| acceleration | The act of accelerating, or the state of being accelerated; increase of motion or action; as, a falling body moves toward the earth with an acceleration of velocity; opposed to retardation. "A period of social improvement, or of intellectual advancement, contains within itself a principle of acceleration." (I. <astronomy> Taylor) Acceleration of the moon, the increase of the moon's mean motion in its orbit, in consequence of which its period of revolution is now shorter than in ancient times. Acceleration and retardation of the tides. See Priming of the tides, under Priming. Diurnal acceleration of the fixed stars, the amount by which their apparent diurnal motion exceeds that of the sun, in consequence of which they daily come to the meridian of any place about three minutes fifty-six seconds of solar time earlier than on the day preceding. Acceleration of the planets, the increasing velocity of their motion, in proceeding from the apogee to the perigee of their orbits. Origin: L. Acceleratio: cf. F. Acceleration. Source: Websters Dictionary (01 Mar 1998) |
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| acceleration phase | <cell biology, cell culture> A period of increasing growth before the log phase in a culture of microbes. After the culture is started on a medium, at first there is no growth (the lag phase) and then the microbes start to gradually grow (acceleration phase) until they reach a constant maximum rate of growth (log phase). (15 Jan 1998) |
| accelerator | 1. Anything that increases rapidity of action or function. 2. In physiology, a nerve, muscle, or substance that quickens movement or response. 3. A catalytic agent used to hasten a chemical reaction. 4. In nuclear physics, a device that accelerates charged particles (e.g., protons) to high speed in order to produce nuclear reactions in a target, often for the production of radionuclides or for radiation therapy. Synonym: accelerant. Origin: L. Accelerans, pres. P. Of ac-celero, to hasten, fr. Celer, swift (05 Mar 2000) |
| accelerator factor | <chemical> Heat- and storage-labile plasma glycoprotein which accelerates the conversion of prothrombin to thrombin in blood coagulation. Factor v accomplishes this by forming a complex with factor xa, phospholipid, and calcium (prothrombinase complex). Deficiency of factor v leads to owren's disease. Chemical name: Blood-coagulation factor V (12 Dec 1998) |
| accelerator fibres | Postganglionic sympathetic nerve fibre's originating in the superior, middle, and inferior cervical ganglia of the sympathetic trunk, conveying nervous impulses to the heart that increase the rapidity and force of the cardiac pulsations. Synonym: augmentor fibres. (05 Mar 2000) |
| accelerator globulin | Globulin in serum that promotes the conversion of prothrombin to thrombin in the presence of thromboplastin and ionised calcium. See: factor Va, factor V, serum accelerator globulin. (05 Mar 2000) |
| accelerator nerves | Certain of the cardiopulmonary splanchnic nerves establishing the sympathetic innervation of the heart; originating from ganglion cells of the superior, middle, and inferior cervical ganglion of the sympathetic trunk, the unmyelinated efferent fibres of the accelerator nerve's stimulate an increase in the heart rate. (05 Mar 2000) |
| accelerin | An obsolete term for what was once considered an intermediary product of coagulation but is no longer thought to exist. (05 Mar 2000) |
| accelerograph | An apparatus for studying the combustion of powder in guns, etc. Origin: Accelerate + -graph. Source: Websters Dictionary (01 Mar 1998) |
| accelerometer | An instrument for measuring the rate of change of velocity per unit of time. (05 Mar 2000) |
| accensor | One of the functionaries who light and trim the tapers. Origin: LL, from p. P. Accensus. See Accend Source: Websters Dictionary (01 Mar 1998) |
| accent | 1. A superior force of voice or of articulative effort upon some particular syllable of a word or a phrase, distinguishing it from the others. Many English words have two accents, the primary and the secondary; the primary being uttered with a greater stress of voice than the secondary; as in as'pira'tion, where the chief stress is on the third syllable, and a slighter stress on the first. Some words, as an'tiap'o-plec'tic, in-com'pre-hen'si-bil'i-ty, have two secondary accents. 2. A mark or character used in writing, and serving to regulate the pronunciation; especially., a mark to indicate the nature and place of the spoken accent; a mark to indicate the quality of sound of the vowel marked; as, the French accents. In the ancient Greek the acute accent (') meant a raised tone or pitch, the grave, the level tone or simply the negation of accent, the circumflex (~ or ^) a tone raised and then depressed. In works on elocution, the first is often used to denote the rising inflection of the voice; the second, the falling inflection; and the third (^), the compound or waving inflection. In dictionaries, spelling books, and the like, the acute accent is used to designate the syllable which receives the chief stress of voice. 3. Modulation of the voice in speaking; manner of speaking or pronouncing; peculiar or characteristic modification of the voice; tone; as, a foreign accent; a French or a German accent. "Beguiled you in a plain accent." . "A perfect accent." . "The tender accent of a woman's cry." (Prior) 4. A word; a significant tone; (pl) expressions in general; speech. "Winds! on your wings to Heaven her accents bear, Such words as Heaven alone is fit to hear." (Dryden) 5. Stress laid on certain syllables of a verse. 6. A regularly recurring stress upon the tone to mark the beginning, and, more feebly, the third part of the measure. A special emphasis of a tone, even in the weaker part of the measure. The rythmical accent, which marks phrases and sections of a period. The expressive emphasis and shading of a passage. 7. <mathematics> A mark used to denote feet and inches; as, 6' 10'' is six feet ten inches. Origin: F. Accent, L. Accentus; ad + cantus a singing, canere to sing. See Cant. Source: Websters Dictionary (01 Mar 1998) |
| accentor | 1. One who sings the leading part; the director or leader. 2. <ornithology> A genus of European birds (so named from their sweet notes), including the hedge warbler. In America sometimes applied to the water thrushes. Origin: L. Ad. + cantor singer, canere to sing. Source: Websters Dictionary (01 Mar 1998) |
| accentuation | Act of accentuating; applications of accent. Specifically . Pitch or modulation of the voice in reciting portions of the liturgy. Origin: LL. Accentuatio: cf. F. Accentuation. Source: Websters Dictionary (01 Mar 1998) |
| accentuator | A substance, such as aniline, the presence of which allows a combination between a tissue or histologic element and a stain that might otherwise be impossible. Origin: L. Accentus, accent, fr. Cano, to sing (05 Mar 2000) |