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Using theoretical chemistry to understand the properties of Polyoxometalates and their potential as energy storage materials
Get PDFPolyoxometalates (POMs) are very appealing compounds as these transition metal oxide nanoclusters exhibit the ability to store multiple electrons
in a reversible manner. Recently, POM-based energy storage devices, like redox flow batteries (RFBs) and alkali-ion batteries, have been extensively employed, since they meet equally the need of higher energy demand and low
impact on the environment. However, POM-based technologies are still at
early stage of development, mostly because of the difficulties to understand
POM electronic behaviour.
In this PhD thesis, it has been presented a theoretical study of POMs in
different environments in order to understand the basic mechanisms behind
their behaviour. In the first part, a general overview of electronic structures
of POMs is given. Furthermore, the advantages and limits of POM-based
batteries are discussed in detail. In Chapter 2 the state-of-the-art theoretical
approaches used to study POMs are discussed, in particular, strong emphasis is given to the density functional theory (DFT), and both classical and
quantum molecular dynamics (MD). In the third Chapter, the redox properties of POMs are investigated by means of simulations in an implicit and
explicit environment. The implicit solvation is semiquantitative, and uncertainties arise due to the limit of the model. Quantum MD simulations reveal
that an explicit environment can improve the calculated redox potentials of
POMs, providing useful insights into their molecular nature. A spectroscopic
study of x-ray absorption near-edge spectra (XANES) and extended x-ray absorption fine structure (EXAFS) is presented in Chapter 4. These techniques
alongside with first-principles calculations have shown to be powerful tools
to unveil the structure-property relationships of super reduced POMs. Chapter 5 is devoted to the study of self-assembly process of POMs. Classical
MD simulations show that a rich network of hydrogen bonds mediates the
POM-POM interaction, and their agglomeration strongly depends on total
charge. Furthermore, first-principles calculations illustrate the effect of POM
agglomeration on their redox potential, and catalytic efficiency towards the
hydrogen evolution reaction.
The results from this study show that it is now possible to adopt a range of
computational approaches to understand the properties of POMs in different
physical contexts. Specifically, the advantages and limits of DFT have been
highlighted when computing the redox potentials of POMs, showing that
further accuracy and insights into their electronic structure can be achieved
by explicitly including the solvent molecules. For instance, it has been shown
that the POM ability to undergo multiple redox reductions is due to possibility of delocalizing further electron density over all metallic atoms, regardless
of the POM type. This behaviour is linked to their molecular structure, which
undergoes an elongation of metal-oxygens bond lengths and formation of
metal-metal bonds when further electrons are added to POMs. Furthermore,
the inclusion of an explicit environment was shown to be an important factor
to understand other properties of POMs, like the profile of their x-ray spectra
or the self-assembly process. In the first case, QM/MM calculations shows
that the polariazation of POM electron density returns more realistic molecular structures with respect to static DFT calculations, thus influencing the
sensitivity of their simulated x-ray spectra. On the other hand, MD simulations revealed that the dynamical behaviour of POMs and the formation of
long-lived agglomerates depends on several factors, like the total charge of
POM, its counter ions, and solvent
Defining the effector(s) and mechanism(s) by which enteropathogenic E. coli (EPEC) inhibits Akt signalling upstream of PI3 kinase
Get PDFPh. D. Thesis.Disease associated with enteropathogenic Escherichia coli (EPEC) depends on a
Type 3 Secretion System (T3SS) that delivers ‘effector’ proteins into infected cells.
