Configuration interactions under pressure

Fig. 6. Variation of the crystal-field parameters of LaCl3 Pr3+ under pressure. Solid lines correspond to the conventional one-electron crystal field, utilizing only the 4f2 wavefunctions as the basis set. S denotes the mean deviation as defined in the text. Dashed lines represent the results derived from the inclusion of the 4f15d1 configuration interactions.

In sect. 4.4.1 the pressure-induced variations of the crystal-field parameters of LaClsiPr " " were shown in fig. 6. In this case the anomalous multiplet I>2 could also be measured under pressure (Troster et al., 1993), which opened a possibility to study the configuration interactions as a function of pressure. Including the 4f 5d configuration in the energy level fits and leaving only the energy distance to the 4f configuration as an adjustable parameter, the mean deviation 5 decreased from around 8 cm to less than 4 cm at ambient pressure (Troster and Holzapfel, 2002). 

Discontinuities are seen in the relationship between increase in film pressure, An, and lipid composition following the injection of globulin under monolayers of lecithin-dihydro-ceramide lactoside and lecithin-cholesterol mixtures. The breaks occur at 80 mole % C 16-dihydrocaramide lactoside and 50 mole % cholesterol. Between 0 and 80 mole % lactoside and between 0 and 50 mole % cholesterol the mixed films behave as pure lecithin. Two possible explanations are the formation of complexes, having molar ratios of lecithin-lactoside 1 to 4 and lecithin-cholesterol 1 to 1 and/or the effect of monolayer configurations (surface micelles). In this model, lecithin is at the periphery of the surface micelle and shields the other lipid from interaction with globulin. 

The large size of the hyaluronic acid molecules and their random-coil configuration lead to molecular interactions, even in dilute solution. As a result of these interactions, solutions of the polymer exhibit non-Newtonian and elastoviscosity (Bll). Synovial fiuid shows an increase in viscosity with reduced shearing force and possesses structural rigidity which is reversibly broken down by shearing. Such viscosity behavior makes synovial fluid an ideal lubricant between joint surfaces, which move slowly under considerable pressure for most of the time but which may be required to accelerate violently (03). 

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