Phase transition phenomena induced by the successive appearances of new types of aggregation states of water molecules in the “l-dipalmitoylphosphatidylcholine-water” system

Thermal analysis of the aggregation state of water molecules m the “L-di-palmitoylphosphatidylcholine (DPPC)-water system revealed that in the low-temperature crystal phase below the sub-transition temperature, there are three kinds of interlamellar water, i.e., tightly, loosely, and more loosely bound water, which are incorporated between the bilayers of l-DPCC molecules, while the Lβ' gel phase lacks the third bound water molecule. Furthermore, we found that both the sub- and pre-transitions below the main transition temperature appear, for the first time, at water contents of around 11 and 18 g%, respectively, just at which point the new types of water structure occur. These findings indicate that the condition necessary for the appearance of these two kinds of phase transition is the existence of the characterized aggregation state of water molecules, that is, more loosely bound water for the sub-transition and bulk free water coexisting with the Lβ' gel phase for the pre-transition.     

Molecular dynamics simulation and energy minimization of O2 adsorbed on a graphite surface

Simulation studies of O₂ on graphite show that the quadrupole interaction strongly affects the orientational correlation between neighbouring molecules in the adsorbed solid. The energy minimization study shows two non-equivalent competing structures with nearest neighbours arranged parallel and at an angle of 60°. The precise value of the quadrupole moment stabilises one structure with respect to the other. For Θ = 0 the simulated structure agrees with experiment. For values of the quadrupole close to the experimental value there is a significant discrepancy between experiment and theory. This discrepancy can be understood in terms of the neglect of the magnetic forces arising from the exchange interaction. The best effective σ₀₀ is 5% higher than the value recommended by bulk solid studies. The minimum energy structure is incommensurate and molecules are aligned preferentially parallel to the surface at the coverage in this study.     

On the nonlinear dielectric function of CuCl in pump and probe experiments

We study the dispersion and the absorption changes of CuCl under high excitation conditions in two-beam experiments with parallel and crossed linear polarizations of both beams. The induced optical non linearities are shown to depend sensitively on the presence of interactions between the degenerate transverse exciton states.     

Spin-resolved photoemission study of in situ grown epitaxial Fe layers on W(110)

Spin- and angle-resolved photoemission spectroscopy of in situ grown epitaxial Fe layers on W(110) shows bulk-like behavior for more than two atomic Fe layers. For about ten and more atomic layers of Fe we find a spin polarization to be about -100% near the Fermi energy and +80 % between 1 eV and 3 eV binding energy. For the bilayer of Fe drastic changes in the spin-resolved spectra and a 20 % enhancement of the spin polarization compared to the bulk value are observed. The monolayer of Fe is ferromagnetically ordered with a spin polarization reduced by about 50%. A switching of the easy magnetization axis from [001] to [11̄0] is observed in the spin polarization with decreasing Fe layer thickness near d = (65±5) Å.     

Conductivity and thermoelectric power of NbS3+δ

The conductivity and thermoelectric power of samples from two different NbS_3+δ compounds have been measured in wide ranges of temperatures below 430K. The compound with the larger excess of sulfur was found to be stable upon treatement with CS₂ and heat treatment. Its conductivity exhibits two anomalies, a sharp one around 360K and a broad one around 150K. The results obtained for these compounds are compared with the results reported in the literature for other NbS_x compounds and for TaS₃.     

Übergangsmetall-substituierte acylphosphane und phosphaalkene: VIII. Dicarbonylcyclopentadienyleisen-substituierte phosphaalkene mit Fe-P-einfachbindung: synthese und struktur

Phosphaalkenyliron complexes with covalent metal-phosphorus bonds are synthesized from (η⁵-C₅H₅)(CO)₂FeP(SiMe₃)₂ and acid chlorides RC(O)Cl (R = Ph, 2,4,6-Me₃C₆H₂, t-Bu). The molecular structure of (Z)-(η⁵-C₅H₅)(CO)₂FePC(OSi-Me₃)(t-Bu) is established by X-ray structure analysis.