H.I. Holst

Successful preservation of canine small intestine by freezing

Abstract Five of fourteen canine intestinal autografts frozen at −196°C for 7 days were surviving 2 wk after reimplantation. The mucosal epithelium sloughed immediately, but repopulated from surviving crypt cells over the ensuing 3–5 days. Absorptive and peristaltic functions were present at 2 wk after reimplantation.

Organ temperature measurement in a microwave oven by resonance frequency shift

Abstract An experimental system has been developed that can indirectly measure temperature in a high-intensity microwave field over a broad range of conditions. A RF amplifier connected closed-loop around a high Q cavity oscillates at one of the natural modes of the oven. A bandpass filter selects the mode of interest. As the frozen sample is thawed, an increase in dielectric constant occurs, decreasing the resonance frequency of the cavity. Calibration of the system is performed by measuring the frequency shift for samples whose temperatures are known, Rotation of samples during thawing often causes oscillations of the resonance frequency. These oscillations are generated by asymmetric sample properties and geometry, and hot spots developed during the thaw. Development of a method that would predict hot spot location from these resonance frequency oscillations and permit modulation of the magnetron or sample rotation to minimize thermal runaway is suggested.