12,821 Works

The carbon mitigation potential of emerging photovoltaic technology

Christopher John MacKay Emmott
Photovoltaic systems provide a solution for harnessing energy from the sun whilst reducing global greenhouse gas emissions. Organic photovoltaics (OPV), based on blends of polymer and fullerene materials, have recently received widespread interest within academia and business due to its potential for low costs, minimum environmental impact and rapid roll-to-roll manufacture. In addition, modules can be customised for flexibility, light-weight and colour. However, OPV modules also show considerably lower efficiencies than mature photovoltaic technologies, as...

Performance modelling of urban metro rail systems: an application of frontiers, regression, and causal inference techniques

Shane Canavan
Metro rail provides a vital role towards facilitating the travel needs of major urban economies, and has contributed substantially in transporting the population within cities. However, implementing a safe service to meet with the statutory requirements of operation is fraught with difficulties. Due to high capital expenditures and need for public money, metros are politically sensitive and are subject to scrutiny. Consequently, understanding variation in metro performance continues to be a major research objective. This...

Silicon nanowires for single slectron transistor fabrication

Chen Wang
As the minimum feature sizes of current integrated circuits approach 10 nm, improvements in the speed, complexity and packing density are becoming increasingly difficult. In particular, at these scale, the operation of `classical' complementary metal-oxide-semiconductor (CMOS) devices is expected to degrade unacceptably. Single-electron devices, where the Coulomb blockade effect can be used to control charge at the one electron level, provide a means to fabricate large scale integration (LSI) circuits with ultra-low power consumption, immunity...

New approaches to coccolith geochemistry and its application to Cenozoic paleoceanography

Katherine Clare Prentice
The use of coccolithophores has until recently been restricted mainly to biostratigraphic indicators. Their small size makes it difficult to obtain species-specific geochemical data and they are often perceived to preserve poorly compared with the larger foraminifer. In the last decade the study of potential coccolithophore bio-geochemical proxies has taken off, but with little to support their use in deep-time records. The suitability of fossil coccolithophores for geochemical proxies has been examined. A large collection...

B-spline ADC: many-body ab initio theory for electron dynamics in strong laser fields

Marco Ruberti
This thesis is focused on the development of an efficient first-principles theoretical and numerical method based on the many-electron algebraic diagrammatic construction [ADC(n)] schemes, in order to describe the correlated ionisation dynamics in atomic and molecular systems interacting with perturbative and non-perturbative laser fields. The first line of research has focused on the calculation of total singlephoton photoionisation cross-sections, applying the Stieltjes-Imaging theory to Lanczos pseudospectra of the ADC Hamiltonian in Gaussian basis. We have...

Triglyceride-rich lipoproteins influence monocyte and macrophage homeostasis and exacerbate experimental kidney injury

Maha Fahad Saja
Hypertriglyceridemia and its associated increase in triglyceride-rich lipoproteins (TGRLs) is a great threat to today’s modern society. Sedentary life style and western type diet subject our bodies to repetitive influx of TGRLs following each meal which is being increasingly recognised as a risk factor for coronary artery disease (CAD). Moreover, a hyper-TGRL state complicates the course of various immunological and non-immunological conditions contributing to both morbidity and mortality. How TGRLs mediate their harmful effects is...

Dual-modal imaging agents for zinc ion sensing

Charlotte Rivas
The area of MRI/optical imaging has received a lot of attention as their combination brings together the high spatial resolution of MRI with the high sensitivity of optical imaging. Changes in pancreatic β-cell mass contribute to the development of both type 1 and type 2 diabetes. Whilst the processes of β-cell loss are fairly well established for type 1, both the extent of the loss and the underlying mechanisms are relatively unknown for type 2....

The coordination chemistry and catalytic applications of nitrogen-centred triphosphine ligands

Andreas Phanopoulos
Tripodal triphosphine ligands featuring a heteroatomic apical moiety of general formula R'E(CH2PR2)3 are under-investigated compared to mono- or bidentate phosphines, and to the carbon-centred analogue CH3C(CH2PPh2)3. The work presented in this thesis is an investigation of the nitrogen-centred triphosphine ligands N(CH2PR2)3 (NP3R), including coordination behaviour and catalytic applications. behaviour and catalytic applications. The modular synthesis of NP3R ligands allowed the substituents at phosphorus to be replaced, generating novel symmetrical ligands (with three identical phosphine arms),...

