nephrology \ni-'fra-b-je\ Branch of medicine dealing with kidney func¬ tion and diseases. An understanding of kidney physiology is important not only in treating kidney disease but in knowing the effect of drugs, diet, and hypertension on kidney disease, and vice versa. The first scien¬ tific observations of the kidney were made in the mid-17th century by Lorenzo Bellini (1643-1704) and Marcello Malpighi; Carl Ludwig was the first to elaborate on their true physiological function (1844). A key devel¬ opment in nephrology was the permanent arteriovenous shunt (1960), which made repeated hemodialysis feasible, instantly changing the out¬ look for chronic-renal-disease patients from certain death to 90% survival. See also dialysis, kidney failure, kidney stone, kidney transplant, nephron.
nephron Functional unit of the kidney that removes waste and excess substances from the blood to produce urine. Each of the million or so nephrons in each kidney is a tubule 1.2-2.2 in. (30-55 mm) long. At one end it is closed, expanded, and folded into a double-walled cuplike struc¬ ture (Bowman’s capsule) enclosing a cluster of capillaries (glomerulus). Fluid forced out of the blood through the capillary walls of the glomer¬ ulus into Bowman’s capsule flows into the adjacent renal tubule, where water and nutrients are selectively reabsorbed from the fluid back into the blood, and electrolytes such as sodium and potassium are balanced in sev¬ eral distinct sections along its length. The final concentrated product is urine. See also urinary system.
Neptune Eighth planet from the Sun, discovered in 1846 and named for the Roman god of the sea. It has an average distance from the Sun of 2.8 billion mi (4.5 billion km), taking nearly 164 years to complete one orbit and rotating every 16.11 hours. Neptune has more than 17 times Earth’s mass, 58 times its volume, and 12% stronger gravity at the top of its atmosphere. It has an equatorial diameter of 30,775 mi (49,528 km). Nep¬ tune consists largely of hydrogen and helium. It has no solid surface; its interior is believed to consist of a fluid mixture of rock, ices, and gas. Its atmosphere contains substantial amounts of methane gas, whose absorp¬ tion of red light causes Neptune’s deep blue-green colour. The Voyager 2 space probe in 1989 discovered winds of over 1,570 mi/hour (700 m/second), the fastest known for any of the Sun’s planets, and dark spots that appear to be storms similar to Jupiter’s Great Red Spot. Neptune receives little solar radiation, but it radiates substantially more energy than it receives, which indicates an internal heat source. Neptune’s weak magnetic field traps charged par¬ ticles in a belt around the planet.
Neptune has a system of rings, made up largely of dust-size particles, and at least 13 moons; the largest is Tri¬ ton, almost as big as Earth’s Moon.
Neptune In Roman religion, the god of water. Neptune was originally the god of fresh water, but by 399 bc he was identified with the Greek god Poseidon and thus became a deity of the sea. His female counterpart, Sala- cia, probably began as a goddess of spring water but was later equated with the Greek goddess Amphitrite.
Neptune’s festival (Neptunalia) took place in the heat of summer (July 23),
when fresh water was scarcest. In art Neptune is often given Poseidon’s attributes, the trident and dolphin.
Nerbudda River See Narmada River
Nerchinsk, Treaty of (1689) Peace settlement between Russia and Qing-dynasty China that checked Russia’s eastward expansion. Russia lost easy access to the Sea of Okhotsk but gained the right of passage to Beijing for its trade caravans. The treaty also gained China’s implied rec¬ ognition of Russia as a state of equal status, something other European countries could not accomplish. The Nerchinsk treaty was the basis of Russo-Chinese relations until 1858-60.
Nereid \'nir-e-od\ In Greek mythology, any of the daughters of the sea god Nereus and of Doris, daughter of Oceanus. The Nereids, who num¬ bered 50 or 100, were depicted as young girls who inhabited any water, salt or fresh, and were benign toward humanity. They were popular fig¬ ures in Greek literature. The best known were Amphitrite, consort of Poseidon; Thetis, wife of Peleus (king of the Myrmidons) and mother of Achilles; and Galatea, a Sicilian loved by the Cyclops Polyphemus.
