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Accurate predictions of basal melt rates on ice shelves are necessary for precise projections of the future behaviour of ice sheets. The computational expense associated with completely resolving the cavity circulation using an ocean model makes this approach unfeasible for multi-century simulations, and parametrizations of melt rates are required. At present, some of the most advanced melt rate parametrizations are based on a one-dimensional approximation to the melt rate that emerges from the theory of subglacial plumes applied to ice shelves with constant basal slopes and uniform ambient ocean conditions; in this work, we present an asymptotic analysis of the corresponding equations in which non-constant basal slopes and typical ambient conditions are imposed. This analysis exploits the small aspect ratio of ice shelf bases, the relatively weak thermal driving and the relative slenderness of the region separating warm, salty water at depth and cold, fresh water at the surface in the ambient ocean. We construct an approximation to the melt rate that is based on this analysis, which shows good agreement with numerical solutions in a wide variety of cases, suggesting a path towards improved predictions of basal melt rates in ice-sheet models., 32 pages, 7 figures

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University Persistent organic pollutants (POPs) are a group of chemical compounds that are toxic to humans and wildlife. They are persistent in the global environment, can be transported over large distances and have the ability to biomagnify and bioaccumulate. Their extensive use in the 20th century led to widespread environmental contamination, causing harm to many wildlife populations. Despite their ban and restriction under the 2001 Stockholm Convention, one of the most critical international agreements administered by the UN Environment, pervasive and widespread contamination of the environment still occurs. As long-lived apex predators, cetaceans are known to be particularly vulnerable to accumulating high body burdens of POPs. To assess the effectiveness of pollution mitigation strategies and ensure cetaceans are adequately protected it is vital to determine the impacts of exposure to POPs in cetaceans. This thesis uses the world’s largest marine mammal strandings toxicology database, collected from stranded cetaceans between 1990 and 2018, to demonstrate that despite their ban under the Stockholm Convention in 2001, POPs are still a significant threat to cetaceans that inhabit the waters of the United Kingdom. I have demonstrated that although levels of POPs are declining, several species are still exposed to concentrations that are deemed to be a toxicological threat. Further, rates of decline vary between taxa and regions, hence some populations are more vulnerable than others. I have also demonstrated that, of the contaminants investigated, polychlorinated biphenyls (PCBs) are present at the highest concentrations, declining at the slowest rate and appear to be the greatest threat to cetacean health. Using harbour porpoises as a model species, this thesis has demonstrated that PCBs are significantly associated with increased disease prevalence and reduced testes weights, which suggests that male fertility may be impacted by exposure to POPs. This could have serious implications on the long-term population viability of harbour porpoises and similar species that are exposed to higher concentrations of PCBs. I also found age and sex related differences in the PCB congener profiles that harbour porpoises are exposed to, which suggests juveniles may be at a higher risk of experiencing neurotoxic effects than adults. Taken together, I believe these findings demonstrate that improved international POP elimination, mitigation and compliance strategies are required alongside conservation and management plans to adequately protect cetaceans from the deleterious effects of POPs.

Accessible summary Active support is one of the best ways of getting people with learning disabilities to be busy and to look after themselves. Good relationships between staff and people with learning disabilities are important. This study looked at organising staff to be better at supporting the person with a learning disability. We also got them to record on video how they worked with the person. They watched these videos back so they could find out how to improve their support. The results showed that the staff were better at helping service users do things for themselves and that service users were busier. It is also showed that staff had better relationships with the service users. AbstractBackground This study evaluated a package of Active Support (AS), which included standard training with additional video informed reflective practice. Materials & Methods The training package was implemented as part of a service improvement initiative in four residential intellectual disability homes, using a concurrent multiple baseline across environments design. Training consisted of a 1-day workshop, and follow-up coaching. Momentary time sampling was used to measure engagement levels and staff assistance. A new observational tool was piloted to code the presence of positive and negative interactions between staff and the people with intellectual disabilities. Results Results showed that service user engagement levels and staff assistance increased significantly following the training. There was also a significant increase in positive interactions and a significant decrease in negative interactions between staff and service users. Conclusion The implications of these results are discussed.

Accurate dynamical models of the Antarctic ice sheet with carefully specified initial conditions and well-calibrated rheological parameters are needed to forecast global sea level. By adapting an inverse method previously used in electric impedance tomography, we infer present-day flow speeds within the ice sheet. This inversion uses satellite observations of surface velocity, snow accumulation rate, and rate of change of surface elevation to estimate the basal drag coefficient and an ice stiffness parameter that influences viscosity. We represent interior ice motion using a vertically integrated approximation to incompressible Stokes flow. This model represents vertical shearing within the ice and membrane stresses caused by horizontal stretching and shearing. Combining observations and model, we recover marked geographical variations in the basal drag coefficient. Relative changes in basal shear stress are smaller. No simple sliding law adequately represents basal shear stress as a function of sliding speed. Low basal shear stress predominates in central East Antarctica, where thick insulating ice allows liquid water at the base to lubricate sliding. Higher shear stress occurs in coastal East Antarctica, where a frozen bed is more likely. Examining Thwaites glacier in more detail shows that the slowest sliding often coincides with elevated basal topography. Differences between our results and a similar adjoint-based inversion suggest that inversion or regularization methods can influence recovered parameters for slow sliding and finer scales; on broader scales we recover a similar pattern of low basal drag underneath major ice streams and extensive regions in East Antarctica that move by basal sliding.

