| carbon-carbon lyases | <enzyme> Enzymes that catalyze the cleavage of a carbon-carbon bond by means other than hydrolysis or oxidation. This subclass contains the decarboxylases, the aldehyde-lyases, and the oxo-acid-lyases. Registry number: EC 4.1 (12 Dec 1998) |
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| colloidal silicon dioxide | A submicroscopic fumed silica prepared by the vapor-phase hydrolysis of a silicon compound; used as a tablet diluent and as a suspending and thickening agent. (05 Mar 2000) |
| hydrogen dioxide | <chemical> Hydrogen peroxide is produced by vertebrate phagocytes and is used in bacterial killing (the myeloperoxidase halide system). (05 May 1997) |
| silicon dioxide | <chemical> Silica. Transparent, tasteless crystals found in nature as agate, amethyst, chalcedony, cristobalite, flint, sand, quartz, and tridymite. The compound is insoluble in water or acids except hydrofluoric acid. Chemical name: Silica (12 Dec 1998) |
| nitrogen dioxide | <chemical> Nitrogen oxide (no2). A highly poisonous gas. Exposure produces inflammation of lungs that may only cause slight pain or pass unnoticed, but resulting oedema several days later may cause death. It is a major atmospheric pollutant that is able to absorb uv light that does not reach the earth's surface. Pharmacological action: oxidants, photochemical, poisons. Chemical name: Nitrogen oxide (NO2) (12 Dec 1998) |
| sulfur dioxide | <chemical> A highly toxic, colourless, nonflammable gas. It is used as a pharmaceutical aid and antioxidant. It is also an environmental air pollutant. Pharmacological action: air pollutants, environmental, antioxidants, pharmaceutic aid. Chemical name: Sulfur dioxide (12 Dec 1998) |
| dioxide | <chemistry> An oxide containing two atoms of oxygen in each molecule; binoxide. An oxide containing but one atom or equivalent of oxygen to two of a metal; a suboxide. Carbon dioxide. See Carbonic acid, under Carbonic. Origin: Pref. Di- + oxide. Source: Websters Dictionary (01 Mar 1998) |
| thorium dioxide | <chemical> Thorium oxide (tho2). A radiographic contrast agent that was used in the early 1930s through about 1954. High rates of mortality have been linked to its use and it has been shown to cause liver cancer. Pharmacological action: carcinogens. Chemical name: Thorium oxide (ThO2) (12 Dec 1998) |
| titanium dioxide | TiO2;contains not less than 99.0% and not more than 100.5% of TiO2, calculated on the dry basis; used in creams and powders as a protectant against external irritations and solar rays. (05 Mar 2000) |
| 1,4-diethylene dioxide | 1,4-dioxane;a colourless liquid used as a solvent for cellulose esters and in histology as a drying agent. Synonym: 1,4-diethylene dioxide. (05 Mar 2000) |
| absorption | The process of absorbing, specifically: 1. <physiology> The movement and uptake of substances (liquids and solutes) into cells or across tissues such as skin, intestine and kiidney tubules, by way of diffusion or osmosis. 2. <chemistry> The drawing of a gas or liquid into the pores of a permeable solid. 3. <psychology> The devotion of thought to one object or activity, with inattention to others. 4. <radiology> The taking up of energy by matter with which the radiation interacts. 5. <physics> The loss of (electromagnetic) energy to a medium. For instance, an electromagnetic wave which propagates through a plasma will set the electrons into motion. If the electrons make collisions with other particles, they will absorb net energy from the wave. 6. <immunology> A process in which an antigen or antibody is used to pull an analogous antigen or antibody out of a solution. Compare: adsorption. Origin: L. Absorptio (12 Nov 1997) |
| absorption band | The range of wavelengths or frequencies in the electromagnetic spectrum where radiant energy is absorbed by passage through a gaseous, liquid, or dissolved substance; it is exploited for analytical purposes in colourimetry or spectrophotometry, and is usually described in terms of the wavelength where maximum absorbance occurs (i.e., lambdamax). (05 Mar 2000) |
| absorption cell | A small glass chamber with parallel sides, in which absorption spectra of solutions can be obtained. (05 Mar 2000) |
| absorption chromatography | <investigation> Techniques for separating molecules based on differential absorption and elution. Term for separation methods involving flow of a fluid carrier over a nonmobile absorbing phase. (18 Nov 1997) |
| absorption coefficient | <physics> Measures the degree of wave absorption defined as the fraction of wave energy lost as the wave travels a unit distance. See: absorption. (15 Jan 1998) |