摘要:
In an electron paramagnetic resonance spectrometer, a closed cycle cryocooler is used to cool gaseous helium, which is then circulated around a sample to cool the sample by direct convection. Since the sample is not mechanically connected to the refrigerator, no vibrations are transmitted from the refrigerator to the sample and the sample can be quickly removed and replaced. The cooled helium can be passed through a Joule-Thomson expansion device before circulating the cooled helium around the sample to further cool the helium. In addition, a vacuum pump can be connected to the helium outlet after circulating the cooled helium around the sample to increase the pressure differential across the Joule-Thomson expansion device and further cool the helium. In order to raise the temperature of the cooled helium, a heater can be placed about the cooled helium line upstream from the sample.
摘要:
A method and an apparatus for investigating the imperishability of n liquid foodstuffs using electron spin resonance (ESR) exposes samples of the foodstuffs to an elevated temperature for an extended time-period. At predetermined intervals during the period, the intensity of an ESR signal of each sample is measured and plotted vs. time in a diagram for that sample. The time of a superproportional increase in intensity is detected for each foodstuff. The number n of different foodstuffs is determined by dividing the predetermined interval by the measurement time. The n samples are investigated simultaneously by sequentially cycling the n samples through a common sample vessel. Each time, the intensity of the ESR signal of the sample is measured and then plotted in a diagram unique to that foodstuff. The sequence of foodstuffs are cycled through the sample vessel until a predetermined number m of measuring points per foodstuff has been attained.