Hydration theory averages

The experimentally fitted hydrate guest Kihara parameters in the cavity potential uj (r) of Equation 5.25 are not the same as those found from second virial coefficients or viscosity data for several reasons, two of which are listed here. First, the Kihara potential itself does not adequately fit pure water virials over a wide range of temperature and pressure, and thus will not be adequate for water-hydrocarbon mixtures. Second, with the spherical Lennard-Jones-Devonshire theory the point-wise potential of water molecules is smeared to yield an averaged spherical shell potential, which causes the water parameters to become indistinct. As a result, the Kihara parameters for the guest within the cavity are fitted to hydrate formation properties for each component. 

The mechanical properties of single hydrated dextran microcapsules (< 10 pm in diameter) with an embedded model protein drug have also been measured by the micromanipulation technique, and the information obtained (such as the Young s modulus) was used to derive their average pore size based on a statistical rubber elasticity theory (Ward and Hadley, 1993) and furthermore to predict the protein release rate (Stenekes et al., 2000). 

The dependence of the interaction force between two undulating phospholipid bilayers and of the root-mean-square fluctuation of their separation distances on the average separation can be determined once the distribution of the intermembrane separation is known as a function of the applied pressure. However, most of the present theories for interacting membranes start by assuming that the distance distribution is symmetric, a hypothesis invalidated by Monte Carlo simulations. Here we present an approach to calculate the distribution of the intermembrane separation for any arbitrary interaction potential and applied pressure. The procedure is applied to a realistic interaction potential between neutral lipid bilayers in water, involving the hydration repulsion and van der Waals attraction. A comparison with existing experiments is provided. 

The above two successes have served the energy industry well for the last 40 years. Before the modifications indicated in the next section, the hydrate formation temperature prediction error to within 0.7 K (average absolute error for uninhibited hydrates) was acceptable, approximately twice the experimental error. With modem modifications of the van der Waals and Platteeuw theory, the energy industry feels confident in making multimillion dollar hydrate formation decisions based on the predictions, without obtaining data for important applications, such as ... 

The oscillating hydration force is superimposed on a longer range repulsive force between the layers, which is predicted to be an osmotic force from the diffuse doublelayer theory (but may still contain a hydration component). Thus, as Figure 8.16 shows, closer separations between the silicate sheets result in the oscillating interlayer force becoming more repulsive on average. 

There are several directions to extend the RISM-SCF/MCSCF method that are not described in the present chapter. One of such directions is a combination of ab initio MO theory with 3D-RISM, which is explained in chapter 4. The site-site treatment of the solute-solvent correlations involving the approximation of radial averaging constitutes a bottleneck of the RISM-SCF method, and thus lacks a 3D picture of the solvation structure for complex solutes. The SCF theory combined with the 3D-RISM is free from such a bottleneck. The test computation on the carbon monoxide in water provides a detailed hydration structure of water solvent as well as polarized CO electronic structure. [25] It is also found that the results from the original RISM-SCF/MCSCF method are in reasonable accord with those following from the 3D-RISM-SCF approach after reduction of the orientational dependence. This shows the RISM-SCF/MCSCF approach gives a proper picture for a solvation process. 

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