicine for the discovery of acquired immunological tolerance, the concept on which tissue transplantation is founded.

megacolon: …megacolon, or Hirschsprung disease, and acquired megacolon. In congenital megacolon, the lowermost portion of the large intestine is congenitally lacking in normal nerve fibres; thus, peristalsis, or involuntary contractions, of the muscles of this part of the intestine cannot occur, and the bowel’s contents are not pushed onward. The area…

ptosis: Acquired ptosis has many potential causes, but it is usually due to age-related stretching or displacement of the fibres connecting the levator palpebrae superioris muscle to structures within the upper eyelid. It can also result from muscular diseases (such as muscular dystrophy or myasthenia gravis)…

strabismus: Acquired strabismus appears later in life and has many potential etiologies. For example, acquired strabismus can be due to diseases or trauma affecting the actual muscles responsible for moving the eye or the nerves or brain stem centres controlling those muscles. In addition, poor vision…

agnosia: Types of agnosia: In young children, acquired verbal auditory agnosia, which is a symptom of Landau-Kleffner syndrome, may lead to mutism, or loss of the ability or will to speak. The sensory organ of hearing is intact, and pure tones can be perceived. Individuals with amusia are unable to recognize that…

memory: Patterns of acquisition in working memory: In the course of a typical day, humans receive a continuous stream of information from the world around them as well as from their own thought processes and physical experiences. They manage this constant stimulation through a combination of conscious and…

adverse possession, in Anglo-American property law, holding of property under some claim of right with the knowledge and against the will of one who has a superior ownership interest in the property. Its legal significance is traced back to the English common-law concept known as seisin, a

Richard Henry Tawney: …most provocative and influential book, The Acquisitive Society (1920), he held that the acquisitiveness of capitalist society was a morally wrong motivating principle. Acquisitiveness, he said, corrupted both rich and poor. He argued that in capitalist societies work is deprived of its inherent value and thus becomes drudgery, for it…

acquittal, in criminal law, acknowledgment by the court of the innocence of the defendant or defendants. Such a judgment may be made by a jury in a trial or by a judge who rules that there is insufficient evidence either for conviction or for further proceedings. An acquittal removes all guilt in

Lepidoptera: Annotated classification: …complexes; most of the pantropical Acraeinae are also highly protected and aposematic models; some nymphalids, such as the monarch butterfly, are migratory. Family Pieridae (white, orange-tip, and sulfur butterflies) Approximately 1,000 small to medium-size species; no native species are found in New

Agrigento, city, near the southern coast of Sicily, Italy. It lies on a plateau encircled by low cliffs overlooking the junction of the Drago (ancient Hypsas) and San Biagio (Acragas) rivers and is dominated from the north by a ridge with twin peaks. Agrigento was a wealthy ancient city founded

cephalochordate, any of more than two dozen species belonging to the subphylum Cephalochordata of the phylum Chordata. Small, fishlike marine invertebrates, they probably are the closest living relatives of the vertebrates. Cephalochordates and vertebrates have a hollow, dorsal nerve cord,

Acrasieae, class name for cellular slime molds (division Myxomycophyta). The class contains a single order, Acrasiales, and about a dozen species. The vegetative phase of these slime molds consists of amoeba-like cells (myxamoebas) that group together ultimately to form a fruiting (reproductive)

Acrasieae: …class contains a single order, Acrasiales, and about a dozen species. The vegetative phase of these slime molds consists of amoeba-like cells (myxamoebas) that group together ultimately to form a fruiting (reproductive) structure.

Acrasieae, class name for cellular slime molds (division Myxomycophyta). The class contains a single order, Acrasiales, and about a dozen species. The vegetative phase of these slime molds consists of amoeba-like cells (myxamoebas) that group together ultimately to form a fruiting (reproductive)

Acrasieae, class name for cellular slime molds (division Myxomycophyta). The class contains a single order, Acrasiales, and about a dozen species. The vegetative phase of these slime molds consists of amoeba-like cells (myxamoebas) that group together ultimately to form a fruiting (reproductive)

Acre, city, northwestern Israel. It lies along the Mediterranean Sea, at the north end of the Bay of Haifa (formerly Bay of Acre). Its natural harbor was a frequent target for Palestine’s many invaders over the centuries. The earliest mention of Acre is in an Egyptian text dating from the 19th

acre, unit of land measurement in the British Imperial and United States Customary systems, equal to 43,560 square feet, or 4,840 square yards. One acre is equivalent to 0.4047 hectare (4,047 square metres). Derived from Middle English aker (from Old English aecer) and akin to Latin ager (“field”),

Acre, westernmost estado (state) of Brazil. Acre covers the southwesternmost part of Brazil’s Hiléia (Hylea), the forest zone of the Amazon River basin. Bounded north by Amazonas state, it has western and southern frontiers with Peru and southeastern with Bolivia. The capital is Rio Branco on the

