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Large surface ships have traditionally used steel for their construction, which provides good blast resistance and predictable behaviour in use. This research project, however, considered the use of polymeric foam core sandwich panels for the construction of ship hulls, with the intention of reducing the radar signature of the vessel; increasing the maximum speed; reducing fuel consumption; and providing control over desired mechanical properties for specific applications. This project specifically considered the resistance of the sandwich composites to non-contact explosives, specifically sea mines and areal blast. This research project firstly presents air blast testing performed on polymeric foam core sandwich panels with glass fibre face-sheets. The foam polymer type, the effect of the face-sheet material and the effect of using a graded density foam core for blast wave attenuation were all investigated. When subjected to air blast loading it was found that by grading the core density a smoother back face-sheet displacement was witnessed. This was a significant discovery as protecting the back face-sheet is key to maintaining structural integrity of the ship hulls. In a comparison of foam polymers in the cores of the sandwich panel it was concluded that styrene acrylonitrile offers optimum fracture and adhesion properties. Furthermore, it was found that by interleaving high modulus polypropylene fibres between the glass fibre front face-sheets, front face-sheet cracking and delamination can be prevented, restricting water ingress into the sandwich panel if it were subjected to blast loading. Advances in using 3D high speed imaging for digital image correlation were also achieved, whereby the results were used to estimate core shear strain during deformation, and the kinetic energy and strain energy in the sandwich panel were estimated by comparison with blast wave pressure simulations. The residual flexural and edgewise compression properties of the air blasted sandwich panels were then determined to calculate the flexural stiffness and strength and edgewise stiffness and strength with varying damage. It was found that the construction of the sandwich panel properties were unaffected by the construction, and that debonding of the face-sheets and the core was the key performance reducing damage mechanism. Residual properties were determined for the sandwich materials, with the intention that these could be used in simulations to predict performance of the ship hulls after successfully withstanding a blast. In underwater blast scenarios it was discovered that using a graded density foam core reduced the central deflection of the sandwich panel due to the increase in energy absorption due to crushing of the stepwise increase in foam core density. This effect was greater in carbon fibre sandwich panels than in glass fibre panels, due to the increased stiffness of the face-sheets. The central deflection was calculated by averaging the strains measured on the two face-sheets with electronic strain gauges, which was a novel technique and took advantage of the symmetry present in the square sandwich panels. As the focus of this research project was on foam core properties, the polymeric foam materials were characterised in quasi-static and dynamic tension, and quasi-static and dynamic compression. Dynamic compression tests were performed using a split-Hopkinson pressure bar which was designed specifically for testing low density foam materials. Stress equilibrium was achieved in these tests using a textured polypropylene pulse shaper. Stress equilibrium was checked for by performing high speed digital image correlation during deformation, to ensure that core crushing did not begin at the incident bar. The final stage of the research project was to construct finite element simulations of the air blast tests, using the polymeric foam material properties measured in the quasi-static and dynamic tests. A large number of simulations were performed with varying charge sizes and stand-off distances, to determine a combination of blast peak pressure and impulse values at which the sandwich panels failed. Developments were achieved in the use of a brittle cracking material model and the effect of the boundary conditions on the simulations was also studied. This research project furthered the understanding of sandwich composite materials to air and underwater blast loading. Advancements were made into the use of stepwise graded density foam cores and in characterising foams at dynamic tensile and compressive rates. A major conclusion of the project is that the use of graded density cores can be utilised to prevent damage of the sandwich panel on the rear side and can be used to absorb blast energy due to core crushing. The results of the project aid in simulating the response of composite ship hulls to blast loading and better predict the usability of the ships after being subjected to a blast event.

