Antarctic tourism represents the largest and fastest growing commercial activity on the Antarctic continent. Under consideration of its unprecedented growth and diversification, the Antarctic tourism sector is viewed with increasing scrutiny and concern. This concern is expressed in discussions surrounding the success and effectiveness of the existing regulatory framework for Antarctic tourism and asks what changes might be required to adequately protect the Antarctic continent in the future. Viewpoints and interests among Antarctic tourism operators, policy-makers, researchers and other stakeholders diverge, and Antarctic tourism is discussed as being either or both benefactor and detractor to the environmental and political integrity of Antarctica. This thesis discusses, regulations drawing on regime theory, the effectiveness of Antarctic tourism. It postulates the theory that the combined regulatory efforts of Antarctic Treaty Consultative Parties (ATCPs) and industry self-regulation through the International Association of Antarctica Tour Operators (IAATO) define the Antarctic tourism regime. Using interviews and a Delphi study as the primary methods of inquiry, stakeholder viewpoints on regulatory and operational characteristics of Antarctic tourism were collected and integrated into a discussion of the effectiveness of the current regulatory regime and an assessment of potential options for regulating Antarctic tourism in the future. The interviews provide insights particularly into operational matters and the in situ practice of tour operators and their compliance with existing regulations. The Delphi study focuses on how the current regulatory issues are addressed, how rules and regulation are enacted and whether the current regulatory framework needs improvement. The thesis research shows that Antarctic tourism stakeholders are concerned about the increasing scale and diversification of Antarctic tourism and generally subscribe to a conservation imperative when assessing potential options for the future regulation of Antarctic tourism. The Antarctic Treaty System is regarded as being stable and having matured over the years, although the regime has not been tested to any great extent. Tourism development in the Antarctic may well prove to be a first test of the stability and success of the Antarctic Treaty System. Stakeholders desire a continued strong partnership between Antarctic Treaty Parties and IAATO regarding the regulation of Antarctic tourism, but conclude that in view of the rapid development of Antarctic tourism, structural, institutional and legislative changes are necessary if Antarctic tourism regulation is to remain successful. The thesis argues that these necessary changes do not inevitably involve a complete overhaul of the existing regulatory regime for Antarctic tourism and that a new overarching regulatory instrument such as a tourism convention may neither be the most desirable nor feasible approach to regulating tourism to the Antarctic. Instead, this thesis research suggests that regulatory improvements need to build on the strengths of the current regime and on a strategic vision that should guide the future regulation of Antarctic tourism.

In this paper, focus is on the global vector autoregressive (GVAR) model. Its attractiveness stems from an ability to incorporate global interdependencies when modeling local economies. The model is based on a collection of local models, which in general are estimated as regular VAR models. This paper examines alternative specifications of the local models by estimating them as regime-switching VAR models, where transition probabilities between different states are studied using both constant and time-varying settings. The results show that regime-switching models are appealing as they yield inferences about the states of the economy, but these inferences are not guaranteed to be reasonable from an economic point of view. Furthermore, the global solution of the model is in some cases non-stationary when local models are regime-switching. The conclusion is that the regime-switching alternatives, while theoretically reasonable, are sensitive to the exact specification used. At the same time, the issue of specifying the regime-switching models in such a way that they perform adequately speaks in favor of the simpler, yet functional, basic GVAR model.

This thesis investigates bacterial motility from the mechanism permitting individual selfpropulsion to the complex collective flocking motility in Escherichia coli and Bacillus subtilis cells. Understanding bacterial swimming has intrigued scientists for decades and recently there has been a growing interest in collective swimming behaviour. The first part of this thesis reviews the characteristics of E. coli and B. subtilis cells subsequently describing the governing physics and constraints of self-propulsion in the low Reynolds regime. The second part of this thesis presents three self-contained experimental sections, examining individual swimming in non-conventional body shaped cells and subsequently focusing on concentrated bacterial swimming in normal cells. We first investigated motility in mutant spherical E. coli cells KJB24 motivated by simulations, which often model bacteria as self-propelled spheres. Somewhat unexpectedly these spherical cells do not exhibit runs and tumbles but diffuse slower than expected. As an introduction to working with microbiology and to familiarise with microbiology techniques we investigated why these spherical cells do not swim. Secondly we investigated how cellular motility varies as a function of body length by inhibiting cell division in wild-type E. coli with cephalexin; which remained motile despite body elongation. Fluorescent flagella visualization provided evidence of multiple bundle formations along the lateral walls as a mechanism to sustain motility. The average swimming velocity, body and flagella rotation rates, the number of flagella and number of flagella bundles were extracted experimentally as a function of length. The extracted experimental parameters for normal sized cells were consistent with Purcell’s model. We explored simple adaptations and scaling of this model to describe motility for filamentous cells, which agrees with experimental values. The main focus is on collective behaviour of B. subtilis by examining the onset from individual swimming to collective motility using time-lapse microscopy. Results demonstrated a smooth transition where cells self-organize into domains expanding rapidly by recruiting cells. We present advancements in B. subtilis fluorescent flagella staining which revealed unexpected multiple flagella bundle arrangements during runs, contradictory to general conjectures. Novel visualisation of flagella filaments during reversal events is presented in both E. coli and B. subtilis cells, providing experimental evidence for complex flagella ‘flipping’. Cellular reversal is hypothesized as a mechanism for quorum polarity facilitating collective swimming. We present novel flagella imaging in the setting of collective behaviour showing evidence to support quorum polarity. Subsequently we extracted the run length distributions of cells as a function of concentration, yielding a decreasing trend with increasing concentration. Using particle tracking we quantitatively extracted the mean squared displacement of swimming cells versus passive tracers at different concentrations during collective swimming, these novel results are discussed in respect to recent simulations. These presented experiments provide new insights into collective behaviour improving current understanding of this phenomenon.

The material that is covered in this thesis concerns the calibration and application of a set of optical tweezers to be used for one- and two-point micro-rheology experiments on hard sphere colloidal suspensions. The colloidal suspensions that were used in this study were all quasi-monodisperse density- and refractive index-matched PMMA particles that had a radii, a = 0:90 ± 0:05μm or a = 0:86 ± 0:07 for one-point microrheology experiments and radii a = 0:90 ± 0:05μm or a = 0:133 ± 0:010μm for the two-point micro-rheology experiments. By collecting the forward scattered light from a single optically trapped particle the particle's displacements in time were used to determine passive microviscosity, η(Passive) μ , for colloidal suspension in the range of 0:10 < Ø < 0:57 and comparison with literature data has been made and agreement found. Actively dragging an optically trapped particle through suspensions with volume fractions of the same range has yielded the active microviscosities, η(Active) μ , for both high and low shear regimes, displaying shear thinning behaviour. Comparison to literature data has been made and agreement found as well. Collecting the forward scattered light from two optically trapped particles has been used to determine the cross-correlated motion of the two particles in bare solvent and in suspensions with volume fraction Ø = 0:02. The friction coefficients ξ1;1 and ξ1;2 were extracted from the cross-correlated motion of the particles and agreement was found with theoretical predictions for bare solvent only. The suspensions with volume fraction Ø = 0:02 were found to have a friction coefficient ξ1;1 that was greater than what theory predicted with the suspension with bath particles a = 0:90 ± 0:05μm had the greater magnitude. The magnitude ξ1;2 was found to decrease for the suspension with bath particles of radius a = 0:133 ± 0:010μm and to increase for the suspension with bath particles a = 0:90 ± 0:05μm.