Acre River, river, chiefly in western Brazil, rising on the Peruvian border, along which it continues eastward to form part of the Brazil–Bolivia border. Turning north at Brasiléia, the remainder of its 400-mi (645-km) course flows in a north-northeasterly direction, through the Brazilian states of

Palestine: Land: The most northerly is the Plain of Acre, which extends with a breadth of 5 to 9 miles (8 to 14 km) for about 20 miles (32 km) from the Lebanon border in the north to the Carmel promontory, in Israel, in the south, where it narrows to a mere…

Acre River, river, chiefly in western Brazil, rising on the Peruvian border, along which it continues eastward to form part of the Brazil–Bolivia border. Turning north at Brasiléia, the remainder of its 400-mi (645-km) course flows in a north-northeasterly direction, through the Brazilian states of

Siege of Acre, Napoleon’s unsuccessful siege of the Ottoman-controlled, walled city of Acre (today in northwest Israel) that lasted from March 18 to May 20, 1799. It was his first setback in the Egyptian campaign and one of his few defeats, and it marked the end of his hopes of carving out an

John Boehner: Later career: …joined the advisory board of Acreage Holdings, a cannabis company. Boehner, who had earlier opposed the legalization of marijuana, stated that his views had “evolved.” He later released the memoir On the House (2021), in which he was sharply critical of the Republican Party, especially former president Donald Trump, whom…

Russell Conwell: Conwell delivered his lecture “Acres of Diamonds” no fewer than 6,000 times. The theme of the lecture was that opportunity lurks in everyone’s backyard. Everyone, Conwell believed, can and ought to get rich and then use that money for the good of others. “Keep clean, fight hard, pick your…

rocket and missile system: Air-to-air: …medium-range radar-guided missile, while the AA-6 Acrid was similar to the Anab but larger and with greater range. The AA-7 Apex, a Sparrow equivalent, and the AA-8 Aphid, a relatively small missile for close-in use, were introduced during the 1970s. Both used semiactive radar guidance, though the Aphid was apparently…

lobelia: Major species: Similarly, acrid lobelia (L. urens) is found locally in damp pastures in England and western Europe.

short-horned grasshopper, (family Acrididae), family of more than 10,000 species of insects, the largest group of grasshoppers. They are herbivorous and include some of the most destructive agricultural pests known. The plague, or migratory, species are called locusts. Taxonomy See also list of

short-horned grasshopper: Major genera and species: The slant-faced grasshoppers, subfamily Acridinae, are characterized by a slanted face and clear hind wings. They are usually found around marshes and wet meadows in small numbers and do little damage to vegetation.

mynah: The crested mynah (A. cristatellus) is black, with white wing patches and yellow legs and bill. Native to China and Indochina, the crested mynah was introduced into Vancouver Island, British Columbia, in 1900 but has not spread. For pied mynah, see starling.

mynah: …common, or Indian, mynah (Acridotheres tristis) is about 20 cm long, black and brown, with white in the wings and tail, orange skin around the eyes, and heavy dark wattles; it has been introduced into Australia, New Zealand, and Hawaii. The crested mynah (A. cristatellus) is black, with white…

acriflavine, dye obtained from coal tar, introduced as an antiseptic in 1912 by the German medical-research worker Paul Ehrlich and used extensively in World War I to kill the parasites that cause sleeping sickness. The hydrochloride and the less irritating base, neutral acriflavine, both are

Tyler Perry: …from 2018 included the thriller Acrimony, in which Taraji P. Henson played a wife seeking revenge against her deceptive husband, and the comedy Nobody’s Fool, which starred Tiffany Haddish as a recently paroled ex-convict who helps her straitlaced sister with her love life. A Fall from Grace (2020), about an…

cricket frog, either of two species of small, nonclimbing North American tree frogs of the genus Acris (family Hylidae). Their call is a series of rapid clicks, sounding much like the song of crickets. They occur in the eastern and central United States, usually along the open, grassy margin of

Perseus: … and Danaë, the daughter of Acrisius of Argos. As an infant he was cast into the sea in a chest with his mother by Acrisius, to whom it had been prophesied that he would be killed by his grandson. After Perseus had grown up on the island of Seriphus, where…

Acrisol, one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO). Acrisols form on old landscapes that have an undulating topography and a humid tropical climate. Their natural vegetation is woodland, which in some areas has given way to tree savanna

Pittsburgh: The contemporary city: …city’s professional baseball team, and Acrisure Stadium houses the Steelers, its professional football team. The Penguins, Pittsburgh’s professional ice hockey team, plays at PPG Paints Arena. Popular summertime attractions include riverboat excursions on Pittsburgh’s waterways and Kennywood, an amusement park southeast of the city in West Mifflin.

