A national coastal erosion susceptibility model for Scotland

The upland nature of the Scottish landscape means that much of the social and economic activity has a coastal bias. The importance of the coast is further highlighted by the wide range of ecosystem services that coastal habitats provide. It follows that the threat posed by coastal erosion and flooding has the potential to have a substantial effect on the socioeconomic activity of the whole country. Currently, the knowledge base of coastal erosion is poor and this serves to hinder the current and future management of the coast. To address this knowledge gap, two interrelated models have been developed and are presented here: the Underlying Physical Susceptibility Model (UPSM) and the Coastal Erosion Susceptibility Model (CESM). The UPSM is generated within a GIS at a 50 m2 raster of national coverage, using data relating to ground elevation, rockhead elevation, wave exposure and proximity to the open coast. The CESM moderates the outputs of the UPSM to include the effects of sediment supply and coastal defence data. When validated against locations in Scotland that are currently experiencing coastal erosion, the CESM successfully identifies these areas as having high susceptibility. This allows the UPSM and CESM to be used as tools to identify assets inherently exposed to coastal erosion, areas where coastal erosion may exacerbate coastal flooding, and areas are inherently resilient to erosion, thus allow more efficient and effective management of the Scottish coast

The value of carbon sequestration and storage in coastal habitats

Coastal margin habitats are globally significant in terms of their capacity to sequester and store carbon, but their continuing decline, due to environmental change and human land use decisions, is reducing their capacity to provide this ecosystem service. In this paper the UK is used as a case study area to develop methodologies to quantify and value the ecosystem service of blue carbon sequestration and storage in coastal margin habitats. Changes in UK coastal habitat area between 1900 and 2060 are documented, the long term stocks of carbon stored by these habitats are calculated, and the capacity of these habitats to sequester CO2 is detailed. Changes in value of the carbon sequestration service of coastal habitats are then projected for 2000–2060 under two scenarios, the maintenance of the current state of the habitat and the continuation of current trends of habitat loss. If coastal habitats are maintained at their current extent, their sequestration capacity over the period 2000–2060 is valued to be in the region of £1 billion UK sterling (3.5% discount rate). However, if current trends of habitat loss continue, the capacity of the coastal habitats both to sequester and store CO2 will be significantly reduced, with a reduction in value of around £0.25 billion UK sterling (2000–2060; 3.5% discount rate). If loss-trends due to sea level rise or land reclamation worsen, this loss in value will be greater. This case study provides valuable site specific information, but also highlights global issues regarding the quantification and valuation of carbon sequestration and storage. Whilst our ability to value ecosystem services is improving, considerable uncertainty remains. If such ecosystem valuations are to be incorporated with confidence into national and global policy and legislative frameworks, it is necessary to address this uncertainty. Recommendations to achieve this are outlined

Environmental coupling in a quantum dot as a resource for quantum optics and spin control

A single spin confined to a semiconductor quantum dot is a system of significant interest for quantum information science, as a potential optically-addressable qubit. In many respects, a quantum dot behaves like a single atom with high quality single photon emission. By controlling the light-matter coupling in such a system, it is possible to generate highly non-classical states of light and coherently control a single spin confined to the quantum dot. A departure from the ideal atomic picture appears once we consider the mesoscopic environment with which the quantum dot interacts. Charge fluctuations in the surroundings of the quantum dot affect the photon emission frequency leading to inhomogeneous broadening. Further broadening of the emission is caused by coupling to phonon modes of the host semiconductor material. Finally, coupling between the spin of a confined electron and a large bath of nuclear spins residing in the quantum dot leads to fast dephasing of the electron spin. All of these effects are typically considered detrimental to the potential use of quantum dots for quantum technologies. In this thesis, we develop the environmental coupling of a negatively charged quantum dot as a resource for quantum optics and spin control. First, the phonon-assisted fluorescence is shown to be a useful independent channel for feedback stabilisation of the quantum dot emission frequency, without requiring a measurement of the indistinguishable zero-phonon line. With stabilisation, the corresponding frequency broadening is drastically improved, and the sub-Hz frequency fluctuations are no longer resolved. Next, we show low-power resonance fluorescence emission spectra of the negatively charged trion transition. In the low power regime of resonance fluorescence, the excited state is not populated and most of the emission is coherent. In addition to elastic Rayleigh scattering, we observe coherent Raman sidebands, linked to an effective magnetic field created by the hyperfine interaction, the Overhauser field. This fluctuating effective field lifts the electron spin degeneracy in the absence of a magnetic field, and dictates the optical selection rules of the trion system. These spectra therefore allow for a measurement of the time-averaged distributions of in-plane and out-of-plane Overhauser field components. In the final part of the thesis, we use this hyperfine-generated Λ -scheme to optically create electron spin superpositions through two-colour excitation and coherent population trapping. We then show that rapid shifts in the relative phase of the lasers lead to initialisation of the electron spin into a rotated dark state

The effects of nanopattern surface technology and targeted metabolic therapies on orthopaedic implant related infections

