Pressure studies on the bilayer phase transitions of phospholipids with different polar head groups (i.e., phosphatidylcholine and phosphatidylethanolamine) and different types of acyl chains (i.e., saturated and unsaturated acyl chains) are reviewed. Phase behavior of these lipid bilayers is elucidated thermodynamically by the temperature-pressure phase diagrams and the results of DSC measurements. The phase stability of bilayers is also discussed in connection with molecular structure of lipids.
The phase transition of the adsorbed films of long chain fluorocarbon alcohol, hydrocarbon alcohol, and their mixtures at the hexane/water interface was reviewed mainly from the viewpoint of pressure effect on them. It is shown that the bulk concentration at the phase transition is lowered substantially by hydrostatic pressure. The phase transition is further examined in terms of the volume associated with adsorption and the composition of alcohols at the interface, and also by the X-ray reflectivity measurements.
Amphiphilic molecules conform nanometer-scale structures by adsorbing at oil and water interfaces or aggregating in water. The origins of forming such the structures are interesting issues to be solved not only for the field of soft-matter physics but also for neighbouring fields. In this viewpoint, the pressure-induced phase transitions of microemulsion systems composed of amphiphilic molecules, water and oil were investigated by means of small-angle neutron scattering, small-angle X-ray scattering, and neutron spin echo spectroscopy. The result shows that pressure mainly affects the interactions among hydrocarbon chains of amphiphilic molecules and/or between chains and surrounding oil molecules. This tendency is confirmed both in the cases of the ionic surfactant and of the non-ionic surfactant.
The phase behavior and microscopic structure of polymer aqueous solutions and hydrogels were investigated by means of small-angle neutron scattering (SANS) and light scattering (LS). Attention was focused on pressure (P) and/or temperature (T) induced phase transitions, such as microphase and macrophase separation transitions. In the case of poly(N-isopropylacrylamide) solutions and gels, coexistence and spinodal curves in the P-T coordinate were found to be convex-upward functions. At the phase boundary, the correlation length of the solution diverged. When charges were introduced to the gels, a scattering maximum originating from charge interactions appeared. This peak disappeared and reappeared by scanning P, showing reentrancy with respect to P. In the case of block copolymer solutions consisting of thermosensitive and hydrophilic block chains, both microphase and macrophase separation transitions were observed depending on T and P. It was found that the phase behavior was classified into several regimes with respect to the strength of hydrophobic solvation. All of these facts indicate that the roles of T and P in the thermodynamics of hydrophobic interaction are quite different.
Recent Raman studies on the pressure-induced amorphization of ice in aqueous MX solutions (M = Li, K, Rb, Cs; X = Cl, Br, I) are reviewed. We have investigated the change of in situ Raman spectra as functions of pressure and temperature to establish the phase transition behavior of the ice in aqueous electrolyte solutions. It is found that the ice phase in LiCl·12H2O transforms first to an amorphous phase at ca. 0.5 GPa and then to a low temperature ice VII'-like phase at ca. 3 GPa. The transition pressures are much lowered by addition of LiCl salt, as compared with the corresponding results in pure ice phase (Ih → high density amorphous ice (HDA) → VII'). On the other hand, the ice in other aqueous MX solutions, such as MX = KCl, transforms to a crystalline phase of ice VII' (the frozen-in disorder of ice VII) at ca. 0.8 GPa. Thus, the obtained results show differences depending on the salts dissolved in water; the salt to form a glassy state upon quick cooling at a normal pressure transforms to an amorphous phase on compression, and the salt solution to form a crystalline state on cooling transforms to a crystalline ice phase, such as ice VII'.
Recent advances in the high pressure researches of the structure of liquid metals and liquid semiconductors are reviewed. In the liquid metals and liquid semiconductors, electrons spread over the whole liquids and play an important role on the interaction between atoms, which strongly depends on the electron density. The pressure dependence of the local structure of liquids is found to be different from that of crystals. Results of the static structure factor of liquids, S(Q) and the pair distribution function, g(r) for liquid alkali metals, liquid halogen, liquid chalcogen, liquid group 15 elements, liquid IV-VI compounds, liquid group 14 elements and liquid III-V, II-VI, I-VII compounds are discussed in relation to the bonds between atoms.
Kinetics of high-pressure transformations in Earth's mantle minerals have been studied up to 35 GPa and 2,000 K based on time-resolved X-ray diffraction measurements with energy-dispersive method by combining Kawai-type high-pressure apparatus and synchrotron radiation. Kinetic behaviors are different among various types of transformations occurred in the mantle transition zone, and the rates of transformations depend on not only temperatures but also water contents. These metastable phase transformations would affect the density and viscosity of the down going cold current of mantle convection.
First of all, hydrogen energy related government budgets in Japan, USA and EU were summarized. Among a number of required technology to introduce hydrogen society, the hydrogen storage technique was focused in this article. The technique is classified in three ways, such as pressurized hydrogen, liquid hydrogen and hydrogen storage medium tank. In each technique, the high pressure science and technology is important to materialize applications of hydrogen storage systems. In addition, the recent research of new hydrides prepared by autoclave synthesis and high-pressure work in solid-state was also mentioned.