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First-principles studies on Pt-doped fcc MoC catalysts for low-temperature water-gas shift reaction
Get PDFThe role of hydrogen in future net-zero energy emissions is beyond doubt, both in the transport sector and stationary power generation. As the storage and transportation of hydrogen still present a huge challenge, methanol as a hydrogen carrier and portable hydrogen production have been proposed. However, the hydrogen produced by methanol through the catalytic reaction is inevitably mixed with carbon monoxide as a by-product. To ensure the purity of the hydrogen, the by-product carbon monoxide is usually controlled by the water-gas shift reaction. Thus, the development of water-gas shift catalysts at low temperatures is very important. Recently, the Pt atom doped molybdenum carbide with a face-centred cubic structure (M1/fcc MoC) has shown great catalytic potential for the low-temperature water-gas shift reaction. However, the Pt-doped fcc MoC catalyst exhibits different crystalline facets that show different physiochemical properties. More importantly, the surfaces can evolve to different surface phase structures under the H2/H2O atmosphere due to the thermodynamic stability. Therefore, the reaction mechanism of water-gas shift at different crystal faces and the phase structures of Pt1/fcc MoC remains controversial.
This work has therefore focused on systematic mechanistic studies on low-temperature water-gas shift reaction of Pt doped fcc MoC catalysts, considering the evolution of surface phase structure and different facets, based on first-principles methods including density functional theory and ab initio thermodynamics while different reaction pathways were evaluated through turnover frequencies (TOFs) calculated by the energetic span model (ESM) which is more appropriate for the catalytic cycles. The species, including OH*, O*, and H*, were all readily formed on the (001) surface according to the reaction rate constants, but the comprehensive investigation showed that the H2O*, OH*, and O* species tended to cover the (001) surface instead of H*, justifying the importance of the evolved surface in the water-gas shift reaction. Disregarding the evolution of the surface phase structure, the WGS reaction on the Pt1/(111)-Mo surface occurred mainly through the redox mechanism, whereas on the Pt1/(001) surface, it occurred mainly through the associative mechanism. However, considering the evolution of the surface phase structure, the predicted results for the WGS reaction were quite different. The Mo‒O monolayer phase enabled redox and H2O-assisted associative mechanisms to predominate on the Pt1/(111)-Mo surface, whereas the associative mechanism still predominated on the Pt1/(001) surface.
From a macro perspective, the original (111)-Mo surface cannot compete with the original or the evolved (001) surfaces in the WGS reaction. However, with the original (111)-Mo surface evolved to the thermodynamically more stable Mo‒O monolayer phase, catalytic efficiencies of the redox route and the H2O-assisted associative route could increase sharply to a level comparable with those of (001) surfaces. Thus, the (111)-Mo and (001) surfaces exhibit similar catalytic efficiencies for the WGS reaction, although through different surface phase structures and pathways
The diversifying, politicising and maturing of anglophone chick lit alongside changing feminist ideologies and genre fluidity
Get PDFThis thesis traces the evolution of the genre of chick lit, from the 1990s to 2010s, and its changing relationship with contemporary feminisms. During the 1990s and 2000s, postfeminism gained significant prominence, and the 2010s witnessed the emergence of a fourth wave of feminism. Through applying feminist concepts associated with these strands, this thesis explores the ways in which chick lit, a genre closely connected to feminism, has adapted for contemporary readers. This study offers a new perspective on contemporary literature and demonstrates how the genre of chick lit, in the 1990s and 2010s, both acknowledges and challenges discriminations based on gender, age, race, ethnicity and sexual orientation.
The thesis is comparative, and deliberately brings together ‘classic’ 1990s chick lit texts and authors (Candance Bushnell, Helen Fielding, Terry McMillan and Lauren Weisberger), with more recent publications published in the 2010s, in order to explore continuities and differences within these genre works. I analyse these texts within the context of postfeminist and fourth-wave feminist perspectives, while also considering criticisms and shortcomings within the movements. Each chapter focuses on a key theme of significance for both chick lit and feminism: Chapter 1 explores single womanhood and dating, Chapter 2 concentrates on sex and sexual politics, Chapter 3 examines friendship and women’s relationships with other women, and Chapter 4 considers representations of women’s careers and the workplace environment.
