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This study constitutes the first reconstruction of Pleistocene palaeoenvironmental change from the Gordano Valley, a low-lying valley marginal to the Severn Estuary in southwest England. The valley lies at the limit of Pleistocene glacial expansion and the threshold of terrestrial, marine and fluvial environments. An axial alignment opposite to that of the Severn Estuary provides a regionally unique preservational environment for valley floor Pleistocene sediments. These sediments potentially contain an important archive of palaeoenvironmental information yet they have received limited attention from previous researchers. Data from 489 manual cores are used to determine the aerial extent, surface morphology and geometry of the uppermost minerogenic sediments. These reveal a patchwork of sands, silts and gravels with a hummocky surface topography and a central basin or channel. Stratigraphic, sedimentological and palaeontological analysis of eight percussion cores reveals thinly bedded, very poorly sorted gravel, silt and sand units with an altitude range of c. -2.5 to +3 m OD. Two units record abundant temperate freshwater and intertidal fossil material. Using a multi-faceted methodology, detailed analysis of relatively small volumes of material from core samples of the Gordano Valley’s minerogenic sediment archive has identified complex sequences of depositional and post-depositional environmental change. The sediments are characterised as representing a range of Pleistocene palaeohydrological environments interspersed with a number of periods of non-deposition, and involving a number of processes (aeolian, colluvial, pedogenetic, various fluvial, intertidal). Radiocarbon and optically stimulated luminescence dating and amino acid geochronology indicate Mid-to-Late Pleistocene deposition. A revised model of the Pleistocene Gordano Valley, presented here, suggests a landscape in which alluvial fans formed close to the valley margins and freshwater streams and interconnected pools which were open to tidal influence formed along the valley axis. The elevation of intertidal deposits appears to provide terrestrial validation for a low late-MIS 7 sea-level, in terms of known global sea-level, without recourse to a regional uplift model. This thesis has demonstrated the potential to produce high-resolution reconstructions of environmental change from relatively small volumes of material, contributing an enhanced geochronology of landscape response to Mid-to-Late Pleistocene climate change in the Bristol Channel/Severn Estuary region that has wider national importance in the context of coastal lowlands.

In this thesis I investigate how students account for their choices of whether or not to study further mathematics within an after-school widening participation programme, the Further r-.Iathematics Network (PMNetwork). I seek to conceptualise how patterns of participation in advanced mathematics arise not only from unequal school provision but in the 'logics' of individual students' decision-making. I draw on a qualitative research project examining a) fourteen promotional, administrative and evaluati\Te FMNetwork documents, and b) observations, interviews and email qucstionnaircs with twcnty four studcnts in three sitcs. These sites were chosen to include differences in socio-geographic and classroom contexts amid the shared feature that without the FMNetwork these students could not study further mathematics. I use a thcoretical framework based in Foucauldian ideas that sociocultural discourses construct within them practices of the self: the possibilities for being a knowing, active, choosing self in that system of knowledge and social practice. In the texts and students' accounts I analyse the discourses that shape meaning in further mathematics and look for ways they support or conflict with practices of the self in contemporary society. I argue that mathematics and (FMNetwork) further mathematics draw on different discourses, and that the discourses of further mathematics contain inherent ambiguities that students can use productively or struggle to reconcile. Mathcmatics students arc positioned as making secure developmental progress to practical maturity and autonomous self-management. Further mathematics accelerates and/or distorts this progress. I show the students' precarious positioning as self-entreprencurs who choosc risk and face consequenccs, and also as children whose self-promotion may be illusory. I arguc that students' choice and participation in the FMNetwork are best understood as a project of becoming independent. Thus doing further mathematics allows students to contest their experience of some school or social exclusions, notably where experiences do not fit a dominant model that learning mathematics successfully feels fast, effortless and requires the validation of others. Howcvcr, this project of doing further mathematics as becoming independent adds to the insecurities they experience about progress and responsibility, leaving them exposed to the logic that giving up is the mature response.

