| mass chest X-ray | X-ray screening of large groups of persons for diseases of the lung and heart by means of radiography of the chest. (12 Dec 1998) |
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| mass defect | <chemistry, radiobiology> Of a nucleus, the difference between the sum of the masses of the constituent nucleons and the mass of the nucleus. (16 Dec 1997) |
| mass effect | <neurology> Damage to the brain due the bulk of a tumour, the blockage of fluid or excess accumulation of fluid within the skull. (16 Dec 1997) |
| mass energy absorption coefficient | <physics> The mass energy absorption coefficient, uen/p of a material for uncharged ionising particles is the product of the mass energy transfer coefficient, utr/p and (1 - g) where g is the fraction of the energy of secondary charged particles that is lost to bremsstrahlung in the material. (16 Dec 1997) |
| mass fragmentography | A microanalytical technique combining mass spectrometry and gas chromatography for the qualitative as well as quantitative determinations of compounds. (12 Dec 1998) |
| mass hysteria | Spontaneous, en masse development of identical physical and/or emotional symptoms among a group of individuals, as seen in a classroom of schoolchildren, a socially contagious frenzy of irrational behaviour in a group of people as a reaction to an event. Synonym: epidemic hysteria. (05 Mar 2000) |
| mass infection | Infection resulting from the entrance of a large number of pathogens into the circulation or tissues. (05 Mar 2000) |
| mass law | <chemistry> This law states that the rate of a given chemical reaction is proportional to concentration of the reactants. (09 Oct 1997) |
| 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) |