Cambrian Period: Photosynthetic organisms: The phytoplankton, consisting of acritarchs and blue-green algae, also diversified near the base of the Cambrian. Acritarchs are widespread in many kinds of marine rocks and seem to have potential for an improved zonation of Lower Cambrian rocks. They are difficult to study, however, because of their microscopic size.

skiing: Freestyle skiing: …acrobatics and includes three events: acro, aerials, and moguls. Formerly known as ballet, acro was invented in the early 1930s in Europe. Utilizing moves from figure skating and gymnastics, the acro skier performs a 90-second routine set to music, in which jumps, flips, and spins are executed while skiing a…

Adobe Inc.: Application software: …company initiative in the 1990s—the Adobe Acrobat product family—was designed to provide a standard format for electronic document distribution. Once a document had been converted to Acrobat’s portable document format (PDF), regardless of its origins, users of any major computer operating system could read and print it, with formatting, typography,…

feathertail, small marsupial mammal, a species of glider

acrobatics, (Greek: “to walk on tip-toe,” or “to climb up”), the specialized and ancient art of jumping, tumbling, and balancing, often later with the use of such apparatus as poles, one-wheel cycles, balls, barrels, tightropes, trampolines, and flying trapezes. In 1859 the invention of the flying

marsupial: Classification: Family Acrobatidae (feathertail glider and feathertail possum)2 species in 2 genera. Tiny arboreal nectar feeders. Family Tarsipedidae (honey possum)1 species of southwestern Western Australia, adapted for feeding on nectar of flowers. Family

Mordecai Richler: …(1952), Richler published the novel The Acrobats (1954). Set in Spain, it deals with the experiences of a young Canadian painter with a group of disillusioned expatriates and revolutionaries. Shortly afterward Richler settled in England. He returned to Montreal in the 1970s. His subsequent novels, which manifest evidence of the…

acrocephalosyndactyly, congenital malformation of the skeleton affecting the skull and limbs. The disorder most often is hereditary, but it may appear spontaneously. The head appears pointed (acrocephaly) because of premature closing of the cranial sutures between the individual bones that make up

animal social behaviour: Social interactions involving sex: Similarly, male European sedge warblers (Acrocephalus schoenobaenus) with the longest and most elaborate birdsongs are the first to acquire mates in the spring.

warbler: Reed (see photograph ), bush, and swamp warblers (Acrocephalus, Bradypterus, Calamocichla, and Cettia) are mostly brown-plumaged and harsh-voiced birds. Among other well-known genera of Old World warblers are the fantail warblers (see cisticola) and longtail warblers (see

balloon fly, (family Acroceridae), any member of a family of flies in the insect order Diptera that are named for their swollen abdomen. It is also characterized by an extremely small head and a humped back. Some adults have a slender proboscis (feeding organ) and feed from flowers, whereas others

wart snake, (genus Acrochordus), any of three species of fish-eating aquatic snakes occurring from southern Asia to northern Australia, constituting the family Acrochordidae, which is sometimes considered a subfamily of the Colubridae. Wart snakes have thick bodies, loose skins, tiny pyramidal

file snake: The elephant-trunk snake (Acrochordus arafurae), which is also commonly known as the Arafura file snake, is an unrelated nonvenomous species that lives along the coasts of northern Australia and New Guinea.

harlequin beetle, (Acrocinus longimanus), large tropical American beetle with an elaborate variegated pattern of black with muted red and greenish yellow markings on its wing covers. The common name refers to the beetle’s gaudy pattern; the Latin longimanus of the species name refers to the

palm: Economic importance: …the gru gru palm (Acrocomia) and the coquito palm (Jubaea) in America. The sago palm and, to a lesser extent, the sugar palm and the gebang palm are sources of starch obtained from the pith. The fruit of the date palm (Phoenix dactylifera) is a staple in parts of…

acrocyanosis, bluish discoloration of the hands caused by spasms in arterioles (small arteries) of the skin. Less commonly, the feet are affected. The fingers or toes are usually cold and sweat copiously. The cause of the condition is unknown. Acrocyanosis is most common in women, particularly in

nutritional disease: Zinc: …inherited zinc-responsive syndrome known as acrodermatitis enteropathica. Symptoms of zinc deficiency may include skin lesions, diarrhea, increased susceptibility to infections, night blindness, reduced taste and smell acuity, poor appetite, hair loss, slow wound healing, low

chameleon: …bundles of two and three), acrodont dentition (with the teeth attached to the edge of the jaw), eyes that move independently, atrophied venom glands that produce harmless trace amounts of venom, and a long, slender projectile tongue. The name has also been applied to the false chameleon, or anole, a…