The research project described in the thesis uses atomic-scale computational modelling to investigate the storage of hydrogen in graphite intercalate compounds (GICs). The work is relevant to the energy economy, as hydrogen is a source of clean energy, and can be used efficiently in fuel cells to generate electricity. Storing hydrogen safely has long been a challenge in materials science and, since the proposal of a hydrogen-based transport economy, has attracted great attention. Graphite intercalate compounds offer the possibility of dense storage, because they contain large absorption pores for hydrogen to bind. The absorption mechanisms and patterns in different intercalate compounds are not well understood, and this is the motivation for this work. Alkali and alkaline-earth metal GICs (A/AE-GICs) were modelled using density func- tional theory (and benchmarked with quantum chemistry) to investigate their hydrogen storage capabilities and their stability against decomposition into the metal hydride and pure graphite upon hydrogenation. Detailed studies of the calcium-GIC were per- formed and also a survey of the other A/AE-GICs. The effect of the commonly modelled MC14 GIC compared with the experimental MC12 stoichiometry has been investigated to bridge the gap between experiment and theory. The calcium-GIC was found to favourably absorb hydrogen within U.S. Department of Energy targets, but was found to be extremely unstable. Our investigations showed that all AE-GICs are unstable. Heavier A-GICs were found to stably absorb hydrogen at reasonable volumetric densities at the cost of gravimetric densities. The theoreti- cally modelled MC14 stoichiometry was found to be fundamentally different from the experimental MC12 stoichiometry, with the latter breaking the simple symmetry of the former and offering many more distinct absorption sites and barriers to diffusion. Pair potentials have been built and parametrised to KC14 to aid simple modelling of KCn GICs in, for example, classical molecular dynamics.

The optical dipole force from a singe focussed laser beam was used to study the role of laser-induced molecular alignment on the centre-of-mass motion of carbon disulphide molecules in a molecular beam. The translational, rotational and vibrational temperatures of the carbon disulphide molecules were measured to be 3.4\pm0.2 K, 35\pm10 K and 250\pm14 K respectively. The velocity of the beam was measured to be 542\pm22 m s ^{-1}. Time-of-flight mass spectroscopy was used to measure the acceleration and deceleration of the molecules. Maximum velocity changes of 7.5 m s ^{-1} and 10 m s ^{-1} were recorded for linearly and circularly polarised light respectively. These results showed that the dipole force, \digamma \alpha \bigtriangledown [\alpha_e_f_f(I)I(r)], where \alpha_e_f_f is the effective polarisability and determined through laser-induced alignment, can be modified by changing the laser polarisation. For linearly and circularly polarised light, a 12% difference in effective polarisability was measured to produce a 20% difference in dipole force. The dipole force from a single focussed laser beam produces a molecular optical lens and the downstream density of the molecular focus was probed by measuring the ion signal for both laser polarisations. The focal lengths for linearly and circularly polarised light were found to be separated by \approx 100 \mu m. By altering the laser polarisation from linearly through elliptically to circularly polarised light, the focal length of the molecular optical lens could be smoothly altered over the \approx 100 \mu m focal range. The role of the effective polarisability of each rotational state was also studied numerically. Separate rotational states were found to significantly alter the focal properties of a molecular optical lens. In carbon disulphide, higher rotational states (J > 10), exhibit less molecular alignment and when occupied, the focal length of the molecular optical lens for these states was increased by 60 % compared to the ground state.

The MINOS experiment is a long-baseline neutrino oscillation experiment which sends a high intensity muon neutrino beam through two functionally identical detectors, a Near detector at the Fermi National Accelerator Laboratory in Illinois, 1km from the beam source, and a Far detector, 734km away, in the Soudan Mine in Minnesota. MINOS may be able to measure the neutrino mixing angle parameter sin{^2}2\theta{_1_3} for the first time. Detector granularity, however, makes it very hard to distinguish any \nu{_e} appearance signal events characteristic of a non-zero value of \theta{_1_3} from background neutral current (NC) and short-track \nu{_\mu} charged current (CC) events. Also, uncertainties in the hadronic shower modeling in the kinematic region characteristic of this analysis are relatively large. A new data-driven background decomposition method designed to address those issues is developed and its results presented. By removing the long muon tracks from \nu{_\mu}-CC events, the Muon Removed Charge Current (MRCC) method creates independent pseudo-NC samples that can be used to correct the MINOS Monte Carlo to agree with the high-statistics Near detector data and to decompose the latter into components so as to predict the expected Far detector background. The MRCC method also provides an important cross-check in the Far detector to test the background in the signal selected region. MINOS finds a 1.0-1.5 \sigma\nu{_e}-CC excess above background in the Far detector data, depending on method used, for a total exposure of 3.14x10{^20} protons-on-target. Interpreting this excess as signal, MINOS can set limits on sin{^2}2\theta{_1_3}. Using the MRCC method, MINOS sets a limit of sin{^2}2\theta{_1_3} < 0:265 at the 90% confidence limit for a CP-violating phase \delta = 0.

