No description available.

No description available.

Pyrite is a ubiquitous mineral in shales. It results from the bacterial reduction of seawater sulphate to sulphide and the reaction of that sulphide with iron to form iron sulphides and subsequently pyrite. Five Jurassic shales were examined. 1 The Upper Oxford Clay (Oxfordian) Warboys Cambridgeshire. 2 The Dunans Clay (Callovian-oxfordian) Isle of Skye. 3 The Lower Oxford Clay (Callovian) East midlands. 4 The Posidonia Shales (Lias ε) Southern Germany. 5 The Dunans Shale (Callovian) Isle of Skye. The five shale units are divisible into three major biofacies "Normal" (Units 1& 2), "Restricted" (3) and "Bituminous" (4 & 5), which show varying pyrite contents and isotopic compositions, that reflect the changing influence of the three limiting factors of pyrite formation (sulphate, organic carbon, and iron). Samples of shale were analysed for fine grained pyrite content and isotopic composition, organic and carbonate carbon, and hydrochloric acid soluble iron. The Normal shales showed low pyrite sulphur (<1.3%) and organic carbon (<2%), degree of pyritization (D. O. P. ) (<0.5) and negative (<-28%o) δ34S values. These are consistent with the formation of pyrite near the sediment surface, limited by organic carbon. In the Restricted shales higher pyrite sulphur (av. 1.4%) and organic carbon (av. 5%), degree of pyritization (0.5 to 0.7) and less negative (>-28%o, <-9%o) δ34S values indicate the continuation of pyrite formation deeper into the sediment, where it is limited by sulphate diffusion. High D. O. Ps in the Posidonia Shales (>0.8) suggest that pyrite formation is limited by the availability of iron in Bituminous shales. Heavier δ34S values (>-28%o) in the Posidonia Shale suggest limitation of sulphate reduction by sulphate diffusion, and lighter values in the Dunans Shale (<-28%o) suggest limitation by organic matter. Petrographic and isotopic studies of shell replacement and associated concretionary pyrite from the Lower Oxford Clay show types of replacement related to the differences between the porewaters within the shell and those of the shale, particularly as regards iron supply.

No description available.

There are three related studies within this thesis that examine the relationships between the properties of coals and the characteristics of the chars produced during rapid pyrolysis in a laboratory based Entrained Flow Reactor (EFR) which simulates the rapid rates of heating (104 to 105 °C s-1 ) typical of pulverised fuel boilers. The first study, using a suite of nine coals, investigates the influence of coal rank upon the generation of specific types of char, their respective physical and structural characteristics and their relative combustabilities. The second study, using a suite of twenty-two coals, examines various coal characterisation techniques and the correlations between those techniques and the associated char, and specifically investigates petrographic techniques as a means of characterising coal feedstock. The third study, using freshly mined coals, investigates the effects of oxidation (100°C, air) and weathering (ambient) upon standard analytical techniques and relates such changes to the physical, structural and combustion characteristics of the associated char. There is a common relationship between the elemental oxygen content of the parent coal and the generation of specific types of char for both vitrinite rich coals of differing coal rank and for the oxidised or weathered coals. There is also an inverse relationship (R 2 = 0.97) between the elemental oxygen content of a vitrinite rich coal and the proportion of cenospheres generated by pyrolysis at 1000°C using the EFR. Furthermore, the enhancement of char combustion at 1000°C (in an EFR) is related to the physical and structural characteristics of the char, i.e. the presence or absence of porosity (visible using SEM and TEM), the CO2 surface area and optical texture. A relationship exists (R2 = 0.83) between the morphology of a char (1000°C / N2) and the petrographic composition of the parent coal. The new term microlithotype, is an amalgamation of various vitrinite rich microlithotype classes that simplifies the nomenclature. A combination of calorific value, microlithotype, and coal rank (vitrinite reflectance) illustrates the influence of petrographic composition upon calorific value and also suggests a 'Province' dependency amongst the Cretaceous/Tertiary and Carboniferous coals studied. The coal properties calorific value, microlithotype, and coal rank can be related (R 2 = 0.91) to the proportion of porous chars for the Cretaceous/Tertiary suite of coals, illustrating the use of multivariate analyses when characterising coal feedstock. The effects of oxidation and weathering upon vitrinite fluorescence is also reported. The oxidation of coal at 100°C produces rims of quenched fluorescence which are not apparent within the weathered coals. Furthermore, the intensity of fluorescence at 650 nm (1650) decreases due to progressive oxidation or weathering, but decreases at a rate that is dependent upon the severity (temperature) of the conditions employed. The proposed oxidation quotient (0/Q = I65W%Romax) is a sensitive indicator of the oxidative conditions up to 100°C.

No description available.

No description available.

The title compounds were synthesized from methyl 3-aryl(alkyl)thio crotonic acids by deprotonation followed by silylation. The reactions of dienes with a number of carbonyl electrophiles under Lewis-acid catalysed conditions were investigated. The dienes exclusively give $ gamma$-alkylated products. The thio substituent enhances the $ gamma$-selectivity. / The reactions of dienes with a number of 1,3-dicarbonyl equivalents have been studied and a cycloaromatization reaction has been developed for the regiocontrolled synthesis of aryl sulfides in a 3C + 3C combination. The role of dienes in Diels-Alder reactions has also been investigated. / A new 4C + 2C annulation reaction has been developed based on the propensity of dienes to undergo Michael reaction with $ alpha$,$ beta$-unsaturated ketones under Lewis-acid catalysed conditions. These Michael adducts in turn were cyclized either with potassium tert-butoxide or with lithium thiophenoxide. Further, the tandem Michael-Claisen annulation reaction can be controlled to give either cis- or trans-fused 9-methyldecalin system with three carbonyl groups which are differently masked. The chemoselective transformations of the carbonyl groups were also described.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references. / Also available by subscription via World Wide Web / xvii, 281 leaves, bound ill., charts 29 cm

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (p. 63). / xi, 101 leaves, bound ill. 29 cm