Aconcagua River, river in central Chile. It rises in the northwestern foothills of Mount Aconcagua of the Andes Mountains and flows westward from the Argentine border area to enter the Pacific Ocean north of the city of Viña del Mar after a course of 120 miles (190 km). Much of the Chilean trackage

Mount Aconcagua, mountain in western Mendoza province, west-central Argentina, on the Chilean border. It is the highest point in the Western Hemisphere. Aconcagua lies in the Southern Andes Mountains; although its peak is in Argentina, its western flanks build up from the coastal lowlands of Chile,

Mount Aconcagua, mountain in western Mendoza province, west-central Argentina, on the Chilean border. It is the highest point in the Western Hemisphere. Aconcagua lies in the Southern Andes Mountains; although its peak is in Argentina, its western flanks build up from the coastal lowlands of Chile,

Aconcagua River, river in central Chile. It rises in the northwestern foothills of Mount Aconcagua of the Andes Mountains and flows westward from the Argentine border area to enter the Pacific Ocean north of the city of Viña del Mar after a course of 120 miles (190 km). Much of the Chilean trackage

Jacobus Acontius was an advocate of religious toleration during the Reformation whose revolt took a more extreme form than that of Lutheranism. Acontius served as secretary to Cristoforo Madruzzo, a liberal cardinal. When the more conservative Paul IV became pope, Acontius repudiated Roman Catholic

metabolism: Formation of coenzyme A, carbon dioxide, and reducing equivalent: …and isocitrate—remain closely associated with aconitase, the enzyme that catalyzes the isomerization process, and that most of the cis-aconitate is not released from the enzyme surface but is immediately converted to isocitrate.

metabolism: Formation of coenzyme A, carbon dioxide, and reducing equivalent: …from citrate to form cis-aconitate and then the re-addition of water to cis-aconitate in such a way that isocitrate is formed. It is probable that all three reactants—citrate, cis-aconitate, and isocitrate—remain closely associated with aconitase, the enzyme that catalyzes the isomerization process, and that most of the cis-aconitate is…

aconite, any member of two genera of perennial herbs of the buttercup family (Ranunculaceae): Aconitum, consisting of summer-flowering poisonous plants (see monkshood), and Eranthis, consisting of spring-flowering ornamentals (see winter

monkshood, (genus Aconitum), genus of more than 200 species of showy perennial herbs of the buttercup family (Ranunculaceae). They occur in the north temperate zone, usually in partial shade and in rich soil. Some species are cultivated as ornamental plants, and several are used in traditional

monkshood: Major species: …species contain the powerful poison aconitine. The common monkshood, or friar’s cap (A. napellus), native to mountain slopes in Europe and east to the Himalayas, has been the most important source of this drug, which in ancient times was administered to criminals and has been used in minute amounts for…

monkshood, (genus Aconitum), genus of more than 200 species of showy perennial herbs of the buttercup family (Ranunculaceae). They occur in the north temperate zone, usually in partial shade and in rich soil. Some species are cultivated as ornamental plants, and several are used in traditional

monkshood: Major species: …‘Sparks variety’ monkshood (Aconitum henryi), Carmichael’s monkshood (A. carmichaelii), and southern blue monkshood (A. uncinatum). All species contain the powerful poison aconitine. The common monkshood, or friar’s cap (A. napellus), native to mountain slopes in Europe and east to the Himalayas, has been the most important source of this drug,…

monkshood: Major species: …are cultivated in gardens, including ‘Sparks variety’ monkshood (Aconitum henryi), Carmichael’s monkshood (A. carmichaelii), and southern blue monkshood (A. uncinatum). All species contain the powerful poison aconitine. The common monkshood, or friar’s cap (A. napellus), native to mountain slopes in Europe and east to the Himalayas, has been the most

monkshood: Major species: The common monkshood, or friar’s cap (A. napellus), native to mountain slopes in Europe and east to the Himalayas, has been the most important source of this drug, which in ancient times was administered to criminals and has been used in minute amounts for reducing fever…

monkshood: Major species: carmichaelii), and southern blue monkshood (A. uncinatum). All species contain the powerful poison aconitine. The common monkshood, or friar’s cap (A. napellus), native to mountain slopes in Europe and east to the Himalayas, has been the most important source of this drug, which in ancient times was…

Tucumán: …province is occupied by the Sierra del Aconquija, which consists of northeast-southwest–trending outlying ridges of the Andes Mountains with elevations of 8,000 to 18,000 feet (2,400 to 5,500 metres). The eastern part of the province, by contrast, is flat, alluvial, and agriculturally fertile. Tucumán owes its prosperity to the Sierra…

Acontius, in Greek legend, a beautiful youth of the island of Ceos. During the festival of Artemis at Delos, Acontius saw and loved Cydippe, a girl of a rich and noble family. He wrote on an apple the words “I swear to wed Acontius” and threw it at her feet. She picked it up and mechanically read

Jacobus Acontius was an advocate of religious toleration during the Reformation whose revolt took a more extreme form than that of Lutheranism. Acontius served as secretary to Cristoforo Madruzzo, a liberal cardinal. When the more conservative Paul IV became pope, Acontius repudiated Roman Catholic

