Two-dimensional Monte Carlo studies of lipid molecules in a bilayer membrane

We present a new model to study in-plane liquid properties of lipid membranes. The different conformations of lipids are represented by a seven-state system of hard triatomic particles, or triples, of varying lengths which correspond to the different cross-sectional areas of the lipids in the plane of the membrane. Two-dimensional Monte Carlo simulations are performed in both the constant NVT and NPT ensembles. The distribution of states has a strong density dependence and a small temperature dependence over the biologically relevant range. There is no long range orientational order in the systems before freezing. The short range orientational order increases with density. Widom's particle insertion method is used to obtain the excess chemical potential of the system for the seven states. These values, along with the pressure, are in excellent agreement with estimates from scaled particle theory.     

Thermisch hervorgerufene Oberfl?chendeformationen von Polypropylen-Monofilamenten

Ohne Zusammenfassung     

Mössbauer effect study of Gd- and Eu-doped CaSO4

Mössbauer spectra have been taken of rare earth doped CaSO₄ using the¹⁵¹Eu and¹⁵⁵Gd transitions. Site assignments have been made to the five principal Gd³⁺ configurations principally on the basis of point charge calculations. We were unable to distingiush different Eu³⁺ sites and no conversion of Eu³⁺ to Eu²⁺ could be observed after prolonged x-irradiation.