Relaxation calorimetry enables us to measure the heat capacity of small samples with high accuracy, particularly at low temperatures. However, extracting accurate heat capacities at first-order or very sharp second-order phase transitions is extremely difficult. As a key to overcome this challenge, we focused on the“scanning method”and introduced several corrections in the data analysis. Using this method, we made heat capacity measurements around first-order transition of KH₂PO₄ around 122 K and BaTiO₃ around 203 K by a commercial relaxation calorimeter PPMS (Physical Property Measurement System). The results for KH₂PO₄ were shown to be excellent; a very sharp peak in heat capacity was obtained and the absolute values were shown to agree well with the previous results obtained by adiabatic calorimetry on much larger samples. The critical behavior of the heat capacity in the vicinity of the transition temperature, as well as the thermodynamic quantities such as the transition enthalpy and entropy, also agreed very well with the previous results. For BaTiO₃, clear hysteretic behavior of the transition was observed for heating and cooling curves.

View full abstract

From viewpoint of establishment of a standard system to determine the absolute amount and/or concentration of high-level tritium which is used as fuel of a future fusion reactor and one of radioactive materials, the applicability of a specially designed twin type conduction calorimeter has been examined at the tritium handling facility in Hydrogen Isotope Research Center, University of Toyama. Two examples of the examinations were shown: one is the measurement of a given amount of tritium stored in ZrNi alloy powder, and the other is the measurement of tritiated water. Both examinations gave enough results as a standard device. It was seen, therefore, that the present calorimeter has high potential for measurements of the absolute amount of tritium. Furthermore, an example that the present calorimeter was applied to nondestructive measurement of the amount of tritium in a glass ampoule was described.

View full abstract

Amorphous matrices formed by sugars are widely used as bulk-forming agents, stabilizing agents for physically/chemically labile ingredients such as proteins in the drug manufacturing industries. The intermolecular interactions involved in the amorphous sugar matrix closely relate to the physical properties of the amorphous sugar matrix: Hydrogen bonds among sugar molecules largely contribute to holding the amorphous sugar matrix in the solid state; The interactions between sugar and substances embedded in the sugar matrix (polymer, salts etc.) significantly affect the physical stability of the amorphous matrix; In the sugar-protein mixture, the sugar-protein hydrogen bonds play an essential role in the stabilization of protein. In this study, the intermolecular interactions in amorphous sugar matrices and the mixtures with polymer additive (polyvinylpyrrolidone, PVP) and protein were analyzed using temperature scanning Fourier transform infrared spectroscopy, TS-FTIR. From the investigations, the following findings were obtained: 1) The amorphous sugar matrix, in which sugar molecules can be fixed by fewer hydrogen bonds, has a higher glass transition temperature (T_g). 2) The heat-induced conformational changes of proteins were significant at temperatures above the glass transition temperature. 3) The addition of PVP to amorphous matrix tended to prevent the disruption of hydrogen bonds due to increasing temperature.

View full abstract

A series of D-erythro (2S, 3R) sphingomyelins (SMs) was synthesized by the acylation of D-erythro-sphingosylphosphorylcholine. In this synthesis, the acyl chain was varied in length from16 to 24 carbons at intervals of 2 carbons, in contrast to a fixed length of 18 carbons for the other sphingosine chain. For all the SM aqueous dispersions, reversible and reproducible thermal behavior was observed to show the gel-to-gel and the main gel-to-liquid crystal phase transition in heating DSC scan. The main transition enthalpy (∆H_M) decreased with increasing the effective chain length (N) per molecule of lipid estimated on the basis of a model structure of SM molecule, which contrasted with the generally accepted phenomenon for lipid-water systems. The decrease in ∆H_M with an increase in N was discussed from the viewpoint of the effect of the inequivalent chain segment in the acyl chain on the chain-chain van der Waals interaction energy that accounts for 2/3 of ∆H_M.

View full abstract