MgCl2 brines present a number of potential advantages for the processing of saprolite ores for nickel production. Concentrated MgCl2 solutions enhance the activity of acid used, allow atmospheric leaching at elevated temperature and inhibit magnesium dissolution, which reduces acid consumption and increases metal selectivity. However, with a chloride system it is economically requisite to recover hydrochloric acid, conventionally accomplished by pyrohydrolysis. This work was performed in conjunction with a novel flowsheet for the processing on saprolite ores, which recovers HCl by the precipitation and subsequent decomposition of magnesium hydroxychlorides, alleviating some of the issues with pyrohydrolysis. Leaching and iron control experiments have been conducted in concentrated MgCl2 brines, up to 4.5 m, to determine the most amenable process conditions. It was determined that > 95% extraction of metals was possible using both aqueous and gaseous HCl. In addition, the feasibility of iron control by precipitation with MgO addition was proven.

I have investigated the evolutionary response of Pseudomonas aeruginosa to salt (NaCl) stress, and the physiological mechanisms responsible for this adaptation. Populations of P. aeruginosa founded from the same ancestral genotype were selected at three different concentrations of NaCl, low, moderate and high for about 660 generations with four independent replicates for each concentration. Adaptation was measured as the fitness of the evolved populations relative to the ancestor assessed in direct, head-to-head competition experiments conducted in the same environment in which they were selected (direct response) as well as in all alternative environments (correlated response). Results suggest that selection in each salt environment led to adaptation to that environment and a modest degree of specialization that evolved because correlated responses to selection were smaller than direct responses. In order to identify the physiological mechanisms contributing to the populations' adaptation in high NaCl concentration, I chose a sample of evolved lines that showed the strongest evidence for specialization to salt and competed them against the common ancestor in KCl and sucrose. Results suggested that increased Na+ /H+ antiporter activity is probably the primary mechanism behind adaptation to high NaCl concentration, however alternative mechanisms cannot be excluded. Tolerance curves, which measure the performance of a genotype across a gradient of salt concentrations, suggested no change in the high salt group’s ability to tolerate extreme concentrations of NaCl. We conclude that high salt evolved population showed improvements to its ionic/osmotic stress resistance strategies mainly to Na+ efflux strategies but with no changes to salt niche.

Non-typhoidal Salmonella enterica serovars continue to be the leading cause of foodborne illnesses in United States. Chlorine, chlorine related, and quaternary compounds are generally used for disinfecting carcasses and equipment in processing industries. The current study was aimed at understanding the inactivation kinetics of four Salmonella serovars to chlorine, chlorine dioxide and cetylpyridinium chloride (CPC). The transcriptomic responses to oxidative stress was investigated in stationary and log phase cells of S. Typhimurium. The study was also aimed at understanding the effect of the chemicals on the expression of virulence genes associated with the Salmonella Pathogenecity Island 1 (SPI1). The possible induction of the viable but nonculturable (VBNC) state in Salmonella due to CPC was also investigated. The inactivation parameters for each serovar and the chemical were estimated based on the Hom's model, ln (N/N0) = -k C^n T^m and it appeared that while disinfectant contact time was significant, biocide concentration in the overall disinfection was insignificant. This was true especially for chlorine and CPC with subtle differences observed between the serovars. The inactivation efficacy was, however, dependent on both concentration and the exposure time for chlorine dioxide. The highest degree of inactivation was obtained with chlorine followed by chlorine dioxide and CPC. Transcriptomic responses of S. Typhimurium revealed significant downregulation of several metabolic processes such as tricarboxylic acid cycle, oxidative phosphorylation, and amino acid biosynthesis in both log and stationary phase cells. Several stress related genes such as usp, rpoS and ompR were upregulated in the stationary phase cells. Majority of the virulence genes associated with the SPI1 were found to be downregulated for all the treatments. While treatment with chlorine and CPC caused downregulation of all the virulence genes, treatment with chlorine dioxide caused significant upregulation of few (hilC, invC, sipA and sipB) genes associated with the SPI1. Finally, the induction of VBNC state was not concluded as a result of treatment with CPC. However, significant percentage of cells (45 percent) with intact membrane was established based on the BacLight assayTM.

