(from the article "malacostracan") ...by internal mechanisms. Organs of sound reception include, in brachyurans, the chordotonal organs on the hinges of walking legs. Highly specialized sound and vibration receptors include the antennal calceoli of amphipods, the individual microstructure of which consists of receiving elements ...
(from the article "Diaguita") Indian peoples of South America, formerly inhabiting northwestern Argentina and the Chilean provinces of Atacama and Coquimbo. The Calchaqui, a northwestern Argentine subgroup of the Diaguita, are the best-documented. Their language affiliation remains uncertain.
in Greek mythology, the son of Thestor (a priest of Apollo) and the most famous soothsayer among the Greeks at the time of the Trojan War. He played an important role in the quarrel between Achilles and Agamemnon that begins ...
(from the article "amphibole") ...this group. The mineral nomenclature of the amphiboles is divided into four principal subdivisions based on B-group cation occupancy: (1) the iron-magnesium-manganese amphibole group, (2) the calcic amphibole group, (3) the sodic-calcic amphibole group, and (4) the sodic amphibole group. ...
(from the article "Platonism") In the 4th century the Christian exegete Calcidius (Chalcidius) prepared a commentary on Plato's Timaeus, which exerted an important influence on the medieval interpretation of the Timaeus. A Christian Platonic theism of the type of which Boethius is the finest ...
(from the article "animal disease") ...of animals, may occur in the liver as a result of certain inherited diseases of animals; the condition is known as glycogen infiltration. The abnormal deposition of calcium salts, which is known as hypercalcification, may occur as a result of ...
(from the article "sedimentary rock") In addition to the ancient analogues of the modern carbonate deposits described above are freshwater limestones (marls) and limestone muds (or calcilutites) of deep-water abyssal plains. Freshwater limestones of limited extent represent a spectrum of small-scale settings developed within and ...
(from the article "metallurgy") Calcination of carbonates to oxides is done in a horizontal rotary kiln, which is a mild-steel circular shell lined with refractory material and having a length 10 to 12 times the diameter. Sloping slightly downward from feed to discharge ends, ...
(from the article "sponge") ...small in size; inhabit shallow waters of all seas, from intertidal regions to depths of 200 m (660 ft); a few species to 800 m (2,600 ft); about 300 species.Larva called parenchymella (solid, compact, with outer layer of flagellated ...
(from the article "aluminum processing") Calcined alumina is aluminum oxide that has been heated at temperatures in excess of 1,050° C (1,900° F) to drive off nearly all chemically combined water. In this form, alumina has great chemical purity, extreme hardness (9 on the Mohs ...
(from the article "sports") ...activity more as an art form than as a combat. Northern Europeans emulated them. Humanistically inclined Englishmen and Germans admired the cultivated Florentine game of calcio, a form of football that stressed the good looks and elegant ...
one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO). Calcisols are characterized by a layer of translocated (migrated) calcium carbonate-whether soft and powdery or hard and cemented-at some depth in the soil ...
the most common form of natural calcium carbonate (CaCO3), a widely distributed mineral known for the beautiful development and great variety of its crystals. It is polymorphous (same chemical formula but different crystal structure) with the minerals aragonite and vaterite ... [22 Related Articles]
(from the article "ocean") Carbonate oozes cover about half of the world's seafloor. They are present chiefly above a depth of 4,500 metres; below that they dissolve quickly. This depth is named the Calcite Compensation Depth (or CCD). It represents the level at which ...
(from the article "mineral") The common anhydrous carbonates are divided into three groups that differ in structure type: calcite, aragonite, and dolomite. The copper carbonates azurite and malachite are the only notable hydrous varieties (see Table 7).calcitemagnesite
(from the article "calcite") When sedimentary and diagenetic limestones undergo metamorphism, the calcite is frequently recrystallized and tends to become coarsely crystalline. The resulting rocks are calcite marbles. Some calcite marbles, however, appear to have had dolostone rather than limestone precursors; i.e., the dolostone ...
a protein hormone secreted in humans and other mammals by parafollicular cells in the thyroid gland, and in birds, fishes, and other nonmammalian vertebrates by cells of the ultimobranchial bodies, which are discrete calcitonin-secreting glands. Calcitonin lowers the concentration of ... [8 Related Articles]
(from the article "bone") ...the tubular reabsorption of calcium from the ultrafiltrate that would otherwise be excreted into the urine. It also stimulates the kidney to activate the major circulating form of vitamin D to calcitrial. Calcitrial enters the circulation and travels to the ...
