(from the article "sports") ...the discus. The historian Livy writes of Greek athletes' appearing in Rome as early as 186 BC; however, the contestants' nudity shocked Roman moralists. The emperor Augustus instituted the Actian Games in 27 BC to celebrate his victory over Antony and Cleopatra, and several of his successors began similar games, ...
protein that is an important contributor to the contractile property of muscle and other cells. It exists in two forms: G-actin (monomeric globular actin) and F-actin (polymeric fibrous actin), the form involved in muscle contraction. In muscle, two long strands of beadlike actin molecules are twisted together to form a ... [13 Related Articles]
(from the article "cell") Actin is a globular protein that polymerizes (joins together many small molecules) to form long filaments. Because each actin subunit faces in the same direction, the actin filament is polar, with different ends, termed "barbed" and "pointed." An abundant protein in nearly all eukaryotic cells, actin has been extensively studied ...
the performing art in which movement, gesture, and intonation are used to realize a fictional character for the stage, for motion pictures, or for television. [16 Related Articles]
(from the article "ultraviolet radiation") ...nm), far (200-100 nm), and extreme (below 100 nm). In biology, three conventional divisions have been observed: near (400-315 nm), which is absorbed relatively poorly by organisms; actinic (315-200 nm), which is absorbed most readily by organic matter and thus has the greatest effects on organisms; and vacuum (less than ...
(from the article "Seaborg, Glenn T.") ...and placement of these and many heavier elements in the periodic table of the elements was helped greatly by an important organizing principle enunciated by Seaborg in 1944 and known as the actinide concept. This was one of the most significant changes in the periodic table since Russian chemist Dmitry ...
any of a series of 15 consecutive chemical elements in the periodic table from actinium to lawrencium (atomic numbers 89-103). As a group they are significant largely because of their radioactivity. Although several members of the group, including uranium (the most familiar), occur naturally, most are man-made. Both uranium and ... [1 Related Articles]
(from the article "Ericales") Actinidiaceae are usually shrubs, small trees, or lianas; they are largely tropical and especially abundant from Southeast Asia to Malesia. There are 3 genera and 355 species in the family. Saurauia (300 species) grows throughout the range of the family, while Actinidia (some 30 species) is Indo-Malesian and East Asian. ...
(from the article "coloration") A relatively rare pigment, actiniochrome occurs in red or violet tentacle tips and in the stomodeum (oral region) of various sea anemones. The pigment plays no recognized physiological role.
(from the article "crossopterygian") The Actinistia, especially the family Coelacanthidae, unlike the Rhipidistia, have exhibited exceptional evolutionary stability. The same fossil deposits contain both marine and freshwater types, both already specialized during the Devonian. They were thought to have disappeared 50,000,000 to 70,000,000 years ago, but in 1938 a live specimen was taken in ...
(Ac), radioactive chemical element, in Group IIIb of the periodic table, atomic number 89. Actinium was discovered (1899) by Andre-Louis Debierne in pitchblende residues left after Pierre and Marie Curie had extracted radium and was also discovered (1902) independently by Friedrich Otto Giesel. A ton of pitchblende ore contains about ... [1 Related Articles]
(from the article "actinium series") set of unstable heavy nuclei constituting one of the four radioactive series (q.v.).FIGUREradioactive seriesThe four radioactive series of chemical el
(from the article "actinium") The most common isotope of actinium is actinium-227; the others, natural and artificial, are too short-lived to accumulate in macroscopic quantity. Actinium-227, which is one of the decay products of uranium-235, has a 21.6-year half-life and in turn decays almost entirely to thorium-227, but about 1 percent decays to francium-223. ...
an amphibole mineral in the tremolite-actinolite series of calcium, magnesium, and iron silicates. The minerals in this series are abundant in regionally metamorphosed rocks, such as schists. Tremolite may weather to talc, and both tremolite and actinolite may alter to chlorite or carbonates. For chemical formula and detailed physical properties, ... [1 Related Articles]
in chemistry, a substance or a mixture of substances that reacts through the action of light and that, because of the easily determined quantitative relationship between the extent of the reaction and the energy of the absorbed light, is used as a standard for measurement of light energies involved in ...
(from the article "flower") A flower may be radially symmetrical (see photograph), as in roses and petunias, in which case it is termed regular or actinomorphic. A bilaterally symmetrical flower, as in orchids (see photograph) and snapdragons, is irregular or zygomorphic.floral symmetrysymmetryWhen the different ...
(from the article "pneumonia") ...variety of organic dusts. These pneumonias may occur following exposure to moldy hay or sugarcane, room humidifiers, and air-conditioning ducts, all of which contain the fungus Actinomyces. Other fungi found in barley, maple logs, and wood pulp may cause similar illnesses. In addition, people exposed to rats, ...
