A technique reduces cost, complexity andor power consumption of a memory system by including intelligence in a memory buffer circuit of the memory system. The use of such a capturing agent as a therapeutically active substance, as well as in chromatography and diagnosis are also disclosed. Rollers in the conveyors protrude through the thickness of the conveyors and ride on underlying supporting bearing surfaces that cause the rollers to rotate as the conveyors advance in the conveying direction. The DC torque is calculated as a function of the DC motor power and the motor speed.