chemical element, one of the alkaline-earth metals of main Group 2 (IIa) of the periodic table. It is the most abundant metallic element in the human body and the fifth most abundant element in the Earth's crust. [46 Related Articles]
(from the article "bentonite") ...emulsions, insecticides, soaps, pharmaceuticals, and paints; in the manufacture of paper; for clarifying water, juices, and liquors; and as a water softener to remove calcium from hard water. Calcium bentonites are nonswelling and break down to a finely granular aggregate ...
(from the article "chemical industry") ...to light if this box were magnified and examined closely. These substances, however, can in general also be made from acetylene, and acetylene can also be made from a completely different source, calcium carbide.
(from the article "bivalve") The bivalve shell is made of calcium carbonate embedded in an organic matrix secreted by the mantle. The periostracum, the outermost organic layer, is secreted by the inner surface of the outer mantle fold at the mantle margin. It is ...
(from the article "nervous system") As with potassium channels, there is more than one type of calcium channel. The inward calcium current is slower than the sodium current. There are at least two types of current in certain neurons of the central nervous system-a long-lasting ...
(from the article "deliquescence") The effectiveness of calcined calcium chloride in settling road dust is a result of its deliquescence. When spread in the form of a powder or flakes, it absorbs more than its own weight of water and forms a liquid that ...
(from the article "carbide") ...→ C2H2 + Ca(OH)2 Calcium carbide also reacts with nitrogen gas at elevated temperatures (1,000-1,200 °C [1,800-2,200 °F]) to form calcium cyanamide, CaCN2.CaC2 + N2 → CaCN2 + C This is an important industrial reaction because CaCN2 finds extensive...
condition in which calcium is insufficient or is not utilized properly. Calcium is the mineral that is most likely to be deficient in the average diet. It is the chief supportive element in bones and teeth. Calcium salts make up ... [1 Related Articles]
(from the article "cadmium poisoning") ...from inhalation may cause a loss of the sense of smell, coughing, difficult breathing, weight loss, and injury of the liver and kidneys. Treatment usually includes the oral administration of calcium edetate.
(from the article "optical ceramics") ...optical transparency with high scratch resistance. Similarly, single-crystal or infrared-transparent polycrystalline ceramics such as sodium chloride (NaCl), rubidium-doped potassium chloride (KCl), calcium fluoride (CaF), and strontium fluoride (SrF2) have been used for erosion-resistant infrared radomes, windows for infrared detectors, and ...
(from the article "parturient paresis") ...circulatory collapse and death. The death rate in untreated animals may run as high as 90 percent. Fever is not a sign in this disorder. The most effective treatment is the intravenous injection of calcium gluconate, upon which the animal ...
(from the article "calcium") Calcium hydroxide, also called slaked lime Ca(OH)2, is obtained by the action of water on calcium oxide. When mixed with water, a small proportion of it dissolves, forming a solution known as limewater, the rest remaining as a suspension called ...
(from the article "Industrial chemicals") ...finishing the bleaching process is used to produce white cloth, to prepare fabrics for other finishes, or to remove discoloration that has occurred in other processes. Chlorine, sodium hypochlorite, calcium hypochlorite, and hydrogen peroxide are commonly used as bleaches.
(from the article "Processes affecting the major chemical components of groundwater") ...channels in the cell membrane, (2) regulation of cellular activity by way of intracellular chemical signals, such as cyclic adenosine 3',5'-monophosphate (cAMP), inositol phosphates, or calcium ions, and (3) regulation of gene expression.
(from the article "geology") There are two main branches of sedimentary petrology. One branch deals with carbonate rocks, namely limestones and dolomites, composed principally of calcium carbonate (calcite) and calcium magnesium carbonate (dolomite). Much of the complexity in classifying carbonate rocks stems partly from ...
(from the article "polymer, inorganic") ...ion to rather complex structures containing chains and rings of three- and four-coordinated boron atoms. (See chemical bonding for a description of molecular shapes.) For example, calcium metaborate, CaB2O4, consists of infinite chains of B2O42− units, whereas potassium borate,...
