brain death State of irreversible destruction of the brain. Before the invention of life-support systems, brain death always led quickly to death of the body. Ethical considerations are crucial to defining criteria for brain death, which in most countries must be met before efforts to extend life may be ended. Such criteria include deep coma with a known cause, absence of any brainstem functions (e.g., spontaneous respiration, pupil reactions, gag and cough reflexes), and exclusion of hypothermia, drugs, and poison as causes. Electroencephalography is useful but not essential in determining brain death. Organ donors must be declared brain-dead before their organs may be removed for transplant. The question of when life support can legally be ended has been the subject of numerous court cases.
brain laterality See laterality
Brain Trust Group of advisers to Franklin Roosevelt in his 1932 presi¬ dential campaign. Its principal members were the Columbia University professors Raymond Moley, Rexford Tugwell, and Adolf A. Berle, Jr. (1895— 1971). They presented Roosevelt with analyses of national social and economic problems and helped him devise public-policy solutions. The group did not meet after Roosevelt became president, but members served in government posts. See also New Deal.
brainwashing Systematic effort to destroy an individual’s former loy¬ alties and beliefs and to substitute loyalty to a new ideology or power. It has been used by religious cults as well as by radical political groups such as the Chinese Communists in 1949. The techniques of brainwashing usually involve isolation from former associates and sources of informa¬ tion; an exacting regimen calling for absolute obedience and humility; strong social pressures and rewards for cooperation; physical and psycho¬ logical punishments for noncooperation, including social ostracism and criticism, deprivation of food, sleep, and social contacts, bondage, and torture; and constant reinforcement. Its effects are sometimes reversed through deprogramming, which combines confrontation and intensive psychotherapy.
brake Device for decreasing the speed of a body or stopping its motion. Most brakes act on rotating mechanical elements and absorb kinetic energy mechanically, hydrodynamically, or electrically. Mechanical brakes are the most common; they dissipate the kinetic energy as heat generated by mechanical friction between a rotating drum or disk and a stationary fric¬ tion element. A hydrodynamic (fluid) brake has a rotor (rotating element) and a stator (stationary element). Resistance to rotation is created by fluid
Louis Braille, portrait bust by an unknown artist.
ARCHIV FUR KUNST UND GESCHICHTE, BERUN
cerebrum — frontal lobe
— parietal lobe corpus callosum
occipital lobe thalamus midbrain
hypothalamus
pituitary gland
temporal lobe
pons-
medulla oblongata spinal cord-
Side view of the brain showing its major structures. The large cerebrum is divided into two halves, or hemispheres, connected by the corpus callosum, a band of nerve fibres. Two grooves divide the hemispheres into four lobes: frontal, temporal, pari¬ etal, and occipital. Many nerve cells are found in the convoluted cerebrum's outer surface, or cerebral cortex, which controls sensory and motor activities. The thala¬ mus relays incoming sensory impulses from the spinal cord to the cortex. The hypo¬ thalamus's many functions include control of breathing, blood flow, temperature regulation, and emotions. The pituitary gland is attached to and regulated by the hypothalamus. The midbrain relays signals between the forebrain and hindbrain. The cerebellum, along with the cerebrum, plays a role in voluntary movement as well as balance. The pons serves as a relay point linking the medulla oblongata, midbrain, cerebellum, and cerebrum. The medulla, lying between the pons and the spinal cord and continuous with both, plays a role in essential involuntary regula¬ tory and reflexive responses (including breathing, swallowing, and heartbeat) and relays signals between the spinal cord and other brain regions.
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brake shoe
piston
caliper housing
brake
piston
boot
hub
disc (rotor)
piston seal
A disc brake assembly. Wheel rotation is slowed by friction when the hydraulic pis¬ tons squeeze the caliper, pressing the brake pads (shoe and lining assemblies) against the spinning disc (rotor), which is bolted to the wheel hub.
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© 2006 Encyclopaedia Britannica, Inc.
brake ► Brandes I 267
friction and circulation of the liquid (usually water) from a series of pock¬ ets in the rotor to a series of complementary pockets in the stator. See also AIR BRAKE.
brake See bracken
Bramah, Joseph (b. April 13, 1748, Stainborough, Yorkshire, Eng.—d. Dec. 9, 1814, London) British engineer and inventor. Originally a cabinetmaker, Bramah in 1784 devised a pick-proof lock, which defied all efforts for 67 years. Since the success of his locks depended on their complexity, they could be produced in quantity only after the creation of a set of well-designed and precisely engineered machine tools, for which he hired a brilliant young blacksmith, Henry Maudslay. Their prototype machines were essential to the founding of the machine-tool industry. Bra¬ mah’s hydraulic press found many industrial uses and led to the devel¬ opment of hydraulic machinery.
Bramante \bra-'man-ta\, Donato (b. 1444, probably at Monte Asdru- valdo, Duchy of Urbino—d. April 11, 1514, Rome) Italian architect and perspectivist painter. The son of a farmer, he was working as a painter by 1477. His early architectural works included the church of Santa Maria presso San Satiro (c. 1480), in which the choir is painted in perspec¬ tive to give an illusion of a much larger space. In 1499 he went to Rome, where he spent the rest of his life. His Tempietto was the first mas¬ terpiece of the High Renaissance.
Under the patronage of Pope Julius II, he drew up plans for the immense Belvedere courtyard in the Vatican (begun c. 1505) and the new St.
Peter's Basilica (begun 1506), his greatest work. These ambitious projects were far from complete at the time of his death. Despite the grandiose scale of the St. Peter’s undertaking, Bramante continued to work on other projects and played an important role in Julius II’s plans for rebuilding Rome.
bramble Any plant of the genus Rubus (rose family), consisting of usu¬ ally prickly shrubs, including raspberries and blackberries. Brambles grow wild throughout North America, as well as in Europe and Asia, and are widely cultivated for their fruits.
Brampton City (pop., 2001: 325,428), southeastern Ontario, Canada. Located west of Toronto, it was founded c. 1830. It was incorporated as a town in 1873 and as a city in 1976. Its industries include flower grow¬ ing, tanning, lumbering, and the manufacture of automobiles, shoes, sta¬ tionery, furniture, and optical equipment.
Bran Vbran\ In Celtic religion, a gigantic deity described in the Mabino- gion as king of Britain. He was so large that he and his court lived in a tent rather than a house. When Bran was mortally wounded, he asked his companions to cut off his head and keep it with them, telling them it would provide entertainment and allow them to forget their sorrows. His com¬ panions passed 80 joyous years, eventually following his instructions and burying the head on the White Mount in London, where it protected England from invaders until it was finally unearthed.
bran Edible broken seed coat, or protective outer layer, of wheat, rye, or other cereal grain, separated from the kernel. In flour processing, it is normally removed from the ground kernels by sifting them in a rotating, meshed, cylindrical frame; whole-grain flours retain the bran. Wheat bran, the most widely processed, contains 16% protein, 11% natural fibre, and 50% carbohydrate. Most bran is coarsely ground for stock feed. In a more refined form, it is used in breakfast cereal, breads, and muffins for its value to the human digestive system as roughage.