Dissimilatory metal-reducing bacteria (DMRB) play an important role in the biogeochemical cycling of metals. DMRB are unique in that they possess the ability to couple metal reduction with their metabolism. Microbial Fe(III) respiration is a central component of a variety of environmentally important processes, including the biogeochemical cycling of iron and carbon in redox stratified water and sediments, the bioremediation of radionuclide-contaminated water, the degradation of toxic hazardous pollutants, and the generation of electricity in microbial fuel cells. Despite this environmental and evolutionary importance, the molecular mechanism of microbial Fe(III) respiration is poorly understood. Current models of the molecular mechanism of microbial metal respiration are based on direct enzymatic, Fe(III) solubilization, and electron shuttling pathways. Fe(III) oxides are solid at circumneutral pH and therefore unable to come into direct contact with the microbial inner membrane, these bacteria must utilize an alternative strategy for iron reduction. Reduced organic compounds such as thiols are prominent in natural environments where DMRB are found. These thiol compounds are redox reactive and are capable of abiotically reducing Fe(III) oxides at high rates S. oneidensis wild-type and ΔluxS anaerobic biofilm formation phenotypes were examined under a variety of electron donor-electron acceptor pairs, including lactate or formate as the electron donor and fumarate, thiosulfate, or Fe(III) oxide-coated silica surfaces as the terminal electron acceptor. The rates of biofilm formation under the aforementioned growth conditions as well as in the presence of exogenous thiol compounds indicate that ∆luxS formed biofilms at rates only 5-10% of the wild-type strain and ∆luxS biofilm formation rates were restored to wild-type levels by addition of a variety of exogenous compounds including cysteine, glutathione, homocysteine, methionine, serine, and homoserine. Cell adsorption isotherm analyses results indicate that wild-type is can attach to the surface of hematite particles attachment , but ΔluxS is unable to attach the hematite surfaces. These results indicate that biofilm formation is not required for Fe(III) oxide reduction by S. oneidensis ∆luxS anaerobic biofilm formation rates were restored to wild-type levels by addition of exogenous auntoinducer-2 (AI-2), a by-product of homocysteine production in the Activated Methyl Cycle. This discovery led to subsequent experiments performed to detect the production and utilization of AI-2 by wild-type and ∆luxS strains under aerobic and anaerobic conditions. AI-2 production experiments showed wild-type, but not ΔluxS, was capable of producing AI-2. The addition of exogenous S. oneidensis and Vibrio harveyi-produced AI-2 to wild-type and ∆luxS resulted in the swift depletion of AI-2 from the media. These results provide evidence that S. oneidensis can produce AI-2 and subsequently utilize its’ own AI-2 as well as AI-2 produced by other bacteria as a carbon and electron source in the absence of preferred carbon sources. S. oneidensis produces and secretes a suite of extracellular thiols under anaerobic Fe(III)-reducing and Mn(III) and Mn(IV)-reducing conditions including cysteine, homocysteine, glutathione, and cyteamine. Exogenous thiols produced by S. oneidensis are intermediates of the Activated Methyl Cycle (AMC) and Transulfurylation Pathway (TSP). Reduced and oxidized thiols were detected, indicating that the thiols are in a constant state of flux between the reduced and oxidized forms and that the concentration of reduced thiols to its’ oxidized counterpart is indicative of the state of metal reduction by the microorganisms. Respiratory phenotypes Based on Fe(III) and Mn(IV) respiratory phenotypes observed in the AMC and TSP pathway mutants (∆luxS, ∆metB, ∆metC and ∆metY) we can infer that cysteine, glutathione, and cysteamine contribute to metal reduction by serving as efficient electron shuttling molecules, while homocysteine is critical for maintenance of the AMC, propagation of thiol biosynthesis, and maintenance of cellular metabolism via the AMC intermediate SAM. Furthermore, these findings suggest that all metal-reducing bacteria require thiol formation to reduce solid metal oxides. Direct contact mechanism is not the dominant means through electrons are transferred and metals are reduced, instead electron shuttles are the maid reduction mechanism.

