| activated sludge | See: activated sludge method. (05 Mar 2000) |
|---|---|
| activated sludge method | A method of sewage disposal in which the sewage is treated with 15% bacterially active, liquid sludge, which is produced by repeated vigorous aeration of fresh sewage to form floccules or sediment; when this flocculation process is complete, the resulting activated sludge contains large numbers of bacteria, together with yeasts, molds, and protozoa, which actively effect the oxidation of organic compounds; this mixture is piped to a sedimentation tank, the effluent from which is completely treated sewage. (05 Mar 2000) |
| activated sludge process | <procedure> A method of treating sewage and wastewater through microbial oxidation. Sewage previously treated in settling tanks is aerated to encourage the growth of nonpathogenic aerobic microorganisms (bacteria, yeasts, moulds and protozoans) which break the organic matter down into carbon dioxide, water and simple salts. After this activated sludge is produced, the wastewater undergoes further processing through anaerobic digestion, filtering and chlorination. (29 Dec 1997) |
| sludge | 1. Mud; mire; soft mud; slush. 2. Small floating pieces of ice, or masses of saturated snow. 3. <chemical> See Slime. Sludge hole, the hand-hole, or manhole, in a steam boiler, by means of which sediment can be removed. Origin: CF. Slush. Source: Websters Dictionary (01 Mar 1998) |
| upflow sludge blanket | <apparatus> An apparatus for anaerobic digestion in which the microbes form thick flocculations that are kept suspended near the bottom of the reaction tank. (09 Oct 1997) |
| atrial echo | Electrical reactivation of the atrium by a retrograde impulse returning from the A-V node while the antegrade impulse continues to the ventricle; characterised electrocardiographically, by a pair of P waves enclosing a QRS complex, the second P wave being inverted, indicating that it is the reverse (the retrograde pathway) of the pathway of the first P wave (the antegrade pathway). (05 Mar 2000) |
| spin echo | A commonly used technique to recover T2 relaxation signals in magnetic resonance imaging, by using a 180 |
| nodus sinuatrialis echo | A postectopic sinus beat occurring earlier than would be expected from the preceding sinus node discharge interval; i.e., the interval following a premature beat of supraventricular origin is less than the ordinary cycle length between sinus beats, whereas ordinarily the interval would be expected to exceed cycle length. (05 Mar 2000) |
| echo | Origin: L. Echo, Gr. Echo, sound, akin to, sound, noise; cf. Skr. Va to sound, bellow; perh. Akin to E. Voice: cf. F. Echo. 1. A sound reflected from an opposing surface and repeated to the ear of a listener; repercussion of sound; repetition of a sound. "The babbling echo mocks the hounds." (Shak) "The woods shall answer, and the echo ring." (Pope) 2. Sympathetic recognition; response; answer. "Fame is the echo of actions, resounding them." (Fuller) "Many kind, and sincere speeches found an echo in his heart." (R. L. Stevenson) 3. A wood or mountain nymph, regarded as repeating, and causing the reverberation of them. "Sweet Echo, sweetest nymph, that liv'st unseen Within thy airy shell." (Milton) A nymph, the daughter of Air and Earth, who, for love of Narcissus, pined away until nothing was left of her but her voice. "Compelled me to awake the courteous Echo To give me answer from her mossy couch." (Milton) Echo organ, a stop upon a harpsichord contrived for producing the soft effect of distant sound. To applaud to the echo, to give loud and continuous applause. "I would applaud thee to the very echo, That should applaud again." (Shak) Source: Websters Dictionary (01 Mar 1998) |
| echo beat | Extrasystole produced by the return of an impulse in the heart retrograde to a focus near its origin which then returns antegradely to produce a second depolorization. (05 Mar 2000) |
| echo-free | The property of appearing echo-free or without echoes on a sonographic image; a clear cyst appears anechoic. See: transonic. Synonym: echo-free. Origin: G. An-priv. + echo + ic (05 Mar 2000) |
| echo planar | A method of magnetic resonance imaging that allows rapid image acquisition during free induction decay, using technically difficult rapidly oscillating radiofrequency gradients. (05 Mar 2000) |
| echo-planar imaging | A type of magnetic resonance imaging that uses only one nuclear spin excitation per image and therefore can obtain images in a fraction of a second rather than the minutes required in traditional mri techniques. It is used in a variety of medical and scientific applications. (12 Dec 1998) |
| echo reaction | A disorder of speech where there is an involuntary repetition several times of the same word. (27 Sep 1997) |
| echo speech | A disorder of speech where there is an involuntary repetition several times of the same word. (27 Sep 1997) |