[en] Thiobacillus thiooxidans is an acidophilic, obligately autotrophic bacterium which derives its energy by oxidizing reduced or partially reduced sulfur compounds and obtains its carbon by fixing carbon dioxide from the atmosphere. The strain is able to live in inorganic, acidic environments and is present in large numbers in coal mine drainage and in mineral ores. T. thiooxidans has been used industrially in metal leaching from mineral ores and in the microbial desulfurization of coal in combination with Thiobacillus ferrooxidans. Although T. thiooxidans has been well studied physiologically, very little is known about it genetics. The broad-host-range IncP plasmids RP4, R68.45, RP1::Tn501, and pUB307 were transferred directly to extremely acidophilic Thiobacillus thiooxidans from Escherichia coli by conjugation at frequencies of 10^-5 to 10^-7 per recipient. The ability of T. thiooxidans to receive and express the antibiotic resistance markers was examined. The plasmid RP4 was transferred back to E. coli from T. thiooxidans at a frequency of 1.0 x 10^-3 per recipient

[en] A combined theoretical and experimental study is performed to investigate natural convection pipe flows at high Rayleigh number. The wall conduction effects and thermal property variations of the fluid and pipe wall are also considered in the analysis. A low-Reynolds-number k-ε turbulence model is employed to treat the transitional and turbulent flow regime including buoyancy effects. The predicted and measured distributions of wall temperature and Nusselt number are in good agreement. Empirical correlations for the induced flow rate and average Nusselt number are proposed. Results show that the characteristics of natural convection heat transfer in a vertical pipe approach those along a single vertical plate for large Rayleigh number. (author)

[en] This work deals with the problem of transient conjugated forced convection heat transfer in turbulent pipe flows. The external surface of the pipe over a finite heated section is subjected to either uniform heat flux or uniform wall temperature. The governing parameters identified in this work are the Reynolds number Re, the wall-to-fluid conductivity ratio K, the wall-to-fluid diffusivity ratio A, the dimensionless wall thickness Δ, and the Prandtl number Pr. A modified low-Re κ-ε turbulent model is adopted to solve for the fully developed velocity and eddy viscosity distributions. Predicted results show that effects of wall conduction and wall heat capacity have a significant impact on the unsteady heat transfer, especially in the early transient period