Continuous cover forestry (CCF), an alternative forest management approach to clearfelling, is increasingly being adopted in the UK. It aims at enhancing stand structural diversity and favouring natural regeneration and subsequent seedling growth below the existing canopy of plantation forests. One area of limited knowledge is the critical level of below-canopy light for the growth of naturally regenerating seedlings. In addition, plant growth beneath canopies is influenced by other factors (e.g. herbivory). Picea sitchensis (Bong.) Carr. (Sitka spruce) seedlings under canopies have been observed to be severely damaged by Elatobium abietinum (Walker) (green spruce aphid) attacks. The combined effects of light availability and insect attack on seedling growth are not well understood, however, this understanding is crucial in order to ensure successful management of regeneration within CCF systems. A controlled experiment, which mimicked different natural understorey light levels along with repeated artificial aphid infestation, was conducted over two years to look at seedling performance through structural and physiological (chlorophyll fluorescence) measurements. Aphid population assessments showed significant increased population density under shaded conditions. Nevertheless, aphid impacts were mainly localised in extent while the impact of light was the major component that described seedling growth. Light was the primary factor affecting the whole-plant biomass, whereas aphids had only localised effects on the total dry weight of older needles and roots, and on leader extension growth. A significant interaction between light levels and presence/absence of aphid infestation was found for main leader extension growth of the seedlings during the second year of the experiment, with lower values at low light levels under infestation. Plant biomass allocation was affected strongly by light, while aphid presence did not result in significant changes. At the leaf physiologylevel, the light environment was found to be the main driving factor affecting photosynthetic response, whilst aphid presence had only a short-term localised effect on photosynthesis. The impact of light levels and aphid presence on seedling growth were also determined at an experimental field site where plots were located across two light regimes typical of CCF conditions in upland UK coniferous forests. The comparison of the photosynthetic response of the seedlings in both the controlled and field experiment highlighted the importance of considering the temporal heterogeneity of the light environment experienced by understorey seedlings in CCF stands, while aphid and aphid x light interaction effects could not be determined due to very low aphid levels during the year. Finally, a pre-existing light model was parameterised to predict the understorey light environment required to promote successful seedling growth in CCF stands. Sensitivity and validation analyses were also performed.

Numerous authoritarian states use institutions usually associated with democratic regimes like a constitution, elections, and a legislature. This seems to be counterintuitive. Authoritarian regimes should rather shrink away from democratic institutions. Elections can be won by the opposition and legislatures can make decisions against the interests of the ruler. So, why do autocratic regimes install institutions which limit their power and threaten their survival in office? Assuming actors behave rationally, one should expect authoritarian rulers only to introduce procedures working in their favor. This study looks at the effect of institutions in authoritarian regimes. The findings suggest that legislatures significantly lower the chances of regime breakdown in the long run. However, particularly in election years, authoritarian regimes are facing a higher likelihood of failure.

Large wildfires in California cause significant socioecological impacts, and half of the federal funds for fire suppression are spent each year in California. Future fire activity is projected to increase with climate change, but predictions are uncertain because humans can modulate or even override climatic effects on fire activity. Here we test the hypothesis that changes in socioecological systems from the Native American to the current period drove shifts in fire activity and modulated fire-climate relationships in the Sierra Nevada. We developed a 415-y record (1600-2015 CE) of fire activity by merging a treering-based record of Sierra Nevada fire history with a 20th-century record based on annual area burned. Large shifts in the fire record corresponded with socioecological change, and not climate change, and socioecological conditions amplified and buffered fire response to climate. Fire activity was highest and fire-climate relationships were strongest after Native American depopulation-following mission establishment (ca. 1775 CE)-reduced the self-limiting effect of Native American burns on fire spread. With the Gold Rush and EuroAmerican settlement (ca. 1865 CE), fire activity declined, and the strong multidecadal relationship between temperature and fire decayed and then disappeared after implementation of fire suppression (ca. 1904 CE). The amplification and buffering of fire-climate relationships by humans underscores the need for parameterizing thresholds of human-vs. climate-driven fire activity to improve the skill and value of fire-climate models for addressing the increasing fire risk in California.

