| mass law | <chemistry> This law states that the rate of a given chemical reaction is proportional to concentration of the reactants. (09 Oct 1997) |
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| mass media | Instruments or technological means of communication that reach large numbers of people with a common message: press, radio, television, etc. (12 Dec 1998) |
| mass movement | Forcible peristaltic movements of short duration, occurring only three or four times a day, which move the contents of the large intestine from one division to the next, as from the ascending to the transverse colon. Synonym: mass movement. (05 Mar 2000) |
| mass number | The mass of the atom of a particular isotope relative to hydrogen-1 (or to 1/12 the mass of carbon-12), generally very close to the whole number represented by the sum of the protons and neutrons in the atomic nucleus of the isotope (indicated in the name or symbol of the isotope; e.g., oxygen-16, 16O); not to be confused with the atomic weight of an element, which may include a number of isotopes in natural proportion. (05 Mar 2000) |
| mass peristalsis | Forcible peristaltic movements of short duration, occurring only three or four times a day, which move the contents of the large intestine from one division to the next, as from the ascending to the transverse colon. Synonym: mass movement. (05 Mar 2000) |
| mass reflex | In cases of gross injury to the spinal cord, as the stage of reflex activity follows the primary flaccidity of the shock, a condition arises in which a strong stimulus to any part of one of the paralysed limbs will be followed by contraction of the hip, knee, and ankle of the same side and often, when the stimulus is applied to the middle line of the body, of both sides, as well as of the abdominal wall, and even evacuation of the bladder and sweating over an area corresponding to the level of the lesion. (05 Mar 2000) |
| mass screening | Organised periodic procedures performed on large groups of people for the purpose of detecting disease. (12 Dec 1998) |
| mass spectrograph | An instrument that subjects charged and accelerated ions (atomic or molecular) to a magnetic field that imparts a curved path that differs for each mass-to-charge ratio, thus separating individual species; used in detecting and assaying isotopic ratios and in molecular structure determinations. (05 Mar 2000) |
| mass stopping power | <physics> The mass stopping power (S/r) of a material for charged particles is the quotient dEs by the product of dl and r, where dEs is the average energy lost by a charged particle of specified energy in traversing a path length dl and r is the density of the medium. (16 Dec 1997) |
| MASS syndrome | <syndrome> A syndrome closely resembling both the Marfan's syndrome and the Barlow syndrome. However, no dislocation of the lenses or aneurysmal changes occur in the aorta, and the mitral valve prolapse is by no means invariable. at present it has been assigned no separate OMIM number, but shares that of the Barlow syndrome. Origin: mitral valve prolapse, aortic anomalies, skeletal changes, and skin changes. (05 Mar 2000) |
| parotid gland mass | <radiology> Pleomorphic adenoma, sialocele, adenoid cystic carcinoma, adenocarcinoma, lymphoma, lymph node, abscess, metastasis (12 Dec 1998) |
| relative molecular mass | The sum of the atomic weight's of all the atoms constituting a molecule; the mass of a molecule relative to the mass of a standard atom, now 12C (taken as 12.000). Relative molecular mass (Mr) is the mass relative to the dalton and has no units. See: atomic weight. Synonym: molecular mass, molecular weight ratio, relative molecular mass. (05 Mar 2000) |
| middle ear mass | <radiology> Glomus tumour (multiple in 10%; 8% malignant), glomus tympanicum, from cochlear promontory, seldom erodes bone, glomus jugulare, invasion of middle ear from below, destruction of bony roof of jugular fossa and bony spur separating vein from carotid artery, abberant carotid artery (no bony margin), enlarged jugular bulb (dehiscent bony covering), cholesteatoma, rhabdomyosarcoma (orbit greater than nasopharynx greater than ear), adenocarcinoma (rare) (12 Dec 1998) |
| middle mediastinal mass | <radiology> Mnemonic: not VD, 90% malignant, Nodes, tumour (metastasis, lymphoma/leukaemia), infection, inhalational disease, Castleman disease, Tumour, primary lung, trachea, oesophagus carcinoma, Vascular, aneurysm, haematoma, Duplication cyst, bronchogenic, enteric, neurenteric (12 Dec 1998) |
| molar mass | See: molecular weight. (05 Mar 2000) |