and are time derivatives and are preferably determined as {TAIL ~ mean values} of gradients determined from {HEAD ~ a series} of measurement points 
and are time derivatives and are preferably determined as { TAIL ~ mean values } of gradients determined from { HEAD ~ a series } of measurement points
OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH