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This thesis addresses the challenges with utilising diamond for integrated optical devices; a platform where its impressive material properties can be exploited. The major objective was to develop a process by which diamond could be heterogeneously integrated with non-native device platforms, to overcome its limited geometry. A process was developed for fabrication, handling, and hybrid integration of ultra thin diamond membranes. Plasma-etch chemistries were developed, that enabled such processing, and provided sub-nm r.m.s. roughness. Two sets of monolithic diamond structures were fabricated and transfer printed with a thickness down to ~10 nm. For thickness characterisation, diamond platelets, finding a low local-variation across typical device geometries. Diamond resonator devices were also fabricated and when integrated with SOI waveguides they showed high Q-factors as large as 1.8 x 10⁵. Thermo-optic tuning of these devices by > 450 pm at low mW powers was demonstrated, which has great significance to all integrated optical fields where resonant frequency of a cavity is important. The techniques developed are independent of integration platforms and are of wide reaching relevance to the optics community.

This thesis considers the fatigue and fracture behaviour of ultra-high strength steel, AerMet 100. Two variants of AerMet 100 were tested, which had different desulphurisation and deoxidation methods. The first was desulphurised and deoxidised using mischmetal, designated MMAerMet 100. The second was desulphurised using calcium and deoxidised using titanium, designated Ca-AerMet 100. Axial fatigue testing below the 0.2% proof stress was carried out between stress ranges of 900-1700 MPa. Fractography revealed that the fatigue initiation sites could be traced to non-metallic inclusions. Samples tested in the longitudinal orientation had better fatigue lives compared to samples tested in the transverse orientation. A stress intensity factor range at the cracked inclusion at the point of initial fatigue crack growth showed a good correlation with fatigue life. Ca-AerMet 100 consistently had a better fatigue life compared to MM-AerMet 100. Fracture toughness testing showed that both variants of AerMet 100 had similar fracture toughness values and fractured by micro-void coalescence. Fractography revealed that 90% of the fracture surface was made from voids formed from secondary particles with approximate diameters of 90 nm. The work suggests that changing the desulphurisation and deoxidation method for AerMet 100 has not significantly affected the fracture toughness.

Converging cognitive and neuroimaging evidence reveals that episodic memory and episodic future thinking (EFT) share component processes. Much less is known about the relationship between EFT and working memory (WM) processes. We hypothesized that WM capacity might provide a crucial componential cognitive role during EFT by supporting the translation of information from discrete episodic memories into a novel future event. We tested this hypothesis in two studies. In Study 1, we collected functional magnetic resonance imaging data during a dual-task interference paradigm that varied WM load and processing demands during EFT. Events imagined while actively maintaining bound item-location representations were less vivid than those imagined during low WM load control trials. Measures of functional and effective connectivity indicated that this behavioral effect corresponded with reduced coupling between the dorsomedial prefrontal cortex and right temporoparietal junction. Events imagined while simultaneously manipulating items in WM took longer to construct than events imagined during control trials and were associated with less functional coupling between the right hippocampus and posterior visuospatial regions. In Study 2, participants completed a similar WM dual-task while simultaneously recalling past events or imagining future events during scalp-recorded encephalography (EEG). As in Study 1, future events imagined while maintaining item-location representations were less vivid than control trials. This effect was specific to future events and corresponded to reduced theta reactivity over bilateral temporoparietal sites. Relative to episodic memory, EFT was associated with alpha synchronization over frontal and parietal sites as well as greater theta-gamma phase amplitude coupling in the right dorsolateral prefrontal cortex. In contrast, episodic memory was associated with greater cross-frequency coupling between frontal theta and occipital gamma oscillations. These results provide novel empirical support for previous theoretical accounts suggesting that WM capacity provides the cognitive workspace necessary to temporarily store and recombine details from discrete episodes into a future event representation.

Since the 9/11 attacks, American legislation and legal policy in regards to classifying and processing captured terrorists has fallen short of being fully effective and lawful. Trial and error by the Bush and Obama administrations has uncovered two key lessons: (1) captured terrorists are not typical prisoners of war and thus their detainment must involve more legal scrutiny than the latter; and (2) captured terrorists are not ordinary criminals and thus the civilian criminal court system, due to constitutional constraints, is not capable of adequately trying every count of terrorism. Other nations, including France and Israel, approach this problem with different solutions, such as special jurisdictions and specific legislation. Now, the Trump administration must craft a new approach using the available examples.

