| adrenal mass | <radiology> Metastasis, most common (especially lung, melanoma), primary adenocarcinoma, large at diagnosis (greater than 5 cm), usually functional (increased corticosteroids most likely to be Cushing's), rapid growth, benign adrenal adenoma, with or without functional, nonfunctional occurs in 2-8% of population, diff from metastasis: MRI (metastasis bright on T2), biopsy, follow, pheochromocytoma, neuroblastoma, myelolipoma, cyst / pseudocyst see also: adrenal calcification, haemorrhage (12 Dec 1998) |
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| apperceptive mass | The already existing knowledge base in a similar or related area with which the new perceptual material is articulated. (05 Mar 2000) |
| atomic mass | <chemistry, physics> The mass of an atom relative to other atoms. The present-day basis of the scale of atomic weights is carbon, the most common isotope of this element has arbitrarily been assigned an atomic weight of 12. The unit of the scale is 1/12 the weight of the carbon atom or roughly the mass of one proton or one neutron. The atomic weight of any element is approximately equal to the total number of protons and neutrons in is nucleus (16 Dec 1997) |
| atomic mass unit | <chemistry> One-twelfth the mass of a neutral atom of the most abundant isotope of carbon. (16 Dec 1997) |
| bilateral adrenal mass | <radiology> Acute granulomatous disease (e.g., TB), metastases (bilateral in 15%), pheochromocytoma (bilateral in 10%), adrenal hyperplasia (adenoma), spontaneous adrenal haemorrhage (12 Dec 1998) |
| body mass index | One of the anthropometric measures of body mass; it has the highest correlation with skinfold thickness or body density. (12 Dec 1998) |
| breast mass | <oncology, surgery> A breast lump may be benign or cancerous. Examples of breast lumps include: breast abscess, fat necrosis, fibroadenoma, fibrocystic breast disease and breast cancer. A breast biopsy is the best way to determine the aetiology of a breast lump. Remember, 80 to 85% of all biopsies are benign. (27 Sep 1997) |
| para-sellar mass | <radiology> Mnemonic: SATCHMO, S sphenoid sinus tumour, A aneurysm / adenoma of pituitary, T teratoid lesion, C craniopharyngioma, H hypothalamic glioma / histiocytoma, M meningioma / metastasis, O optic glioma less common lesions: germinoma, epidermoid, hamartoma, chordoma, arachnoid cyst (12 Dec 1998) |
| mass | <chemistry> The quantity of matter in an object. (09 Jan 1998) |
| mass-action ratio | The ratio of the product of all of the product concentrations divided by the product of all of the reactant concentrations of a particular reaction; when the reaction has been completed (i.e., t = ∞), then this ratio is equal to the equilibrium constant. (05 Mar 2000) |
| mass action theory | That large areas of brain tissue function as a whole in learned or intelligent action. (05 Mar 2000) |
| mass action transmission | <epidemiology> Transmission of infection which occurs at a rate directly proportional to the number or density of both susceptibles and infecteds present. Some authors reserve the name mass action for transmission processes of the form b X Y/N , which we associate with STD-type transmission, and describe transmission rates of the form b X Y , as pseudo-mass action ; the two are equivalent if the population size is unchanging. (05 Dec 1998) |
| mass at base of tongue | <radiology> Lingual thyroid, thyroglossal duct cyst, haemangioma, other neoplasm (12 Dec 1998) |
| mass attenuation coefficient | <physics> The mass attenuation coefficient, u/p, of a material for uncharged ionising particles is the quotient of DN/N by pdl, where DN/N is the fraction of particles that experience interactions in traversing a distance dl in a material of density p. (16 Dec 1997) |
| mass behaviour | Collective behaviour of an aggregate of individuals giving the appearance of unity of attitude, feeling, and motivation. (12 Dec 1998) |