抄録
By an ac calorimeter the heat capacity of aqueous suspensions of dipalmitoylphosphatidylcholine has been measured near the pretransition and main transition. The anomaly at the main transition exhibits a sharp divergence, i.e., the fluctuation at the transition is certainly dominant, although they undergo first-order transition. The pseudo-critical behavior is analyzed in terms of critical-exponent expressions: α and α′ are 0.40±0.05 and 0.4±0.1, respectively. Using Pippard’s relation, the dependence of the transition temperature on pressure is discussed, which is almost consistent with that of the direct experiments. The anomaly at the pretransition observed by a differential scanning calorimeter is extremely reduced in ac calorimetry. This is due to the frequency dispersion of the heat capacity, since the relaxation at this transition is very long.
