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.
When using a variable-ratio (VR) schedule of reinforcement the delivery of reinforcement will âvaryâ but must average out at a specific number. Just like a fixed-ratio schedule, a variable-ratio schedule can be any number but must be defined.