Figure 3. Phase slip, lag, and drift.
(a) Phase angle difference 
as a function of time for various applied torques on helix 
and the distance 
. The torque 
is changed from 200 (top) to 920 (bottom) with an increment of 40; the constant torque is 
. (b) Average phase lag 
as a function of the torque 
. The red line indicates the fit 
, where 
. The blue line is the tangent at 
. The inset provides an approximate measure of the number of occurring slips during the time interval 
as a function of the applied moment 
.