Surface studies chemical factors

As noted before, thin film lubrication (TFL) is a transition lubrication state between the elastohydrodynamic lubrication (EHL) and the boundary lubrication (BL). It is widely accepted that in addition to piezo-viscous effect and solid elastic deformation, EHL is featured with viscous fluid films and it is based upon a continuum mechanism. Boundary lubrication, however, featured with adsorption films, is either due to physisorption or chemisorption, and it is based on surface physical/chemical properties [14]. It will be of great importance to bridge the gap between EHL and BL regarding the work mechanism and study methods, by considering TFL as a specihc lubrication state. In TFL modeling, the microstructure of the fluids and the surface effects are two major factors to be taken into consideration. 

The percent pesticide volatilized in one day from wet soil correlated positively with the factor [vapor pressure/(water solubility X binding constant)]. This factor has been reported to be linearly related to the volatilization rate of chemicals from soil surfaces (27). For pesticides with Henry s law constants and soil binding constants within the range studied, the factor is also approximately proportional to the fraction of chemical in soil air at equilibrium (28). In the present study, it was found that four of the pesticides had low factors, and less than 1% volatilized in 1 day (Table III). Diazinon, on the other hand, had a higher factor, and 2% of it volatilized. The use of this factor therefore does seem to have some merit for qualitative prediction. 

The primary issue is whether the final products are determined by the initial stage of the surface reactions, or if the initial products are subject to subsequent reactions such as surface isomerization. The question regarding whether and why the [4 + 2] product is exclusively formed ultimately bears on the chemical selectivity of the Si(100)-(2 x 1) surface toward conjugated diene systems. By studying the factors that govern the reactivity of these reactions, one hopes to gain control over these surface reactions to an extent that eventually leads to a technique to tailor the reaction selectivity. 

It should be realized that a complete study of a particular surface reaction involves a correlation of the chemical factors with the physical... 

The proper evaluation of the importance of atmospheric transformation of PAH will require a better understanding of the physical and chemical factors, which influence the reactivity of aerosol constituents during gas-particle interactions, e.g. particle size and specific surface, catalysis of the particle matrix. Thus, more elaborated kinetic and product identification studies are needed. These should not be limited to simplified model systems, but also include the direct exposure of combustion related particles in a reaction chamber to ambient levels of gaseous pollutants. 

---