A honeycomb body includes a honeycomb structure through which a fluid can flow and which is disposed in a tubular casing that is substantially gas-impermeable in a radial direction. The belt structure enables the modular plastic belt to be retrofitted in a spiral system normally carrying a steel conveyor belt. Furthermore, a refrigerant radiating portion is provided for radiating heat of refrigerant while the decompression portion decompresses and expands refrigerant. The apparatus and method presented can also be used to calibrate testing and production equipment allowing for more reliable and accurate measurements. In various embodiments, stimulation is applied to the vagus nerve, and evoked responses are detected to verify that the stimulation captures the vagus nerve and to adjust one or more stimulation parameters that control the stimulation intensity.