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.
The first and most important rule of VR is this: never turn VR on unless it's actually needed. Yes, this rule flies in the face of what most everyone in the world seems to do and what Nikon implies with their advertising and marketing.The simple fact is that VR is a solution to a problem, and if you don't have that problem using VR can become a problem of its own.ut that's not all: when you have VR turned on, your composition isn't going to be exactly what you framed. Yes, the viewfinder shows the VR impact, but Nikon's VR system re-centers the VR elements just prior to the shutter opening. This means that you can get slightly different framing than you saw.