The monodromy group of a function on a general curve

Let C_g be a general curve of genus g>3. Guralnick and others proved that the monodromy group of a cover C_g-> P^1 of degree n is either S_n or A_n. We show that A_n occurs for n>2g. The corresponding result for S_n is classical

A GAP package for braid orbit computation, and applications

Let G be a finite group. By Riemann's Existence Theorem, braid orbits of generating systems of G with product 1 correspond to irreducible families of covers of the Riemann sphere with monodromy group G. Thus many problems on algebraic curves require the computation of braid orbits. In this paper we describe an implementation of this computation. We discuss several applications, including the classification of irreducible families of indecomposable rational functions with exceptional monodromy group

Integrated biogas systems

An integrated biogas system is a synergistic cycle of processes sustainably recovering energy and nutrients by anaerobic digestion systems. It is a value adding sequence managing waste and biomass with a final gaseous by-product biogas or biomethane (a natural gas substitute). This thesis explored its core process, technology and strategies of biogas production and upgrading to biomethane. Various studies of this thesis highlight pathways to conduct and optimise anaerobic digestion at intensified conditions while improving reactor utilisation. An increase in substrate throughput and loading was attained by a pre-treating first stage hydrolysis reactor. The solubilisation of substrate provided upstream carbon dioxide segregation and high quantities of readily available liquid fermentation products. A downstream digester increased methane yields and enriched the methane content to levels of 71% of the biogas composition. Intensified conditions and mono-digestion of a single substrate such as food waste can exhibit deficiencies in essential nutrients and inhibition of methanogenic activity. Supplementation of undersupplied trace elements induced immediate recovery allowing stable digestion at loading rates as high as 5 g VS L-1 d -1 at mesophilic temperatures. An increase in temperature further improved degradation kinetics and stimulated higher biomethane yields at shorter substrate retention in grass digestion. In an integrated biogas system, biogas may be upgraded in conjunction with in-situ and ex-situ biological methanation strategies. The addition of hydrogen revealed positive effects on the methanogenic process. Adverse effects of elevated dissolved hydrogen concentrations on acetogenesis became evident in-situ. A biomethane with methane concentrations in excess of 96% successfully demonstrated the potential for gas grid injection at methane formation rates of 3.7 L per litre reactor volume per day. An approach, supplying gases continuously into a sequential ex-situ reactor system and steadily displacing the upgraded biogas, confirmed similar methane formation yields. A hybrid model, where an in-situ grass digester is followed by an ex-situ reactor suggested an alternative approach to conventional biogas upgrading. The contribution of this thesis is the successful demonstration of optimisation potential in novel and existing digestion systems. The employed biogas upgrading strategies proved to be efficient and suitable for gas grid injection

Factors controlling headspace pressure in a manual manometric BMP method can be used to produce a methane output comparable to AMPTS

The manual manometric biochemical methane potential (mBMP) test uses the increase in pressure to calculate the gas produced. This gas production may be affected by the headspace volume in the incubation bottle and by the overhead pressure measurement and release (OHPMR) frequency. The biogas and methane yields of cellulose, barley, silage and slurry were compared with three incubation bottle headspace volumes (50, 90 and 180ml; constant 70ml total medium) and four OHPMR frequencies (daily, each third day, weekly and solely at the end of experiment). The methane yields of barley, silage and slurry were compared with those from an automated volumetric method (AMPTS). Headspace volume and OHPMR frequency effects on biogas yield were mediated mainly through headspace pressure, with the latter having a negative effect on the biogas yield measured and relatively little effect on methane yield. Two mBMP treatments produced methane yields equivalent to AMPTS

Moral (dis)engagement with anthropogenic climate change in online comments on newspaper articles

Anthropogenic climate change (ACC) is widely acknowledged to be morally significant, but little is known about everyday moralising around ACC. We addressed this gap via quantified thematic analysis of 300 online comments to British newspaper articles on ACC, drawing on Bandura’s moral disengagement theory. Moral disengagement through denial of ACC was widespread. Other disengagement strategies, such as palliative comparison and diminishing agency, occurred less often. There was also some moral engagement, most often through assertions of the existence of ACC and/or its harmful effects. Moral disengagement was significantly more common in comments on right wing than left wing newspapers, while the opposite was true of moral engagement. While Bandura’s framework provided a useful starting point to make sense of ACC moralising, it did not capture moral concerns that extended beyond its ‘harm / care’ remit. In particular, many ‘denial’ comments included a ‘dishonesty’ discourse, whereby ACC proponents were accused of deception for ulterior motives. To classify this discourse as moral disengagement obscures its engagement with a different set of moral issues around trust and honesty. We suggest that Bandura’s theory represents one possible ‘moral landscape’ around ACC, and could be extended to encompass a broader range of moral concerns