Lower light permeability

Pigments for finishes are selected on the basis of their colour, but special attention must be paid to inertness in the chosen binder and stability and light fastness under the conditions of application and exposure. Flake pigments such as aluminium and micaceous iron oxide give finishes of lower moisture-vapour permeability than conventional pigments, and consequently contribute to better protection. 

In terms of C9-Cn and corresponding range of aromatic compounds, there is a similarity to Class 1 oils (Figures 4 and 5), an observation which would be consistent with a common source. However, there is a difference in the normal alkane distribution when Class 4 oils are compared to Class 1 or Class 2 oils. Class 4 oils have a lower benzene and toluene content and appear more biodegraded relative to Class 1 oils (see Tables I and III). The Class 4 oils are all in a Miocene reservoir, the L-5, which is in permeable contact with the Eocene B sands below. Other oils in the area do not show the same normal alkane distribution, but these differences are insufficient to invoke a separate source rock. The TJ-210 oil (Class 5) is also reservoired in an L-5 sand and is unusual in that it is depleted in normal alkanes between C9 and C13 (Figure 2). It is possible that the Class 5 and the Class 4 oils are related by some process of natural distillation as reported (6) for Trinidad oils. In this process the light ends (C15+)... 

If appropriate dermal penetration data are available for rats in vivo and for rat and human skin in vitro, the in vivo dermal absorption in rats may be adjnsted in light of the relative absorption throngh rat and human skin in vitro. The latter adjustment may be carried out because the permeability of human skin is often lower than that of animal skin (McDougal et al., 1990 Sato et al., 1991 Barber et al., 1992 Howes et al., 1996). A generally applicable correction factor for extrapolation to man can, however, not be derived, because the extent of overestimation appears to be agent- and animal-specific (Bronaugh and Maibach, 1987 ECETOC, 1993). 

Fletcher s example is of great importance. It is the clearest, simplest treatment of a situation where only one material moves, but moves by two separate mechanisms—a volume-conserving viscous change of shape plus a diffusive mass transfer from higher-compression sites to lower-compression sites. The two mechanisms resemble those operating in situation (1), the elastic permeable host plus mobile fluid Fletcher clearly brings to light the fact that the two movement mechanisms remain distinct even when the same material travels by them both. 

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