Novel approaches to the assessment of patients with chest systoms in the acute medical and outpatient settings: the use of multislice computed tomography

Caroline Patterson
This thesis evaluated the clinical utility of cardiopulmonary computed tomography (CT) in patients presenting with chest pain and dyspnoea. Studies within this thesis confirmed the following. Firstly, there is a requirement for improved diagnostic pathways to minimise patients being discharged without a diagnosis, which currently occurs in 30-40% of patients admitted with chest pain and dyspnoea. Historically, CT has been utilised in 32% of admissions with chest pain and 10% of admissions with dyspnoea. Secondly,...

Palaeomagnetic studies of the Etendeka volcanics and the resulting implications for the duration of volcanic activity and for magnetic field evolution in the early Cretaceous

Sarah Catherine Dodd
There is a long-standing temporal correlation between large igneous provinces and major mass extinction events in the Geological Record. This is postulated to be due to the emission of large quantities of volcanic gases over a geologically short period of time causing major climatic perturbations within the Earth system. The Paran´a – Etendeka large igneous province represents one of the few large igneous provinces where post volcanic environmental effects seem to have been minor. This...

Graphene-based membranes for fluid separations

Jeng Yi Chong
Graphene-based materials have attracted great interest to develop ultra-thin and high performance membranes due to their unique 2D structure, one-atomic thickness and high mechanical strength. While many studies have shown excellent performance of graphene-based membranes in fluid separations, scaling up of the membranes is still challenging. In addition, the transport mechanism in the membranes, especially in graphene oxide (GO) membranes is still not well understood. In this study, graphene-based membranes were fabricated on hollow fibre...

Interactions between vegetation and microclimate in a heterogeneous tropical landscape

Stephen Robert Hardwick
Land use change and forest fragmentation threaten biodiversity in the tropics. One important mechanism by which species are affected by land use change is the change in microclimate that occurs with modifications to the vegetation cover. We quantified the link between vegetation and microclimate in the tropics for the first time, finding strong relationships between leaf area index and five key microclimate variables. The mean daily maximum air temperature 1.5 m above the ground was...

Nesting and brood-rearing opportunities for farmland birds in and around Miscanthus and short rotation coppice biomass crops

Henrietta Pringle
Reaching the EU target for renewable energy is likely to encourage a rapid expansion of biomass crop production in the UK. This expansion could pose a considerable threat to farmland birds, via the loss of suitable nesting habitat for ground-breeding birds or by decline in availability and accessibility of foraging resource for other farmland birds. Alternatively, the low-input management of biomass crops may provide benefits over more intensively managed arable crops. The potential impacts of...

Numerical calculation of inflationary non-Gaussianities

Jonathan Horner
In this thesis the numerical calculation of non-Gaussianity from inflation is discussed. Despite a strong interest in non-Gaussianity from inflation models in recent years, not much attention has been devoted to its numerical computation. Calculating the inflationary bispectrum in an efficient and accurate manner will become more important as observational constraints on primordial non-Gaussianity continue to increase. Despite this, attention given to numerically calculating the primordial bispectrum has been relatively low. The approach presented here...

Development and assessment of vascular phantoms for research and education

Ali Aldhebaib
Ultrasound practices encompass a wide variety of diagnostic and interventional procedures that increasingly fall under a wide variety of medical specialities. The major drawback of ultrasound use, is that considerable experience is required to gain the most from procedures. The skill of Ultrasound (U/S) operator is known to positively correlate with the number of scans performed. The practice of U/S is expanding in clinical medicine, and as a consequence, there is an increasing demand for...

Internal metabolic state and metabolic costs in human motor control

Scott Taylor
The brain controls behaviour and has to manage the body’s resources (including energy) at the same time. How the brain coordinates and combines computations for controlling behaviour in response to metabolic state is little understood. I examined internal metabolic state and its role in motor coordination. I found that internal metabolic state modulates human motor coordination, with a lower energy expenditure associated with performing a velocity-controlled centre-out reaching task when in a low metabolic state....

Solution-processed nanomaterials for applications in photoelectrochemical solar cells

Xuemei Zhang
Quaternary Cu2ZnSnS4 (CZTS) and binary Bi2S3 are considered as potential photovoltaic materials due to their suitable electronic and optical properties, low-toxicity and earth-abundant elemental constitution. This thesis investigates the preparation of CZTS and Bi2S3 nanocrystals in solution-based approaches and examines their applicability in photoelectrochemical solar cells with an aim of fabricating low-cost photovoltaics. CZTS nanocrystals with the kesterite crystal structure were prepared by a hot-injection method in which elemental sulfur was used as the sulfur...