(from the article "actinomycosis") ...by two anaerobic species of the genus Actinomyces. The disease is characterized by multiple painful, hard swellings filled with pus, most often seen on the face, neck, chest, and abdomen. Actinomyces bovis is responsible for the disease in cattle and Actinomyces israeli for that in humans.
(from the article "actinomycosis") ...is characterized by multiple painful, hard swellings filled with pus, most often seen on the face, neck, chest, and abdomen. Actinomyces bovis is responsible for the disease in cattle and Actinomyces israeli for that in humans.
any member of a heterogeneous group of gram-positive, generally anaerobic bacteria noted for a filamentous and branching growth pattern that results, in most forms, in an extensive colony, or mycelium. The mycelium in some species may break apart to form rod- or coccoid-shaped forms. Many genera also form spores; the ... [4 Related Articles]
a noncontagious bacterial infection of humans and cattle that is caused by two anaerobic species of the genus Actinomyces. The disease is characterized by multiple painful, hard swellings filled with pus, most often seen on the face, neck, chest, and abdomen. Actinomyces bovis is responsible for the disease in cattle ... [1 Related Articles]
any parasitic microorganism of the class Actinomyxidia (Actinosporea), phylum Myxosporidia (Myxospora). It inhabits the alimentary canal of certain aquatic worms. The characteristic spores develop in the host's gut after the union of large and small gametes. The spores contain three polar filaments (possibly anchoring devices) enclosed in capsules and one ...
(from the article "protist") All with axopodia; pseudopodia with microtubular cores; elaborate endoskeletal systems generally present; tubular mitochondrial cristae; complex central capsule characteristic of many; primarily marine; 11,000 to 12,000 reported species, more than half of which are extinct forms.protozoanAnnotated classification....(Gymnamoebia), testate forms (Testacealobosia), ...
(from the article "vertebrate") ...scales; paired nostrils with or without internal nares; lateral-line system; mostly oviparous with external fertilization; some ovoviviparous or viviparous.Generally lack choanae; no fleshy base to paired fins; no internal nares; air sacs usually function as swim...fishAnnotated classification...types ...
(from the article "cnidarian") ...craspedote). Colonial forms commonly polymorphic. Coelenteron undivided. Gametes ripen in ectoderm. Only class with some freshwater members. 2,700 species.Curious groups of solitary, motile cnidarians with features of both polyps and medusae. Europe; in marine sand.
(from the article "applied logic") The propositional modalities relating to normative (or valuational) classifications of actions and states of affairs, such as the permitted, the obligatory, the forbidden, or the meritorious, are characterized as deontic modalities (Greek deontos, "of that which is binding") and systematized in deontic logic. Though this subject was first treated as ...
(from the article "keyboard instrument") In the three surviving examples of Cristofori's pianos, which date from the 1720s, the mechanism, or "action," differs somewhat from that described and pictured by Maffei; however, rather than merely representing an earlier phase of Cristofori's work, Maffei's diagram may be in error. In the surviving instruments a pivoted piece ...
in theoretical physics, an abstract quantity that describes the overall motion of a physical system. Motion, in physics, may be described from at least two points of view: the close-up view and the panoramic view. The close-up view involves an instant-by-instant charting of the behaviour of an object. The panoramic ... [2 Related Articles]
(from the article "small arm") Practical shoulder-fired small arms started with the perfection of the flintlock ignition system in the mid-17th century (see military technology). Earlier gunpowder small arms, based on the matchlock or wheel lock mechanisms, were generally too heavy, too unreliable, or too expensive to allow for general issue to infantry forces. Indeed, ...
(from the article "mechanics") ...bodies interacting with one another by means of the force of gravity. In the previous discussion of circular orbits, the Sun was assumed to be at rest at the centre of the orbit, but, according to Newton's third law, it must actually be accelerated by a force due to the ...
(from the article "chess") ...to be a bridge between serious and quick chess. The most popular new format, which appeared in the mid-1980s, limited an entire game to 25 minutes for each player. This control, variously called action chess, active chess, quickplay, and game/25, became popular because it provided a livelier tempo in which ...
(French: "French Action"), influential right-wing antirepublican group in France during the first 40 years of the 20th century. Action Francaise was also the name of a daily newspaper (published from March 21, 1908, to Aug. 24, 1944) that expressed the group's ideas. [3 Related Articles]
(from the article "Akintola, Samuel Ladoke") ...of the Baptist Teachers' Union and the Nigerian Youth Movement. He left teaching to study public administration and law in England and returned to Nigeria in 1950. He became a legal adviser to the Action Group, the dominant Western Region party, and by 1954 was deputy leader under Oba Femi ...
(from the article "Suriname") ...a coalition government of the NPS and the VHP. In 1961 the left-wing Nationalist Republican Party (Partij Nationalistische Republiek; PNR) was established. Among the East Indian population the Action Group (Aktie Groep) became active. A split occurred in the NPS-VHP coalition after the 1967 elections, which led to a coalition ...