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Recent developments in the atmospheric treatment of low-grade nickel laterite ores at Anglo American plc has culminated in the conceptual iron-focused laterite (ARFe) process. In addition to the recovery of nickel and cobalt from laterite ore, this process uniquely aims to recover iron as a saleable by-product. The reduction of soluble iron(III) (Fe(III)) by sulfur dioxide gas (SO2) is central to the ARFe concept and represents a complex, multiphase system involving simultaneous gas-liquid mass transfer, thermodynamic speciation and chemical reaction. The chemistry of iron-containing systems is generally poorly understood and accurately predicting their behaviour is challenging, especially under aggressive hydrometallurgical conditions. The primary objective of this work is the development of an engineering model capable of describing the rate and extent of ferric reduction with SO2 under conditions typical of the ARFe process. Thermodynamic considerations provide a rigorous framework for the interpretation of chemical reactions, however little experimental data are openly available for the associated solution species in acidic iron sulfate systems. A key contribution of this work, and critical for the development of the overall model, is the direct measurement of speciation in iron sulfate solutions. Raman and UV-vis spectroscopy were utilised to make direct speciation measurements in the various subsystems of the Fe2(SO4)3-FeSO4-H2SO4-H2O system that were previously unavailable in the open literature. The FeSO+4 and Fe(SO4)– 2 species were explicitly identified and measurements were supported and rationalised by static computational quantum mechanical calculations and ultimately permit the calibration of a robust, ion-interaction solution model with the explicit recognition of the important solution species up to 1.6 mol/kg Fe2(SO4)3, 0.8 mol/kg H2SO4 over 25 – 90 C. Batch and continuous Fe(III) reduction kinetics were measured and the effects of initial Fe2(SO4)3 and H2SO4 concentrations, temperature and in-situ neutralisation quantified. The retardation effect of sulfuric acid was observed to be the most significant factor influencing the initial reaction rate and the achievable extent of reduction at fixed residence time, which varied between about 20 and 80 % after 180 minutes of reaction. A reaction mechanism that is limited by the slow ligand-to-metal electron transfer in the FeIIISO+3 solution species’ decomposition is proposed and spectroscopic measurements and computational quantum mechanical calculations are used to support this mechanism. A kinetic model, comprising a system of differential mass-balance equations, is incorporated into the thermodynamic framework. This reaction model permits the prediction of kinetic profiles over the full range of experimental conditions and can be incorporated into more elaborate simulation models of the ARFe circuit. The specific original contributions of this work are • The direct measurement of aqueous speciation in the Fe2(SO4)3-H2SO4-H2O system by Raman and UV-vis spectroscopy • The development of a modelling framework to characterise speciation, activity coefficients and solubility in the mixed Fe2(SO4)3-FeSO4-H2SO4-H2O system. • The measurement of Fe(III) reduction kinetics using SO2 in concentrated sulfate solutions as a function of initial composition and temperature. • The development of a solution reaction model of Fe(III) reduction with SO2 that accurately predicts the solution speciation and reaction rate with time as a function of composition and temperature. Lastly, the vast complexity of industrial systems will nearly always result in a lack of specific experimental data that are required for the development of phenomenological models. This work emphasises the crucial role that engineering studies hold in the generation of such data to derive maximum practical value for industrial process development and optimisation. / AFRIKAANSE OPSOMMING: Onlangse ontwikkelinge in die