| isocyclic compound | Any compound in which the constituent atoms, or any part of them, form a ring. Used mainly in organic chemistry where: 1) numerous compound's contain rings of carbon atoms (carbocyclic compound's) or carbon atoms plus one or more atoms of other types (heterocyclic compound's), usually nitrogen, oxygen, or sulfur; 2) where the atoms in the ring are all of the same element (homocyclic or isocyclic compound); 3) where the ring is saturated or contains nonconjugated double bonds (alicyclic compound), the compound is similar in properties to the corresponding acyclic compound (e.g., cyclohexane resembles hexane); 4) where the ring contains conjugated double bonds in a closed loop in which there are 4n + 2 (where n is an integer) delocalised π electrons (Huckel's rule) (aromatic compound; e.g., benzene, pyridine), it is more stable than the corresponding saturated ring and exhibits unusual chemical properties characteristic of itself and not of other types of rings or of acyclic compound's. These aromatic compounds have the ability to sustain an induced ring current. Synonym: closed chain compound, ring compound. (05 Mar 2000) |
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| open chain compound | An organic compound in which the chain does not form a ring. Synonym: aliphatic compound, open chain compound. (05 Mar 2000) |
| organic compound | <chemistry> A compound containing carbon. (11 Jan 1998) |
| lens, compound | <microscopy> A lens composed of two or more separate pieces of glass or other optical maternal. These component pieces or elements may or may not be cemented together. A common form of compound lens is a two-element objective, one element being a converging lens of crown glass and the other a diverging lens of flint glass. The combination of suitable glasses or other optical materials (plastics, minerals) properly ground and polished reduces aberrations normally present in a single lens. (05 Aug 1998) |
| acquired nevus | A melanocytic nevus that is not visible at birth, but appears in childhood or adult life. (05 Mar 2000) |
| balloon cell nevus | A nevus in which many of the cells are large, with clear cytoplasm. (05 Mar 2000) |
| basal cell nevus | A hereditary disease noted in infancy or adolescence, characterised by lesions of the eyelids, nose, cheeks, neck, and axillae, appearing as uneroded flesh-coloured papules, some becoming pedunculated, and histologically indistinguishable from basal cell epithelioma; also noted are punctate keratotic lesions of the palms and soles; the lesions usually remain benign, but in some cases ulceration and invasion occur and are evidence of malignant change; autosomal dominant inheritance. (05 Mar 2000) |
| basal cell nevus syndrome | <syndrome> An inherited group of defects which involve abnormalities of the skin, eyes, nervous system, endocrine, glands and bones. The condition is characterised by an unusual facial appearance and a predisposition for skin cancer. (27 Sep 1997) |
| bathing trunk nevus | These large pigmented (often hairy) congenital nevi are important because of their increased risk (10 to 15%) of conversion into malignant melanoma. A biopsy can confirm if cells have turned malignant. Any change in a pre-existing nevus should prompt a physician evaluation. (27 Sep 1997) |
| Becker's nevus | A nevus first seen as an irregular pigmentation of the shoulders, upper chest, or scapular area, gradually enlarging irregularly and becoming thickened and hairy. Synonym: pigmented hair epidermal nevus. (05 Mar 2000) |
| blue nevus | A dark blue or blue-black nevus covered by smooth skin and formed by heavily pigmented spindle-shaped or dendritic melanocytes in the reticular dermis. Synonym: Jadassohn-Tieche nevus. (05 Mar 2000) |
| blue rubber bleb nevus syndrome | <radiology> Bean syndrome, sporadic (some autosomal dominant), rubbery, raised blue-black skin nevi (cavernous haemangiomata, 0.1 - 5 cm), GI mucosal haemangiomata, bowel: polypoid filling defects of varying sizes, visceral haemangiomata (by angio) associated with: leukaemia, medulloblastoma, hypernephroma, Mafucci syndrome More info: blue rubber bleb nevus syndrome (12 Dec 1998) |
| capillary nevus | Capillary haemangioma of the skin. (05 Mar 2000) |
| verrucous nevus | A skin-coloured or darker wartlike, often linear, lesion appearing at birth or early in childhood, and occurring in various sizes and locations, single or multiple. (05 Mar 2000) |
| giant hairy nevus | <dermatology> These large pigmented (often hairy) congenital nevi are important because of their increased risk (10 to 15%) of conversion into malignant melanoma. A biopsy can confirm if cells have turned malignant. Any change in a pre-existing nevus should prompt a physician evaluation. (17 Dec 1997) |