The main finding of this thesis is that the genre of chick lit has diversified, matured and become increasingly politicised, while concurrently retaining established chick lit themes and tropes. Publishers and critics have claimed that chick lit is a dead genre, narrowly defined by specific and static tropes, drawn from the genre’s heyday in the 1990s. This thesis challenges this contention by showcasing how chick lit is alive, relevant, adaptable and versatile. By comparing older and newer works, I identify a new subgenre of contemporary literature that can be termed ‘neo chick lit.’ The texts suggest a diversification and maturation of a genre which is often critiqued for its centring of young, white, middle-class and heterosexual women. My comparison of chick lit also highlights the genre’s fluid representations of changing feminist ideologies. Feminist concepts related to dating, sex, friendship and workplace remain similar in works of chick lit published concurrently with both postfeminism and fourth-wave feminism. However, there are distinctions too. Neo chick lit more overtly challenges the gender inequalities that works of foundational chick lit imply. The politicisation of the genre is most notable in this change in tone. Genre tropes and ideologies of 1990s chick lit thus persist in neo chick lit, but with some significant and important differences
The role of interpersonal trust in ‘scaling up’ negotiations from Track II to Track I diplomacy in conflict situations: a case study of the Oslo Backchannel, December 1992-September 1993
No full textIndividuals engaging in face-to-face interactions may develop interpersonal trust (IPT) based on a judgement of the other’s trustworthiness. But can an individual’s perceptions of another’s trustworthiness be transferred to others? If so, how? Existing international relations (IR) trust research has yet to address this question.
This creates a puzzle that speaks directly to the transfer issue in track diplomacy, between official diplomatic processes (Track I), and unofficial initiatives (Track II). This thesis seeks to address this puzzle testing three potential mechanisms to examine which one best explains how perceptions of trustworthiness are transferred between individuals operating at both Track I and Track II levels (‘trustworthiness transfer’). These mechanisms are tested against a single case study, the 1992-1993 Oslo Channel between Israel and the Palestine Liberation Organization (PLO).
The main conclusion of the thesis is that trustworthiness transfer takes place through the interplay of all three mechanisms, and also explains how the Oslo Channel ‘scaled up’ from a Track II initiative to a Track I process. This thesis supports the centrality of IPT and personal connections as a mechanism of transfer between Track II and Track I, and the possibility of ‘scaling up’ from one level to the next. The thesis contributes to the IR debate on IPT, proposing the concept of ‘trustworthiness transfer’ as a potential mechanism to explain how decision-makers develop perceptions of trustworthiness in scenarios where they do not directly engage in face-to-face interactions with individuals from the other side
Urban carnivores in Asia: survival, occupancy and conservation
Get PDFIncreased urbanization has led to significant changes in land use types and landscapes, resulting in substantial negative impacts on biodiversity. This thesis aims to analyze which urban environmental and biological factors affect the survival and occupancy of urban carnivores in Asia and how to develop corresponding habitat connectivity programs to restore carnivore populations.
Chapter 2 investigated the potential for carnivore survival and presence in different Asian cities through a literature search. The effects of different urban environmental variables and species' physiological traits on urban carnivore survival were assessed. Chapter 3 compares leopard cat occupancy in two cities, Shenzhen and Hong Kong, by camera trapping, and patterns of occupancy variation were assessed according to different urban environmental factors. Chapter 4 investigated the distribution range and temporal activity patterns of leopard cats in Shenzhen using kernel density estimation. The spatiotemporal distribution pattern overlap of humans, domestic cats, and dogs, as well as the interactions and potential ecological niche competition between leopard cats and the different species, are explored. In Chapter 5, potential leopard cat ecological corridors in Shenzhen were simulated using the minimum cumulative resistance (MCR) model (with cost analysis), considering the distribution density of leopard cats and environmental factors such as topography and human and social factors.
Chapter 2 found that the percentage of urban built-up area was the most critical factor affecting urban carnivore survival, with a significant coefficient of -0.5 in my regression model (p<0.05). Regarding physiological characteristics, the urban survival rate of non-diurnal carnivores was 28.4\% higher than that of diurnal carnivores. The urban survival rate of solitary carnivores was 45.1\% lower than that of group carnivores.