Sand transport in hilly terrain geometry is different and complex to understand compared to horizontal pipeline, due to the influence of the geometry that greatly affect multiphase flow and sand behaviour at the dip. The overall aim of this research work is to use experimental method to investigate the effects of multiphase flow behaviour on sand transport in a dip configuration. Experimental work was carried out to understand the complex dynamic mechanisms that exist during sand multiphase flow using 2” inch dip test facility with different inclination angles of ±24° and ±12° configurations. In order determine the multiphase flow parameters and sand flow regimes, extensive data were collected and analysed from continuous local measurement of instantaneous liquid hold up and sand hold up using conductivity rings. Significant observations were made during this study from which several conclusions were made. In the air–water test, three slug behaviours were observed at the dip: complete stratified flow downhill with slug initiation at dip; stratified flow (with energetic ripple) downhill with slug initiation and slug growth upward dip; and aerated slug downhill and slug growth at the dip. These behaviours are different from published work on this subject with low angle of inclination. The data analysis revealed that the two types of slug initiation mechanisms (wave growth and wave coalescence) observed are geometry specifics. The slug translational velocities (at the dip and uphill section) were used as criterion to determine the flow condition for each slug initiation mechanism at the dip. Significant observations were made during this study from which several conclusions were made. In the air–water test, three slug behaviours were observed at the dip: complete stratified flow downhill with slug initiation at dip; stratified flow (with energetic ripple) downhill with slug initiation and slug growth upward dip; and aerated slug downhill and slug growth at the dip. These behaviours are different from published work on this subject with low angle of inclination. The data analysis revealed that the two types of slug initiation mechanisms (wave growth and wave coalescence) observed are geometry specifics. The slug translational velocities (at the dip and uphill section) were used as criterion to determine the flow condition for each slug initiation mechanism at the dip. Five sand-water flow regimes (full suspension, streak, saltation, sand dune, and sand bed) were established by physical observation and data analysis. It was also observed that sand streaks were denser towards the central line of pipe bottom in the downhill pipe than that in uphill pipe. At downhill pipe section, there were sand gathering toward the central line of the pipe bottom. The characteristics of sand transportation at the dip section were found slightly different from downhill and uphill pipe for higher sand concentrations. When dense streak occurred at the downhill, the sand particles become dispersed at the dip. The minimum transport conditions (MTC) were determined at different sand concentration. The sand minimum transport condition in the dip section was found to be slightly lower than those in the downhill and uphill section. The minimum transport condition for a single phase water flow for the 24˚ dip. test section was slightly higher (with difference of about 0.1m/s) than that of the 12˚ at the downward and upward of the dip section at low sand concentration. In addition, local sand measurements using conductivity time series results at the downhill and uphill section showed the influence of sand concentration and flow condition on sand flow patterns. The air-water-sand results showed that sand deposits occurred in uphill section after sand transport at the downhill and dip sections. This was due to different flow regimes exhibited at the different pipe sections. The stratified (wavy) flow was the dominant flow in downhill pipe; therefore sand was observed transporting within the liquid film as thin streak for most of test conditions. The slug initiation at the dip section was observed to be a major factor that influences the sand behaviour. Sand particles in the slug unit (at the dip and uphill of the pipe) were observed to be entrained in the slug body once slug is initiated, thereby changing the force vector generating turbulence flow at the front of slug body. Once the sand particles entered the film zone of the slug unit, they immediately stopped moving forward due to the film velocity significantly lower than the slug body coupled with gravity effect. . Sand particles were found to be falling back while travelling with the water film at some conditions, until they were picked up by the next slug body. The results of this work provide a better understanding to the study of multiphase flow for pipeline design and most especially sand behaviour at the dip. The sand dune regime is identified distinctively using conductivity ring technique which would assist in determining the operating conditions that allow sand dune formation. The knowledge of flow condition at full suspension of sand is an important parameter to determine the erosion rate over the life span of the pipeline. Also, the quantity of sand bed and flow condition of sand settling at the dip is useful information for production chemist in order to determine the effectiveness of corrosion inhibitor at the bottom of the pipe. In conclusion, sand transport characteristics and MTC were strongly dependent on the gas-liquid flow regime and pipe geometry; and cannot be generalised on the superficial liquid and gas velocities of the transport fluid.