atmosferiese behandeling van lae-graad nikkel lateriet erts by Anglo American plc het gelei tot die konseptuele yster gefokus lateriet (ARFe) proses. Bykommend tot die herwinning van nikkel en kobalt uit laterite erts is hierdie proses uniek en daarop gemik om yster te herwin as ’n verkoopbare by-produk. Die vermindering van oplosbare yster(III) (Fe(III)) met swaeldioksied (SO2) is sentraal tot die ARFe konsep en verteenwoordig ’n komplekse, multifase stelsel wat gelyktydige gas-vloeistof massa-oordrag, termodinamiese spesiasie en chemiese reaksie behels. Die oplossingschemie van ysterstelsels word, oor die algemeen, swak verstaan en om hul gedrag akuraat te voorspel is ’n uitdaging, veral onder aggressiewe hidrometallurgiese kondisies. Die primêre doel van hierdie werk is die ontwikkeling van ’n ingenieursmodel wat die tempo en omvang van yster(III) vermindering met SO2 onder tipiese ARFe proses toestande beskryf. Termodinamiese oorwegings stel ’n streng raamwerk voor vir die interpretasie van chemiese reaksies, alhoewel daar egter min eksperimentele data openlik beskikbaar is vir die gepaardgaande oplossing spesies in suur yster(III) sulfaat stelsels. ’n Belangrike bydrae van hierdie werk, en van kritieke belang vir die ontwikkeling van die algehele model, is die direkte meting van spesiasie in yster(III) sulfaat oplossings. Raman en UV-vis spektroskopie is gebruik om direkte spesiasie metings te maak in die verskillende subsisteme van die Fe2(SO4)3-FeSO4-H2SO4-H2O stelsel wat voorheen nie in die oop literatuur beskikbaar was nie. Die FeSO+4 en Fe(SO4)– 2 spesies is ekplisiet geïdentifiseer, terwyl die metings ondersteun en gerasionaliseer is deur statiese kwantummeganiese berekeninge wat uiteindelik die kalibrasie van ’n robuuste, ioon-interaksie model tot gevolg hê wat ook die belangrike oplossingspesies duidelik beklemtoon tot en met 1.6 mol/kg Fe2(SO4)3, 0.8 mol/kg H2SO4 en tussen 25 – 90°C. Enkellading en kontinue yster(III) verminderingskinetika is gemeet en die gevolge van die aanvanklike Fe2(SO4)3 en H2SO4 konsentrasies, temperatuur en in-situ neutralisasie is gekwantifiseer. Die waargeneemde vertragingseffek van swaelsuur is die mees beduidende faktor wat die aanvanklike reaksietempo en die haalbare reaksie omvangsvermindering na ’n vaste residensietyd van 180 minute bepaal, wat wissel tussen ongeveer 20 en 80%. ’n Reaksiemeganisme word voorgestel wat beperk word deur die stadige ligand-totmetaal elektronoordrag in ontbinding van die Fe(III)SO+3 oplossing-spesies en wat verder deur spektroskopiese metings en kwantummeganiese berekenings ondersteun word. A kinetiese model, wat bestaan uit ’n stelsel van gedifferensieerde massa-balans vergelykings, is in die termodinamiese raamwerk geïnkorporeer. Hierdie reaksie-model laat die voorspelling van kinetiese profiele toe oor die volle omvang van die eksperimentele toestande en kan in meer uitgebreide simulasie modelle van die ARFe proces geinkorporeer word. Die spesifieke en oorspronklike bydraes van hierdie werk is • Die direkte meting van die spesiasie in die Fe2(SO4)3-H2SO4-H2O stelsel deur Raman en UV-vis spektroskopie • Die ontwikkeling van ’n modelraamwerk om spesiasie, aktiwiteitskoëffisiënte en oplosbaarheid in die gemengde Fe2(SO4)3-FeSO4-H2SO4-H2O stelsel te karakteriseer. • Die meting van yster(III) vermideringskinetieka deur SO2 in gekonsentreerde sulfate oplossings te gebruik as ’n funksie van die aanvanklike samestelling en temperatuur. • Die ontwikkeling van ’n oplossingsreaksie-model van yster(III) vermindering met SO2 wat die oplossing-spesiasie en reaksietempo met die tyd as ’n funksie van samestelling en temperatuur akkuraat voorspel. Laastens, die oorgrote kompleksiteit van industriële stelsels sal byna altyd lei tot ’n gebrek van spesifieke eksperimentele data wat nodig is vir die ontwikkeling van fenomenologiese modelle. Hierdie werk beklemtoon die belangrike rol wat ingenieursstudies speel in die generasie van data wat sodanig tot maksimum praktiese waarde vir industriële prosesontwikkeling en optimalisering lei.

