| Section A | A index | 261-269 of 917 terms |
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aerosol—A colloidal system in which the dispersed phase is composed of either solid or liquid particles, and in which the dispersion medium is some gas, usually air. There is no clear-cut upper limit to the size of particles composing the dispersed phase in an aerosol, but as in all other colloidal systems, it is rather commonly set at 1 μm. Haze, most smokes, and some fogs and clouds may thus be regarded as aerosols. However, it is not good usage to apply the term to ordinary clouds with drops so large as to rule out the usual concept of colloidal stability. It is also poor usage to apply the term to the dispersed particles alone; an aerosol is a system of dispersed phase and dispersing medium taken together. Compare airborne particulates, particles, PM-2.5, PM-10.
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aerostatic balance—(Also called air poise.) An instrument for weighing air. Compare aerodynamic balance.
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aestival—(Also spelled estival.) Pertaining to summer. The corresponding adjectives for autumn, winter, and spring are autumnal, hibernal, and vernal.
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aestivation—A state of torpidity induced in some animals by the heat and dryness of the summer.
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Afer—(Also called Africo, Africino, Africuo, Africus ventus.) In Italy, the southwest wind.
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afghanets—A strong, gusty, wind that occurs on the upper course of the Amu Darya (river) in Turkmenistan (i.e., coming from Afghanistan). It is preceded and accompanied by duststorms.
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African jet—A low-level easterly jet in the summer months over the Sahara Desert of North Africa. The wave disturbances drawing energy from this jet propagate westward to the Atlantic Ocean. They are also known as African waves. Some of them under favorable conditions become hurricanes that reach North America. Compare easterly wave.
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