| 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) |
|---|---|
| high forceps delivery | Delivery by forceps applied to the foetal head before engagement has taken place. (05 Mar 2000) |
| outlet forceps delivery | Delivery by forceps applied to the foetal head when it has reached the perineal floor and is visible between contractions. (05 Mar 2000) |
| forceps delivery | Assisted birth of the child by an instrument designed to grasp the foetal head. (05 Mar 2000) |
| low forceps delivery | Delivery by forceps applied to the foetal head after it is clearly visible, the skull has reached the perineal floor, and plus 2 (+2) station. This classification of forceps delivery may be with or without rotation of the foetal head. (05 Mar 2000) |
| extractor | One who, or that which, extracts; as: A device for withdrawing a cartridge or spent cartridge shell from the chamber of the barrel. Source: Websters Dictionary (01 Mar 1998) |
| ALL | <haematology> A rapidly progressing cancer of the blood affecting the type of white blood cell known as lymphocytes. Approximately 650 new cases are diagnosed every year in the UK and it is the most common form of childhood leukaemia. Acronym: ALL Origin: Gr. Haima = blood (11 Nov 1997) |
| all or none | Consistently total response to any effective stimulus. Synonym: all or none law. (05 Mar 2000) |
| all or none law | Consistently total response to any effective stimulus. Synonym: all or none law. (05 Mar 2000) |
| all-or-nothing phenomenon | <physiology> Refers to the phenomenon where the strength of a nerve impulse is not dependent on the strength of the stimulus. Instead, there is a threshold level of stimulus strength that must be reached before the nerve will fire an impulse (at full capacity). Below the threshold, the nerve will not fire at all. <cardiology> It also refers to the same phenomenon observed in the heart muscle, which will either contract fully or not at all. <psychology> In studies of behaviour, it refers to the same phenomenon where a behavioural stimulus will either produce a complete response or no response at all. Also called all-or-nothing principle, all-or-none law, all-or-none responsiveness, etc. (15 Nov 1997) |
| all souls' day | The second day of November; a feast day of the Roman Catholic church, on which supplications are made for the souls of the faithful dead. Source: Websters Dictionary (01 Mar 1998) |
| all-trans-retinal | The orange retinaldehyde resulting from the action of light on the rhodopsin of the retina, which converts the 11-cis-retinal component of the rhodopsin to all-trans-retinal plus opsin. Synonym: trans-retinal, visual yellow. (05 Mar 2000) |
| stains-all | 4,5,4',5'-Dibenzo-3,3'-diethyl-9-methylthiocarbocyanine bromide;a dye that stains phosphoproteins blue, proteins red, nucleic acids purple, and mucoproteins and mucopolysaccharides various colours on acrylamide gels; also used on tissue sections. (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) |