A nitrogen-cooled and an argon-cooled hydrogen flame have been used for the determination of sulfur containing species in solids by molecular emission cavity analysis (MECA). The argon-cooled flame is much more sensitive for the determination of SO₄²⁻. In a solid mixture containing S₈, S²⁻, SO₃²⁻, and SO₄²⁻, the presence of one or more of these sulfur containing species can be determined with the argon-cooled flame. The nitrogen-cooled flame can be useful, for example, in the determination of a mixture of S₈ and SO₃²⁻ in a solid matrix. All these sulfur containing species can be quantitatively determined in the argon-cooled flame in the concentration range from about 10 ppm to 5000 ppm. The variation from 10 percent to 30 percent in the reproducibility of these measurements has been attributed to the non-homogeneity of the solid materials and the small sizes required. Sulfur dioxide has been used for the reduction of ammoniacal copper(II) solutions to solutions containing various copper(I) compounds. These copper(I) compounds can be reduced further to copper metal by varying the solution conditions. The mechanisms of the reactions involved must be understood before they can be successfully used for the large scale production of copper. Porth et al.'s method was followed for the synthesis of Cu(I) intermediates. Several compounds were isolated and their compositions determined. The changes in the relative concentrations of Cu(I) and Cu(II) are also important for unraveling the kinetics and mechanisms of these reactions. A simple spectrophotometric method using 2,9-dimethyl-1,10-phenanthroline was developed to monitor the Cu(I) concentration in solution. The sensitivity of the method is sufficient to determine 10⁻⁵ M Cu(I) in the presence of Cu(II); SO₂, however, interferes with the method. Other possible methods including the use of a mixture of EDTA and 2,9-dimethyl-1,10-phenanthroline were also examined. Evidence is presented for the formation of a ternary complex of copper(I), 2-9-dimethyl-1,10-phenanthroline, and EDTA. The possibility of using a mixture of Cu(II) and 2,9-dimethyl-1,10-phenanthroline to determine SO₂ was tested. Oxygen was found to interfere with this method.

Depth profiles of S(IV) and S(VI) in snow exposed to 20-140 ppbv SO₂ for 6 to 12 hours have been determined in 48 laboratory experiments. Surface deposition velocity (v(d)) averaged 0.06 cm s⁻¹. Well-metamorphosed snow, longer run times, higher SO₂ concentrations and colder snow were associated with lower values of v(d), and vice versa. Melting followed by draining increased v(d) greatly (0.14 cm s⁻¹. Any effect of ozone on SO₂ v(d) was undetectable. Most sulfur in the snow was as S(VI), even without added ozone, indicating the presence of other oxidants, especially in new snow. Four NO₂ deposition experiments (average v(d) = 0.007 cm s⁻¹), and one combined SO₂-NO₂ deposition experiment were conducted. Ozone, sunlight and SO₂ did not enhance NO₂ deposition; NO₂ and sunlight did not enhance SO₂ deposition. The deposition of SO₂ into a snowpack is modelled as an aqueous system, where the liquid water is considered to be present on snow grain surfaces. Gas transport into the snow, air-water partitioning, and aqueous-phase reactions are explicitly considered. Three oxidants (Fe- or Mn-catalyzed O₂, O₂, and H₂O₂) act to convert S(IV) to S(VI), acidify the film, and inhibit further S(IV) uptake. Model calculations illustrate the primary importance of liquid-water mass fraction (X(m)) and the secondary importance of oxidative reactions on SO₂ v(d) to snow. Model and experimental results are similar for assumed X(m) on the order of one percent. Experiments were also conducted on the incorporation of SO₂ into ice depositing from the vapor at -7 and -15°C. Remarkably, SO₂ is captured in deposited ice at concentrations comparable to Henry's Law equilibrium with water at 0°C. Ozone and HCHO appear to inhibit, not enhance, SO₂ capture. An aqueous-film model accounting for the capture of SO₂ by depositing ice was developed. S(IV) concentrations may be enhanced in the liquid-like layer on growing ice surfaces due to solute exclusion from the bulk ice and greatly-retarded diffusional transport from the ice/film interface, leading to significant incorporation into the ice despite low distribution coefficients. SO₂ snow scavenging ratios may be comparable to sulfate scavenging ratios in the remote troposphere.

No description available.