(from the article "calculus of variations") ...principle of least action (c. 1744), which sought to explain all processes as driven by a demand that some property be economized or minimized. In particular, minimizing an integral, called an action integral, led several mathematicians (most notably the Italian-French Joseph-Louis Lagrange in the 18th century and the Irish William ...
direct, instinctual, and highly dynamic kind of art that involves the spontaneous application of vigorous, sweeping brushstrokes and the chance effects of dripping and spilling paint onto the canvas. The term was coined by the American art critic Harold Rosenberg to characterize the work of a group of American Abstract ... [9 Related Articles]
the brief (about one-thousandth of a second) reversal of electric polarization of the membrane of a nerve cell (neuron) or muscle cell. In the neuron an action potential produces the nerve impulse, and in the muscle cell it produces the contraction required for all movement. Sometimes called a propagated potential ... [8 Related Articles]
(from the article "Czechoslovak region, history of") ...since then. The Ministry of the Interior was under the control of another purge victim, Josef Pavel. The newly elected Presidium of the Communist Party consisted largely of newcomers, and the Action Program was compiled by young party intellectuals.
(from the article "criminology") Action research, which is often contrasted with experimental research, consists of drawing upon the observations of field-workers and other persons directly involved with delinquents, potential delinquents, or prisoners. For example, social workers have attempted to help children and adolescents living in slums cope with their problems and at the same ...
(from the article "Italy") ...cautiously revived in 1942 and 1943. The Communists helped to organize strikes, the leading Roman Catholics formed the Christian Democratic Party (now the Italian Popular Party) in 1943, and the new Party of Action was founded in January 1943, mainly by republicans and Radicals. Leading Communists began to reenter Italy, ...
(from the article "nature, philosophy of") ...at which differentials (small or infinitesimal distances or quantities) in several dimensions change with respect to their neighbours-electrodynamics is a local-action theory rather than an action-at-a-distance theory as in older formulations modelled after Newton's law of gravitation. The principle of local action states that the variations of electromagnetic magnitudes at ...
(from the article "Xerxes I") ...men according to Herodotus and 360,000 by modern estimate, supported by 700 to 800 ships. Their passage was facilitated by a massive engineering works: a channel was dug across the Isthmus of Actium so that the peaks of Mount Athos might be avoided. Nevertheless, the army's size was of no ...
(September 2, 31 BC), naval battle off a promontory in the north of Acarnania, on the western coast of Greece, where Octavian (known as the emperor Augustus after 27 BC), by his decisive victory over Mark Antony, became the undisputed master of the Roman world. Antony, with 500 ships and ... [7 Related Articles]
(from the article "aluminum processing") Activated alumina is a porous form of aluminum oxide from which much of the chemically combined water has been driven off at temperatures low enough to avoid sintering. It is chemically inert to most gases, nontoxic, and will not soften, swell, or disintegrate in water. It has the ability to ...
(from the article "environmental works") An effective method for removing dissolved organic substances that cause tastes, odours, or colours is adsorption by activated carbon. Adsorption is the capacity of a solid particle to attract molecules to its surface. Powdered carbon mixed with water can adsorb and hold many different organic impurities. When the carbon is ...
sewage-treatment process in which sludge, the accumulated, bacteria-rich deposits of settling tanks and basins, is seeded into incoming waste water and the mixture agitated for several hours in the presence of an ample air supply. Suspended solids and many organic solids are absorbed or adsorbed by the sludge, while organic ... [2 Related Articles]
in psychology, the stimulation of the cerebral cortex into a state of general wakefulness, or attention. Activation proceeds from various portions of the brain, but primarily from the reticular formation, the nerve network in the midbrain that monitors ingoing and outgoing sensory and motor impulses. Activation, however, is not the ... [2 Related Articles]
(from the article "rare-earth element") Analytical methods involving activation analysis (production of artificial radioactivity) and mass spectroscopy (separation of atoms on the basis of mass) have made it possible to make accurate measurements of the relative abundances of these elements, even when they are present in extremely small amounts. Such measurements are of great interest ...
(from the article "electronic voting") ...somehow interact with another electronic device. Thus, connection to the Internet or to wireless devices is usually disallowed. However, a voting session is typically initiated through the use of an activation card. A poll worker, upon verification of eligibility, sets the card to enable one voting session. After the session ...
in chemistry, the minimum amount of energy that is required to activate atoms or molecules to a condition in which they can undergo chemical transformation or physical transport. In terms of the transition-state theory (q.v.), the activation energy is the difference in energy content between atoms or molecules in an ... [6 Related Articles]
(from the article "Table 5: Applications of Radiation Interactions in Detectors") For radiation energies of several MeV and lower, charged particles and fast electrons do not induce nuclear reactions in absorber materials. Gamma rays with energy below a few MeV also do not readily induce reactions with nuclei. Therefore, when nearly any material is bombarded by these forms of radiation, the ...
