| MEC | median effective concentration; middle ear canal; middle ear cell; minimum effective concentration |
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| PC | avoirdupois weight [Lat. pondus civile]; packed cells; paper chromatography; paracortex; parent cell... |
| RC | an electronic circuit containing a resistor and capacitor in series; radiocarpal; reaction center; r... |
| RCT | radiotherapy and chemotherapy; randomized clinical trial; randomized controlled trial; registered ca... |
| RF | radial fiber; radio frequency; receptive field; regurgitant fraction; Reitland-Franklin [unit]; rela... |
| threshold | 1. The point at which a stimulus first produces a sensation. 2. The lower limit of perception of a stimulus. 3. The minimal stimulus that produces excitation of any structure; e.g., the minimal stimulus eliciting a motor response. Synonym: limen. Origin: A.S. Therxold (05 Mar 2000) |
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| threshold body | Any material (e.g., glucose) that is excreted in the urine only when its plasma concentration exceeds a certain value, termed its threshold. Synonym: threshold body. (05 Mar 2000) |
| threshold differential | The smallest difference which can be discriminated between two stimuli or one which is barely above the threshold. (12 Dec 1998) |
| threshold limit value | The maximum concentration of a chemical recommended by the American Conference of Government Industrial Hygienists for repeated exposure without adverse health effects on workers. (05 Mar 2000) |
| threshold of consciousness | The lowest point at which a stimulus sensation can be perceived. (05 Mar 2000) |
| threshold of island of Reil | The band of transition between the anterior portion of the gray matter of the insula and the anterior perforated substance; it is formed by a narrow strip of olfactory cortex along the lateral side of the lateral olfactory stria. Synonym: threshold of island of Reil. (05 Mar 2000) |
| threshold of nose | A ridge marking the boundary between the nasal cavity proper and the vestibule. Synonym: threshold of nose. (05 Mar 2000) |
| threshold percussion | Percussion effected by means of a glass rod as a plessimeter, the rod being inclined to the wall of the chest or abdomen and touching it only by one extremity. (05 Mar 2000) |
| threshold shift | Measurement of the degree of hearing loss or impairment in terms of a decibel shift from an individual's previous audiogram. (05 Mar 2000) |
| threshold stimulus | A stimulus of threshold strength, i.e., one just strong enough to excite. See: adequate stimulus. Synonym: liminal stimulus. (05 Mar 2000) |
| threshold substance | Any material (e.g., glucose) that is excreted in the urine only when its plasma concentration exceeds a certain value, termed its threshold. Synonym: threshold body. (05 Mar 2000) |
| threshold trait | A trait that falls into natural groups that originate not in categorically distinct causes but in whether or not the outcome attains critical values; e.g., gallstones may result from a categorical cause or from unusual levels of causal factors that themselves show no evidence of grouping. Synonym: liminal trait. (05 Mar 2000) |
| transmission threshold | <epidemiology> Occurs for a parasite when the basic reproductive rate Ro is equal to 1. Below this threshold level the disease is unable to maintain itself within the host population. Typically, for directly transmitted parasites there is a transmission threshold for the host population size. (05 Dec 1998) |
| erythema threshold | The amount of radiation that causes redness of the skin. (09 Oct 1997) |
| fibrillation threshold | Least intensity of an electrical stimulus that will initiate fibrillation. (05 Mar 2000) |