Hydration forces between phospholipid bilayers

In this paper, theoretical and experimental approaches to flow, hydrodynamic dispersion, and miscible and immiscible displacement processes in reservoir rocks are reviewed and discussed. Both macroscopically homogeneous and heterogeneous rocks are considered. The latter are characterized by large-scale spatial variations and correlations in their effective properties and include rocks that may be characterized by several distinct degrees of porosity, a well-known example of which is a fractured rock with two degrees of porosity---those of the pores and of the fractures. First, the diagenetic processes that give rise to the present reservoir rocks are discussed and a few geometrical models of such processes are described. Then, measurement and characterization of important properties, such as pore-size distribution, pore-space topology, and pore surface roughness, and morphological properties of fracture networks are discussed. It is shown that fractal and percolation concepts play important roles in the characterization of rocks, from the smallest length scale at the pore level to the largest length scales at the fracture and fault scales. Next, various structural models of homogeneous and heterogeneous rock are discussed, and theoretical and computer simulation approaches to flow, dispersion, and displacement in such systems are reviewed. Two different modeling approaches to these phenomena are compared. The first approach is based on the classical equations of transport supplemented with constitutive equations describing the transport and other important coefficients and parameters. These are called the continuum models. The second approach is based on network models of pore space and fractured rocks; it models the phenomena at the smallest scale, a pore or fracture, and then employs large-scale simulation and modern concepts of the statistical physics of disordered systems, such as scaling and universality, to obtain the macroscopic properties of the system. The fundamental roles of the interconnectivity of the rock and its wetting properties in dispersion and two-phase flows, and those of microscopic and macroscopic heterogeneities in miscible displacements are emphasized. Two important conceptual advances for modeling fractured rocks and studying flow phenomena in porous media are also discussed. The first, based on cellular automata, can in principle be used for computing macroscopic properties of flow phenomena in any porous medium, regardless of the complexity of its structure. The second, simulated annealing, borrowed from optimization processes and the statistical mechanics of spin glasses, is used for finding the optimum structure of a fractured reservoir that honors a limited amount of experimental data.

Flow phenomena in rocks : from continuum models to fractals, percolation, cellular automata, and simulated annealing

This paper describes the swelling/exfoliation process in which a layered protonic titanate, HxTi2-x/4□x/4O4·H2O (x ∼ 0.7; □, vacancy), undergoes high degrees of hydration in aqueous media containing tetrabutylammonium (abbreviated as TBA hereafter) ions. A high content of electrolyte (25-fold excess of TBA ions to the exchangeable protons in the titanate) induced the formation of an osmotically swollen hydrate yielding a well-defined basal diffraction series. Intersheet separation of 4.2 nm at this stage expanded further to exceed 10 nm with reducing the dose of TBA ions. Along this swelling, exfoliation into single sheets became prevalent while the swollen component declined. This was followed by X-ray diffraction data for wet colloids centrifuged from suspensions that revealed a broad diffraction envelope besides the sharp basal reflections. Profile simulations demonstrated that the hump is attributable to scattering from a pile of exfoliated nanosheets and that its appearance is diagnostic for delamina...

Osmotic Swelling to Exfoliation. Exceptionally High Degrees of Hydration of a Layered Titanate

Stabilization of emulsions by fine particles I. Partitioning of particles between continuous phase and oil/water interface

Recent developments in the direct measurements of forces between surfaces in liquids at the angstrom resolution level are reviewed. The results reveal a rich variety of interactions and interaction potentials that depend on the nature of the surfaces and intervening liquids. These results also shed new insights into liquid structure adjacent to surfaces and the interactions occurrig in complex systems, with implications in many different areas of chemical physics, biology, and technology. The origin of some important fundamental interactions, such as repulsive "hydration" forces and attractive "hydrophobic" forces, are still not understood and offer a challenge for experimental and theoretical work in this area.

https://science.sciencemag.org/content/sci/241/4867/795.full.pdf

Forces between surfaces in liquids.

Direct measurement of the relation between interlayer force and interlayer distance in the swelling of montmorillonite

To test the double-layer theory of swelling as applied to layer silicates, the interlayer separation, λ, in a Li-saturated vermiculite from Grouse Creek, Utah, was measured as a function of the swelling pressure, II. An oriented sample of the vermiculite (46-105 μm) was placed in an environmental chamber mounted on an X-ray diffractometer and compressed between N2 gas and a porous membrane in contact with a solution draining to the outside atmosphere. After equilibration at each of several successively higher gas pressures, the c-axis spacing was measured by X-ray diffraction, and the corresponding X was calculated by subtracting the thickness of an elementary silicate layer. The results of these measurements showed that. (1) the relation between II and λ for vermiculite is the same as that previously observed for Na-montmorillonite, i.e., II is an exponential function of 1/λ. (2) the values of II predicted by double-layer theory are much smaller than those observed if the surface potential is assigned the appropriate value; an. (3) the observed relation between II and λ does not have the form predicted by this theory. On the basis of these results, a repulsive force not ascribable to double-layer overlap must be primarily responsible for swelling; this force must result from the in-depth perturbation of the water by the surfaces of the vermiculite layers.

Direct Measurement of the Relation Between Swelling Pressure and Interlayer Distance in Li-Vermiculite1

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Direct measurement of the relation between interlayer force and interlayer distance in the swelling of montmorillonite

Direct Measurement of the Relation Between Swelling Pressure and Interlayer Distance in Li-Vermiculite1