Chapter 3 found that the occupancy rate of leopard cats in Shenzhen was 18.8\% lower than in Hong Kong (p < 0.01). The number of leopard cats decreased with increasing distance from the road, and in Shenzhen, the occupancy probability of leopard cats was higher in agricultural areas (0.75) than in urban areas (0.35).
Chapter 4 found that the spatial overlap between leopard cats and humans, domestic cats, domestic dogs, and wild pigs was > 55\%. Regarding temporal overlap, leopard cats had the highest overlap with domestic cats, with peak activity times at 06:00 and 23:00, 3-4 hours later than the peak activity times of domestic cats (02:00 and 20:00).
In Chapter 5, combined with the estimated spatial extent of core leopard cat density, this study proposes 118 potential ecological corridors in Shenzhen to aid leopard cat migration. The 23 most important major ecological corridors were identified. The average width of the best corridors was 727 m, with a total corridor area of 97.7 and an estimated total cost of RMB 55.74 billion.
This study increases our understanding of urban carnivores in East Asia, confirms the importance of natural habitats for urban carnivores, and provides evidence that will be useful for prioritizing carnivore species conservation, controlling alien species and human disturbance, and restoring carnivore habitat connectivity.
Based on the results of this thesis, I suggest conserving remaining native habitats, restricting the expansion of urban built-up areas (for example, by laws of "ecological red lines"), and giving priority to the conservation of heavy, nocturnal, and solitary carnivores. Increased surveillance and stern action against poaching are also needed. In order to avoid endangering wild predators, my results also suggest reducing the amount of stray cats and dogs in urban habitat regions. Additionally, recreational users' access to carnivore habitats has to be controlled in order to lessen the negative effects of growing human-wildlife distributional overlap. Finally, it is important to identify the hotspots where wildlife is most active in cities, as well as the key connecting corridors that these animals use through the urban matrix. Fences that point animals in the direction of ecological corridors should also be created. When building the corridor habitat, native plants should be useful, and managers should also pay attention to the quality of the vegetation
Microstructure and oxidation behaviour of Inconel 625 manufactured by laser powder bed fusion
Get PDFThe high temperature oxidation of L-PBF IN625 was investigated following heat-treatment and surface finishing. Sub-parabolic oxidation behaviour was shown, demonstrating similar growth rates to wrought IN625. Regardless of surface morphology and stress-state, chromia (Cr2O3) scale was formed alongside a near-continuous δ-phase layer (Ni3Nb) at the scale/alloy interface. The continuity of the δ-phase layer was influenced by surface finishing via changes to the oxide morphology. Less δ-phase at the scale/alloy interface was correlated to increased spallation. This was related to modelled values for the temperature change required for spallation (ΔTC) alongside physical measurements of stress (XRD sin^2(ψ)) within the scale. It was concluded that surface finish is key in the maintenance of a continuous δ-phase layer to ensure relaxation of Cr2O3 upon cooling.
Internal oxide (Al2O3) was detected at grain boundaries in the sub-scale. Significant fractions of Coincident Site Lattice (CSL) boundaries formed in L-PBF IN625 following heat-treatment and oxidation (up to 70%). Nucleation of internal oxide was strongly influenced by grain boundary character, forming preferentially along random orientation grain boundaries. Higher fractions of CSL boundaries in the substrate corresponded to a shallower depth of internal oxidative attack.
Corrosion of L-PBF IN625 was investigated following heat-treatment and surface finishing in simulated Pressurised Water Reactor (PWR) hydrogenated water. Oxidation was not influenced significantly by L-PBF microstructure, but by changes to surface finish. Rougher and/or stressed surfaces led to scale spallation at early exposures. Mass gain was observed after 1500 hours (h), with similar oxide crystallite size and morphology to wrought IN625. No pitting corrosion was observed. A duplex layered oxide formed, comprised of an Fe-rich outer scale (Ni(Fe,Cr)2O4), on a Cr-rich dense inner scale. Grain orientation directly influenced oxidation. EBSD revealed the following grain orientation-oxidation relationship, in order of increasing oxidation rate: [100] < [101] < [111]. Overall, electropolished surfaces were deemed most suitable for PWR environments
A mixed methods study to explore the impacts of screens and social media use on mental health, sleep, and physical activity among adolescents in China
Get PDFGeneration Z adolescents grow up in a social media environment. Some studies based in Western countries and high-income countries have shown social media use is associated with several health-related outcomes. This study focuses on Chinese adolescents, given the unique social media context of China, and explores the association between screen time, mobile phone and social media use, and a series of health-related outcomes (mental wellbeing, sleep, and physical activity).
