Search

It is argued that the communications-intensive nature of processes found in today's organizations calls for a focus on communication-flow representations and methods that differs in fundamantal ways from traditional materials transformation processes.

Classical pharmacokinetic models used in computer-controlled infusion pumps (CCIPs) assume instantaneous mixing of drug in blood; however, the average recirculation time of blood in man is approximately one minute. To investigate the effects of recirculation dynamics on the transient performance of CCIPs, we propose a hybrid physiologically-based pharmacokinetic model for the narcotic alfentanil. A three-compartment model was derived from the response of the hybrid model to a short infusion and used to compute a CCIP infusion targeting 450 micrograms/l. For this infusion, the hybrid model predicts that the arterial plasma concentration will overshoot the target concentration by 39 percent with an average prediction error of 3 percent. The overshoot and average prediction error increase to 100 and 25 percent respectively when using a three-compartment pharmacokinetic model derived from a bolus. The overshoot can be reduced by decreasing the maximum possible infusion rate, or by increasing the zero-order hold infusion interval.

A novel computer-controlled micropump is developed for various flow analyses and offers a number of improvements to the limitations of conventional pumping systems. With flow patterns which are easily programmed, the pump allows precise microliter delivery and complete in-line mixing to be conveniently achieved. This instrument is particularly suitable for both heterogeneous flow analysis and flow analysis based on slow reaction because it provides a large interface between immiscible phases or miscible streams just after merging and hence promotes mass transfer in radial directions. The improvement of radial mass transfer results in a complete reaction and high sensitivity with limited dispersion volume of the sample. The mechanical stability and reproducibility of this pump is excellent, allowing it to be applied successfully in process analysis over long periods of time.