The ocean is both a source and a sink for atmospheric methyl bromide (CH3Br) and methyl chloride (CH3Cl). It plays a significant role in their global biogeochemical cycling. In response to the Montreal Protocol, the atmospheric CH3Br is declining and the saturation state of CH3Br in the surface ocean is becoming more positive. Results from two large-scale transect studies in the eastern Pacific and the eastern Atlantic suggest that the ocean became near equilibrium with atmospheric CH3Br in 2010. Results from a "top-down" two-box model indicate that, if the remaining anthropogenic emissions are eliminated, atmospheric CH3Br is likely to drop to the pre-industrial level and the ocean would become a net source to atmospheric CH3Br. This study also represents an effort to improve current understanding of the oceanic and atmospheric budgets of CH3Cl. The global net sea-to-air flux of CH3Cl was estimated at 335 (210 ? 480) Gg yr-1 with improved parameterizations on the solubility, seasonal saturation anomaly ? (sea surface temperature, wind speed) relationships and the use of an updated parameterization on gas transfer velocity. For the first time, we estimated the gross oceanic emission and gross oceanic uptake rates of CH3Cl in the surface ocean, which was 700 (490 to 920) Gg yr^-1 and -370 (-440 to -280) Gg yr^-1, respectively. The ocean accounts for 10 - 19 % in the global CH3Cl emission and 6 - 9 % in its global sinks. Methane (CH4) is a potent greenhouse gas, which has a warming potential 72 times that of carbon dioxide over a 20 year time horizon. Gas hydrates are the largest CH4 reservoir in the planet. How much CH4 is transported from marine gas hydrates to the atmosphere is under debate. In this study, we investigated CH4 fluxes over three deepwater hydrocarbon seeps in the northern Gulf of Mexico using continuous air-sea flux measurements. Extrapolating the highest daily flux from this study to other deepwater seeps in the northern Gulf of Mexico suggests that CH4 fluxes to the atmosphere from the deepwater hydrocarbon seeps in this region are an insignificant source to atmospheric CH4 budget.

ClC-1 is the major skeletal muscle chloride channel and is essential for re-establishing the resting membrane potential of muscle cells after an action potential has occurred. Many mutations throughout the CLCN1 gene, which codes for the CIC-1 protein, have been demonstrated via characterisation in heterologous expression systems, to be causative mutations for either Dominant Myotonia Congenita or Recessive Generalised Myotonia. Recently, increasing numbers of myotonic mutations have been found in the carboxyl tail of CIC-1, which demonstrates its importance as a domain that is essential for the normal function of CIC-1 channels. Previous studies in our laboratory defined a region of 18 amino acids in the immediate post D13 segment of rat CIC-1, essential for the expression of functional channels. / Thesis (PhDBiomedicalScience)--University of South Australia, 2002.

Doctor of Philisophy (PhD) / Despite their early discovery, relatively few classes of ruthenium dinitrogen complexes are known. This work describes the successful coordination of dinitrogen to the electron-rich alkylphosphine cores [RuCl(dmpe)2]+ and [RuCl(depe)2]+ by chloride abstraction from both the cis and trans dichloro derivatives. One such complex, trans-[RuCl(N2)(dmpe)2](BArF24), possesses the most activated ruthenium νNN reported to date. A variety of chloride abstraction agents were tested on the cis and trans isomers of [RuCl2(P-P)2] (P-P = dmpe, depe) with the choice of abstracting agent, anion and solvent all found to significantly affect the outcome. Reaction with silver triflate and trimethylsilyl triflate was found to give dichlororuthenium(III) products, which could be readily reduced to the ruthenium(II) starting materials with common reducing agents, as well as by alcohols and hydrazine. The use of thallium triflate avoided oxidation and led to the formation of the crystallographically characterised polymeric incorporation product, [{trans-[RuCl2(dmpe)2]•Tl(OTf)}n] from trans-[RuCl2(dmpe)2] and the interesting chloride-bridged ruthenium dimer cis-[{Ru(depe)2}2(μ-Cl)2](OTf)2 from trans-[RuCl2(depe)2]. Anion exchange of the complex [{trans-[RuCl2(dmpe)2]•Tl(OTf)}n] with the non-coordinating anion tetrakis(3,5-bis(trifluoromethyl)phenyl)borate resulted in removal of thallium from the system and coordination of dinitrogen to give trans-[RuCl(N2)(dmpe)2](BArF24). Cis-[{Ru(depe)2}2(μ-Cl)2](OTf)2 was found to readily react with a variety of small ligands and gave products such as cis-[RuCl(CO)(depe)2](OTf), cis-[RuCl(NCMe)(depe)2](OTf), cis-[RuCl(CNtBu)(depe)2](OTf), cis-[RuCl(NH3)(depe)2](OTf), cis-[RuCl(N3)(depe)2], and trans-[RuCl(η2-H2)(depe)2](OTf). A preliminary X-ray single crystal structure analysis was conducted on the complex cis-[RuCl(CNtBu)(depe)2](OTf). The thallium(I) salt Tl(BArF24) was found to be an efficient chloride abstraction agent under mild conditions. Reactions with cis- and trans-[RuCl2(depe)2] and cis-[RuCl2(dmpe)2] furnished dinitrogen complexes of the form cis-[{RuCl(P-P)2}2(μ-N2)](BArF24)2, whilst reaction of trans-[RuCl2(dmpe)2] with Tl(BArF24) led to the stable five-coordinate complex trans-[RuCl(dmpe)2](BArF24). Vapour diffusion techniques applied to a solution of cis-[{RuCl(depe)2}2(μ-N2)](BArF24)2 gave rise to crystals of trans-[RuCl(N2)(depe)2](BArF24), on which preliminary X-ray molecular structure analysis was performed. Reactions of both cis-[{Ru(depe)2}2(μ-Cl)2](OTf)2 and trans-[RuCl2(dmpe)2] with high pressure (140 psi) dinitrogen at 140 150°C in methanol or tetrahydrofuran resulted in solvent carbonyl abstraction to afford trans-[RuCl(CO)(depe)2](OTf) and trans-[RuCl(CO)(dmpe)2](Cl) from the depe and dmpe complexes respectively. The molecular structure of trans-[RuCl(CO)(dmpe)2](Cl) was determined via single crystal X-ray structure analysis.