We use an ice sheet model with realistic initial conditions to forecast how the Amundsen Sea sector of West Antarctica responds to recently observed rates of submarine melting. In these simulations, we isolate the effects of a positive feedback, driven by submarine melt in new ocean cavities flooded during retreat, by allowing the present climate, calving front and melting beneath existing ice shelves to persist over the 21st century. Even without additional forcing from changes in climate, ice shelf collapse, or ice cliff collapse, the model predicts slow, sustained retreat of West Antarctica, driven by the marine ice sheet instability and current levels of ocean-driven melting. When observed rates of melting are included in new subglacial ocean cavities, the simulated sea level contribution increases, and for sufficiently intense melting it accelerates over time. Conditional Bayesian probabilities for sea level contributions can be derived but will require improved predictions of ocean heat delivery.

Inverse methods, where surface data are ‘inverted’ in order to quantify basal properties of ice sheets, play a major role in initializations. The balance-velocity method is a unique linear initialization, in which accumulation, surface elevation and thickness data are used to calculate the velocities and basal conditions required to maintain the observed ice-sheet altimetric signal, resulting in an estimate of the basal sliding viscosity that is guaranteed to be non-negative. We examine the observation that balance velocities based on the shallow-ice approximation (SIA) are extremely dependent on grid size, showing that Antarctic balance velocities on a 1 km grid are excessively over-channelized. Incorporating the membrane-stress approximation into balance-velocity calculations and comparing them with a simplified analytical solution shows that numerical error monotonically decreases with grid resolution and over-channelization is eliminated for Newtonian and non-Newtonian rheology. In contrast, for the SIA reducing grid size below the membrane-stress coupling length fails to improve accuracy. However, since this approach is nonlinear, a unique viscosity solution is not guaranteed, and in practice ‘sliding viscosity’ estimates are noisy. This raises problems of the sensitivity of these estimates to data and model errors, which may mean using inverse or smoothing techniques in association with balance-velocity methods in many, if not all, practical applications.

SUMMARYThe term bioconvection encapsulates the intricate patterns in concentration, due to hydrodynamic instabilities, that may arise in suspensions of non-neutrally buoyant, biased swimming microorganisms. The directional bias may be due to light (phototaxis), gravity (gravitaxis), a combination of viscous and gravitational torques (gyrotaxis) or other taxes. The aim of this study is to quantify experimentally the wavelength of the initial pattern to form from an initially well-mixed suspension of unicellular, swimming green algae as a function of concentration and illumination. As this is the first such study, it is necessary to develop a robust and meticulous methodology to achieve this end. The phototactic, gyrotactic and gravitactic alga Chlamydomonas augustae was employed, with various red or white light intensities from above or below, as the three not altogether separable taxes were probed. Whilst bioconvection was found to be unresponsive to changes in red light, intriguing trends were found for pattern wavelength as a function of white light intensity, depending critically on the orientation of the illumination. These trends are explored to help unravel the mechanisms. Furthermore, comparisons are made with theoretical predictions of initial wavelengths from a recent model of photo-gyrotaxis, encouragingly revealing good qualitative agreement.

Background Germline mutations of the SDHD, SDHB and SDHC genes, encoding three of the four subunits of succinate dehydrogenase, are a major cause of hereditary paraganglioma and pheochromocytoma, and demonstrate that these genes are classic tumor suppressors. Succinate dehydrogenase is a heterotetrameric protein complex and a component of both the Krebs cycle and the mitochondrial respiratory chain (succinate:ubiquinone oxidoreductase or complex II). Methods Using conformation sensitive gel electrophoresis (CSGE) and direct DNA sequencing to analyse genomic DNA from peripheral blood lymphocytes, here we describe the mutation analysis of the SDHB and SDHC genes in 37 patients with sporadic (i.e. no known family history) head and neck paraganglioma and five pheochromocytoma and/or paraganglioma families. Results Two sporadic patients were found to have a SDHB splice site mutation in intron 4, c.423+1G>A, which produces a mis-spliced transcript with a 54 nucleotide deletion, resulting in an 18 amino acid in-frame deletion. A third patient was found to carry the c.214C>T (p.Arg72Cys) missense mutation in exon 4 of SDHC, which is situated in a highly conserved protein motif that constitutes the quinone-binding site of the succinate: ubiquinone oxidoreductase (SQR) complex in E. coli. Together with our previous results, we found 27 germline mutations of SDH genes in 95 cases (28%) of sporadic head and neck paraganglioma. In addition all index patients of five families showing hereditary pheochromocytoma-paraganglioma were found to carry germline mutations of SDHB: four of which were novel, c.343C>T (p.Arg115X), c.141G>A (p.Trp47X), c.281G>A (p.Arg94Lys), and c.653G>C (p.Trp218Ser), and one reported previously, c.136C>T, p.Arg46X. Conclusion In conclusion, these data indicate that germline mutations of SDHB and SDHC play a minor role in sporadic head and neck paraganglioma and further underline the importance of germline SDHB mutations in cases of familial pheochromocytoma-paraganglioma.