Figure 5

The thermal grill consisted of two systems of 0.75 cm-flattened copper tubing cut into approximately 10 cm in length and placed one cm apart. The inflow and outflow of the two separate systems were connected via a series of four-way valves to two separate heating and cooling water baths. The exact temperatures at the copper tubings were monitored with two separate temperature probes (Mallinckrodt Medical, Inc, St Louis, MO), which were attached to the copper tubings.