The study is a mixed methods design. The quantitative study involved 4791 Chinese adolescents (ages 12–15, years 2020-2021) in a cross-sectional survey. The qualitative study involved 48 adolescents (ages 12-15, years 2020-2021) who participated in 8 focus groups. Findings from the two studies were integrated through the explanatory design.
The results of the quantitative study indicated that moderate social media (less than 2 hours) use may have beneficial associations with health outcomes such as higher mental wellbeing, and lower depression, and higher intensity activity in leisure time. Greater than two hours of social media use had detrimental associations with a wide range of health problems, such as poorer sleep quality, higher levels of anxiety, less numbers of days adolescents are physically active for at least 60 minutes, and less sleep duration. The findings of the qualitative study centred on three main themes of interaction, accessibility, and supervision in relation to social media use and physical activity: adolescents communicated with peers, celebrities, internet celebrities, and friends about physical activity on social media; it provided a range of opportunities and resources for learning about physical activity; and social media also acted as a supervisory tool for adolescents' physical activity. The mixed methods study, through integration of the findings relating to the associations between social media use and physical activity and the qualitative findings relating to the content and types of physical activities accessed through social media, brings a more comprehensive understanding of how social media affects adolescents' physical activity.
This study provides a better understanding of the uses of social media in relation to mental health/wellbeing, sleep, and physical activity among Chinese adolescents, mitigating the research gap left by previous studies conducted in Western countries and high-income countries. The findings of the mixed methods study will help to inform future public health approaches to encouraging physical activity in this age group using social media as a tool. This may also have wider relevance to public health approaches which aim to promote adolescents' development and health
Data-driven classification approaches for radar bird-drone surveillance
Get PDFThis thesis addresses the topic of drone classification using radar spectrograms to provide warning of unauthorised drone intrusions. Radar is an excellent detection sensor, but the similar size, speed and flying height of drones and birds necessities the development of robust methods for target classification. Deep learning approaches may allow classification of drone targets in benign and challenging circumstances, but in a security critical scenario where lives may be at stake, several advances in their training and validation are required. This thesis seeks to accelerate the reliability of deep learning approaches, and to substantiate such developments a collection of 564 drone flights and 932 bird tracks were gathered over ranges up to 5km by two L-band staring radar systems in a high-clutter, densely urban environment at the heart of Birmingham, England. Raw-data spectrograms crafted from these flights were used to train and test a convolutional neural network for the classification of real targets in a challenging operational condition, where we show drones possessing rotor micro-Doppler can be classified to >98% accuracy, while drones without any micro-Doppler are still able to be classified ∼90%.
As radar data is usually a scarce resource, this thesis also proposes approaches for synthetically increasing the quantities of available data, and additionally, a method to use such limited data more effectively in the training of classifiers. Initially, this work shows the production of highly-realistic synthetic micro-Doppler spectrograms that novelly uses motor speed recordings extracted from drone flight logs. This approach vastly increases the ease of creation and visual fidelity of simulated drone returns. The resampling of the recorded motor speed signal to fit the radar’s temporal reference was shown to have a strong effect on the results achieved with synthetic training. Finally, unsupervised deep learning implemented with an elementary convolutional autoencoder trained with a modest amount of synthetic and real radar data, was demonstrated to have both performance and interpretability advantages over the use of an optically trained, transfer learned classifier
Measurement of extracellular vesicles by a novel fluorescent imaging method
Get PDFExtracellular vesicles (EV) are small phospholipid delimited particles released by virtually all cells that cannot replicate. EV are difficult to measure, partially due to their small size and isolation contaminants including lipoproteins. EV isolation and measurement are not standardised and can be associated with bias in measured populations. An instrument that can measure EV in complex biofluids without the need for isolation may improve standardisation of EV research. The use of immunoaffinity capture combined with fluorescent labelling would allow for a greater depth of phenotypic characterisation and could have use diagnostically with EV increasingly being identified as biomarkers of health and disease. Here I test whether ExoView, a new chip-based immunocapture platform for EV measurement, can measure EV without the need for purification.
