New Articles

Lebanese Civil War Lebanese Civil War, civil conflict (1975–90) in Lebanon emanating from the deterioration of the Lebanese state and the coalescence of militias that provided security where the state could not. These militias formed largely along communal lines: the Lebanese Front (LF), led by the Phalangists (or...
Five-Power Naval Limitation Treaty Five-Power Naval Limitation Treaty, arms limitation treaty signed by the United States, the United Kingdom, Japan, France, and Italy on February 6, 1922. The agreement fixed the respective numbers and tonnages of capital ships to be possessed by the navies of each of the contracting nations. It was...
Mutual assured destruction Mutual assured destruction, principle of deterrence founded on the notion that a nuclear attack by one superpower would be met with an overwhelming nuclear counterattack such that both the attacker and the defender would be annihilated. By the early 1950s both the Soviet Union and the West were...
Propaganda Movement Propaganda Movement, reform and national consciousness movement that arose among young Filipino expatriates in the late 19th century. Although its adherents expressed loyalty to the Spanish colonial government, Spanish authorities harshly repressed the movement and executed its most prominent...
Israeli settlement Israeli settlement, any of the communities of Israeli Jews built after 1967 in the disputed territories captured by Israel in the Six-Day War—the West Bank, the Gaza Strip, the Golan Heights, and the Sinai Peninsula. Most, but not all, were authorized and supported by the Israeli government. Since...
Estimated regression equation Estimated regression equation, in statistics, an equation constructed to model the relationship between dependent and independent variables. Either a simple or multiple regression model is initially posed as a hypothesis concerning the relationship among the dependent and independent variables. The...
Primary productivity Primary productivity, in ecology, the rate at which energy is converted to organic substances by photosynthetic producers (photoautotrophs), which obtain energy and nutrients by harnessing sunlight, and chemosynthetic producers (chemoautotrophs), which obtain chemical energy through oxidation....
Homo sapiens sapiens Homo sapiens sapiens, in anthropology and paleontology, the subspecies of Homo sapiens that consists of the only living members of genus Homo, modern human beings. Traditionally, this subspecies designation was used by paleontologists and anthropologists to separate modern human beings from...
Density-independent factor Density-independent factor, in ecology, any force that affects the size of a population of living things regardless of the density of the population (the number of individuals per unit area). Density-independent factors often arise from physical and chemical (rather than biological) phenomena. Such...
Conservation of linear momentum Conservation of linear momentum, general law of physics according to which the quantity called momentum that characterizes motion never changes in an isolated collection of objects; that is, the total momentum of a system remains constant. Momentum is equal to the mass of an object multiplied by...
Cable-stayed bridge Cable-stayed bridge, bridge form in which the weight of the deck is supported by a number of nearly straight diagonal cables in tension running directly to one or more vertical towers. The towers transfer the cable forces to the foundations through vertical compression. The tensile forces in the...
Connecticut Compromise Connecticut Compromise, in United States history, the compromise offered by Connecticut delegates Roger Sherman and Oliver Ellsworth during the drafting of the Constitution of the United States at the 1787 convention to solve the dispute between small and large states over representation in the new...
Density-dependent factor Density-dependent factor, in ecology, any force that affects the size of a population of living things in response to the density of the population (the number of individuals per unit area). Density-dependent factors often arise from biological phenomena, rather than from physical and chemical...
Temporal isolation Temporal isolation, in biology, a type of reproductive isolation mechanism among sexual organisms in which the differences in the timing of critical reproductive events prevent members of closely related species, which could otherwise breed with one another, from mating and producing hybrid...
Rib cage Rib cage, in vertebrate anatomy, basketlike skeletal structure that forms the chest, or thorax, and is made up of the ribs and their corresponding attachments to the sternum (breastbone) and the vertebral column. The rib cage surrounds the lungs and the heart, serving as an important means of bony...
Continental crust Continental crust, the outermost layer of Earth’s lithosphere that makes up the planet’s continents and continental shelves and is formed near subduction zones at plate boundaries between continental and oceanic tectonic plates. The continental crust forms nearly all of Earth’s land surface....
Refuse Refuse, nonhazardous solid waste that requires collection and transport to a processing or disposal site. Refuse includes garbage and rubbish. Garbage is mostly decomposable food waste or yard waste that is highly putrescible, while rubbish is mostly dry material such as glass, paper, cloth, or...
Hamilton's rule Hamilton’s rule, in ecology and sociobiology, mathematical formula devised by British naturalist and population geneticist W.D. Hamilton that supports the notion that natural selection favours genetic success, not reproductive success per se. It recognizes that individuals can pass copies of their...
Magnetic field strength Magnetic field strength, the part of the magnetic field in a material that arises from an external current and is not intrinsic to the material itself. It is expressed as the vector H and is measured in units of amperes per metre. The definition of H is H = B/μ ? M, where B is the magnetic flux...
Plant cell Plant cell, the basic unit of all plants. Plant cells, like animal cells, are eukaryotic, meaning they have a membrane-bound nucleus and organelles. The following is a brief survey of some of the major characteristics of plant cells. For a more in-depth discussion of cells, see cell. Unlike animal...
