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nuclear reaction ... Nunez de Arce, Gaspar

nuclear reaction: change in the identity or characteristics of an atomic nucleus, induced by bombarding it with an energetic particle. The bombarding particle may be an alpha particle, a gamma-ray photon, a ...
nuclear reactor: any of a class of devices that can initiate and control a self-sustaining series of nuclear fissions. Such devices are used as research tools, as systems for producing radioisotopes, and ...
Nuclear Regulatory Commission: an independent regulatory agency that is responsible for overseeing the civilian use of nuclear materials in the United States. The NRC was established on Oct. 11, 1974, by President Gerald ...
Nuclear Test-Ban Treaty: treaty that banned all tests of nuclear weapons except those conducted underground.
nuclear weapon: bomb or other warhead that derives its force from either the fission or the fusion of atomic nuclei and is delivered by an aircraft, missile, Earth satellite, or other strategic ...
nuclear weapon: bomb or other warhead that derives its force from either the fission or the fusion of atomic nuclei and is delivered by an aircraft, missile, Earth satellite, or other strategic ...
nuclear winter: the environmental devastation that certain scientists contend would probably result from the hundreds of nuclear explosions in a nuclear war. The damaging effects of the light, heat, blast, and radiation ...
nuclease: any enzyme that cleaves nucleic acids. Nucleases, which belong to the class of enzymes called hydrolases, are usually specific in action, ribonucleases acting only upon ribonucleic acids (RNA) and deoxyribonucleases ...
nucleation: the initial process that occurs in the formation of a crystal from a solution, a liquid, or a vapour, in which a small number of ions, atoms, or molecules become ...
nucleic acid: naturally occurring complex phosphorus compound, acidic in character, and capable of being broken down chemically to yield phosphoric acid, sugars, and a mixture of organic bases (purines and pyrimidines). Nucleic ...
nucleon: either of the subatomic particles, the proton and the neutron, constituting atomic nuclei. Protons (positively charged) and neutrons (uncharged) behave identically under the influence of the short-range nuclear force, both ...
nucleophile: in chemistry, an atom or molecule that in chemical reaction seeks a positive centre, such as the nucleus of an atom, because the nucleophile contains an electron pair available for ...
nucleoprotein: conjugated protein consisting of a protein linked to a nucleic acid, either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid). The protein combined with DNA is commonly either histone or protamine; ...
nucleoside: a structural subunit of nucleic acids, the heredity-controlling components of all living cells, consisting of a molecule of sugar linked to a nitrogen-containing organic ring compound. In the most important ...
nucleosynthesis: production on a cosmic scale of all the species of chemical elements from perhaps one or two simple types of atomic nuclei, a process that entails large-scale nuclear reactions including ...
nucleotide: any member of a class of organic compounds in which the molecular structure comprises a nitrogen-containing unit (base) linked to a sugar and a phosphate group. The nucleotides are of ...
nucleus: in physics, the core of an atom. See atom.
nucleus: in biology, a specialized structure occurring in most cells (except bacteria and blue-green algae) and separated from the rest of the cell by a double layer, the nuclear membrane. This ...
nuclide: species of atom as characterized by the number of protons, the number of neutrons, and the energy state of the nucleus. A nuclide is thus characterized by the mass number ...
nudibranch: any of the marine gastropods that constitute the order Nudibranchia (subclass Opisthobranchia of the class Gastropoda). Nudibranchs characteristically lack a shell, gills, and mantle cavity. The delicately coloured body has ...
nudism: the practice of going without clothes, generally for reasons of health or comfort. Nudism is a social practice in which the sexes interact freely but commonly without engaging in sexual ...
nuee ardente: highly destructive, fast-moving, incandescent mass of gas-enveloped particles that is associated with certain types of volcanic eruptions. See pyroclastic flow.
Nuer: people who live in the marshy and savanna country on both banks of the Nile River in the southern Sudan. They speak an Eastern Sudanic language of the Nilo-Saharan language ...
Nueva Casas Grandes: (Mexico): see Nuevo Casas Grandes.
Nueva Esparta: island estado ("state"), northeastern Venezuela. It lies off the Araya Peninsula of the mainland. Nueva Esparta consists of Margarita (q.v.), largest of the islands, and two small neighbours, Cubagua and ...
