| half and half nail | Division of the nail by a transverse line into a proximal dull white part and a distal pink or brown part; seen in uraemia. (05 Mar 2000) |
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| half-time | The time, in a first-order chemical (or enzymic) reaction, for half of the substance (substrate) to be converted or to disappear. Compare: half-life. (05 Mar 2000) |
| saturation | 1. The act of saturating, or the state of being saturating; complete penetration or impregnation. 2. <chemistry> The act, process, or result of saturating a substance, or of combining it to its fullest extent. 3. <optics> Freedom from mixture or dilution with white; purity; said of colours. The degree of saturation of a colour is its relative purity, or freedom from admixture with white. Origin: L. Saturatio: cf. F. Saturation. Source: Websters Dictionary (01 Mar 1998) |
| saturation analysis | General term for an assay in which a binder competes for labelled versus unlabelled ligand; following separation of free and bound ligand, the ligand (the analyte assayed) is quantitated by relating bound and unbound ratios to known standards. See: enzyme-linked immunosorbent assay, radioreceptor assay, immunoassay, enzyme-multiplied immunoassay technique, radioimmunoassay. Synonym: displacement analysis, saturation analysis. (05 Mar 2000) |
| saturation index | An indication of the relative concentration of haemoglobin in the red blood cells, calculated as: grams of haemoglobin per 100 ml (expressed as percent of normal) ÷ haematocrit value (expressed as percent of normal) = saturation index The normal index for adults and infants is 0.97 to 1.02; in primary and secondary anaemia, the index is usually considerably less than 0.97. (05 Mar 2000) |
| saturation of receptors | Saturation, the state in which all receptors are effectively occupied all the time, can be said to occur in a simple binding equilibrium when the concentration of ligand is more than 5 times the Kd value, although strictly this will only be true at infinite ligand concentration. (18 Nov 1997) |
| secondary saturation | A technique of nitrous oxide anaesthesia consisting of an abrupt curtailment of the oxygen in the inhaled mixture to produce a deep plane of anaesthesia, following which oxygen is administered to correct hypoxia. (05 Mar 2000) |
| biological half-life | <biochemistry, biology> This is the time required for one-half of the total amount of a particular substance in a biological system to be consumed or broken down by biological processes when the rate of removal is approximately exponential. Toxic chemicals with a long biological half-life (such as some pesticides) will tend to accumulate in the body and are, therefore, more likely to be harmful. A substance with a short biological half-life may still accumulate if a portion of it it becomes tightly bound to bone or other tissues, even if most of it is quickly cleared from the body. (21 Mar 1998) |
| red half-moon | <clinical sign> Irregular red discoloration of the usually pale demilune at the base of the fingernail; may be seen in congestive failure, malignant disease, or liver disease, but not specific for any of these. (05 Mar 2000) |
| physical half-life | The time required for half the atoms of a radionuclide to undergo disintegration. (05 Mar 2000) |
| half | In an equal part or degree; in some pa appromating a half; partially; imperfectly; as, half-coloured, half done, half-hearted, half persuaded, half conscious. "Half loth and half consenting." "Their children spoke halfin the speech of Ashdod." (Neh. Xiii. 24) 1. Consisting of a moiety, or half; as, a half bushel; a half hour; a half dollar; a half view. The adjective and noun are often united to form a compound. 2. Consisting of some indefinite portion resembling a half; approximately a half, whether more or less; partial; imperfect; as, a half dream; half knowledge. "Assumed from thence a half consent." (Tennyson) Half ape, a middle or intermediate tint, as in drawing or painting. See Demitint. Half truth, a statement only partially true, or which gives only a part of the truth. Half year, the space of six moths; one term of a school when there are two terms in a year. Origin: AS. Healf, half, half; as a noun, half, side, part; akin to OS, OFries, & D. Half, G. Halb, Sw. Half, Dan. Halv, Icel. Halfr, Goth. Halbs. Cf. Halve, Behalf. Source: Websters Dictionary (01 Mar 1998) |
| half-a-gram stain | <technique> A lab technique used to detect the presence of members from the bacterial family Legionellaceae in samples of sputum. (09 Oct 1997) |
| half amplitude pulse duration | The time, in milliseconds, required for a wave form to reach half of its full magnitude. (05 Mar 2000) |
| half-axial projection | Reverse tilted AP radiographic projection devised to permit demonstration of the entire occipital bone, foramen magnum, and dorsum sellae, as well as the petrous ridges. Synonym: half axial view, half-axial projection, Towne view. (05 Mar 2000) |
| half axial view | Reverse tilted AP radiographic projection devised to permit demonstration of the entire occipital bone, foramen magnum, and dorsum sellae, as well as the petrous ridges. Synonym: half axial view, half-axial projection, Towne view. (05 Mar 2000) |