The EPEC E2348/69 strain has approximately 6Mb of horizontally acquired DNA
provided, mostly, by 21 prophage (PP) and integrative element (IEs). The T3SS,
six effectors and two chaperones - latter aid the export of T3SS substrates - are
encoded on an IE named LEE (Locus of Enterocyte Effacement). The remaining
effectors are encoded on 7 other IE/PPs. EPEC inhibits the activity of a host kinase,
Akt, that regulates important cellular processes, including cell survival, but the
responsible effectors and inhibitory mechanism remain undefined. Previous work
discounted roles for 17 of 21 known effectors but linked the inactivation process to
Akt dephosphorylation in a manner requiring the LEE chaperone, CesT. Here,
additional screening strategies undertaken to identify the responsible effector(s)
uncovered key but redundant roles for two, previously unexamined, T3SS
substrates: LifA (3223 residue, IE6-encoded) and LifA-like (2624 residue, IE2-
encoded) proteins. These proteins have putative glycosyltransferase and protease
activities with LifA thought to be delivered into host cells. Other studies support
CesT dependence of the inhibitory process and, surprisingly, revealed LifA’s
inhibitory activity requires IE2-encoded factor(s). Screening IE2-related fragments
implicated factor(s) on a cloned 1.7kB region but further studies are needed to
confirm the results and provide mechanistic insights. Studies on LifA’s inhibitory
mechanism revealed its T3SS- and CesT-dependent accumulation with host
membrane proteins with dephosphorylation of Akt not requiring motifs needed for
its known glycosyltransferase and protease activities. By contrast,
immunoprecipitation studies linked the inhibitory mechanism to O-glycosylation of
Akt and revealed infection-induced O-GlcNAc of an Akt-sized band that gradually
disappeared in a T3SS-dependent manner. Studies described in this thesis not
only identify the EPEC effectors responsible for inhibiting Akt activity, but also
provide important insights into the inhibitory mechanism
A Formal Methodology for Engineering Heterogeneous Railway Signalling Systems
Get PDFPh. D. Thesis.Over the last few decades, the safety assurance of cyber-physical systems has become one of the
biggest challenges in the field of model-based system engineering. The challenge arises from an
immense complexity of cyber-physical systems which have deeply intertwined physical, software
and network system aspects.
With significant improvements in a wireless communication and microprocessor technologies,
the railway domain has become one of the frontiers for deploying cyber-physical signalling
systems. However, because of the safety-critical nature of railway signalling systems, the
highest level of safety assurance is essential. This study attempts to address the challenge of
guaranteeing the safety of cyber-physical railway signalling systems by proposing a development
methodology based on formal methods. In particular, this study is concerned with the safety
assurance of heterogeneous cyber-physical railway signalling systems, which have emerged by
gradually replacing outdated signalling systems and integrating mainline with urban signalling
systems. The main contribution of this work is a formal development methodology of railway
signalling systems. The methodology is based on the Event-B modelling language, which
provides an expressive modelling language, a stepwise model development and a proof-based
model verification. At the core of the methodology is a generic communication-based railway
signalling Event-B model, which can be further refined to capture specific heterogeneous or
homogeneous railway signalling configurations. In order to make signalling modelling more
systematic we developed communication and hybrid railway signalling modelling patterns.
The proposed methodology and modelling patterns have been evaluated on two case studies.
The evaluation shows that the methodology does provide a system-level railway signalling
modelling and verification method. This is crucial for verifying the safety of cyber-physical
systems, as safety is dependent on interactions between different subsystems. However, the study
has also shown that automatic formal verification of hybrid systems is still a major challenge and
must be addressed in the future work in order to make this methodology more practical.(EPSRC and Siemens
Rail Automation
Control and visual navigation for unmanned underwater vehicles
Get PDFPh. D. Thesis.Control and navigation systems are key for any autonomous robot. Due to environmental
disturbances, model uncertainties and nonlinear dynamic systems, reliable functional control is
essential and improvements in the controller design can significantly benefit the overall
performance of Unmanned Underwater Vehicles (UUVs). Analogously, due to electromagnetic
attenuation in underwater environments, the navigation of UUVs is always a challenging
problem.
In this thesis, control and navigation systems for UUVs are investigated. In the control field,
four different control strategies have been considered: Proportional-Integral-Derivative Control
(PID), Improved Sliding Mode Control (SMC), Backstepping Control (BC) and customised
Fuzzy Logic Control (FLC). The performances of these four controllers were initially simulated
and subsequently evaluated by practical experiments in different conditions using an underwater
vehicle in a tank. The results show that the improved SMC is more robust than the others with
small settling time, overshoot, and error.
