| density gradient centrifugation | <technique> High-speed centrifugation inwhich molecules float at a point wheretheir density equals that in a gradient of cesium chloride or sucrose. (12 Jan 1998) |
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| systolic gradient | The difference in pressure during systole between two communicating cardiovascular chambers, e.g., between the left ventricle and aorta in aortic stenosis. (05 Mar 2000) |
| electrochemical gradient | A measure of the tendency of an ion to move passively from one point to another, taking into consideration the differences in its concentration and in the electrical potentials between the two points; commonly expressed as the additional voltage needed to achieve equilibrium. (05 Mar 2000) |
| ficoll gradient | A density gradient of ficoll (synthetic sucrose polymer) in solution, where concentration of the ficoll varies continuously through the solution. It is often used to separate different types of cells from each other during the process of sedimentation. (09 Oct 1997) |
| field gradient | In magnetic resonance imaging, a magnetic field that varies with location, superimposed on the uniform field of the magnet, to alter the resonant frequency of nuclei and allow recovery of their spatial position. Synonym: field gradient. (05 Mar 2000) |
| Abbott's method | A method of treatment of scoliosis by use of a series of plaster jackets applied after partial correction of the curvature by external force. (05 Mar 2000) |
| Abell-Kendall method | A standard method for estimation of total serum cholesterol involving saponification of cholesterol ester by hydroxide, extraction with petroleum ether, and colour development with acetic anhydride-sulfuric acid; the method avoids interference by bilirubin, protein, and haemoglobin. (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) |
| Altmann-Gersh method | The method of rapidly freezing a tissue and dehydrating it in a vacuum. (05 Mar 2000) |
| Anel's method | Ligation of an artery immediately above (on the proximal side of) an aneurysm. (05 Mar 2000) |
| Antyllus' method | Ligation of the artery above and below an aneurysm, followed by incision into and emptying of the sac. (05 Mar 2000) |
| aristotelian method | A method of study that stresses the relation between a general category and a particular object. (05 Mar 2000) |
| Ashby method | A differential agglutination method for estimating erythrocyte life span; compatible blood possessing a group factor that the recipient lacks is transferred to the recipient; after the transfusion, sera with potent agglutinins for the recipient's red cells are added to samples of the recipient's blood, and the unagglutinated red cells are counted; using this technique the red cell life span in normal persons is found to be 110 to 120 days. (05 Mar 2000) |
| auxanographic method | A method for the study of bacterial enzymes in which agar is mixed with the material (e.g., starch or milk) which is to serve as an indicator of the enzyme action and is inoculated and plated; if the bacteria produce enzymes digesting the admixed material, there will be a zone of clearing in the medium about each colony. Synonym: diffusion method. (05 Mar 2000) |
| Barraquer's method | Zonulysis Dissolution of the zonula ciliaris by enzymes (alpha-chymotrypsin) to facilitate surgical removal of a cataract. Synonym: Barraquer's method. Origin: zonule + G. Lysis, dissolution (05 Mar 2000) |