Definition. 1  Troponins are specific proteins found in heart muscle. Troponin testing is done to diagnose heart attacks (myocardial infarctions). 2  When heart muscle is damaged, as in a myocardial infarction (MI), troponins leak out of cells and into the bloodstream.
Variable Ratio Schedule (VR) This is going to be a little confusing at first, but hang on and it will become clear. A variable ratio schedule (VR) is a type of operant conditioning reinforcement schedule in which reinforcement is given after an unpredictable (variable) number of responses are made by the organism. This is almost identical to a Fixed-Ratio Schedule but the reinforcements are given on a variable or changing schedule.
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