In the navigation field, three underwater visual navigation systems have been developed in the
thesis: ArUco Underwater Navigation systems, a novel Integrated Visual Odometry with
Monocular camera (IVO-M), and a novel Integrated Visual Odometry with Stereo camera
(IVO-S). Compared with conventional underwater navigation, these methods are relatively
low-cost solutions and unlike other visual or inertial-visual navigation methods, they are able to
work well in an underwater sparse-feature environment. The results show the following: the
ArUco underwater navigation system does not suffer from cumulative error, but some segments
in the estimated trajectory are not consistent; IVO-M suffers from cumulative error (error ratio is
about 3 - 4%) and is limited by the assumption that the “seabed is locally flat”; IVO-S suffers
from small cumulative errors (error ratio is less than 2%).
Overall, this thesis contributes to the control and navigation systems of UUVs, presenting the
comparison between controllers, the improved SMC, and low-cost underwater visual navigation
methods
Foreign direct investment location and tax incentive policy in Indonesia
Get PDFPhD ThesisForeign Direct Investment (FDI) has become a ‘mantra’ for developing countries, as not only
is it a source of capital to boost economic development, but an important source of employment
and technology. Many developing countries provide incentives to attract foreign investors, such
as preferential taxes, but the evidence for these is mixed. Some find they are important, but
others that they do not affect FDI location. Indonesia is of interest, since it is a large and rapidly
developing Asian economy, which has pursued a policy of ‘openness’ towards FDI. This is
supported by a programme of taxes and other incentives, but despite using these measures for
more than fifty years their effect is uncertain, and they remain controversial.
The purpose of this thesis is to analyse the characteristics of FDI location in Indonesia and to
explore the role of tax and other incentives. Overall, the thesis makes three main contributions.
First, it provides an up-to-date analysis of FDI location in Indonesia using an original dataset
and covering the ‘New Order’ period from the mid-1990s. Second, it undertakes a large-scale
questionnaire survey of foreign-owned plants in Indonesia to establish their nature and motive
for location. Third, the thesis carries out face-to-face interviews with Indonesian policymakers
at a high-level to explore the rationale for inward investment and tax incentive policies.
Inward FDI to Indonesia has grown steadily over the last decade, and it is now about US$20
billion per annum. This represents about 2.1% of Indonesian GDP, while comparable domestic
investment is about two-thirds smaller, indicating its importance. Making use of realization
data provided by the Indonesian Investment Coordinating Board, the thesis shows that the vast
majority of FDI in Indonesia is located on Java, the most populous region, and reflects market
and labour resource-seeking. Regions outside Java are important more recently and are a target
for FDI in mining and agriculture, especially from Europe and America. However, most FDI
is from Asia, especially Singapore and Japan. The manufacturing share of FDI has increased
over time, although the mean project size is smaller. The thesis finds a sharp division between
the Special Areas, in which the incentives are applied intensively, as FDI seeks labour resources
and exports, whereas outside these areas it supplies the domestic market.
The survey shows that tax incentives are not the main factor for influencing investors’ decisions
to locate in Indonesia. Thus, while investors include these incentives in their appraisal, they
tend not to be the critical factor for investment in Indonesia. This seems to be well-perceived
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by policymakers, so that political economy considerations are important for the continuance of
these incentives. Other developing countries offer these incentives, so that the expectation of
investors and policymakers is that these subsidies will also be available in Indonesia. Further,
the tax incentives have largely evaded scrutiny, and the location of FDI has been attributed to
other factors. Finally, by being seen to ‘do something’ to attract FDI in a fairly minimal way,
the tax incentives are a means by which the government garners political support.The government of
Indonesia, which sponsored my PhD study through the Indonesia Endowment Fund for
Education (LPDP
Bodies, cultures and health: young people constructing and contesting gender and sexuality through design and digital technology
Get PDFPh. D. Thesis.Digital technology holds a pivotal role in the construction of young people’s gender
identities and sexualities. Concern revolves around adult fears associated with risk and
danger, yet digital technology can also radically reconstitute how young people construct
and contest gendered and sexual identities. In this thesis, I use a method pioneered in
Human-Computer Interaction (HCI) and design, Design Workshops, to explore empirically
young people’s talk around gender, sexuality and digital technology, analysing this
workshop data in a thematic discourse analysis informed by Discursive Psychology. First, I
analyse a body-mapping activity, where I examine how young people collectively constitute
the sexual body with socio-cultural scripts, arguing that young people rehearse
traditionalistic scripts of sex, sexuality and appearance, yet navigate mature (visual)
gendered and sexual identities through notions of self-authentication, individuality and
rebellion. Second, I examine how young people navigate gendered and sexual cultures
through their talk about digital technology, finding that young people use this talk to assert
positions of a mature sexual self, make judgements about correct/incorrect sexual conduct,
and make inquiries of sexuality, particularly in relation to marginalised sexual practices.