Bacterial biofilm infections cause significant morbidity in orthopaedic joint replacement. One of the most common bacteria in orthopaedic prosthetic infections is Staphylococcus aureus. Infection causes implant failure due to bacterial adherence and subsequent biofilm production. Nanotopography refers to the topography of a surface at the nanometre level and has major effects on cell behaviour. Studies suggest that surface nanotopography impacts the differential ability of staphylococci species to adhere, and may reduce orthopaedic implant infection rate. This research thesis focuses on bacterial adhesion on nanofabricated materials, and investigates the related metabolic changes and possible interventions. Staphylococcus aureus growth and quantification methods were optimised, with regard to growth media, incubation time and lysozyme incubation time. Both polystyrene and titanium (Ti) nanosurfaces were studied. Adhesion analysis was performed using fluorescence imaging, quantitative PCR, and bacterial percentage coverage. Metabolomic analysis was conducted by substitution with ‘heavy’ labelled glucose into growth medium, thus allowing for bacterial metabolomic analysis and identification of up-regulated, labelled metabolites and pathways. Bacterial growth was optimal using DMEM + supplement media, with adhesion occurring after 1hr bacterial incubation. Optimal lysozyme incubation for bacterial quantification using qPCR was 2hr. These parameters were used for all subsequent experimentation. Surface topography affects cell behaviour, bacterial adhesion and long term implant survival can be affected. This study found reduced bacterial adhesion on the SQ and HEX polystyrene patterns. While not found to be significant, this trend was supported by a lower average percentage bacterial coverage on both the SQ and HEX patterns (P=0.05 and P=0.01, respectively). It may be that the SQ and HEX nanopatterns are the optimal nanopit orientation required to prevent bacteria microcolony formation, keeping the bacteria in small, isolated clusters. In addition, this series of investigations showed an increase in bacterial concentrations on both the 2.5Hr and 3Hr treated Ti nanowire discs when compared to the polished Ti control disc, suggesting nanoroughness increases are associated with elevated bacterial adhesion. This theory was further supported by average percentage coverage, being significantly higher on the 2.5Hr and 3Hr treated discs. If, however, a disordered NC Ti nanopattern, hexagonal in nature, is used bacterial adhesion is significantly reduced when compared to a polished, control surface. The bacterial percentage coverage was also noted to be significantly lower on the NC surfaces, with over a 10-fold reduction when compared to the control surface. It is postulated that this reduction is through similar mechanisms to those described by Ivanova et al, and primarily related to altered surface interactions. Metabolomic analysis demonstrated increased intensity counts for key metabolites (pyruvate, aspartate, alanine and carbamoyl aspartate) involved in bacterial aggregation, proteoglycan and DNA synthesis. These pathways are also known to be important in bacterial biofilm production. Therapeutic targeting of these pathways was found to result in significantly reduced bacterial adhesion. This study shows that by altering nanotopography bacterial adhesion, and therefore, biofilm formation can be affected. Specific nanopatterned surfaces may reduce implant infection associated morbidity and mortality. The identification of metabolic pathways involved in adhesion allows for a targeted approach to biofilm eradication in S. aureus. This is of significant benefit to the patient, the surgeon and the NHS, and may well extend far beyond the realms of orthopaedics

A method for modelling coastal erosion risk: the example of Scotland

It is thought that 70% of beaches worldwide are experiencing erosion (Bird in Coastline changes: a global review, Wiley, Hoboken, 1985), and as global sea levels are rising and expected to accelerate, the management of coastal erosion is now a shared global issue. This paper aims to demonstrate a method to robustly model both the incidence of the coastal erosion hazard, the vulnerability of the population, and the exposure of coastal assets to determine coastal erosion risk, using Scotland as a case study. In Scotland, the 2017 Climate Change Risk Assessment for Scotland highlights the threat posed by coastal erosion to coastal assets and the Climate Change (Scotland) Act 2009 requires an Adaptation Programme to address the risks posed by climate change. Internationally, an understanding and adaption to coastal hazards is imperative to people, infrastructure and economies, with Scotland being no exception. This paper uses a Coastal Erosion Susceptibility Model (CESM) (Fitton et al. in Ocean Coast Manag 132:80–89. https://doi.org/10.1016/j.ocecoaman.2016.08.018 , 2016) to establish the exposure to coastal erosion of residential dwellings, roads, and rail track in Scotland. In parallel, the vulnerability of the population to coastal erosion, using a suite of indicators and Experian Mosaic Scotland geodemographic classification, is also presented. The combined exposure and vulnerability data are then used to determine coastal erosion risk in Scotland. This paper identifies that 3310 dwellings (a value of £524 m) are exposed to erosion, and the Coastal Erosion Vulnerability Index (CEVI) identifies 1273 of these are also considered to be highly vulnerable to coastal erosion, i.e. at high risk. Additionally, the CESM classified 179 km (£1.2 bn worth) of road and 13 km of rail track (£93 m to £2 bn worth) to be exposed. Identifying locations and assets that are exposed and at risk from coastal erosion is crucial for effective management and enables proactive, rather that reactive, decisions to be made at the coast. Natural hazards and climate change are set to impact most on the vulnerable in society. It is therefore imperative that we begin to plan, manage, and support both people and the environment in a manner which is socially just and sustainable. We encourage a detailed vulnerability analysis, such as the CEVI demonstrated here for Scotland, to be included within future coastal erosion risk research. This approach would support a more sustainable and long-term approach to coastal management decisions

The evolution of pebble size and shape in space and time

We propose a mathematical model which suggests that the two main geological observations about shingle beaches, i.e. the emergence of predominant pebble size ratios and strong segregation by size are interrelated. Our model is a based on a system of ODEs called the box equations, describing the evolution of pebble ratios. We derive these ODEs as a heuristic approximation of Bloore's PDE describing collisional abrasion. While representing a radical simplification of the latter, our system admits the inclusion of additional terms related to frictional abrasion. We show that nontrivial attractors (corresponding to predominant pebble size ratios) only exist in the presence of friction. By interpreting our equations as a Markov process, we illustrate by direct simulation that these attractors may only stabilized by the ongoing segregation process.Comment: 22 pages, 8 figure