| absolute dehydration | Actual water deficit as measured by a difference from the normal or from a given water content. (05 Mar 2000) |
|---|---|
| relative dehydration | Water deficit relative to content of solutes contributing effective osmotic pressure; a state of increased effective osmotic pressure of body fluids. (05 Mar 2000) |
| voluntary dehydration | That physiologic lag or deficit that results when sensations of thirst are not strong enough to bring about complete replacement of water loss, as in rapid sweating. (05 Mar 2000) |
| dehydration | The condition that results from excessive loss of body water. Synonym: anhydration, deaquation, hypohydration. Origin: L. De = away, Gr. Hydor = water (18 Nov 1997) |
| dehydration-condensation reaction | The joining of two molecules to each other with the release of a water molecule in the process. Compare: hydrolysis. (09 Oct 1997) |
| dehydration fever | An elevation of temperature in infants after reduction of fluid intake, diarrhoea, or vomiting; probably caused by reduced available body water, with reduced heat loss by evaporation; an analogous condition in adults is seen when exertion is continued in the face of dehydration. Synonym: dehydration fever, exsiccation fever, inanition fever. (05 Mar 2000) |
| vacuum | Origin: L, fr. Vacuus empty. See Vacuous. 1. <physics> A space entirely devoid of matter (called also, by way of distinction, absolute vacuum); hence, in a more general sense, a space, as the interior of a closed vessel, which has been exhausted to a high or the highest degree by an air pump or other artificial means; as, water boils at a reduced temperature in a vacuum. 2. The condition of rarefaction, or reduction of pressure below that of the atmosphere, in a vessel, as the condenser of a steam engine, which is nearly exhausted of air or steam, etc.; as, a vacuum of 26 inches of mercury, or 13 pounds per square inch. Vacuum brake, a kind of continuous brake operated by exhausting the air from some appliance under each car, and so causing the pressure of the atmosphere to apply the brakes. <medicine> Vacuum pan, a glass tube provided with platinum electrodes and exhausted, for the passage of the electrical discharge; a Geissler tube. Vacuum valve, a safety valve opening inward to admit air to a vessel in which the pressure is less than that of the atmosphere, in order to prevent collapse. Torricellian vacuum. See Torricellian. Source: Websters Dictionary (01 Mar 1998) |
| vacuum casting | The casting of a metal in the presence of a vacuum. (05 Mar 2000) |
| vacuum curettage | Aspiration of the contents of the uterus with a vacuum curette. (12 Dec 1998) |
| vacuum desiccator | A desiccator that can be evacuated. (05 Mar 2000) |
| vacuum disk phenomenon | The appearance of a radiolucent stripe in an intervertebral disk, a manifestation of disk degeneration; a misnomer since there is gas present. (05 Mar 2000) |
| vacuum extraction, obstetrical | Removal of the foetus from the uterus or vagina at or near the end of pregnancy with a metal traction cup that is attached to the foetus' head. Negative pressure is applied and traction is made on a chain passed through the suction tube. (12 Dec 1998) |
| vacuum extractor | Device for producing traction upon the head of a foetus by means of a soft cup held by a vacuum. (05 Mar 2000) |
| vacuum flask | <apparatus> A glass vessel, often silvered, with two walls, the space between which is evacuated; used for maintaining materials at constant temperature or, more usually, at low temperature. Synonym: vacuum flask. (05 Mar 2000) |
| vacuum headache | Headache due to closure of the frontal sinus. (05 Mar 2000) |