Kernel density estimation of transfer entropy. Scan of the estimated transfer entropies from Ca2+ to active protein Pact in the stochastically simulated system (k2 = 2.85, bursting). x-axis: ε values. y-axis: estimates of the transfer entropy in simulated systems of volumes 10-12 to 10-9 [arbitrary units] respectively. Also, the estimating process was applied to a deterministically simulated calcium signal (det. signal). In this case, the reaction volume of the (stochastically) simulated enzyme was 10-10.