Africa's climate is prone to extended rainfall deficits. In extreme cases these may lead to droughts and humanitarian disasters. Skilful prediction of seasonal rainfall would bring sound humanitarian and economic benefit to the many African countries that depend on rain-fed agriculture. Seasonal rainfall hindcast skill from the DEMETER multi-model ensemble system is examined across Africa. Skill at 0-month lead is found to be weak over much of Africa, except for the August-October (ASO) season in the Sahel and the November-January (NJD) season in equatorial East Africa, Nigeria and South Africa. For the ASO season, correlation values of 0.3-0.8 (p-values < 0.1) are found across the sub-Sahara belt. For the NDJ season, correlation values of 0.5-0.6 (p-values < 0.1) occur in Kenya, Tanzania and Uganda. Innovative statistical seasonal rainfall hindcast models are developed for six homogeneous rainfall regions in Kenya, using linear regression techniques. Kenya has experienced seven severe droughts over the period 1991-2008 affecting over 35 million people. Lagged sea surface temperature and atmospheric wind predictors are selected based on having a significant and temporally stable correlation with regional rainfall indices, and a clear physical-linking mechanism. Moderate-to-high rainfall hindcast skill is found for most regions at 0- and 1-month leads for the October-December rainy season. In contrast, no robust predictors are found for the March-May rainy season. In 2009 an improved version of DEMETER, called EUROSIP, was released. This study is the first to assess the skill of the EUROSIP rainfall hindcasts for the Kenyan October-December rainy season and to compare this with the statistical model skill. For the most heavily populated and cultivated West and Southwest regions of Kenya, which are home to 68% of the Kenyan population, the statistical models outperform the EUROSIP model with correlation values ≥ 0.42 (p-values ≤ 0.06) over the common verification period 1987-2005.

The urgent realisation of the low carbon economy requires the development of cheap, safe and lightweight hydrogen storage, both for commercialisation of hydrogen fuel cell vehicles, and for the use of hydrogen as a reservoir of energy from intermittent renewable energy sources. The primary motivation of this PhD project was to investigate (co)electrospinning, a cheap and scalable fibre production technique, for nanostructuring potential solid state hydrogen storage materials. Solid state storage of hydrogen is being extensively investigated worldwide. However, many of the candidate materials are still not able to meet the practical requirements for mobile applications. The principal drawbacks are that these materials either have low capacity for hydrogen storage (physisorption systems), even at cryogenic temperatures, or high release temperatures with slow release rates (chemisorption systems). Because kinetic and thermodynamic properties can be improved by nanoscale processing, nanoengineering of selected materials has emerged as one of the most effective ways of overcoming their associated performance barriers. In this thesis I present two successful approaches to nanostructuring using electrospinning: firstly, by encapsulating chemical hydrides in polymeric nanofibres, as demonstrated by the development of co-axial ammonia borane-encapsulated polystyrene (AB-PS) fibres, and secondly, by post-processing of single-phase electrospun PAN fibres, resulting in the synthesis of potassium-intercalated graphitic nanofibres (K-GNFs). The results show that the micro and nano-structure imparted through electrospinning, can have the effect of reducing dehydrogenation temperatures in AB-PS fibres (from 110 to ~85 °C) and improving the (de)hydrogenation rates by an order of magnitude in both composite fibres (from ~50 to <5 mins in K-GNFs and from ~150 minutes to as low as 15 minutes in AB-PS fibres). The details of co-axial electrospinning as a novel approach to nanoengineering chemical hydrogen storage materials and as a way of possibly overcoming issues regarding reversibility, stability and clean hydrogen release from many of these materials is discussed. The solution selection method I have developed for use in the synthesis of co-axial composite fibres can be applied as an efficient solution selection formula for multi-phase electrospinning in general.