Investigating the dynamics of a Bose Einstein condensate on an atom chip

Iain Barr
In this thesis I discuss work that has been carried out on the dynamics of a Bose Einstein condensate of Rb 87 produced near an atom chip. A Bose Einstein Condensate (BEC) is a quantum state of matter where a single quantum state becomes occupied by a macroscopic number of identical Bosons. In our case this is achieved by cooling a system of trapped identical rubidium 87 atoms to its ground state. To reach temperatures...

Understanding open quantum systems with coupled harmonic oscillators

Vignesh Venkataraman
When a quantum system interacts with many other quantum mechanical objects, the behaviour of the system is strongly affected; this is referred to as an open quantum system (OQS). Since the inception of quantum theory the development of OQSs has been synonymous with realistic descriptions of quantum mechanical models. With recent activity in the advancement of quantum technologies, there has been vested interest in manipulating OQSs. Therefore understanding and controlling environmental effects, by structuring environments,...

Dictionaries for fast and informative dynamic MRI acquisition

Jose Caballero
Magnetic resonance (MR) imaging is an invaluable tool for medical research and diagnosis but suffers from inefficiencies. The speed of its acquisition mechanism, based on sequentially probing the interactions between nuclear atom spins and a changing magnetic field, is limited by atomic properties and scanner physics. Modern sampling techniques termed compressed sensing have nevertheless demonstrated how near perfect reconstructions are possible from undersampled, accelerated acquisitions, showing promise for more efficient MR acquisition paradigms. At the...

Theoretical studies of charge transfer excitations, absorption, and polarisation in organic photovoltaic materials

Sheridan Few
To optimise organic photovoltaic devices, design rules relating chemical and physical structure to the ability of the active material to absorb light, separate charges and transport charges, are required. We assess the predictive power of computational modelling techniques, comparing results with experiment. In Chapter 4, we calculate the influence of chemical structure on conformation and light absorption in conjugated polymers, and explain the remarkably high optical absorption in poly-thieno[3,2b]-thiophene-diketo-pyrrolopyrrole-co-thiophene (PDPP-TT-T) in terms of its high...

Health effects of indoor nitrogen dioxide

Graziella Favarato
Rationale: Exposure to indoor NO2 has been implicated as a cause of respiratory symptoms suggestive of asthma but evidence has been inconsistent. Objective: To review the existing evidence and examine the effects of indoor NO2 in adult asthma-related symptoms using data from an adult multi-centre cohort (ECRHS) followed up for 20 years. Methods: Studies on respiratory health and indoor NO2 were systematically reviewed and meta-analyses performed. Cross-sectional analyses within a sub-set of ECRHS participants with...

Investigation of cold dwell facet fatigue in titanium alloys utilising crystal plasticity and discrete dislocation plasticity modelling techniques

Zebang Zheng
The focus of this project is the mechanistic basis of the load shedding phenomenon that occurs under the dwell fatigue loading scenario. A systematic study was carried out using modelling techniques at different length scales, from atomistic simulations to discrete dislocation plasticity and crystal plasticity, to investigate the effect of crystallographic orientations, localized dislocation behaviour, material intrinsic properties and external loading environments on the dwell sensitivity. A new mechanistic formalism for incorporating thermally activated dislocation...

Neural representations of active whisking in the cerebellum

Susu Chen
Active whisking is an important model sensorimotor behavior, but the function of the cerebellum in the rodent whisker system is unknown. I have made patch clamp recordings from Purkinje cells, granule cells and interneurons in vivo to identify whether and how cerebellar activity encodes kinematic features of whisking including the phase and set point. I show that Purkinje cell spiking activity changes strongly during whisking bouts. On average, the changes in simple spike rate coincide...

Correlation of mechanical stresses with arterial disease frequency in animal models

Ethan Rowland
Atherosclerosis is a complex inflammatory disease which may be triggered by an elevated transport of lipid-carrying macromolecules from the blood into the arterial wall. Its non-uniform distribution has been attributed to local variations in wall shear stress. Intramural stresses and strains are regularly overlooked, despite their heterogeneous distribution and direct effect on vascular cell morphology and function. Stenotic flow models of atherosclerosis inadvertently alter both fluid and solid stresses. Using a tapered flow modifying cuff,...

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