Dissertation submitted in partial compliance with the requirements for the Master's Degree in Technology: Homoeopathy, Durban Institute of Technology, 2002. / The purpose of this study was to investigate whether frequency strength is a parameter requiring consideration when conducting NMR spectroscopy studies on hornoeopathic potencies. To this end, samples of Sulphur 30CH and a Lactose control were analysed using NMR spectrometers operating at three different frequency strengths of 80MHz, 200.MHz and 500.MHz. It was hypothesized that differences existed in the spectra of respective Sulphur samples, control samples, and between parallel samples of Sulphur and control. It was further hypothesized that differences between parallel samples of Sulphur and control would be more noticeable at the lower frequencies. This hypothesis was based on the assumption that a higher frequency strength would have more intense resonance effects on the structure of the homoeopathic potency, thereby disturbing the micro-structural changes induced during potentisation. The design of the investigation was that of a scientific experiment. Potencies of Sulphur and a lactose-based control were prepared to a 30CH potency each, in 87% ethanol. The final prepared volumes (10ml) of Sulphur and control were blinded by means of colour codes by a third party prior to analysis. The blinded samples were transported to the University of Natal, Pietermaritzburg, where they were subjected to analysis using the following instruments: 1) A Varian FT80A 80.MHz instrument 2) A Varian Gemini 200MHz instrument 3) A Varian Inova 500.MHz instrument At each instrument NMR spectroscopy was conducted on ten (10) samples from each group (Sulphur and control). The samples were prepared in coaxial tubes using acetone as both an external lock and reference, and NMR spectra were recorded for each sample. All the samples were run at a thermostatically controlled temperature of 24\xB0C (\xB1 O,2\xB0C), and the laboratory was maintained at a constant temperature of 22\xB0C. The spectra and data of all the samples were recorded in terms of the chemical shift and integration values of their respective CH2, H20 and OH signals. / M

This dissertation is comprised of five chapters detailing advances in the synthesis and preparation of polymers and materials and the application of these materials in lithium-sulfur batteries for next-generation energy storage technology. The research described herein discusses progress towards overcoming three critical challenges presented for optimizing Li-S battery performance, specifically, addressing the highly electrically insulating nature of elemental sulfur, extending the cycling lifetime of Li-S batteries, and enhancing the charge discharge rate capability of Li-S cathodes. The first chapter is a review highlighting the use of polymers in conventional lithium-sulfur battery cathodes. Li-S battery technology presents a grand opportunity to realize an electrochemical energy storage system with high enough capacity and energy density capable of addressing the needs presented by electrical vehicles and base load storage. Polymers are ubiquitous throughout conventional Li-S batteries and their use has been critical in overcoming the challenges presented for optimizing Li-S cathode performance towards practical implementation. The high electrical resistivity of elemental sulfur requires the incorporation of conductive additives in order to formulate it into a functional cathode. A polymer binder must be utilized to integrate the elemental sulfur as the active material with the conductive additives into an electrically conductive composite affixed to a current collector. The electrochemical action of the Li-S battery results in the electroactive sulfur species converting between high and low order lithium polysulfides as the battery is discharged and charged. These lithium polysulfides become soluble at various stages throughout this cycling process that lead to a host of complications including the loss of electroactive material and slow rate capabilities. The use of polymer coatings applied to both the electroactive material and the cathode as a whole have been successful in mitigating the dissolution of lithium polysulfides by confining the redox reactions to the cathode. Elemental sulfur is largely intractable in conventional solvents and suffers from poor chemical compatibility limiting synthetic modification. By incorporating S-S bonds into copolymeric materials the electrochemical reactivity of elemental sulfur can be maintained and allow these polymers to function as the electroactive cathode materials while enabling improved processability and properties via the comonomeric inclusions. The use of inverse vulcanization, which is the direct copolymerization of elemental sulfur, is highlighted as a facile method to prepare polymeric materials with a high content of S-S bonds for use as active cathode materials. The second chapter focuses on the synthesis and polymerization of a novel bifunctional monomer containing both a styrenic group to access free radical polymerization and a propylenedioxythiophene (ProDOT) to install conductive polymer pathways upon an orthogonal oxidative polymerization. The styrenic ProDOT monomer (ProDOT-Sty) was successfully applied to a two-step sequential polymerization where the styrenic group was first leveraged in a controlled radical polymerization (CRP) to afford well defined linear homo- and block polymer precursors with pendant electropolymerizable ProDOT