Finally, I look at strategies of designing for sexual health with young people through two
prototype interventions, where I illustrate the importance of acknowledging young people’s
positionality. This thesis expands on the method of Design Workshops, and of research
around young people’s sexual identities, arguing that the interactional analysis of
collaborative sense-making activities in this context provides a lens to analyse for, and
design around, young people’s positionality as sexual agents. My conclusions discuss the
value of analysing workshop data from a discursive standpoint and, using this, indicate
culturally relevant ways of introducing a ‘discourse of desire’ around young people’s
sexualities for UK sexual health context
Mathematical Modelling of Oxygen and Glucose Conditions for Mesenchymal Stem Cells in Culture and Bone Marrow
Get PDFEngD ThesisThe prevalence of 3D tissue culture systems is increasing in order to overcome the
perceived limitations of 2D culture in terms of providing a biomimetic niche for cells.
However, the move to 3D systems requires that the availability of nutrients and
oxygen within a 3D system is understood. The aim of this project was to develop
mathematical models which would allow conditions in 2D and 3D culture and in vivo
to be better understood. A mass transfer model was developed using physical data
from experiments, the conservation of mass and Fick’s law of diffusion, using the 2D
and 3D culture of mesenchymal stromal cells as an exemplar system.
The model was then used to create oxygen and glucose profiles in 2D and 3D
(spheroids and suspension) culture to provide a basis for comparison between the
different systems. Predicted mass transfer of oxygen was found not to be affected by
spheroid culture when compared to 2D culture, however mass transfer of glucose
was restricted creating significant glucose concentration gradients through the
spheroids. The predicted profiles in spheroid culture were applied to other culture
systems with the aim of inducing the changes observed in the mesenchymal stromal
cells in spheroid culture Altered glucose concentrations were not sufficient to induce
dedifferentiation in 2D adherent mesenchymal stromal cells nor result in the same
cell size decrease as seen in 3D spheroid culture. Using suspension cultures, a
comparable size decrease to 3D spheroid culture was observed. Mass transfer
modelling of the in vivo mesenchymal stromal cells environment in bone marrow was
also developed to compare the in vitro culture conditions to the natural environment.
It is concluded that oxygen concentrations within cell culture are lower than in bone
marrow but relatively stable in the culture systems modelled. Glucose concentrations
are significantly reduced within spheroid culture
Anxiety in Autism Spectrum Disorder (ASD) : the influence of executive and sensory processing dysfunctions
Get PDFPh. D. Thesis.Introduction: Autism Spectrum Disorder (ASD) is a neurodevelopmental
disorder associated with difficulties with social communication and the presence
of restricted and repetitive behaviours. There is significant heterogeneity of
symptom profiles within the disorder. Anxiety is very common in individuals with
ASD. Previous research suggests associations between executive function
deficits and sensory processing atypicalities and anxiety in ASD, though neither
relationship has been explored in detail. Aims: To examine the putative
relationships between anxiety, executive function difficulties and sensory
processing atypicalities in children with ASD, taking into account potential
heterogeneity within the sample. Method: Thirty six families with a child with
ASD were recruited. The children completed an anxiety questionnaire and
standardised assessments of executive function. Parents completed
questionnaire about their child’s anxiety, sensory processing difficulties and
autism severity. 22 parents completed a follow-up study of their child’s anxiety,
everyday executive function and repetitive behaviours. Correlational analysis
and cluster analysis were used to examine the data.
