| isoprene rule | The classical, outmoded statement that naturally occurring terpenes are built up by condensation of isoprene units by either a 1-4 linkage ("head to tail") or a 4-4 linkage ("tail to tail"). (05 Mar 2000) |
|---|---|
| Ogino-Knaus rule | The time in the menstrual period when conception is most likely to occur is at about midway between two menstrual periods; fertilization of the ovum is least likely just before or just after menstruation; the basis for the rhythm method of contraception. (05 Mar 2000) |
| Trusler's rule for pulmonary artery banding | A method that gives guidance as to the correct tightness of the band; the degree of banding for a complex congenital cardiac anomaly with bidirectional shunting less than that for simple ones. (05 Mar 2000) |
| Jackson's rule | After an epileptic attack, simple and quasiautomatic functions are less affected and more rapidly recovered than the more complex ones. (05 Mar 2000) |
| Jordan's rule | <genetics> An evolutionary rule that states that the closest genetic relatives of a given species are found very near it, but the two groups are isolated by some kind of natural barrier (such as a river) that neither species can cross easily. (09 Oct 1997) |
| Young's rule | An obsolete rule to determine a child's dose: 12 is added to the child's age and the sum is divided by the age; the adult dose divided by the figure so obtained gives the proper dose. (05 Mar 2000) |
| Le Bel-van't Hoff rule | The number of stereoisomers of an organic compound is 2n where n represents the number of asymmetric carbon atoms (unless there is an internal plane of symmetry). A corollary of their simultaneously announced conclusions, in 1874, that the most probable orientation of the bonds of a carbon atom linked to four groups or atoms is toward the apexes of a tetrahedron, and that this accounted for all then-known phenomena of molecular asymmetry (which involved a carbon atom bearing four different atoms or groups). See: stereoisomerism. (05 Mar 2000) |
| Liebermeister's rule | In adult febrile tachycardia, about eight pulse beats correspond to an increase of 1캜. (05 Mar 2000) |
| abdominal ring | The opening in the transversalis fascia through which the ductus deferens (or round ligament in the female) and gonadal vessels enter the inguinal canal. Located midway between anterior superior iliac spine and pubic tubercle, it is bounded medially by the lateral umbilical ligament (inferior epigastric vessels) and inferiorly by the inguinal ligament. Indirect inguinal hernias exit the abdominal cavity via the deep inguinal ring Synonym: annulus inguinalis profundus, abdominal ring, annulus abdominalis, internal inguinal ring. (05 Mar 2000) |
| amnion ring | The ring formed by the attachment of the amnion to the umbilical cord at its point of emergence from the umbilicus. (05 Mar 2000) |
| annuloplasty ring | The dilated annulus is sutured, often to a prosthetic ring, thereby reducing it to its normal systolic size. (05 Mar 2000) |
| anterior limiting ring | The periphery of the cornea marking the termination of Descemet's membrane and the anterior border of the trabecular meshwork; an important landmark in gonioscopy. Synonym: Schwalbe's ring. (05 Mar 2000) |
| Balbani ring | An extremely large puff at a band of a polytene chromosome. (05 Mar 2000) |
| Balbiani ring | <cell biology, genetics> The largest puffs seen on the polytene chromosomes of Diptera are called Balbiani rings after the nineteenth century microscopist who first described polytene chromosomes. (18 Nov 1997) |
| Bandl's ring | A constriction located at the junction of the thinned lower uterine segment with the thick retracted upper uterine segment, resulting from obstructed labour; this is one of the classic signs of threatened rupture of the uterus. Synonym: Bandl's ring, Baudelocque's uterine circle, Scanzoni's second os. (05 Mar 2000) |