Rock varnish is a microns-thick manganese- and iron-rich coating that forms on exposed rock surfaces in arid and semi-arid environments. Empirical correlations of the varnish cation ratio (K+Ca)/Ti with age have been used to estimate ages of geomorphic surfaces, with varnish chemistry generally acquired by either proton-induced x-ray emission (PIXE) analysis of natural varnish surfaces. Chemical analyses of rock varnish with SEM/EDX utilize a sequence of accelerating voltages to vary penetration depths into the sample. Using elemental x-ray maps of natural varnish surfaces with SEM/EDX, penetration into the substrate can be recognized at accelerating voltages where contamination with substrate is inferred from SEM/EDX chemical analyses. This demonstrates the ability of the SEM method to obtain varnish chemistry with minimal inclusion of substrate. Calculations of theoretical x-ray depth-distribution ({phi}({rho}z)) curves in varnish indicate that at an accelerating voltage of 10 kV most of the emitted electrons are generated in the upper 0.5 micron of a sample. At a higher voltage of 30 kV most of the signal is still restricted to the upper 2 microns, representing a very small percentage of total varnish volume in many cases. The ability of the SEM method to obtain empirical correlations of the chemistry of …

This talk deals with the investigation of secondary interactions in proton-nucleus and nucleus-nucleus collisions using the Monte Carlo event generator HIJET.

In summary, significant bond cleavage was found only for thiophenol under the supercritical conditions studied. Less than 5% yield was found for the observed reaction products for all the other organosulfur compounds. The hydrogen sulfur bond in thiophenol is clearly the weakest of those studied and therefore it is the easiest to rupture. Also a general trend was observed the solvolysis reaction products such as ethylthiobenzene were the products initially formed at lower temperatures. But with higher temperatures the reaction product were those typically produced from the bimolecular association of free-radicals, such as phenylsulfide for the thiophenol sample. This type of reaction would be expected in pyrolysis reactions. Bimolecular reactions between organosulfur compounds would not be expected when the reaction is occurring at the surface of the solid coal matrix. The probability of the extracted organosulfur radicals having such bimolecular reactions is quite low. However, the reactions that are observed from the interaction of supercritical ethanol and the model coal compounds are not ones that show obvious indications of desulfurization of the compound.

In summary, significant bond cleavage was found only for thiophenol under the supercritical conditions studied. Less than 5% yield was found for the observed reaction products for all the other organosulfur compounds. The hydrogen sulfur bond in thiophenol is clearly the weakest of those studied and therefore it is the easiest to rupture. Also a general trend was observed the solvolysis reaction products such as ethylthiobenzene were the products initially formed at lower temperatures. But with higher temperatures the reaction product were those typically produced from the bimolecular association of free-radicals, such as phenylsulfide for the thiophenol sample. This type of reaction would be expected in pyrolysis reactions. Bimolecular reactions between organosulfur compounds would not be expected when the reaction is occurring at the surface of the solid coal matrix. The probability of the extracted organosulfur radicals having such bimolecular reactions is quite low. However, the reactions that are observed from the interaction of supercritical ethanol and the model coal compounds are not ones that show obvious indications of desulfurization of the compound.