We investigated the effect of different oxygen regimes on growth patterns of Pseudomonas spp. during benzene degradation in microcosm batch studies. Benzene degradation was induced by limiting oxygen available for microbial activity, which consists of three initial-dissolved oxygen (DO) levels of oxic, hypoxic, and anoxic conditions. Batch experiments were performed for cell growth and benzene degradation by inoculating three strains of Pseudomonas spp. (Pseudomonas aeruginosa, Pseudomonas fluorescens, Pseudomonas putida) in mineral salt medium containing aqueous benzene. Results showed that all strains were capable to grow and degrade benzene under all oxygen regimes but in a different manner. The highest cell growth of P. aeruginosa and P. fluorescens was achieved under oxic and anoxic condition, respectively, but there was no substantial difference on benzene degradation between the oxygen treatments with about 25% reduction for both strains. P. putida showed a facultative process for both cell growth and benzene degradation. This reveals that care should be taken in selection of microorganisms with regard to environmental studies since they exhibit different responses for given environmental conditions such as DO levels.

In tetragonal zirconia, the cation is coordinated by two interpenetrating tetrahedra of oxygen ions, implying two different cation-oxygen bond lengths. Neutron powder diffraction was used to study tetragonal ZrO2-2 mol% Y2O3 incorporating various amounts of the different tetravalent ions Ge, Ti, Sn and Ce. Precise and accurate values for the lattice parameters and the variable oxygen position parameter have been obtained, and from these the bond lengths derived. The results are compared with those from an earlier X-ray and Raman study on the same materials. Of interest are the confirmation of the increase in cell volume occurring when Zr is replaced by the smaller Sn ion, and the observation of departures from Vegard's law in the case of substitution of Zr by Ti.