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Concurrent and distributed behaviour encompasses a wide range of ever evolving phenomena and features of computation such as communication, mobility, causality, failure recovery and reversibility. In order to understand better and make precise the properties of such behaviour, concurrent and distributed behaviour needs to be modelled abstractly and with formal rigour. Delay-insensitive networks are a class of asynchronous systems which makes no assumptions about the timing of signals or components. This makes them suitable for the implementation of highly concurrent systems. Unfortunately, concurrency within delay-insensitive networks is an underdeveloped concept which lacks formal rigour. Reversibility of such systems is also typically only studied in the context of serial systems without concurrency. In this thesis, a new model for describing the behaviour of delay-insensitive components is introduced which more naturally permits the modelling and study of concurrency. Reversibility of such components is discussed. The concept of an environment for a component is formalised, and its limitations in terms of interactivity with such a component is also studied. Algorithms for generating the environments for delay-insensitive components, such that desirable properties always hold are given. Universality results and properties of networks of such components are examined in-depth. A new process algebra which allows the encoding of these networks is introduced. This permits rigorously defined notions of implementation and other desirable run-time properties of these networks. A family of new novel cellular automata is defined which allows the encoding of delay-insensitive networks. These cellular automata are competitive with existing CA regarding universality, and number of rules and states. They have a feature we call direction-reversibility, which allows the inversion of behaviour simply by reversing the direction of signals. Finally, two pieces of software called Delay-Insensitive Network Tool Suite and STCA Simulator, developed to aid in this research, are also detailed. more...

Poly(aryl-ether-ether-ketone) (PEEK) is a semi crystalline polymer which exhibits properties that make it an attractive choice for use as an implant material. It displays natural radiolucency, and MRI compatibility, as well as good chemical and sterilization resistance, both of which make it of particular interest in orthopaedic implants. However, PEEK has demonstrated poor cellular adhesion both in vitro and in vivo. This is problematic as implant surfaces that do not develop a layer of adhesive cells are at risk of undergoing fibrous encapsulation, which in turn leads to lack of a strong interface between the implant device and the patient tissue, which can in turn lead to failure of the implant and revision surgery . As incorporating nanotopography into a polymer surface has been demonstrated to be able to direct the differentiation behaviour of stem cells, a possible solution to PEEKs underlying issues with poor cellular response would be to incorporate specific nanoscale topography into the material surface through injection moulding, and then analysing if this is a viable method for addressing PEEKs issues with cellular response. In addition to nanoscale topography, the experimental PEEK surfaces were treated with oxygen plasma to address the underlying cytophobicity of the material. As this type of treatment has been documented to be capable of etching the PEEK surface, experiments were carried out to quantify the effect of this treatment, both on the ability of cells to adhere to the PEEK surface, as well as the effect it has upon the nanotopography present at the PEEK surface. The results demonstrated that there were a range of plasma treatments which would significantly improve the ability of cells to adhere to the PEEK surface without causing unacceptable damage to the nanotopography. Three different types of cells with osteogenic capacity were tested with the PEEK surfaces to gauge the ability of the topography to alter their behaviour: SAOS-2, osteoprogenitors and 271+ MSCs. Due to PEEKs material properties (it is non transparent, exhibits birefringence and is strongly autofluorescent) a number of histological techniques were used to investigate a number of different stages that take place in osteogenesis. The different cell types did display slightly different responses to the topographies. The SAOS-2 cells cultured on surfaces that had been plasma treated for 2 minutes at 200W had statistically significantly higher levels of von Kossa staining on the NSQ surface compared to the planar surface, and the same experiment employing alizarin red staining, showed a statistically significantly lower level of staining on the SQ surface compared to the planar surface. Using primary osteoprogenitor cells designed to look into if whether or not the presence of nanotopography effected the osteogenic response of these cells, we saw a lack of statistically significant difference produced by the surfaces investigated. By utilising HRP based immunostaining, we were able to investigate, in a quantitative fashion, the production of the two osteogenic markers osteopontin and osteocalcin by cells. When stained for osteocalcin, the SQ nanotopography had total percentage of the surface with stained material, average area and average perimeter all statistically significantly lower than the planar surface. For the cells that were stained for osteopontin, the SQ nanotopgraphy had a total percentage of the surface with stained material, average area and average perimeter all highly statistically significantly lower than those of the planar surface. Additionally, for this marker the NSQ nanotopography had average areas and average perimeters that were highly significantly higher than those of the planar surface. There were no significant differences for any of the values investigated for the 271+ MSC’s When plasma treatment was varied, the SAOS-2 cells demonstrated an overall trend i.e. increasing the energy of plasma treatment in turn leads to an increase in the overall percentage of staining. A similar experiment employing stem cells isolated from human bone marrow instead of SAOS-2 cells showed that for polycarbonate surfaces , used as a control, mineralization is statistically significantly higher on the NSQ nanopattern compared to the planar surface, whereas on the PEEK surfaces we observe the opposite trend i.e. the NSQ nanotopography having a statistically significantly lower amount of mineralization compared to the planar surface at the 200W 2min and 30W 1min plasma treatments. The standout trend from the PEEK results in this experiment was that the statistically significant differences on the PEEK substrates were clustered around the lower energy plasma treatments, which could suggest that the plasma treatment disrupted a function of the nanotopograhy which is why, as the energy increases, there are less statistically significant differences between the NSQ nanotopography and the Planar surface This thesis documents the response of a number of different types of cells to specific nanoscale topographies incorporated into the PEEK surface which had been treated with oxygen plasma. It outlines the development of a number of histological methods which measure different aspects of osteogenesis, and were selected to both work with PEEK, and produce quantitative results through the use of Cell Profiler. The methods that have been employed in this body of work would be of interest to other researchers working with this material, as well as those working with similarly autofluorescent materials. more...

A variety of metathetical reactions have been carried out in a liquid medium to explore the variety and depth of such reactions. A comparison with the similar solid-state reactions gives a clear indication of the differences and similarities between the two alternate routes. The fact that these reactions go to completion at all is interesting in that the conditions employed are very mild and do not employ any "forcing" means to induce reaction. Main group and transition metal sulphide, selenide and telluride and transition metal phosphide, arsenide and antimonide binary and ternary compounds were synthesised and characterised. An in-depth investigation into the synthesis and characterisation of the chalcopyrite CuInE2 (E = S, Se, Te) family of ternary compounds has also been carried out with a specific focus on liquid variation, reaction duration and temperature and annealing treatment. Solid-state metathesis synthesis of CuInE2 was also carried out for comparison purposes. The main conclusions drawn from the use of the liquid-mediated metathesis methodology are that the reactions, for the most part, go to completion and produce single-phase products. Reactions require a much lower temperature and take much longer to go to completion as compared with the solid-state metathesis method. The majority of the products are X-ray amorphous before being subjected to annealing, and crystallinity can be induced under relatively mild conditions and with good control of crystallinity level. Product particle size is significantly reduced both before and after annealing. more...