time scale in brownian force

Mehdi Asghari

Hi all;

Just as we know Brownian force is given by this relation:Fb=xi*sqrt(pi*S0/dT) for sub-micron particles .

dT=time scale; Xi=zero-mean, unit variance independent Gaussian random numbers.

My main question is that how time scale(dt) is determined in this formula ?

Another question is how to compare this time scale with time paticle passed on its cell position?

Thanks in advance for any help. M.Asghari