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Plant development, growth and response to varying environmental conditions, involves a complex network of overlapping interactions between plant signalling hormones and gene expression, known as ‘CROSSTALK’, which controls cell proliferation, elongation and differentiation. Hormone response, concentrations and gene expression levels vary through the root tip and display patterning, which ultimately drives development; however, little is known about how this is established. Models have been constructed to explain patterning, including a ‘physical’ auxin flux model in a simple rectangular 2-D multicellular Arabidopsis root which excludes crosstalk (Grieneisen et al., 2007), and a single cell ‘biological crosstalk’ model of multiple hormone and protein interactions in WT and mutants (Liu et al., 2010; Liu et al., 2013). The project goal was to combine these approaches by embedding the single cell biological crosstalk relationships into a 2-D multicellular root structure to reproduce experimentally observed hormone and gene expression patterning. An initial model was constructed and parameter values calibrated to meet fit criteria and produce a WT parameter set. The model proved robust to parameter variation, indicating that results did not rely on unique parameter value selections. Model results were compared to experimental data to test predictive capability and matched experimentally observed patterning and concentration trends for most species and mutants. A more realistic digital root map was then developed with additional auxin carriers to allow improved comparison between model and experimental images at a cell-scale level. The roles of auxin influx and efflux carriers in regulating auxin patterning were investigated by developing a ‘Recovery Principle’, where pattern perturbations due to changes in one carrier set could be recovered by adjustments to the other carrier set. Finally, using additional experimental data from the literature, the crosstalk network was revised to produce more representative cytokinin patterning. The model provides an explanation of crosstalk control of gene expression and patterning, and forms a foundation for future expansion of hormonal crosstalk and gene expression modelling in the Arabidopsis root. In summary, this project has developed predictive models to further explore hormone and gene expression levels and spatiotemporal pattern formation in the Arabidopsis thaliana root tip.

Vitamin B₁₂ (cobalamin) is one of Nature's most complex small molecules. It is a cobalt-containing modified tetrapyrrole that plays a number of key metabolic roles in many prokaryotic systems and is also essential to the biochemistry of higher animals. However, it is made by only certain bacteria, requiring around thirty enzymatic steps for its complete de novo construction. Surprisingly, the nutrient is synthesised by one of two related, though genetically distinct, pathways that represent aerobic or anaerobic routes. The anaerobic pathway has remained poorly characterised due to the instability of the pathway intermediates to oxygen and the low activity of enzymes, and is the focus of the research reported in this thesis. The Gram-positive aerobe Bacillus megaterium has previously been used for the commercial production of cobalamin and has a complete anaerobic pathway. Several genes, (termed chi for cobinamide biosynthesis) from the cobalamin biosynthetic pathway have been cloned and overexpressed individually within the host B. megaterium DSM319. One of the major bottlenecks in the anaerobic pathway is the ring contraction step, where only limited yields (< 5 %) of product had previously been obtained using crude-lysate based incubations. By studying the purified B. megaterium CbiH60 enzyme, an efficient method was developed to allow the generation of the ring-contracted product cobalt-factor IV in high yields. This breakthrough then permitted the characterisation of many of the down-stream steps in the pathway to be characterised by using other purified cobalamin biosynthetic enzymes from B. megaterium, by incubating combinations of purified enzymes with cobalt-factor IV and the appropriate cofactors (SAM, NADH). This has resulted in the successful step-by-step elucidation of the anaerobic cobalamin pathway, including the isolation of the long sought-after and elusive intermediates cobaltprecorrin- 5, -6A, -6B, -7 and -8. An enzyme-cocktail approach has also resulted in a full in vitro synthesis of cobyrinic acid (the first known stable intermediate in the pathway) from 5-aminolevulinic acid has been demonstrated, involving a full 15 enzymatic steps. The exposition of the anaerobic pathway has been interpreted with respect to the chemical logic of the metabolic process and the evolution of multifaceted biochemical pathways.

