Density functional theory analysis of carbonyl sulfide hydrolysis: effect of solvation and nucleophile variation.

The detailed mechanisms of the hydrolysis of carbonyl sulfide (OCS) by nucleophilic water and hydroxide ion in both the gas phase and bulk water solvent have been investigated using density functional theory. Various reaction channels on the potential surface have been identified. The thermodynamic results demonstrate that the hydrolysis of OCS by nucleophilic water and hydroxide ion should proceed more favorably at low temperature. The hydrolysis of OCS by the hydroxide ion is the main reaction channel from thermodynamic and kinetic perspectives, and the bulk solvent can influence the rate-determining step in this channel. However, the solvent barely modifies the activation energy of the rate-determining step. For the hydrolysis of OCS by nucleophilic water, the solvent does not modify the rate-determining step, and the corresponding activation energy of the rate-determining step barely changes. This bulk solvent effect suggests that most of the contribution of the solvent is accounted for by considering one water molecule and a hydroxide ion.

Desiccation responses and survival of Sinorhizobium meliloti USDA 1021 in relation to growth phase, temperature, chloride and sulfate availability.

AIMS: To identify physical and physiological conditions that affect the survival of Sinorhizobium meliloti USDA 1021 during desiccation. METHODS AND RESULTS: An assay was developed to study desiccation response of S. meliloti USDA 1021 over a range of environmental conditions. We determined the survival during desiccation in relation to (i) matrices and media, (ii) growth phase, (iii) temperature, and (iv) chloride and sulfate availability. CONCLUSIONS: This study indicates that survival of S. meliloti USDA 1021 during desiccation is enhanced: (i) when cells were dried in the stationary phase, (ii) with increasing drying temperature at an optimum of 37 degrees C, and (iii) during an increase of chloride and sulfate, but not sodium or potassium availability. In addition, we resolved that the best matrix to test survival was nitrocellulose filters. SIGNIFICANCE AND IMPACT OF THE STUDY: The identification of physical and physiological factors that determine the survival during desiccation of S. meliloti USDA 1021 may aid in (i) the strategic development of improved seed inocula, (ii) the isolation, and (iii) the development of rhizobial strains with improved ability to survive desiccation. Furthermore, this work may provide insights into the survival of rhizobia under drought conditions.

Dispersion and thermodynamics of clouds generated from spills of SO3 and oleum.

A new model describing the dispersion behaviour and the processes that occur in a cloud generated from accidental spills of SO3 and oleum has been developed. Such a cloud may initially behave as a dense gas, with several chemical and physical processes occurring in it. There is not usually enough atmospheric moisture in the air passing immediately above the pool for complete and rapid reaction to sulphuric acid mist. Therefore in the early stages, SO3 vapour, H2SO4 vapour and H2SO4 aerosol will be present. At some distance downwind, transition to passive dispersion behaviour will take place and only sulphuric acid aerosol will be present in the cloud. The dense gas model is based on a box type dispersion model. The passive behaviour is described by a Gaussian model that takes into account deposition of the aerosol particles. The model results suggest a number of lines of experimental investigation that are required to provide data for model validation.