Supramolecular architectures represent an increasingly interesting playground both in the chemistry and physics field. In fact, they give us the possibility to tailor the physical and chemical properties of conjugated systems, opening the doors to new applications. In this dissertation I will present my findings regarding different types of supramolecular structures. The first part is dedicated to the study of the optical properties of conjugated polyrotaxanes: conjugated polymers such as poly(4,4’-diphenylene vinylene) threaded through cyclodextrin macrocycles rings, that sterically impose increased intermolecular distances, leading to preserved single-molecule excitonic photophysics even in high concentration regimes, due to reduced pi-pi stacking of the chromophores. In particular, I will show how it is possible to tune their photoluminescence properties for different applications like polarized emission and optically pumped lasers. The incorporation of polyrotaxanes and their unthreaded analogue in a stretch-oriented polyvinyl alcohol matrix gives rise to a strongly polarized photoluminescence parallel to the stretching direction which I studied using steady-state and time-resolved optical techniques. Furthermore, by exploiting the water-solubility of polyrotaxanes is possible to embed them in three-dimensional photonic crystal and tune their radiative rate to achieve low-threshold optically pumped lasers. In the second part, I will present the application of supramolecular structures in light-emitting diodes. In fact, self-assembled monolayers represent an interesting system to tune the work function of commonly used electrodes in the plastic electronics field, therefore changing the injection barriers for holes at the interface between the organic semiconductor and the metallic electrode. Furthermore, I will show how supramolecular architectures are used to obtain efficient near-infrared photoluminescence and electroluminescence introducing a three-dimensional pi conjugation. Moreover, by adding a pyridine derivative it is possible to suppress the efficient self-quenching in this class of porphyrin based molecular assembly increasing further their applicability in light-emitting diodes.

In the first section of this thesis, we present the atomic part of our investigation. A C2+ atomic target was prepared and used to generate theoretical data required in the investigation of recombination lines that arise from collisions between electrons and ions in thin plasma found in planetary nebulae and other astrophysical objects. The R-matrix method of electron scattering theory was used to describe the C2+ plus electron system. Theoretical data concerning bound and autoionizing states were generated in the intermediate-coupling approximation by R-matrix and Autostructure codes and compared to experimental data. The comparison revealed very good agreement. These theoretical data were then used to generate dielectronic recombination data for C+ which include transition lines, oscillator strengths, radiative transition probabilities, as well as emissivity and dielectronic recombination coefficients. The data were cast in the form of a line list, called SS1, containing 6187 optically-allowed transitions which include many C II lines observed in astronomical spectra. The data were validated by comparison to C+ recombination data obtained from a number of sources in the literature. This line list was used to analyze the spectra from a number of astronomical objects, mainly planetary nebulae, and identify their electron temperature where the observational data were obtained from the literature. The electron temperature investigation was also extended to include free electron energy analysis which uses observational and theoretical data of FF and FB transitions to investigate the long-standing problem of discrepancy between the results of recombination and forbidden lines analysis and its possible connection to the electron distribution (Maxwellian or non-Maxwellian). In the course of this investigation two elaborate methods, one for finding and analyzing resonances (K-matrix method) and the other for analyzing and identifying electron temperature from astronomical spectra (least squares minimization), were employed. A computer program for atomic transition analysis was also developed and used as the main tool for obtaining the line list and analyzing the observational spectra. In the second section of the thesis we present the results of our molecular investigation; the generation of a comprehensive, calculated line list of frequencies and transition probabilities for the singly deuterated isotopologue of H3+, H2D+. The line list, which is the most comprehensive one of its kind in existence, contains over 22 million rotational-vibrational transitions occurring between more than 33 thousand energy levels and covers frequencies up to 18500 cm-1. All energy levels with rotational quantum number, J, up to 20 are considered, making the line list useful for temperatures up to at least 3000 K. About 15% of these levels are fully assigned with approximate rotational and vibrational quantum numbers. The list is calculated using a previously proposed, highly accurate, ab initio model implemented in a high-accuracy computer code based on a two-stage discrete variable representation (DVR) approach. Various consistency checks were carried out to test and validate the results. All these checks confirmed the accuracy of the list. A temperature-dependent partition function, valid over a more extended temperature range than those previously published, and cooling function are presented. Temperature-dependent synthetic spectra for the temperatures T=100, 500, 1000 and 2000 K in the frequency range 0-10000 cm-1 were also generated and presented graphically.