(from the article "saltpetre") ...distinguished as (1) ordinary saltpetre, or potassium nitrate, KNO3; (2) Chile saltpetre, cubic nitre, or sodium nitrate, NaNO3; and (3) lime saltpetre, wall saltpetre, or calcium nitrate, Ca(NO3)2. These three nitrates generally occur as efflorescences caused by the oxidation of ...
(from the article "nitride") There are two principal methods of preparing nitrides. One is by direct reaction of the elements (usually at elevated temperature), shown here for the synthesis of calcium nitride, Ca3N2.3Ca + N2 → Ca3N2A second method is through the loss of ...
(from the article "Table 1: Raw Materials Used in the Manufacture of Portland Cement") Calcium oxide, also known as lime, or quicklime, CaO, is a white or grayish white solid produced in large quantities by roasting calcium carbonate so as to drive off carbon dioxide. Lime, one of the oldest products of chemical reaction ...
(from the article "connective tissue") Like other connective tissues, bone consists of cells, fibres, and ground substance, but, in addition, the extracellular components are impregnated with minute crystals of calcium phosphate in the form of the mineral hydroxyapatite. The mineralization of the matrix is responsible ...
(from the article "cement") The most important hydraulic constituents are the calcium silicates, C2S and C3S. Upon mixing with water, the calcium silicates react with water molecules to form calcium silicate hydrate (3CaO · 2SiO2 · 3H2O) and calcium hydroxide (Ca[OH]2). These compounds are ...
(from the article "calcium") Calcium sulfate, CaSO4, is a naturally occurring calcium salt. It is commonly known in its dihydrate form, CaSO4·2H2O, a white or colourless powder called gypsum. As uncalcined gypsum, the sulfate is employed as a soil corrector. Calcined gypsum is used ...
(from the article "crystal") ...orbitals.) Two electrons are transferred from the cations to the anions, leaving each with a closed shell. The alkaline earth chalcogenides form ionic binary crystals such as barium oxide (BaO), calcium sulfide (CaS), barium selenide (BaSe), or strontium oxide (SrO). ...
(from the article "sedimentary rock") ...If volcanic rock fragments such as andesite and basalt are most abundant, the rock is termed a volcanic arenite. If chert and carbonate rock fragments are predominant, the name chert or calclithite is applied.
calcium-rich duricrust, a hardened layer in or on a soil. It is formed on calcareous materials as a result of climatic fluctuations in arid and semiarid regions. Calcite is dissolved in groundwater and, under drying conditions, is precipitated as the ... [2 Related Articles]
the earliest known calculator, built in 1623 by the German astronomer and mathematician Wilhelm Schickard. He described it in a letter to his friend the astronomer Johannes Kepler, and in 1624 he wrote again to explain that a machine that ... [1 Related Articles]
(from the article "chemical bonding") There are two strands of approach to the computation of molecular structure. In the semiempirical approach, the calculation draws on a number of experimentally determined characteristics to help in the overall calculation. In the ab initio approach, the calculation proceeds ...
machine for automatically performing arithmetical operations and certain mathematical functions. Modern calculators are descendants of a digital arithmetic machine devised by Blaise Pascal in 1642. Later in the 17th century, Gottfried Wilhelm Leibniz created a more advanced machine, and, especially ... [8 Related Articles]
branch of mathematics concerned with the calculation of instantaneous rates of change (differential calculus) and the summation of infinitely many small factors to determine some whole (integral calculus). Two mathematicians, Isaac Newton of England and Gottfried Wilhelm Leibniz of Germany, ... [23 Related Articles]
(from the article "mineral") ...extent of organically formed aragonite. Minerals also are produced by the human body: hydroxylapatite [Ca5(PO4)3(OH)] is the chief component of bones and teeth, and calculi are concretions of mineral substances found in the urinary system.
(from the article "logic, history of") Another and distinct goal Leibniz proposed for logic was a "calculus of reason" (calculus ratiocinator). This would naturally first require a symbolism but would then involve explicit manipulations of the symbols according to established rules by which either new truths ...
branch of mathematics concerned with the problem of finding a function for which the value of a certain integral is either the largest or the smallest possible. Many problems of this kind are easy to state, but their solutions commonly ... [7 Related Articles]