The calcineurin inhibitors (CNIs), cyclosporine A (CsA) and tacrolimus (FK506), have revolutionized solid organ transplantation with their unprecedented ability to increase graft and patient survival. However, they have a plethora of unwanted side effects, of which nephrotoxicity is predominant. Renal cortical blood flow is majorly suppressed with administration of CsA and FK506, however the impact of these drugs on medullary blood flow is still unclear. It was previously thought that renal medullary blood flow (RMBF) was regulated upstream by the larger arterioles of the cortex, however new evidence suggests that a local regulation of blood flow exist and is partially controlled through the vasoconstriction of renal pericytes on descending vasa recta (DVR) capillaries. Renal pericytes have been shown to contract and/or dilate in response to a variety of endogenous and exogenous factors suggesting they have the ability to locally regulate RMBF and respond accordingly after insult or in stress situations. The first chapter of this thesis demonstrates the ability of CNIs to induce pericyte-mediated vasoconstriction of DVR. A significant decrease of DVR diameter likely results in decreased blood flow in vivo and contributes to increased ischemia. Furthermore, an alternative immunosuppressant, rapamycin, a mammalian target of rapamycin inhibitor (mTOR-i) failed to induce any significant vasoconstriction. The following chapter investigates the use of antihypertensives in combination with CNIs and highlights a mechanism for their potential beneficial use in combating the progression of CNI-induced hypertension and nephrotoxicity. The third results chapter sets out to establish a perfusion method for DVR in situ. The results demonstrate the feasibility of in situ perfusion within the established live kidney slice model, and also the impact of perfused CNIs on the vasoconstriction of vasa recta as defined in chapter 1. The data presented here further demonstrates how CNIs may augment the known nephrotoxic effect but, also how they may instigate medullary ischemia. The final results chapter emphasises how the generation of reactive oxygen species (ROS) induced by CNIs could be a foremost mechanism in pericyte-mediated vasoconstriction of DVR. In addition, prevention of ROS production, rather than it’s scavenging, could be an enhanced approach for the inhibition of CNI induced renal damage and nephrotoxicity. Taken together, the data presented here suggests a role of RMBF in the pathogenesis of CNI nephrotoxicity. Given that our understanding of RMBF is only now coming to light, its role in many disease states, including CNI nephrotoxicity, may have a greater impact than previously assumed and potentially offer a novel therapeutic approach for the prevention of renal decline.

Laser and optical emission spectroscopies have been employed to study the gas phase chemistry in the growth environment for diamond chemical vapour deposition (CVO) in a microwave (MW) reactor. Computational investigations have also been used to explore the energetics of elementary reactions on a diamond surface, to give insight into which species are likely to incorporate into a growing diamond film. The focus of this thesis is on 0 and N containing CIH plasmas.

The investigation of associations between places, people and mental health is complicated and there are serious limitations in the current methodology. Using data from the Caerphilly Health and Social Needs Study (CHSNS), as well as the British Household Panel Survey, this thesis investigated some of these methodological issues. Firstly, motivated by the skewed distribution of the Mental Health Inventory (MHI-5), methods for analysing the mental health score were examined. Five methods for deriving a cutpoint on the MHI-5 based on linking with the General Health Questionnaire, were investigated and cutpoints derived for each. These outpoints and methods were compared and contrasted. When investigating associations between place and health, hierarchical modelling is an extremely useful tool. Sparse levels of information are a potential problem when using this method. In the CHSNS, households represent a sparse level of context. A simulation study was conducted to explore the effect of sparse levels on the results of hierarchical analyses. It was found that, in general, the underestimation of fixed effect standard errors is smaller when a sparse level is included than when it is excluded. Another methodological consideration for hierarchical modelling concerns the choice of geographical hierarchy to use. Administrative hierarchies have been criticised for being heterogeneous and arbitrary. An algorithm was developed to partition regions into areas that are homogenous with respect to a given set of variables, and was applied to Caerphilly county borough. The resulting sets of boundaries were compared with the 2001 census administrative boundaries. These new boundaries performed favourably in comparison with the administrative boundaries, indicating that administrative boundaries may not represent the most suitable hierarchy to employ in hierarchical analyses. The thesis has led to a greater understanding of the effects of context on multilevel analysis and contributed to the area-effects on health literature.