Nereus \'nir-e-3s\ Greek sea god. The son of Pontus (a personification of the sea) and Gaea, he was noted for his gift of prophecy and his ability to change his shape. He lived at the bot¬ tom of the sea with his daughters, the Nereids. Heracles wrestled with him in a variety of shapes in order to gain his advice about recovering the golden apples of the Hesperides.
Nergal In Mesopotamian religion, a secondary god of the Sumero- Akkadian pantheon. He was identi¬ fied with Irra, the god of scorched earth and war, and with Meslamtaea.
The city of Cuthah was the center of his cult. In the 1st millennium bc he was described as a benefactor who hears prayers, restores the dead to life, and protects agriculture and flocks. Later he was called a “destroy¬ ing flame” and was depicted as a god of pestilence, hunger, and devas¬ tation. The other sphere of Nergal’s power was the underworld, where he ruled as king and where the goddess Ereshkigal was his queen.
Neri \'na-re. Saint Philip (b. July 21, 1515, Florence—d. May 26, 1595, Rome; canonized 1622; feast day May 26) Roman Catholic mys¬ tic. He went to Rome to pursue religious studies in 1533. In 1548 he cofounded a society of laymen dedicated to the care of pilgrims, the poor, and the sick. After his ordination in 1551 he moved to the community of San Girolamo della Carita in Rome. From 1564 to 1575 he was rector of the church of San Giovanni, and in 1575 Gregory XIII granted him Santa Maria in Vallicella, where he established his Congregation of the Oratory, a group of priests and clerics engaged in devotion and charitable activi¬ ties. One of the outstanding mystics of the Counter-Reformation, he was noted for his eloquence as a preacher.
Nernst Vnemst\, Walther Hermann (b. June 25, 1864, Briesen, Prussia—d. Nov. 18, 1941, Muskau, Ger.) German scientist, one of the founders of modern physical chemistry. He taught at the Universities of Gottingen and Berlin until forced to retire in 1933 by the Nazi regime. Nernst’s researches on the theory of electric cells (see battery), the ther¬ modynamics of chemical equilibrium, the properties of vapours at high temperatures and of solids at low temperatures, and the mechanism of photochemistry have had important applications. His formulation of the third law of thermodynamics gained him a 1920 Nobel Prize. He also invented an improved electric light and an electronically amplified piano.
Nero in full Nero Claudius Caesar Augustus (or Drusus) Germanicus orig. Lucius Domitius Ahenobarbus (b. Dec. 15, ad 37, Antium, Latium—d. June 9, 68, Rome) Roman emperor (54-68). He was adopted by Claudius when the emperor married Nero’s mother, Agrippina the Younger, and took the throne after Claudius died. He was guided by his tutor, Seneca, and by Agrippina until he murdered her and broke free of his advisers. By respecting the Senate and leaving imperial administration alone, he became popular in the east, but Boudicca’s revolt in Britain (61), unemployment, and contempt for his frivolousness and excesses caused dissatisfaction. In 64 a fire, possibly lit at his orders,
Neptune holding his trident, classical sculpture; in the Lateran Museum, Rome
AUNARI—ART RESOURCE
Nereus struggling with Heracles, detail from a Greek water jar found at Vulci, c. 490 bc; in the British Museum
COURTESY OF THE TRUSTEES OF THE BRITISH MUSEUM
© 2006 Encyclopaedia Britannica, Inc.
Nerses ► Nesselrode I 1345
destroyed much of Rome; he perse¬ cuted the Christians as scapegoats and proceeded to build a garish pal¬ ace, the Domus Aurea, on lands that had been privately held. With his reign in decline, he murdered his wife, Octavia, as well as her succes¬ sor, Poppaea, ordered Seneca to kill himself, and executed senators who criticized him. Revolts in Gaul and Spain were led by Galba, who was declared emperor by his army. Nero came to be regarded as mad, giving public lyre and theatrical perfor¬ mances to the disgust of his subjects.