Surface electrostatic charge, effect products

The effect of surface electrostatic charge on a material on the attachment of the decay products of radon has been known since pioneering work on atomic structure by Rutherford. Extensive research into this area for the radon and thoron progeny has been conducted in this laboratory for environmental monitoring purposes. Several authors have reported on the effect of electrostatic charge on the collecting characteristics of copper for the radon progeny for exploration purposes (Card and Bell, 1979). 

The first step in biofilm formation prior to microbial adhesion is the irreversible adsorption of macromolecules, which leads to a conditioning film (humic substances, lipo-polysaccharides, microbial products). This conditioning film alters the effect of the membrane the electrostatic charge and the critical surface tension may change. 

The high surface potentials and differential polarities of molecular assemblies such as micelles, vesicles and microemulsions suggest that they may be of use in effecting charge separation after a photochemical redox event either by preferential electrostatic repulsion of one of the products or by differential solubilities of the two products in the different phases. This area of research has been extensively reviewed325 330 and we give a brief overview of the use of these systems. 

System 2. The presence of polyvalent lattice ions in the system containing minerals with PDIH+ and OH- leads to their specific adsorption in the EDL and is often accompanied with a change in IP and PZC provided the surface charge has the opposite sign of that of the adsorbing lattice ion. This leads to an inhibition or activation of the mineral surface as shown in Fig. 16179). The same is true for a hydrolytic product of lattice ions exhibiting a stronger surface activity than non-hydrolyzed ions, as a result of a combined electrostatic and chemisorptive effect. 

The ability of micelles to enhance photoionization yields of hydrophobic molecules was demonstrated in the early 1970s. Thus, the photoionization yields of pyrene [59], phenothiazine [60] and tetramethylbenzidine [61] cations increased when these molecules were encapsulated in anionic micelles. The effect was attributed to efficient escape of electrons from the geminate charge-separated species formed within the micelle, which is accelerated by the anionic interface. The negative micellar surface imposes an electrostatic barrier between the cations, which remain with the micelle, and the aqueous electron in the bulk water phase, thus increasing the lifetimes of the photoredox products. 

We apply simple effective medium models in an attempt to understand the diffusion process in the complex pore network of a porous SiC sample. There is an analogy between the quantities involved in the electrostatics problem and the steady state diffusion problem for a uniform external diffusion flux impinging on a coated sphere. Kalnin etal. [17] provide the details of such a calculation for the Maxwell Garnett (MG) model [18]. The quantity involved in the averaging is the product of the diffusion constant and the porosity for each component of the composite medium. The effective medium approach does not take into account possible effects due to charges on the molecules and/or pore surfaces, details in the size and shape of the protein molecules, fouling (shown to be negligible in porous SiC), and potentially important features of the microstructure such as bottlenecks. 

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