Nueva Gerona: city, capital of the Cuban island provincia of Isla de la Juventud ("Isle of Youth"; until 1978, Isla de Pinos ["Isle of Pines"]), in the Caribbean Sea, just south of ...
Nueva Ocotepeque: town, western Honduras. It lies along the Lempa River at 2,641 feet (805 m) above sea level. The town was originally situated just to the northeast, at the site of ...
Nueva Rosita: city, north-central Coahuila estado ("state"), northeastern Mexico. It is situated 1,410 feet (430 m) above sea level, on the Sabinas River, 65 miles (105 km) southwest of Piedras Negras, on ...
Nueva San Salvador: city, west-central El Salvador. Founded in 1854 as Nueva Ciudad de San Salvador at the southern base of San Salvador Volcano, it briefly became the national capital when San Salvador ...
Nuevitas: port city, east-central Cuba. It lies on a peninsula jutting out into the sheltered Nuevitas Bay, into which Christopher Columbus sailed to land in the area in 1492. Despite frequent ...
Nuevo Casas Grandes: city, northern Chihuahua estado ("state"), northern Mexico. It lies along the Casas Grandes River, about 130 miles (210 km) southwest of Ciudad Juarez. The city was established in 1886 by ...
Nuevo Laredo: city and port of entry, northern Tamaulipas estado ("state"), northeastern Mexico. It lies along the Rio Grande (Rio Bravo del Norte), across from Laredo, Texas. The city is a cattle ...
Nuevo Leon: estado ("state"), northeastern Mexico. It is bounded north by the United States, east and southeast by Tamaulipas, south and southwest by San Luis Potosi, and west by Coahuila. The state ...
nuevo sol: monetary unit of Peru. It is divided into 100 centimos. The sol was introduced as the currency of Peru in the 1860s, but it was replaced during Chile's occupation of ...
Nuffield, William Richard Morris, Viscount, Baron Nuffield Of Nuffield: British industrialist and philanthropist whose automobile manufacturing firm introduced the Morris cars.
Nugaaleed Valley: river valley, northeastern Somalia. It is a shallow valley, long and broad, with an extensive network of seasonal watercourses. The valley's principal watercourses, the Nugaaleed and the more westerly Dheere, ...
Nugent, Richard: African American writer, artist, and actor associated with the Harlem Renaissance.
nuisance: in law, a human activity or a physical condition that is harmful or offensive to others and gives rise to a cause of action. A public nuisance created in a ...
Nujoma, Sam: first president of independent Namibia (1990-2005).
Nuku Hiva: volcanic island of the northwestern Marquesas Islands, French Polynesia, in the central South Pacific. Nuku Hiva has an area of 131 square miles (339 square km). It is widely regarded ...
Nuku'alofa: capital and chief port of Tonga, on the northern shore of Tongatapu Island, in the southern Pacific Ocean. Its deep-draft harbour is protected by reefs. Commercial activities centre on the ...
Nukus: city, southwestern Uzbekistan, capital of the Qoragalpoghiston republic. It lies near the head of the Amu Darya (river) delta. The tiny Nukus settlement, which lay amid the desert sands, was ...
Nullarbor Plain: vast limestone plateau, extending westward for 400 miles (650 km) from Ooldea in South Australia into Western Australia and northward from the Great Australian Bight (a wide bay) for 250 ...
nullification: in U.S. history, doctrine upholding the right of a state to declare null and void within its boundaries an act of the federal government. Thomas Jefferson and James Madison advocated ...
Numa Pompilius: second of the seven kings who, according to Roman tradition, ruled Rome before the founding of the Republic (c. 509 BC).
Numan: town and port on the Benue River, Adamawa state, eastern Nigeria. It is located about 30 miles (50 km) from Yola, opposite the mouth of the Gongola River, which is ...
Numantia: a Celtiberian town located near modern Soria in Spain on the upper Douro (Duero) River. Founded on the site of earlier settlements by Iberians who penetrated the Celtic highlands about ...