moieties. Subsequent treatment of the these linear polymer precursors with an oxidant in solution enabled the oxidative polymerization of the pendant ProDOT groups to install conductive polythiophene inclusions. Although the synthesis and CRP of ProDOT-Sty was novel, the key advance in this work was successful demonstration that sequential radical and oxidative polymerizations could be carried out to install conductive polymer pathways through an otherwise nonconductive polymer matrix. The third chapter expands upon the use of ProDOT-Sty to install conductive polymer pathways through a sulfur copolymer matrix. The highly electrically insulating nature of elemental sulfur precludes its direct use as a cathode in Li-S batteries and thus the use of ProDOT-Sty in the preparation of a high sulfur content copolymer with conductive inclusions was targeted to improve electrical properties. Inverse vulcanization of elemental sulfur with ProDOT-Sty and a minimal amount of 1,3-diisopropenylbenzene (DIB) was first completed to afford a sulfur rich copolymer with electropolymerizable side chains. Subsequently, the improved processability of the sulfur copolymer was exploited to prepare thin polymer films on electrode surfaces. The poly(ProDOT-Sty-𝑐𝑜-DIB-𝑐𝑜-sulfur) (ProDIBS) films were then subjected to oxidizing conditions via an electrochemical cell to invoke electropolymerization of the ProDOT inclusions and install conductive poly(ProDOT) pathways. Evaluation of the electrical properties with electrochemical impedance spectroscopy (EIS) revealed that the charge transfer resistance was reduced from 148 kΩ to 0.4 kΩ upon installation of the conductive poly(ProDOT) corresponding to an improvement in charge conductance of more than 95%. This also represented a key advance in expanding the scope of the inverse vulcanization methodology as the first example of utilizing a comonomer with a functional side chain. The fourth chapter focuses on expanding the scope of the inverse vulcanization polymerization methodology to include aryl alkyne based comonomers and the application of new these new sulfur copolymers as active cathode materials in Li-S batteries. The early work on developing inverse vulcanization relied heavily on the use of DIB as one of the few comonomers amenable to bulk copolymerization with elemental sulfur. One of the principal limitations in comonomer selection for inverse vulcanization is the solubility of the comonomer in molten sulfur. Generally it has been observed that aromatic compounds with minimal polarity are miscible and thus common classes of comonomers such as acrylates and methacrylates are immiscible and preclude their compatibility with inverse vulcanization. It was found that aryl alkynes are a unique class of compounds that are both miscible with molten sulfur and provide reactivity with sulfur centered radicals through the unsaturated carbon-carbon triple bonds. Additionally, it was found that internal alkynes were best suited for inverse vulcanization to preclude abstraction of the somewhat acidic hydrogen from terminal alkynes. 1,4-Diphenylbutadiyne (DiPhDY) was selected as a prototypical comonomer of this class of compounds for preparing high sulfur content copolymers via inverse vulcanization. Poly(sulfur-𝑐𝑜-DiPhDY) was prepared with various compositions of S:DiPhDY and these copolymers were formulated into cathodes for electrochemical testing in Li-S batteries. The poly(S-𝑐𝑜-DiPhDY) based cathodes exhibited the best performance reported at the time for a polymeric cathode material with the figure of merit of the first inverse vulcanizate to enable a cycle lifetime of up to 1000 cycles. The fifth chapter details the preparation of composite materials composed of a sulfur or copolymeric sulfur matrix with molybdenum disulfide (MoS₂) inclusions and the use of these materials for Li-S cathodes with rapid charge/discharge rate capabilities. The higher order lithium polysulfide redox products (e.g., Li₂S₈ Li₂S₆) generated during Li-S cycling are soluble in the electrolyte solution of the battery. The rate capability of the Li-S battery is thus fundamentally limited by mass transfer as these electroactive species must diffuse back to the cathode surface in order to undergo further reduction (discharge) or oxidation (charge). In order to limit the effective diffusion length of the soluble lithium polysulfides and therefore mitigate the diffusion limited rate, composite materials with fillers capable of binding the lithium sulfides were prepared. MoS₂ was selected as the filler as simulations had indicated lithium polysulfide had a strong binding interaction with the surface of MoS₂. Furthermore, it was demonstrated for the first time that metal chalcogenides such as MoS₂ readily disperse in molten sulfur which enabled the facile preparation of the composite materials in situ. The composites were prepared by first dispersing MoS₂ in liquid sulfur or a solution of liquid sulfur and DIB below the floor temperature of S₈ (i.e.<160 °C). The dispersions were then heated above the floor temperature of S₈ to induce ring opening polymerization of the sulfur phase and afford the composites. The composites were found to be potent active cathode materials in Li-S batteries enabling extended cycle lifetimes of up to 1000 cycles with excellent capacity retention. Furthermore, the composite materials were successful in enhancing the rate capability of the Li-S cathodes where reversible capacity of >500 mAh/g was achieved at the rapid rate of 5C (i.e. a 12 min. charge or discharge time).