Nitrogen (N) is a major nutrient needed for plant growth. Around 40% of N is considered unavailable for plant use in the form of proteins. Proteins can be broken down into constituents available for plants by extracellular proteases released by microorganisms. Therefore, understanding soil proteases and their role in organic matter breakdown could provide a mechanism for increasing organic N acquisition that would improve N supply in soil leading to increased plant productivity. However, there are ongoing discussions over the lack of standardisation of assays used to measure soil protein and protease activity. The overall aims of the thesis were to a) critically evaluate the methods used to extract proteins from soil and measure soil protease activity and b) determine the factors that influence protein breakdown in the soil-plant-microorganism system. First, I critically evaluated methods to extract proteins from soil by comparing the ability of common extractants to recover soluble proteins from three soil types. I found that the dependence of protein recovery on both extractant and soil type prevents direct comparison of studies using different recovery methods, particularly if no extraction controls are used. Secondly, I investigated how topsoil and subsoil properties affect protein breakdown along a grassland altitude and primary productivity gradient that contained a range of soil types. I concluded that protein breakdown was not regulated by a small number of factors but a wide range of interacting factors which were site specific. Furthermore, I suggested that differences in soil N cycling and the generation of ammonium are more related to the rate of protein supply rather than limitations in protease activity and protein turnover. I then determined whether plants actively secrete proteases to enhance the breakdown of soil protein or are they functionally reliant on soil microorganisms to undertake this role? The results indicated that plant uptake of organic N is only functionally significant when soil protein is in direct contact with root surfaces. The lack of protease upregulation under N deficiency suggests that root protease activity is unrelated to enhanced soil N capture. Next, I determined the spatial distribution of protease activity in the rhizosphere of barley (Hordeum vulgare L.) using in situ zymography. I analysed the effect of root hairs and soluble protein addition on rhizosphere protease activity. The results showed protease activity was highest in the barley genotype with root hairs and with protein addition suggesting that plants with root hairs have a greater advantage in accessing protein hotspots in the soil indirectly via microbial-derived proteases. Lastly, I conducted a systematic review and meta-analysis of the common methods used to measure soil protease activity globally. I collected data on environmental and methodological factors to determine the variation of protease activity in soil. From this, I found soil protease activity to vary widely due to study-biases and observed a lack of reporting of key assay conditions by studies. Together, this research provides a more detailed understanding of protein mineralisation and protease activity in soil. Going forward, comprehensive reporting of enzyme assay conditions is essential to increase the accuracy and reliability of interpreting soil protease activity dynamics in the soil-plant-microorganism system.