The main aims of this thesis are to assess the efficiency of the current bankruptcy system in Oman and to offer specific proposals for bankruptcy reform to be adopted by the Omani legislator. Where appropriate, in proposing solutions for various issues lessons will be taken from the experience of both England and the US. This thesis consists of six chapters. The first chapter is a general introduction to the thesis which outlines the structure and scope of the study. Chapter Two critically explores the main theories underpinning bankruptcy law across the world. The aim of this exploration is to provide a general understanding of the policies underpinning bankruptcy laws and to establish the view of this thesis. Chapter Three discusses the experience of England and the US by identifying the main differences and similarities between bankruptcy proceedings in these jurisdictions; such discussion is necessary as a basis for determining the possibility of taking lessons from these developed bankruptcy regimes. Chapter Four provides a critical analysis of the current bankruptcy regime in Oman and outlines the key features of this regime. This chapter also discusses in detail the main issues with the current bankruptcy regime. This discussion includes: (1) the definition of bankruptcy; (2) the qualification of persons administering bankruptcy processes (3) ranking of creditors; (4) position of employees; (5) available alternatives under the current regime; and (6) the effect of declaration of bankruptcy on existing contracts. Chapter Five outlines the possibility of legal transplants and why it is desirable for Oman to adopt some of the bankruptcy principles that are found in England and the US. However, to avoid the risk of rejection of such transplants, this thesis will highlight the necessity of assessing the functionality and workability of western bankruptcy principles before transplanting them. This chapter also offers a proposal for future bankruptcy reform in Oman. Such reforms include having a clear statutory mandate, making bankruptcy law certain and predictable, and establishing a bankruptcy regime that encourage the rehabilitation of viable enterprises instead of liquidating them. Chapter Six is the overall conclusion of this thesis which explains the main ideas discussed and highlights the main contributions made by this study.

Economic utilisation of biogas arising from sewage sludge is hampered by the need to remove siloxanes, which damage gas engines upon combustion. This thesis applies on-line Fourier transform infrared spectroscopy to measure siloxanes in biogas upstream and downstream of the activated carbon vessels designed to adsorb siloxanes. On-line analysis provides accurate measurement of siloxane concentrations with a detection limit below the siloxane limits set by engine manufacturers, high data intensity and timely identification of breakthrough. Cost savings of up to £0.007 kWh- 1 may be realised compared to existing grab sampling. Using on-line analysis, the performance of full-scale and bench-scale carbon vessels were measured. Full-scale carbon contactors are typically operated at Reynold’s numbers close to the boundary between the laminar and transitional regimes (Re = 40 - 55). This thesis demonstrates, at full- and bench-scale, that increasing the Reynold’s number to site the adsorption process in the transitional regime increases media capacity, by 36% in dry gas and by 400% at 80% humidity. It is postulated that the change in gas velocity profile which occurs as Reynold’s number increases reduces the resistance to siloxane transport caused by gas and water films around the carbon particles, and therefore increases the rate of the overall adsorption process. In the laminar regime (Re = 31) increasing humidity from zero to 80% led to the classical stepwise reduction in adsorption capacity observed by other researchers, caused by the increasing thickness of the water film, but in the transitional regime (Re = 73) increasing humidity had no effect as no significant water film develops. It is therefore recommended that siloxane adsorption vessels should be designed to operate at Reynold’s numbers above 55. By choosing a high aspect ratio (tall and thin) both Reynold’s number and contact time can be optimised.