This study investigates the selective formation of higher oxygenates from a synthesis gas mixture using a variety of copper-based heterogeneous catalysts. The catalysts are prepared by co-precipitation. Full characterisation of the catalysts, both before and after use, is achieved using primarily by spectroscopy, thermogravimetric and X-ray analysis and BET and copper surface area measurements. The catalytic activities and selectivities of the products are determined from the reaction of synthesis gas mixtures (H2/CO/CO2) in a self-built continuous flow microreactor, equipped with on-line gas chromatographic analysis, operating at moderate temperature and pressure. The activity is measured in terms of conversion from reactants and the conversion and product distribution of all products formed determine the selectivity of higher alcohols. These factors can be determined by variation in the reactor gasfeed composition, the pressure, the temperature and the gas hourly space velocity. The effect on selectivity of production by the addition of lower alcohol (methanol or ethanol) to the reactant mixture has also been examined. The variation in microreactor parameters can be related to possible correlations between catalyst structure and catalyst activity and selectivity. Preparation of the initial catalyst, Cu/Cr2O3, formed preferentially methanol; hydrocarbons and dimethyl ether were also produced. Substitution of chromium for aluminium and magnesium caused changes in product distribution; the aluminium for increasing activity and the magnesium to decrease the acidity. However, the initial preparation conditions for the Cu/MgO/Al2O3 (50/10/40) catalyst resulted in incomplete co-precipitation and a consequential decrease in activity such that no alcohols were produced. Methane was the primary product for this catalyst. Binary catalysts of Cu/MgO and Cu/Al2O3 were prepared to optimise the preparation condition to give complete co-precipitation. A main emphasis has been to establish preparation conditions, which have been shown to lead to reproducibility in catalyst structure and catalytic activity. The magnesium concentration was initially fixed at 2 % of the total metal content; however, this still resulted in the production of hydrocarbons and dimethyl ether. The magnesium concentration was gradually increased through 5 % to 7 % with respect to the copper and aluminium components. This increase in magnesium concentration resulted in a precursor with increased crystallinity and a catalyst, which gave a higher yield of higher alcohols. However, methanol was still the predominant alcohol in the total alcohol yield. At this increased magnesium concentration, hydrocarbons and dimethyl ether were still being produced. On the basis that the inhibiting step is the C1-C2 chain growth step, it has been found that this can be overcome by K-promotion of the Cu/Mg/Al203 (60/7/35) catalysts with the K+ ion at 0.005 wt %. This was especially noticeable with the catalyst prepared at pH = 8 and aged in the mother liquor for 30 mins, as a large production of ethanal was observed. Under the conditions used unlike unpromoted catalysts, no induction period in the formation of oxygenates was observed with these catalysts. However, the overall activity as measured by the consumption of the reactants was lower than that observed with unpromoted catalysts. No DME was formed with the K-promoted catalysts.

While there has been much research investigating the consequences of viewing media violence, there is comparatively little research on the antecedents of viewing it. Television relies primarily on visual imagery but as yet there has been little research concernIng viewers' visual Imagery ability. It is hypothesized that viewers with vivid visual imagery have, in contrast to non-vivid visual imagers, the skills necessary to manipulate violent images of real events and distance themselves from them. Thus it was predicted that non-vivid visual imagers would show more elevated physiological and emotional responses to real violence. If physiology is a substrate of aggression then features that have been seen to change levels of behavioural aggression in previous studies should have similar effects on physiology. Previous research has suggested that it is real rather than fictional violence that has the greatest effect on viewers (Berkowitz & Alioto, 1973; Geen, 1975). It has also been suggested that increases in physiological activity can have an intensifying effect on emotional states, giving it "visceral quality" (Schacter & Singer, 1962; Reisenzein, 1983). Thus it was predicted that real violence would produce the greatest increases In both physiology and negative mood experience. In a series of four experiments 140 participants' heart rates, electrodermal activity and mood states were assessed in response to differing types of film violence. As predicted, participants' physiological responses, particularly heart rates, were more elevated to real violence, an effect that was reflected in negative mood ratings. Variables such as violence-justification and the type of violence were also seen to yield differential physiological activity. There was also evidence, as predicted, that non-vivid imagers were more physiologically reactive to real violence than high imagers, although this was not reflected in mood rating differences. These results suggest that physiological responses are a fundamental component of aggression and that they play an important role in determining the level of emotional experience. Individual difference factors such as visual imagery ability also play an influential role In shaping responses to media violence.