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Chain elongation and cyclization of precursors of dihydroxyphenylacetyl-CoA (DPA-CoA) catalyzed by the bacterial type III polyketide synthase DpgA were studied. Two labile intermediates, di- and tri-ketidyl-CoA (DK- and TK-CoA), were proposed and chemically synthesized. In the presence of DpgABD, each of these with [(13)C(3)]malonyl-CoA (MA-CoA) was able to form partially (13)C-enriched DPA-CoA. By NMR and MS analysis, the distribution of (13)C atoms in the partially (13)C-enriched DPA-CoA shed light on how the polyketide chain elongates and cyclizes in the DpgA-catalyzed reaction. Polyketone intermediates elongate in a manner different from that which had been believed: two molecules of DK-CoA, or one DK-CoA plus one acetoacetyl-CoA (AA-CoA), but not two molecules of AA-CoA can form one molecule of DPA-CoA. As a result, polyketidyl-CoA serves as both the starter and extender, whereas polyketone-CoA without the terminal carboxyl group can only act as an extender. The terminal carboxyl group is crucial for the cyclization that likely takes place on CoA.

This study addresses the impact of spatial variability on the angle of distortion between two footings in rock masses. A simple elasto-perfectly-plastic model based on the Hoek–Brown criterion is taken to simulate the spatial variation of rock mass properties in the finite element analyses. This model is calibrated by a large rock mass database. With Monte Carlo simulations, stochastic samples of angle of distortion between two footings are obtained, which are further used to derive reliability-based allowable bearing stresses. The analysis results show that the geological strength index (GSI) of rock masses and uniaxial compressive strength of intact rock are the two dominate factors that affect the reliability-based design. Comparisons to the existing codes show that these codes are appropriate for poor to fair rock masses, conservative for good to very good rock masses and un-conservative for very poor rock masses.