Statistical quality control Statistical quality control, the use of statistical methods in the monitoring and maintaining of the quality of products and services. One method, referred to as acceptance sampling, can be used when a decision must be made to accept or reject a group of parts or items based on the quality found in...
Cobalt-60 Cobalt-60, radioactive isotope of cobalt used in industry and medicine. Cobalt-60 is the longest-lived isotope of cobalt, with a half-life of 5.27 years. It is produced by irradiating the stable isotope cobalt-59 with neutrons in a nuclear reactor. Cobalt-60 is used in the inspection of materials...
Pastoral nomadism Pastoral nomadism, one of the three general types of nomadism, a way of life of peoples who do not live continually in the same place but move cyclically or periodically. Pastoral nomads, who depend on domesticated livestock, migrate in an established territory to find pasturage for their animals....
Thorkell the Tall Thorkell the Tall, Viking warrior and chieftain who gained renown during his lifetime for his fighting prowess and who played a notable role in English history in the 11th century. Little is known of Thorkell’s early life. He was born into a prominent family and was said to be a member of the...
Inca religion Inca religion, Inca religion, religion of the Inca civilization in the Andean regions of South America. It was an admixture of complex ceremonies, practices, animistic beliefs, varied forms of belief in objects having magical powers, and nature worship—culminated in the worship of the sun, which...
New Imperialism New Imperialism, period of intensified imperialistic expansion from the latter half of the 19th century until the outbreak of World War I in 1914. The renewed push to expand territorial control included not only the earlier colonial powers of western Europe but also newcomers such as Germany,...
Three-fifths compromise Three-fifths compromise, compromise agreement between delegates from the Northern and the Southern states at the United States Constitutional Convention (1787) that three-fifths of the slave population would be counted for determining direct taxation and representation in the House of...
Magnetic compass Magnetic compass, in navigation or surveying, an instrument for determining direction on the surface of Earth by means of a magnetic pointer that aligns itself with Earth’s magnetic field. The magnetic compass is the oldest and most familiar type of compass and is used in different forms in...
New Frontier New Frontier, political slogan used by U.S. Pres. John F. Kennedy to describe his concept of the challenges facing the United States in the 1960s. The term was most prominently used by Kennedy in the speech with which he accepted the nomination as presidential candidate of the Democratic Party for...
Flood myth Flood myth, any of numerous mythologies in which a flood destroys a typically disobedient original population. Myths of a great flood (the Deluge) are widespread over Eurasia and America. The flood, with a few exceptions, is an expiation by the water, after which a new type of world is created. The...
Iron Curtain speech Iron Curtain speech, speech delivered by former British prime minister Winston Churchill in Fulton, Missouri, on March 5, 1946, in which he stressed the necessity for the United States and Britain to act as the guardians of peace and stability against the menace of Soviet communism, which had...
Strike-slip fault Strike-slip fault, in geology, a fracture in the rocks of Earth’s crust in which the rock masses slip past one another parallel to the strike, the intersection of a rock surface with the surface or another horizontal plane. These faults are caused by horizontal compression, but they release their...
Electrostatics Electrostatics, the study of electromagnetic phenomena that occur when there are no moving charges—i.e., after a static equilibrium has been established. Charges reach their equilibrium positions rapidly, because the electric force is extremely strong. The mathematical methods of electrostatics...
Mujahideen Mujahideen, members of a number of guerrilla groups operating in Afghanistan during the Afghan War (1979–92) that opposed the invading Soviet forces and eventually toppled the Afghan communist government. Rival factions thereafter fell out among themselves, precipitating the rise of one faction,...
Liturgy of the Eucharist Liturgy of the Eucharist, the second of the two principal rites of the mass, the central act of worship of the Roman Catholic Church, the first being the liturgy of the Word. The liturgy of the Eucharist includes the offering and the presentation of bread and wine at the altar, their consecration...
Apical meristem Apical meristem, region of cells capable of division and growth in the root and shoot tips in plants. Apical meristems give rise to the primary plant body and are responsible for the extension of the roots and shoots. Unlike most animals, plants continue to grow throughout their entire life span...
Coefficient of friction Coefficient of friction, ratio of the frictional force resisting the motion of two surfaces in contact to the normal force pressing the two surfaces together. It is usually symbolized by the Greek letter mu (μ). Mathematically, μ = F/N, where F is the frictional force and N is the normal force....
Copernican Revolution Copernican Revolution, shift in the field of astronomy from a geocentric understanding of the universe, centred around Earth, to a heliocentric understanding, centred around the Sun, as articulated by the Polish astronomer Nicolaus Copernicus in the 16th century. This shift marked the start of a...
Radical Reconstruction Radical Reconstruction, process and period of Reconstruction during which the Radical Republicans in the U.S. Congress seized control of Reconstruction from Pres. Andrew Johnson and passed the Reconstruction Acts of 1867–68, which sent federal troops to the South to oversee the establishment of...
White Revolution White Revolution, aggressive modernization program implemented in Iran in 1963 and continued until 1979. The reforms, undertaken by Mohammad Reza Shah Pahlavi, upended the wealth and influence of the traditional landowning classes, altered rural economies, and led to rapid urbanization and...