Solubility controlling factors

The metanephric mesenchyme has an extremely high rate of proliferation. The metanephros doubles in size every 8 h during the first 5 days. In the prospective renal cortex, the expression of PCNA, a marker for S-phase, occurs in a majority of cells. The proliferation rate is slowed significantly in BMP-7 knockouts (described above) and BF-2 knockouts. BF-2 is a transcription factor in the medullary stroma. It is likely that it controls the synthesis of a soluble growth factor that stimulates mesenchyme proliferation, but the identity of that factor is unknown. 

The uptake coefficients on various surfaces are listed [86]. On NAT-like substrates y is large, near 0.2. On water-ice substrates, y is even larger, on the order of 0.3. The uptake coefficient of HO on liquid sulfuric acid bulk solutions decreases with increasing activity of the mixture [41,82]. The solubility of HC1 in those mixtures is the controling factor. The uptake on sulfuric acid droplets was recently measured [102], The mass accommodation coefficient a was found to be inversely proportional to temperature and increases from 0.06 at 184 K to 1.0 at - 230 K. The uptake of HOC1 on water-ice in the... 

The energy ( ,) to create a cavity can be approximately equated to 4 rr2cx, where cr represents the surface tensions between the fluid and a perfect rigid wall of the cavity and r denotes the radius of the cavity (e.g., Blander et al., 1959). Therefore, if the cavity creation is the dominant controlling factor in noble gas solubility, which is likely to be the case in common silicate melts, the Henry s law constant can be approximately given by... 

Under ideal conditions with a negligible downstream pressure of both components, the separation factor can be equated to the ideal membrane selectivity factored into its mobility and solubility controlled contributions, viz.,... 

This weak correlation indicates that bioconcentration decreases as log Kow increases. Travis and Arms interpret this as meaning that the controlling factor is aqueous solubility, which is inversely related to hydrophobicity. A more likely explanation is that the hydrophobicity of the organic matter of the soil is greater than the hydrophobicity of the vegetation. 

The solubility of the adsorbate is a controlling factor for adsorption with a given adsorbent. Its solubility in the solvent from which adsorption takes place has an inverse relationship with the extent of adsorption of an adsorbate (i.e., Lundelius rule). It may be postulated that strong forces exist between the adsorbate and solvent, and the breakup of such forces should be needed before adsorption can occur. The higher the solubility of the adsorbate in a solvent, the greater the forces and the smaller the extent of adsorption. 

The formation of polyelectrolyte complexes (PEC) is governed by the characteristics of the individual polyelectrolyte components (e.g. properties of ionic sites - strong or weak electrolyte -, position of ionic sites, charge density, rigidity of macromolecular chains) and the chemical environment (e.g. solvent, ionic strength, pH and temperature). Polyelectrolyte complexes are either separated from the solution as solids or liquids or they are still soluble in solution or may settle as gels due to variation of the controlling factors mentioned above. 

Nanostructures primarily result from polyelectrolyte or interpolyelectrolyte complexes (PEC). The PEC (also referred to as symplex [23]) is formed by the electrostatic interaction of oppositely charged polyelectrolytes (PE) in solution. The formation of PEC is governed by physical and chemical characteristics of the precursors, the environment where they react, and the technique used to introduce the reactants. Thus, the strength and location of ionic sites, polymer chain rigidity and precursor geometries, pH, temperature, solvent type, ionic strength, mixing intensity and other controllable factors will affect the PEC product. Three different types of PEC have been prepared in water [40] (1) soluble PEC (2) colloidal PEC systems, and (3) two-phase systems of supernatant liquid and phase-separated PEC. These three systems are respectively characterized as ... 

To form a CBC, control over the dissolution of the bases is crucial. The bases that form acid-base cements are sparsely soluble, i.e., they dissolve slowly in a small fraction. On the other hand, acids are inherently soluble species. Typically, a solution of the acid is formed first, in which the bases dissolve slowly. The dissolved species then react to form the gel. When the gel crystallizes, it forms a solid in the form of a ceramic or a cement. Crystallization of these gels is inherently slow. Therefore, bases that dissolve too fast will rapidly saturate the solution with reaction products. Rapid formation of the reaction products will result in precipitates and will not form well ordered or partially ordered coherent structures. If, on the other hand, the bases dissolve too slowly, formation of the reaction products will be too slow and, hence, formation of the gel and its saturation in the solution will take a long time. Such a solution needs to be kept undismrbed for long periods to allow uninterrupted crystal growth. For this reason, the dissolution rate of the base is the controlling factor for formation of a coherent structure and a solid product. Bases should neither be highly soluble nor almost insoluble. Sparsely soluble bases appear to be ideal for forming the acid-base cements. 

Wilson [666, 667] and Bauman and Maron [47] show that it is possible to express the reaction rate as a function of film thickness, diffusion constant and solubility of oxygen in the film. When the thickness of the film is reduced to less than a certain value, the chemical reaction and not the diffusion becomes the controlling factor. The activation energy of the oxidation reaction amounts to 16—35 kcal mole-1, or even more, whereas the activation energy of the diffusion of gases in polymer films [39] is of the order of only 10 kcal mole-1. Control by diffusion is facilitated at higher temperatures by the decrease of oxygen solubility in the films. 

The liquid acts as a barrier to free migration of gas. The rate of diffusion of gas is brought to a steady state when the rate of diffusion of the gas into the liquid on the upstream side is just equal to the rate at which the gas is diffusing out of the membrane on the downstream side. Various steady-state conditions may exist according to pressure (the solubility of gases in liquids increases with pressure), temperature (the solubility of gases in liquids decreases with temperature but the rate of diffusion increases), and other controllable factors. The inieirelaiionships of these factors can be predicted from Ficl s laws of diffusion and the gas laws. 

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