I generated platelet enhanced plasma (PEP) a platelet EV (PEV) enriched plasma with high procoagulant activity, as measured through thrombin generation and clotting assays. I designed a protocol for measurement of phosphatidylserine (PS) using ExoView which confirmed high PS expression on EV in PEP compared to platelet free plasma (PFP). I also investigate whether PEP may hold potential as a novel resuscitation fluid for use in austere environments where platelets are often unavailable.
Having found ExoView to be capable of measuring PS on EV, I next moved to a trace protein that is also involved in clotting: tissue factor (TF). TF is a lowly expressed protein that can be EV associated. In addition to historic EV measurement problems, TF has its own historic and ongoing controversies. However, a reliable method of TF EV quantification would be useful clinically in ovarian cancer, pancreatic cancer and venous thromboembolism. I utilised custom capture with ExoView to enrich TF expressing EV from plasma followed by fluorescent labelling with a separate anti-TF clone and found ExoView can distinguish unstimulated vs lipopolysaccharide stimulated PFP. However, my TF EV method could not distinguish healthy PFP from clinical cohorts (cancer or trauma).
PEV and megakaryocyte (MK) derived EV are thought to be the largest EV population in circulation, however due to their similar parental lineage unique markers of either are difficult to identify and validate. They are interesting to distinguish as a change in the ratio of PEV:MK EV may indicate an increased risk of cardiovascular disease or may reflect bleeding risk in patients on antithrombotic therapeutics. I utilised ExoView and theoretically unique markers of PEV and MK EV on purified platelet supernatants and MK cell culture supernatants to try and identify unique signatures of PEV and MK EV which were then applied to PFP. The set of markers I used and the conditions I tested did not reveal a unique signature of PEV or MK EV that could be used to determine whether PEV or MK EV are more the more dominant EV source in circulation.
In conclusion, this thesis shows that ExoView has great capacity for EV measurement both in basic characterisation of EV-enriched markers such as tetraspanins, but also has potential for measurement of clinically relevant, rare subpopulations of EV
Super-resolution techniques and waveform design for radar and dual-function radar and communication systems
Get PDFModern vehicles are densely equipped with sensors, and the space available for these sensors is restricted. In this thesis, firstly, novel waveforms that enable simultaneous radar sensing and communication using a single chipset are designed with the aim of not only reducing the quantity of sensor components and the amount of sensor space on the vehicles but also enhancing the spectrum efficiency by utilising the same frequency for both systems. Such waveforms are subsequently utilised for radar sensing with multiple input multiple output (MIMO) beamforming, resulting in better angular resolutions and higher data rates. The validation of the proposed waveforms for both radar and communication is carried out through simulations and experimentation.
Second focus of this thesis is on the antenna design and autoregressive methods. It is known that high angular resolutions are required in automotive radars to extract detailed information about the scene, which can be fulfilled by using large antennas/arrays but may restrict its suitability for applications in vehicle infrastructure. With the purpose of achieving high angular resolutions yet with reduced number of total antenna elements, sparse MIMO antennas are designed using optimisation techniques. Although sparse MIMO arrays are a solution to reduce the cost and weight of the antenna, it requires the same physical size of the antenna as conventional MIMO arrays. With the aim of attaining high angular resolution while keeping the size of the physical antenna compact as well as reducing the number of total antenna elements, the extrapolation and interpolation approach using autoregressive Burg algorithm is developed here to design virtual array elements towards both azimuth and elevation directions. Finally, to achieve further improvement in angular resolutions, motion of the MIMO radar platform is exploited through Doppler beam sharpening (DBS) technique. This thesis proposes a technique that applies the Burg algorithm to MIMO radar data collected by motion of the radar platform to enhance the cross-range resolution in both on- and off-boresight directions. The performance of the proposed methods is evaluated through both simulations and experiments at 77 GHz
Causation and non-reductive physicalism: from overdetermination to multiple realisability
Get PDFThe first of three papers tackles the argument from causal overdetermination. I begin with an elaboration of the causal overdetermination argument. Two premises of this argument are focussed upon: the causal closure premise and the overdetermination premise. Causal closure states that for every physical event with a cause, it has a sufficient physical cause. Overdetermination states that there is no widespread or systemic overdetermining of effects, with overdetermination defined as an instance where one effect has two or more causes where any individual cause would be sufficient to bring about the effect. Following this, I provide several assumptions which underwrite those premises: the causal relata assumption, the causal relation assumption, and the causal singularism assumption, which I refer to collectively as “the sparse view”. Then, several canonical and original arguments against the causal closure premise are outlined, and the ways in which these arguments involve rejection of the highlighted assumptions is brought to attention. Finally, I consider these assumptions as they pertain to the overdetermination premise. I offer a novel assumption, “notional ubiquitous overdetermination”, which supposes a number of sufficient causes across levels of reality for quotidian events. This is defended as an intuitive starting point in opposition to causal singularism, an assumption which prioritises physical causation and which I take to underline the intuitive force of the overdetermination premise.