Much of the climate change impact of agriculture is due to the addition of nitrogen (N) to soil to increase crop yields. The production of mineral N fertiliser from atmospheric N2 causes carbon dioxide (CO2) emissions, and once added to soil, fertiliser N is easily transformed to other forms and lost as leached nitrate (NO3-), ammonia gas (NH3) and the greenhouse gas nitrous oxide (N2O). An alternative to fertiliser N is the use of green manures, plants grown on agricultural land, which after incorporation into soil provide N to the following crop. N fixing green manures gain atmospheric N by a symbiosis with microbes, therefore adding N without CO2 emissions, and providing beneficial organic matter to soil. Counteracting these advantages is a lower land use efficiency due to the space required for green manure cultivation. Green manure additions can result in carbon (C) sequestration, however soil C dynamics are complex and soil C can also be lost by a stimulation of respiration known as priming. N pollution from soil is generally higher when mineral N concentrations are high, which can result from poor synchrony of N supply with crop demand. The incorporation of green manures offers limited scope for effective targeting of N. This synchrony of N supply with demand could be improved by, instead of incorporating green manures, harvesting the plant material and adding it to soil to meet crop demand. Negating the requirement for incorporation, allows use of a wider range of species including shrubs and trees. Growing N fixers suited to lower quality land e.g. wet or exposed areas, could increase land use efficiency by reducing the demand for prime agricultural land. We chose three such N fixing species and refer to these as Perrenial Mobile Green Manures (PMGMs): Alnus glutinosa (Alder), Gunnera manicata (Gunnera), and Ulex europaeus (Gorse). This thesis investigated N provision to a crop, and potential for N pollution by these PMGMs, compared to the conventional green manure, Trifolium pratense (red clover) and ammonium nitrate (NH4NO3) fertiliser, in a one year pot experiment, and field experiments over two seasons. A six week incubation investigated soil C dynamics by use of 14C isotopes. In both pot and field experiments, the PMGMs supplied N to crops at a slower rate than clover or NH4NO3 but by the end of the pot experiment resulted in equal or more biomass and N uptake than from clover. Potential for N pollution from PMGMs was considerably lower than from clover or NH4NO3, with mean NO3- concentrations in the soil solution of the pot experiment reaching only 25 mg N L-1 compared to over 130 mg N L-1 from clover and NH4NO3 additions. Emissions of N2O from PMGMs were considerably lower than those from clover and NH4NO3, in the pot trail, with applied N lost as N2O-N from gunnera and alder being 0.34 %, and 0.61 %, respectively compared to 5.3 % from clover. N2O emissions from all treatments in the field experiment were low which is likely to be due to dry weather conditions. Data from the incubation study indicated that after one year, gunnera and alder additions could result in a net loss of C due to priming. These predictions, however, do not consider factors of cropping soil e.g. roots, and meso and macro fauna and require further investigation. We conclude that PMGMs could improve N use efficiency and reduce NO3- leaching and N2O emissions compared to incorporation of clover, and have potential for a more favourable C balance than NH4NO3. Thus, PMGMs have strong potential for inclusion into a more sustainable agricultural landscape.

Climate change is expected to alter important process operating in soil ecosystems such as microbial activity, biogeochemical cycling, and hydrological processes, and thus soil functioning and the delivery of a range of ecosystem services. Under future climate change scenarios, extreme weather events are predicted to become ever more frequent globally, with rising temperatures and concentrated rainfall events having an impact on soil functioning. It is necessary to study how changes in soil moisture status and/or temperature will affect soil respiration for predicting future changes in soil carbon (C) storage. In the scientific literature, previous studies have frequently observed a CO2 pulse from soil after a freeze-thaw or dry-wet event; however, the mechanisms underlying these effects are not well understood. The first experiment of this thesis (Chapter 3) investigated how a single freeze-thaw or dry-wet event affected microbial C dynamics using 14C tracking. Our results revealed that freeze-thaw or dry-wet events altered the allocation of C into labile and structural microbial C pools. The next experiment (Chapter 4) investigated how the C budget of an intact plant-soil system responded to freeze-thaw and dry-wet events. The presence of plants resulted in significantly greater total CO2 flux following freeze-thaw or dry-wet events in comparison to the unplanted soil. The greater CO2 efflux seen after thawing or rewetting was caused by a disruption of the microbial biomass, rather than a stimulation of soil organic matter turnover (Chapter 5). This was supported by a decrease in extracellular enzyme activity immediately after freeze-thaw or dry-wet event (Chapter 5). We also showed that soil microbes accumulated osmotic solutes (i.e. sugars and polyols) in response to extreme freeze-thaw or dry-wet events. In this thesis, the microbial community quickly responded to freezing or drying events by altering cellular metabolism (Chapter 6). The final experimental chapter (Chapter 7) investigated how future climate scenarios may affect arctic ecosystems. We monitored greenhouse gas (GHG) emissions and nutrients in soil solution throughout a year in response to a 2050 and 2100 climate warming scenario. A simulated warmer winter led to enhanced microbial decomposition of soil organic matter with increased CO2 efflux and more N becoming available to roots and associated mycorrhiza in the Arctic soils. We hypothesize that this could lead to a potential future shift in plant communities. In conclusion, this thesis present events showing that under future climate scenarios, an increase in freezethaw or dry-wet events will alter soil C and N processing in soils and disrupt biogeochemical cycling. We also conclude that the presence of plants is key in determining how ecosystems respond to these extreme events.