Jacobus Acontius was an advocate of religious toleration during the Reformation whose revolt took a more extreme form than that of Lutheranism. Acontius served as secretary to Cristoforo Madruzzo, a liberal cardinal. When the more conservative Paul IV became pope, Acontius repudiated Roman Catholic

Acorales, the sweet flag order of flowering plants and the most basal lineage among the monocotyledons (monocots), which are characterized by having a single seed leaf. This order contains the single family Acoraceae and one genus (Acorus), which comprises two to four species of plants that

Azores, archipelago and região autónoma (autonomous region) of Portugal. The chain lies in the North Atlantic Ocean roughly 1,000 miles (1,600 km) west of mainland Portugal. It includes nine major islands. The Azores are divided into three widely separated island groups: the eastern group,

acorn, nut of the oak. Acorns are usually seated in or surrounded by a woody cupule. They mature within one to two seasons, and their appearance varies depending on the species of oak. Acorns provide food for wildlife and are used to fatten swine and

acorn and nut weevil, (subfamily Curculioninae), any of approximately 45 species of weevils in the family Curculionidae (order Coleoptera) that have extremely long and slender snouts, which in females can be almost twice the length of the body. The mandibles are located at the tip of the snout.

barnacle: Acorn barnacles, also called rock barnacles, are sessile (not stalked); their symmetrical shells tend to be barrellike or broadly conical. This group includes Balanus, responsible for much of the fouling of ships and harbour structures. Wart barnacles, such as Verruca, have asymmetrical shells.

barnacle: Acorn barnacles, also called rock barnacles, are sessile (not stalked); their symmetrical shells tend to be barrellike or broadly conical. This group includes Balanus, responsible for much of the fouling of ships and harbour structures. Wart barnacles, such as Verruca, have asymmetrical shells.

acorn and nut weevil: acorn and nut weevil, (subfamily Curculioninae), any of approximately 45 species of weevils in the family Curculionidae (order Coleoptera) that have extremely long and slender snouts, which in females can be almost twice the length of the body. The mandibles are located at the tip…

woodpecker: The acorn woodpecker (M. formicivorus) is about 20 cm (8 inches) long and is found from the deciduous woodlands of western North America south to Colombia. It depends on acorns for winter food, storing a supply in holes it drills in the bark of trees. The…

acorn worm, any of the soft-bodied invertebrates of the class Enteropneusta, phylum Hemichordata. The front end of these animals is shaped like an acorn, hence their common name. The “acorn” consists of a muscular proboscis and a collar that may be used to burrow into soft sand or mud. The animals

acorn worm, any of the soft-bodied invertebrates of the class Enteropneusta, phylum Hemichordata. The front end of these animals is shaped like an acorn, hence their common name. The “acorn” consists of a muscular proboscis and a collar that may be used to burrow into soft sand or mud. The animals

Acorales: …Acoraceae and one genus (Acorus), which comprises two to four species of plants that resemble the irises.

Acorales: Acorus calamus (sweet flag) occurs in the wetlands of North America and from India to Indonesia. Other species are distributed in temperate areas in Asia and Europe, where they are often found at pond margins or along fast-moving streams.

acosmism, in philosophy, the view that God is the sole and ultimate reality and that finite objects and events have no independent existence. Acosmism has been equated with pantheism, the belief that everything is God. G.W.F. Hegel coined the word to defend Benedict de Spinoza, who was accused of

Joaquín Acosta was a Colombian scientist, historian, and statesman who sought to preserve knowledge of his country’s early history. Acosta entered a military career in 1819, becoming an officer in the patriot army under Simón Bolívar. He subsequently became a member of virtually all the scientific

José de Acosta was a Jesuit theologian and missionary to the New World known chiefly for his Historia natural y moral de las Indias (1590; Natural and Moral History of the Indies), the earliest survey of the New World and its relation to the Old. His works, missionary and literary, mark the zenith

Uriel Acosta was a freethinking rationalist who became an example among Jews of one martyred by the intolerance of his own religious community. He is sometimes cited as a forerunner of the renowned philosopher Benedict de Spinoza. The son of an aristocratic family of Marranos (Spanish and

acouchy, (genus Myoprocta), either of two species of South American rodents that resemble the small tropical-forest-dwelling hoofed animals of Africa and Asia (see royal antelope; chevrotain). Weighing 1 to 1.5 kg (2.2 to 3.3 pounds), acouchys are 30 to 39 cm (12 to 15 inches) long, with a very

acouchy, (genus Myoprocta), either of two species of South American rodents that resemble the small tropical-forest-dwelling hoofed animals of Africa and Asia (see royal antelope; chevrotain). Weighing 1 to 1.5 kg (2.2 to 3.3 pounds), acouchys are 30 to 39 cm (12 to 15 inches) long, with a very

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: Children’s and young adult books: Acoustic Rooster and His Barnyard Band (2011; TV movie 2025) 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…

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 an Italian Roman Catholic priest and the fifth and youngest general of the Society of Jesus (Jesuits), considered by many to have been the religious order’s greatest leader. The youngest son of the Duke of Atri, he joined the order in 1567. Shortly after completing his studies

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, 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