Dissertation submitted in partial compliance with the requirements for the Masters Degree in Technology: Homoeopathy, Durban Institute of Technology, 2002. / The purpose of this study was to analyse and compare the NMR spectra of homoeopathic Sulphur (the most well-known and often tested homoeopathic remedy) in two commonly used potencies, namely the centesimal (CH) and decimal (DH) potencies. Both potencies were prepared according to the Hahnemannian method. In order to assess the differences and similarities between these two potency scales, remedies with the same levels of deconcentration, and remedies with the same numbers of succussions were tested. The Control substance used was Water-Ethanol 87% without lactose or Sulphur. The Control substance was prepared in the same way as the Sulphur i.e. potentised as the Sulphur. Chemical shift and relative integration values of the H20, OH and CH2 peaks were recorded, calculated and compared. The investigation was designed as a scientific experiment. Firstly, the Sulphur remedies were compared to the Controls. Secondly, Sulphur remedies were compared to Sulphur remedies, and Controls to Controls. The following criteria were used: o Equal deconcentrations of the centesimal scale were compared to their equivalent decimal scale. o Equal numbers of succussions of the centesimal scale were compared to their equivalent decimal scale. The following potencies were assessed for both Sulphur and Control (Water-Ethanol): / M

The eruption of Parícutin (1943–1952), a cinder cone volcano in Michoacán, Mexico, caused dendrochronological and dendrochemical responses that might be useful as general dating tools for eruptions. For the eruption period, pines near Parícutin have slightly suppressed ring widths plus high inter-annual variability of width. Wood anatomy changes include traumatic resin ducts and thin bands of false latewood. Dendrochemistry of tree rings shows little temporal variation in most elements, but beginning in 1943 sulfur content increased in rings of four trees and phosphorus content increased in rings of two trees. Hypotheses for increased S and P include new availability of pre-existing soil S and P and/or new input of S and P from the tephra itself. Pines at Parícutin also show suppressed ring widths for five years beginning in 1970, and had the eruption date not been known, the most likely conclusion from ring-width data alone would have been an eruption from 1970 to 1974. However, the 1970s suppression was in response to defoliation by a pine sawfly outbreak, not an eruption. For dendrochronological dating of cinder-cone eruptions, a combination of multiple characteristics (width, chemistry, and anatomy) would be more reliable than depending on any one characteristic alone.

M.Sc. / [AuCl(PPh3)] was reacted with mixed thiols in the presence of silver(I) oxide, resulting in complexes of the type [Au(SC6H4X)(PPh3)] X= Cl, NH2,CH2, forming silver chloride as a by-product. In addition to the above series [Au(SCH2(C6H4)3(2-C6H5(C6H4N)] was prepared via a different route, where [AuCl3(2-C6H5(C6H4N)] was reacted with benzyl mercaptan under reflux in the presence of silver(I) oxide for 3 h, forming silver chloride as a by-product. Palladium complex [PdCl2(2-C6H5(C6H4N)] was prepared by reacting [PdCl2(MeCN)] with 2-phenylpyridine at room temperature for 2 h. All complexes were characterized by 1H, 13C, 31P{H} NMR, IR, mass spectrometry and elemental analysis. Characterization of the starting materials [AuCl3(2-C6H5(C6H4N)] and [PdCl2(2- C6H5(6H4N)] by single crystal X-ray diffraction confirmed their chemical formula. All complexes were reacted with sulfur dioxide (SO2) and the reactions were monitored by electrochemistry and UV-vis spectroscopy. The electrochemical study of the complexes, using cyclic voltammetry (CV) and Osteryoung square wave voltammetry (OSWV), showed one anodic peak, which is due to gold(I/III) and an unresolved peak due to thiolate ligand. Upon bubbling of SO2 to the complexes, there was an immediate change of colour from clear to yellow, the CV results showing an increase in current of the gold(I/III) peak. UV-vis spectroscopy studies showed a shift of peak form 250-286 nm, upon bubbling of SO2 to complexes.