ClC-1 is the major skeletal muscle chloride channel and is essential for re-establishing the resting membrane potential of muscle cells after an action potential has occurred. Many mutations throughout the CLCN1 gene, which codes for the CIC-1 protein, have been demonstrated via characterisation in heterologous expression systems, to be causative mutations for either Dominant Myotonia Congenita or Recessive Generalised Myotonia. Recently, increasing numbers of myotonic mutations have been found in the carboxyl tail of CIC-1, which demonstrates its importance as a domain that is essential for the normal function of CIC-1 channels. Previous studies in our laboratory defined a region of 18 amino acids in the immediate post D13 segment of rat CIC-1, essential for the expression of functional channels. / thesis (PhDBiomedicalScience)--University of South Australia, 2002.

The overall aims of this thesis were to conduct a broad survey of possible organic corrosion inhibitors in near-neutral chloride solutions and to elucidate the mechanisms of such action. Altogether, 130 organic compounds were studied as possible corrosion inhibitors for pure iron, mild steel, copper and aluminium in aerated near-neutral (pH = 8.4) solutions containing 500 ppm NaCl and 100 ppm NaHCO,, conditions often encountered in water-based automotive engine coolants. Inhibitor behaviour was investigated using steady-state electrochemical techniques including polarisation curves, Stern-Geary and corrosion potential (Em,) measurements. The organic compounds examined were found to be highly specific in their inhibitive action toward the metals studied. Typical examples of highly effective corrosion inhibitors were: sebacate and octanoate for pure iron; oleate and sebacate for mild steel; benzotriazole and 2-mercaptobenzothiazole for copper; and laurate and oleate for aluminium. E, was found to provide a rapid and convenient screening test for evaluating the inhibitor performance of organic compounds toward pure iron, mild steel and aluminium but was less useful for copper. Good organic inhibitors were found to act as anodic inhibitors toward pure iron and mild steel but as anodic or mixed-type inhibitors toward copper. For aluminium, the majority of the compounds studied were found to act as anodic inhibitors. However,However, it was also found that only pit initiation was inhibited, i.e. existing pits were not prevented from developing. Optical microscopy of pitted aluminium surfaces indicated their nature varied considerably with inhibition efficiency. The role of complex formation in organic corrosion inhibitors was found to vary with the metal. Complexation of either iron(I1) or iron(II1) ions was found to have an insignificant effect on mild steel. The corrosion rate of copper was found to increase with the copper(LI) complex stability, thus indicating complex formation to be the rate-determining step. For aluminium, the observed effects were found to depend on complex stability. For weak to moderate complexants, inhibitor efficiency (measured as E,,) increased with increasing complexation. However, very strong complexing agents were sufficiently stable to dissolve the aluminium oxide surface, leading to poor inhibition. Aluminium pit morphology was found, using scanning electron microscopy, to change from hemispherical in the uninhibited solution to irregular in the presence of complexing inhibitors. No simple relationships between inhibitor efficiency and molecular structure were found. However, carbon chain length, the nature of functional group(s) and their location in the molecule were found to be important but varied according to the metal. The inhibiting ability of sebacate (a straight chain C, dicarboxylate) was found not to be compromised by water movement (stirring) or pre-existing corrosion product layers. Immersion tests showed that passive film formation on mild steel in sebacate solution involved two stages and was complete only after -100 h immersion. The ion selective properties of several iron(II1) carboxylates and hydrated iron(II1) oxide films were studied by membrane potential measurements in neutral sodium chloride solutions. Some specimens were also studied by Mossbauer spectroscopy. These results show that dicarboxylates are good inhibitors toward mild steel because they form impermeable films. Poor inhibitor performance is associated with the anion selectivity of the film which in turn appears to be related to the film purity. A model is suggested for the inhibition mechanism of mild steel corrosion by dicarboxylates in aerated near-neutral chloride solutions.

Thesis (Ph. D. in Chemistry)--Vanderbilt University, Dec. 2007. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--Ohio University, August, 1996. / Title from PDF t.p.