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.
Addendum 7/3/2014: Updated to include information on prescribing and recordkeeping requirements.*. Today the Drug Enforcement Administration (DEA) published its decision to schedule tramadol as a Schedule IV controlled substance. The rule becomes effective August 18 of this year. The DEAâs action was fairly swift, having published its proposal to schedule tramadol just eight months ago (see blog post from November 2013).