Coulomb fluid

The electrolyte concentration is very important when it comes to discussing mechanisms of ion transport. Molar conductivity-concentration data show conductivity behaviour characteristic of ion association, even at very low salt concentrations (0.01 mol dm ). Vibrational spectra show that by increasing the salt concentration, there is a change in the environment of the ions due to coulomb interactions. In fact, many polymer electrolyte systems are studied at concentrations greatly in excess of 1.0 mol dm (corresponding to ether oxygen to cation ratios of less than 20 1) and charge transport in such systems may have more in common with that of molten salt hydrates or coulomb fluids. However, it is unlikely that any of the models discussed here will offer a unique description of ion transport in a dynamic polymer electrolyte host. Models which have been used or developed to describe ion transport in polymer electrolytes are outlined below. 

Oleinikova and Bonetti [133] extended this type of measurements to Bu4NPic dissolved in 1-dodecanol, in 1,4-butanediol, and in mixtures of these solvents. From all systems employed in conductance measurements, Bu4NPic + 1-dodecanol may come closest to a Coulombic fluid. The anomaly becomes notable near T = 10 2. The anomalous contribution never exceeded a few percent of the background contribution, which makes any decisive determination of the critical exponent extremely difficult. If correction exponents were included, the fits gave the best results for a (1 - a) anomaly. No essential differences between results for 1-dodecanol and 1,4-butanediole systems seem to be present. 

For nonionic systems the lattice gas has provided essential insight into the criticality of fluids. The striking feature of results discussed now for the lattice analogue of ionic fluids is that this Coulomb gas possesses obviously quite different properties from those of the Coulomb fluid. 

Abstract This chapter discusses the potential usefulness of ionic liquids with respect to biocatalysis by illustrating the stability and activity of enzymes in ionic liquids in the presence or absence of water. Ionic liquids are a class of coulombic fluids composed of organic cations like alkyl-substituted imidazolium, pyrrolidin-ium, and tetraalkylammonium ions and anions such as halides, tetrafluoroborates, hexafluorophosphates, tosylates, etc. The possibility of tunable solvent properties by alternation of cations and anions has made ionic liquids attractive to study biocatalysis which warrants an understanding of enzyme stability and activity in ionic liquids. This chapter systematically outlines the recent studies on the stability of enzymes and their reactivity toward a wide range of catalytic reactions. A careful approach has been taken toward analysis of relationship between stabil-ity/activity of enzymes versus chaotropic/kosmotropic nature of cations and anions of ionic liquids. 

The history of ionic liquids dates back to more than 100 years where its root is seeded on high-temperature molten salts [2]. But industrial chemists or in general synthetic organic chemists wimessed a renaissance of molten salt chemistry with the development of a class of coulombic fluid, i.e., ionic liquids (ILs), as a promising neoteric solvent. Prof. Jerry Atwood first pointed out the early ionic liquid,... 

By considering a simple statistical mechanical theory of bulk point plasmas, we aim to elucidate some general convergence characteristics of successive approximation schemes that are often deployed in free energy density functional calculations for Coulomb fluids. Although only a very crude level of theory is discussed here, we suggest that the conclusions are relevant for more sophisticated analyses of ILs. 

R. Kjellander and S. Marcelja,/. Chem. Phys., 82, 2122 (1985). Inhomogeneous Coulomb Fluids with Image Interactions between Planar Surfaces. I. 

Cationic starches show decreased gelatinization temperature range and increased hot paste viscosity. Pastes remain clear and fluid even at room temperatures and show no tendency to retrograde. This stabiUty is due to Coulombic repulsion between positively charged starch molecules in dispersion. 

Powder Mechanics Measurements As opposed to fluids, powders may withstand applied shear stress similar to a bulk solid due to interparticle friction. As the applied shear stress is increased, the powder will reach a maximum sustainable shear stress T, at which point it yields or flows. This limit of shear stress T increases with increasing applied normal load O, with the functional relationship being referred to as a yield locus. A well-known example is the Mohr-Coulomb yield locus, or... 

In continuum boundary conditions the protein or other macromolecule is treated as a macroscopic body surrounded by a featureless continuum representing the solvent. The internal forces of the protein are described by using the standard force field including the Coulombic interactions in Eq. (6), whereas the forces due to the presence of the continuum solvent are described by solvation tenns derived from macroscopic electrostatics and fluid dynamics. 

The electrolyte solution is modelled as a two-component, electroneutral system of point ions with charges ez, = ezL = ez. The density of the fluid is (p+ = pL = p /2). The fluid-fluid and fluid-matrix Coulomb interactions are... 

When two bodies are in contact and there is a tendency for them to slide with respect to each other, a tangential friction force is developed that opposes the motion. For dry surfaces this is called dry friction or coulomb friction. For lubricated surfaces the friction force is called fluid friction, and it is treated in the study of fluid mechanics. Consider a block of weight W resting on a flat surface as shown in Figure 2-5. The weight of the block is balanced by a normal force N that is equal and opposite to the body force. Now, if some sufficiently small sidewise force P is applied (Figure 2-5b) it will be opposed by a friction force F that is equal and opposite to P and the block will remain fixed. If P is increased, F will simultaneously increase at the same rate until... 

The velocity profile is uniform across the entire width of the channel if the channel is open at the electrodes, as is most often the case. However, if the electric field is applied across a closed channel (or a backpressure exists that just counters that produced by the pump), a recirculation pattern forms in which fluid along the center of the channel moves in a direction opposite to that at the walls further, the velocity along the centerline of the channel is 50% of that at the walls (Fig. 11.32a, see Plate 12 for color version). Figure 11.32b (see Plate 12 for color version) illustrates an electric field generating a net force on the fluid near the interface of the fluid/solid boundary, where a small separation of charge occurs due to the equilibrium between adsorption and desorption of ions. The charge region from excess cations localized near the interface by coulombic... 

The bare Coulombic interaction (p = 1) and interactions of charges with rotating dipoles (p = 4) do not fall into this class, and it has been argued for a long time [30] that in this case one expects analytical ( classical ) behavior. This implies that the system can be described by a mean-field Hamiltonian, in which the interaction of a particle is ascribed to the mean field of all other particles, thus ignoring local fluctuations [10]. In real ionic fluids the... 

Comparison with nonionic fluids is possible through the corresponding-states principle [37]. If, as usual, the reduced temperature T is defined as the ratio of the thermal energy kBT to the depth of the potential, one finds for a symmetrical Coulomb system with charges q = z+e = z e... 

Most work has dealt with the RPM as a generic model for ionic criticality. MC data suggest that the replacement of the solvent s dielectric continuum by discrete solvent molecules does not change the principal topology of the phase diagram. This ensures that the simple RPM covers the major features of real ionic fluids, at least in cases where Coulombic interactions prevail. 

We turn now to theories of ionic criticality that encompass nonclassical phenomena. Mean-field-like criticality of ionic fluids was debated in 1972 [30] and according to a remark by Friedman in this discussion [69], this subject seems to have attracted attention in 1963. Arguments in favor of a mean-field criticality of ionic systems, at least in part, seem to go back to the work of Kac et al. [288], who showed in 1962 that in D = 1 classical van der Waals behavior is obtained for a potential of the form ionic fluids with attractive and repulsive Coulombic interactions have little in common with the simple Kac fluid. 

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