Isolation of Bisphenol A-Tolerating/degrading Shewanella haliotis Strain MH137742 from an Estuarine Environment

Applied Biochemistry and Biotechnology - The human exposure to bisphenol A (BPA) occurs frequently. Once, this compound was one of the highest volume chemicals produced worldwide and used as a...     

Intercomparison of retrieval codes used for the analysis of high-resolution, ground-based FTIR measurements

A rigorous and systematic intercomparison of codes used for the retrieval of trace gas profiles from high-resolution ground-based solar absorption FTIR measurements is presented for the first time. Spectra were analyzed with the two widely used independent, retrieval codes: SFIT2 and PROFFIT9. Vertical profiles of O₃, HNO₃, HDO, and N₂O were derived from the same set of typical observed spectra. Analysis of O₃ was improved by using updated line parameters. It is shown that profiles and total column amounts are in excellent agreement, when similar constraints are applied, and that the resolution kernel matrices are also consistent. Owing to the limited altitude resolution of ground-based observations, the impact of the constraints on the solution is not negligible. It is shown that the results are also compatible for independently chosen constraints. Perspectives for refined constraints are discussed. It can be concluded that the error budget introduced by the radiative transfer code and the retrieval algorithm on total columns deduced from high-resolution ground-based solar FTIR spectra is below 1%.     

Direct dynamics trajectory study of the reaction of formaldehyde cation with D2: vibrational and zero-point energy effects on quasiclassical trajectories

Quasiclassical, direct dynamics trajectories have been used to study the reaction of formaldehyde cation with molecular hydrogen, simulating the conditions in an experimental study of H2CO+ vibrational effects on this reaction. Effects of five different H2CO+ modes were probed, and we also examined different approaches to treating zero-point energy in quasiclassical trajectories. The calculated absolute cross-sections are in excellent agreement with experiments, and the results provide insight into the reaction mechanism, product scattering behavior, and energy disposal, and how they vary with impact parameter and reactant state. The reaction is sharply orientation-dependent, even at high collision energies, and both trajectories and experiment find that H2CO+ vibration inhibits reaction. On the other hand, the trajectories do not reproduce the anomalously strong effect of nu2(+) (the CO stretch). The origin of the discrepancy and approaches for minimizing such problems in quasiclassical trajectories are discussed.     

Trajectory studies of S(N)2 nucleophilic substitution. 8. Central barrier dynamics for gas phase Cl(-) + CH(3)Cl

Quasiclassical direct dynamics trajectories, calculated at the MP2/6-31G level of theory, are used to study the central barrier dynamics for the C1(-) + CH(3)Cl S(N)2 reaction. Extensive recrossings of the central barrier are observed in the trajectories. The dynamics of the Cl(-)-CH(3)Cl complex is non-RRKM and transition state theory (TST) is predicted to be an inaccurate model for calculating the Cl(-) + CH(3)Cl S(N)2 rate constant. Direct dynamics trajectories also show that Cl(-) + CH(3)Cl trajectories, which collide backside along the S(N)2 reaction path, do not form the Cl(-)-CH(3)Cl complex. This arises from weak coupling between the Cl(-)-CH(3)Cl intermolecular and CH(3)Cl intramolecular modes. The trajectory results are very similar to those of a previous trajectory study, based on a HF/6-31G* analytic potential energy function, which gives a less accurate representation of the central barrier region of the Cl(-) + CH(3)Cl reaction than does the MP2/6-31G* level of theory used here. Experiments are suggested for investigating the non-RRKM and non-TST dynamics predicted by the trajectories.