William Edward Lee

Rebaudiosides A and D are sweeteners derived from the Stevia plant and are 300 times sweeter than sugar. They are more soluble together than individually, an example of enhanced joint solubility. This project assesses how to speed up molecular dynamics based joint solubility calculations. Key to calculating solubility is evaluating the chemical potential from the simulated configurations. We provide a map of options for speeding up these calculations, including their relative speeds and accuracy. We find that the most efficient and accurate methods are Free Energy Perturbation, which calculates free energy differences between related states, and Umbrella Sampling, which biases simulations to enhance sampling of otherwise inaccessible regions of configurational space. Future work will focus on improving the accuracy of the method comparisons, identifying failure modes, and extending the assessment to hybrid approaches and alternative force fields, with the aim of integrating these methods into commercial software.

In espresso brewing, soluble content is extracted from a bed of ground coffee beans by forcing hot water through the bed at high pressure. An important part of this process is the infiltration stage in which water permeates the initially dry bed. This process is investigated by a combination of x-ray tomography and fluid mechanical modeling. Tomography is used to track the infiltration front of the water via the contrast in density. The experimental data are compared with a one-dimensional unsaturated porous medium flow model, which divides the bed into wet and dry regions and incorporates the espresso pump dynamics. Good agreement is seen between the experimental data and the model predictions.

Johnson & Johnson (J & J) Vision Care manufacture billions of soft contact lenses each year at their site in Limerick. One aspect of contact lens production which is time and energy intensive is the curing process, where a liquid monomer solution is converted into a soft solid in a photopolymerisation reaction. This study develops models of the photopolymerisation process during contact lens manufacture, incorporating the important physicochemical mechanisms, to facilitate process understanding and optimisation. The developed models account for light propagation, heat transport and polymerisation kinetics. The relationship between curing time and lens thickness, monomer solution properties and oxygen inhibition is probed in a series of simulations, showing the potential of the models to explore optimal processing conditions for specific lens configurations. A separate model is developed to assess the relationship between the degree of cure of the lens and its distortion under gravity.

Mathematical modelling is used to address the oral processing of chocolate. Chocolate is a suspension of fat (cocoa butter), sugar, cocoa solids and other components such as milk power and emulsifiers. Models are developed for phase change and dissolution, both spatially averaged and tracking interfaces between components. Where data is available parameters are estimated, otherwise estimates are made of the relative importance of different terms. Models are analysed by non-dimensionalisation and asymptotic reduction. Where analytic solutions cannot be calculated models are solved numerically.

A series of TiZrNb(V) high entropy alloy-based metallic coatings have been deposited using high-power impulse magnetron sputtering (HiPIMS), with variable V concentrations and constant ratios among the other metals. The coatings were analyzed regarding their composition, surface and cross-sectional morphologies, microstructure, roughness, mechanical properties, oxidation resistance, and thermal stability. The structure of the deposited coatings reveals a transition from the bcc crystal structure to an amorphous phase as the V concentration increases. The addition of V also led to a decrease in roughness Ra and an improvement in adhesion, while it did not affect hardness, which remained at ∼10–11 GPa for all samples. Annealing under a protective atmosphere at 400 °C caused structural ordering, which was followed by an increase in mechanical properties. The purpose of the present paper is, therefore, to present a study on the deposition of TiZrNb coatings with increasing V concentration prepared by HiPIMS and to understand the role of V concentration on their structure, chemical composition, mechanical properties, and oxidation resistance. Comparison of the results with those achieved for a reference TiZrNb coating is presented too.

Confidence in the justice system relies on it being both impartial and being seen to be impartial. It is therefore troubling that there are well-documented disparities between men and women and between ethnic groups at various stages of the criminal justice process. We report statistical analysis of existing data to (1) better understand the existing disparities, (2) investigate what information is available that might be useful in drawing a distinction between causation (discrimination) and association, (3) consider what statistical tools could be used to quantitatively investigate these relationships. Two datasets were investigated, looking at two different ends of the justice system. The first dataset describes the Metropolitan Police Force’s stop and search practices, an entry point into the criminal justice system. The second dataset describes sentencing, the final stage of that system, focusing on shoplifting offences dealt with by a sample of magistrates' courts.

Congestion in Edinburgh is a major issue, especially during peak visitor periods. The primary aim of this study was to develop a practical forecasting tool providing visitor volume, and visitor segmentation projections, to assist the travel and hospitality sectors in their planning. To address this a predictive model has been established based on Edinburgh Castle visitor records in conjunction with the Google Trends popularity index for Edinburgh Castle. Popularity of attractions was found to increase around major events with on-line search trends offering an indication of expected volume. Preliminary findings indicate predictions are feasible and could be improved should data relevant to other attractions and sectors be available.

We present a theoretical analysis of the physical mechanisms underlying blood filtration through artificial kidneys, also known as dialysis, enhanced by the introduction of pulsation. We formulate a mathematical modelling framework describing chemical transport and fluid flow on the scale of a single fibre, separating the flow of blood from a counter flow of dialysate, a physiologically similar, toxin-free liquid. The wall, or membrane, of each fibre is porous, allowing transport of toxins, but not red blood cells and other physiologically important molecules, across the membrane from the blood to the dialysate. We model the membrane as a thin porous layer, separating the blood from the dialysate, and formulate mathematical models for the transport of toxins across the membrane and the fluid flow within the blood and dialysate. We use our mathematical modelling framework to examine physical mechanisms underlying enhanced toxin transport under pulsation and to inform future modelling efforts.

A recent experiment showed that, contrary to theoretical predictions, beyond a cutoff point, grinding coffee more finely results in lower extraction. One potential explanation for this is that fine grinding promotes non-uniform extraction in the coffee bed. We investigate the possibility that this could occur due the interaction between dissolution and flow promoting uneven extraction. A low dimensional model in which there are two possible pathways for flow is derived and analyzed. This model shows that, below a critical grind size, there is a decreasing extraction with decreasing grind size as is seen experimentally. This is due to a complicated interplay between an initial imbalance in the porosities and permeabilities of the two pathways in the model, which is increased by flow and extraction, leading to the complete extraction of all soluble coffee from one pathway.

As members of the UK fusion community (covering national laboratories, academia and industry), we approached various colleagues to put together articles for this special issue of the Journal of Physics: Energy covering the materials challenges through to successful roll-out of fusion reactors. This paper serves to introduce the special issue and gives our opinion on the key challenges, many of which are covered in more detail in the submitted papers. Others may have differing opinions about what the key challenges are, but what we will all agree on is that they are substantial and will require sizeableresources to be addressed. Further, while we are all UK-based, all humankind will benefit from successful commercial roll-out of fusion for energy production, and the effort has been and will continue to be global. Fusion has entered the engineering era. Moving from plasma science to experiments demonstrating the benefits of modified torus shapes and advanced divertor geometries, the ‘field’ has become an ‘industry’. Investors now focus on whether superconducting magnet joints are feasible in large tokamak designs and how to deliver net energy to the grid. As with all technology trajectories, materials (both structural and functional) are the key enablers. For fusion materials, the three major challenges remain resilience to the combined damaging effects of tritium, transmutation and neutron bombardment (a veritable ‘triple whammy’), achieving suitable irradiation strategies for adequate damage studies (with optimal use of modelling as complementary science) and defining material safety and waste guidance in an era of evolving regulation. In the following, we highlight issues around ‘the triple whammy’, the resulting need for testing facilities and modelling proxies, and aspects of regulating materials in, and waste generated from, operating fusion reactors.