Characteristics of sulfide corrosion products on 316L stainless steel surfaces in the presence of sulfate-reducing bacteria

It has been found that microbial communities play a significant role in the corrosion process of steels exposed in aquatic and soil environments. Biomineralization influenced by microorganisms is believed to be responsible for the formation of corrosion products via complicated pathways of electron transfer between microbial cells and the metal. In this study, sulfide corrosion products were investigated for 316L stainless steel exposed to media with sulfate-reducing bacteria media for 7 weeks. The species of inorganic and organic sulfides in the passive film on the stainless steel were observed by epifluorescence microscope, environmental scanning electron microscope combined with energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The transformation from metal oxides to metal sulfides influenced by sulfate-reducing bacteria is emphasized in this paper. (c) 2005 Elsevier B.V. All rights reserved.

Dichloridobis[N-(2-pyridylmethyl)-benzamide-kappa N-2,O]cadmium(II)

In the title compound, [CdCl2(C13H12N2O)(2)], the Cd-II ion is situated on an inversion centre, coordinated by two 0 atoms [Cd-O=2.3878 (17) angstrom] and two N atoms [Cd-N = 2.3404 (15) angstrom] from two N-(2-pyridylmethyl)benzamide ligands, and two Cl atoms [Cd-Cl = 2.5566 (6) angstrom], in a distorted octahedral geometry. In the crystal structure, intermolecular N-H center dot center dot center dot Cl hydrogen bonds [N center dot center dot center dot Cl = 3.1705 (18) angstrom] and pi-pi interactions, with a distance of 3.868 (3) angstrom between the centroids of the phenyl and pyridyl rings of neighbouring molecules, lead to the formation of two-dimensional layers parallel to the bc plane.

cis-Dichloridobis(1,10-phenanthroline-kappa N-2,N ')-cadmium(II) hemihydrate

The title compound, [ CdCl2( C12H8N2)(2)]center dot 0.5H(2)O, crystallizes with two independent complex molecules and one water molecule in the asymmetric unit. The Cd atoms in both independent complexes display a distorted octahedral coordination geometry formed by four N atoms from two phenanthroline ligands and two Cl atoms. In the crystal structure, pi-pi stacking interactions link complexes in two symmetry- independent ladders parallel to the c axis. Intermolecular O-H center dot center dot center dot Cl hydrogen bonds stabilize the crystal packing.

Copper-catalysed asymmetric sulfide oxidation

The focus of this thesis is the preparation of enantiopure sulfoxides by means of copper-catalysed asymmetric sulfoxidation, with particular emphasis on the synthesis of aryl benzyl and aryl alkyl sulfoxides. Chapter 1 contains a review of the methods employed for the asymmetric synthesis of sulfoxides, compounds with many applications in stereoselective synthesis and in some cases with pharmaceutical application. Chapter 1 describes asymmetric oxidation, including metal-catalysed, non metal-catalysed and enzyme-catalysed, in addition to synthetic approaches via nucleophilic substitution of appropriately substituted precursors. Kinetic resolution in oxidation of sulfoxides to the analogous sulfones is also discussed; in certain cases, access to enantioenriched sulfoxides can be achieved via a combination of asymmetric sulfoxidation and complementary kinetic resolution. The design and synthesis of a series of sulfides to enable exploration of the substituent effects of the copper-mediated oxidation was undertaken, and oxidation to the racemic sulfoxides and sulfones to provide reference samples was conducted. Oxidation of the sulfides using copper-Schiff base catalysis was undertaken leading to enantioenriched sulfoxides. The procedure employed is clean, inexpensive, not air-sensitive and utilises aqueous hydrogen peroxide as oxidant. Extensive investigation of the influence of the reaction conditions such as solvent, temperature, copper salt and ligand was undertaken to lead to the optimised conditions. While the direct attachment of one aryl substituent to the sulfide is essential for efficient enantiocontrol, in the case of the second substituent the enantiocontol is dependent on the steric rather than electronic features of the substituent. Significantly, use of naphthyl-substituted sulfides results in excellent enantiocontrol; notably 97% ee, obtained in the oxidation of 2-naphthyl benzyl sulfide, represents the highest enantioselectivity reported to date for a copper-mediated sulfur oxidation. Some insight into the mechanistic features of the copper-mediated sulfur oxidation has been developed based on this work, although further investigation is required to establish the precise nature of the catalytic species responsible for asymmetric sulfur oxidation. Full experimental details, describing the synthesis and structural characterisation, and determination of enantiopurity are included in chapter 3.

The controlled delivery of hydrogen sulfide for the preservation of heart tissue

Gemstone Team Organ Storage and Hibernation

Effect of Grazing-Mediated Dimethyl Sulfide (DMS) Production on the Swimming Behavior of the Copepod Calanus helgolandicus

Chemical interactions play a fundamental role in the ecology of marine foodwebs. Dimethyl sulfide (DMS) is a ubiquitous marine trace gas that acts as a bioactive compound by eliciting foraging behavior in a range of marine taxa including the copepod Temora longicornis. Production of DMS can rapidly increase following microzooplankton grazing on phytoplankton. Here, we investigated whether grazing-induced DMS elicits an increase in foraging behavior in the copepod Calanus helgolandicus. We developed a semi-automated method to quantify the effect of grazing-mediated DMS on the proportion of the time budget tethered females allocate towards slow swimming, typically associated with feeding. The pooled data showed no differences in the proportion of the 25 min time budget allocated towards slow swimming between high (23.6 +/- 9.74%) and low (29.1 +/- 18.33%) DMS treatments. However, there was a high degree of variability between behavioral responses of individual copepods. We discuss the need for more detailed species-specific studies of individual level responses of copepods to chemical signals at different spatial scales to improve our understanding of chemical interactions between copepods and their prey.