Numazu: city, southeastern Shizuoka ken (prefecture), central Honshu, Japan. It lies at the mouth of the Kano River, facing Suruga Bay, at the base of the Izu Peninsula. ...
numbat: (Myrmecobius fasciatus), marsupial mammal of the family Dasyuridae (some authorities classify it as a family in its own right, Myrmecobiidae). It forages by day for termites in forests of southwestern ...
number: any of the positive or negative integers, or any of the set of all real or complex numbers, the latter containing all numbers of the form a + bi, where a and ...
number game: any of various puzzles and games that involve aspects of mathematics.
number symbolism: cultural associations, including religious, philosophic, and aesthetic, with various numbers.
number theory: branch of mathematics concerned with properties of the positive integers (1, 2, 3, &elipsis;). Sometimes called "higher arithmetic," it is among the oldest and most natural of mathematical pursuits.
Numbers: the fourth book of the Bible. The English title is a translation of the Septuagint (Greek) title referring to the numbering of the tribes of Israel in chapters 1-4.
numbers game: the most widespread lottery game in the United States before lottery games were legalized in many states, though illegal wherever it is played. Patrons of the numbers game are drawn ...
Numenius of Apamea: Greek philosopher chiefly responsible for the transition from Platonist idealism to a Neoplatonic synthesis of Hellenistic, Persian, and Jewish intellectual systems, with particular attention to the concept of ultimate being, ...
numeral system: any of various sets of symbols and the rules for using them to represent numbers, which are used to express how many objects are in a given set. Thus the ...
numerals and numeral systems: a collection of symbols used to represent small numbers, together with a system of rules for representing larger numbers.
Numerian: Roman emperor 283-284.
numerical analysis: area of mathematics and computer science that creates, analyzes, and implements algorithms for obtaining numerical solutions to problems involving continuous variables. Such problems arise throughout the natural sciences, social sciences, ...
numerology: use of numbers to interpret a person's character or to divine the future. The theory behind numerology is based on the Pythagorean idea that all things can be expressed in ...
Numic languages: North American Indian language group that was spoken by Native Americans in Nevada, Utah, and portions of California, Oregon, Idaho, Wyoming, Arizona, Colorado, and Oklahoma. These languages are currently divided ...
Numidia: under the Roman Republic and Empire, a part of Africa north of the Sahara, the boundaries of which at times corresponded roughly with those of modern Algeria. Its earliest inhabitants ...
nummulite: any of the thousands of extinct species of relatively large, lens-shaped foraminifers (single-celled marine organisms) that were abundant during the Tertiary Period (66.4 to 1.6 million years ago). Nummulites were ...
nun: woman who is a member of a monastic religious order or group. See monasticism.
Nun: oldest of the ancient Egyptian gods and father of Re, the sun god. Nun's name means "water," and he represented the primeval waters of chaos out of which Re-Atum began ...
Nun River: river in southern Nigeria that is considered the direct continuation of the Niger River. After the Niger bifurcates into the Nun and Forcados rivers about 20 miles (32 km) downstream ...
nunatak: isolated mountain peak that once projected through a continental ice sheet or an Alpine-type ice cap. Because they usually occur near the margin of an ice sheet, nunataks were thought ...
Nunavut: vast territory of northern Canada that stretches across most of the Canadian Arctic. Created in 1999 out of the eastern portion of the Northwest Territories, Nunavut encompasses the traditional lands ...
nunbird: any of certain puffbird species. See puffbird.
Nunc Dimittis: in the New Testament, a brief hymn of praise sung by the aged Simeon, who had been promised by the Holy Spirit that he would not die until he had ...
nuncio: a Vatican representative accredited as an ambassador to a civil government that maintains official diplomatic relations with the Holy See. He promotes good relations between the government and the Holy ...
Nuneaton and Bedworth: borough (district), administrative and historic county of Warwickshire, in the Midlands of England. The town of Nuneaton seems to have grown around a 12th-century Benedictine nunnery, but the main impulse ...
Nunes, Pedro: mathematician, geographer, and the chief figure in Portuguese nautical science, noted for his studies of the Earth, including the oceans.
Nunez Cabeza de Vaca, Alvar: Spanish explorer who spent eight years in the Gulf region of present-day Texas and whose accounts of the legendary Seven Golden Cities of Cibola probably inspired the extensive explorations of ...
Nunez de Arce, Gaspar: Spanish poet and statesman, once regarded as the great poet of doubt and disillusionment, though his rhetoric is no longer found moving.