My next paper concerns the exclusion argument against non-reductive physicalism, due to Kim. I summarise the exclusion argument, which concludes that mental properties are ruled out as causes under non-reductive physicalism under certain seemingly reasonable premises. The paper addresses the exclusion premise specifically, which holds that there cannot be both a sufficient mental and physical cause for some later event. I consider Edwards’ Dictum, holding there to be a tension between vertical determination and horizontal causation, as an intuitive basis for the exclusion principle. The basic idea is that we do not require a prior mental cause, M1, of some future mental effect, M2, where there is already a physical property giving rise to M2 at that time. I consider the basis of the Dictum at length and suggest a disanalogy between the original use of Edwards’ Dictum and its use in support of an exclusion principle for mental and physical events. With exclusion undermined, a novel model is presented which allows for autonomous mental causation of macrophysical or everyday events in line with our common-sense understanding. I draw upon work by List and Menzies, and Yablo, to show that mental causes are commensurate with certain effects in a way that microphysical putative causes are not. The other part of my model involves incorporating behaviours as commensurate with mental events such that we can assert that some prior mental cause leads to some behavioural, macrophysical event. With Edwards’ Dictum and Kim’s exclusion principle undermined earlier in the paper, this model can allow for mental causation at a higher level without excluding base-physical properties as the generative bases of all those mental and behavioural events. The final section of the paper addresses some potential objections to the model. Causation and dependence or generation are thus not in competition, and mental causation is preserved for the non-reductive physicalist.
My third and final paper likewise concerns non-reductive physicalism. Non-reductive physicalism is motivated by multiple realisability, which pushes physicalists away from type-identity given the possibility of multiple physical properties being co-extensive with the same mental property. I suggest that the failure of type-identity, coupled with a persisting philosophical commitment to the notion that mental properties are dependent on and nothing-over-and-above physical properties, leads to the adoption of a certain type of relation by non-reductive physicalists to characterise the mental-physical relation. I call such relations “thin non-identity”, since they either involve identity somewhere in their formulation- say an identity between causal powers rather than the properties themselves- or they risk dissolution into identity on close inspection. Multiple realisability concerns re-emerge for such positions, if this is right. I suggest that one can satisfy the dependence commitment without maintaining that mental properties are nothing-over-and-above physical properties, and provide reasons for supporting a loosened “Nothing-Left” constraint instead which maintains the intuitive appeal of nothing-over-and-above without overly constraining theory-building. Next, two proposed formulations of non-reductive physicalism are introduced with this loosened constraint in mind, and which construe the mental-physical relation as causal, though not diachronically causal. I show not only that such views, once elaborated, can maintain mental properties are wholly dependent upon physical properties in an intuitively satisfying way, but that such formulations avoid multiple realisability objections and carry various theoretical benefits that prior formulations of non-reductive physicalism lack. Non-reductive physicalism is thus protected from the threat of multiple realisability, and either of my proposed solutions are also shown to fit with the sort of causal solution to the exclusion problem posited in my second paper. My thesis concludes, then, with non-reductive physicalism protected from the overdetermination argument, the exclusion argument, and concerns about multiple realisability, along with novel models of both non-reductive causation and mental-physical relations
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