Results: Anxiety scores were high and remained stable over a twenty month
period. No significant associations were found between objective measures of
executive function difficulties and anxiety, though parent reported child
executive difficulties were associated with heightened parent reported child
anxiety.High anxiety was associated with sensory processing atypicalities, and
higher levels of ASD severity. Importantly, cluster analysis revealed distinct
subgroups of children in relation to anxiety, sensory and executive profiles,
illustrating heterogeneity within the sample.
Conclusions: The findings supports previous research that anxiety is high in
children with ASD and remains high over time and is associated with sensory
processing atypicalities. The relationship between executive function and
anxiety varied as a function of the source of the data. Cluster analysis illustrates
the importance of considering heterogeneity in ASD. Implications for clinical
practice and future research are discussed.Ministry of Health Malaysi
The Effects of Cigarette Smoke on Airway Smooth Muscle Function
Get PDFPh. D. Thesis.Cigarette smoking is the largest risk factor for developing chronic obstructive pulmonary
disease (COPD), which is associated with hyperresponsiveness of airway smooth muscle.
While it is well established that chronic exposure to cigarette smoke (CS) leads to dysregulated
calcium signalling, airway inflammation and remodelling of the airway smooth muscle, there
is limited information about the acute effects of CS or CS extract (CSE) on human airway
smooth muscle cell (hASMC) function, particularly Ca2+ homeostasis. Dysfunction of the cystic
fibrosis transmembrane conductance regulator (CFTR) anion channel is also linked to disrupted
Ca2+ homeostasis in ASMC, but its role in ASMC function remains poorly understood.
This study investigated the following: (1) The role of CFTR in regulating Ca2+ homeostasis in
ASMC; (2) The acute effects of aqueous CSE on hASMC Ca2+ homeostasis; and (3) The acute
effects of gaseous CS on hASMC Ca2+ homeostasis. The results demonstrate that (1) CFTR
inhibition in rat ASMC had minor effects on store-operated Ca2+ entry and the extent of Ca2+
reuptake; (2) Acute exposure to CSE or CS rapidly elevated cytosolic Ca2+ in hASMC through
stimulation of plasmalemmal Ca2+ influx, but not through the release of calcium from
intracellular sarcoplasmic reticulum stores; (3) Both CSE and CS specifically stimulated Ca2+
influx through the neurogenic pain receptor channel, transient receptor potential ankyrin 1
(TRPA1), but not through L-type or store-operated Ca2+ channels; (4) The CSE/CS-induced
calcium influx through TRPA1 led to myosin light-chain phosphorylation, a key process
regulating ASMC contractility.
Overall, results suggest that CFTR plays a minor role in regulating calcium homeostasis in
ASM. However, this study provides the first experimental evidence that TRPA1 is an important
target of both CSE and CS in hASMC. The CSE/CS-induced activation of TRPA1 may lead to
exacerbated ASMC contraction thus contributing to airway hyperresponsiveness in COPD.Newcastle Universit
Impacts of quality management relations on sustainability performance
Get PDFPhD ThesisThis study utilises the business relations theory as the theoretical lens to illustrate the links between quality management relations and the three dimensions of sustainability. The goal is to investigate the influences of the internal and external dimensional views of quality management (QM) relations in enhancing sustainability performance empirically. The internal quality management relations are associated with management and employees’ factors, while the external quality management relations are connected with customers’ and suppliers’ factors. Sustainability performance is measured through the social, environmental, and economic sustainability performance dimensions, which represent the triple bottom line (TBL).
Additionally, this study examines the moderating impact of stakeholder pressure on the relationships between quality factors and sustainability dimensions. Also, the mediating effects of quality training, employee relations, supplier relations and customer relations were tested. Finally, this study examines group differences between the service and manufacturing sectors to enhance the generalisation of the survey findings. From this, a model is established to examine 24 hypothesised relationships.
Questionnaires were used to collect data from top managers of 467 UK service and manufacturing firms. Statistical analysis and structural equation modelling (SEM) techniques were applied to test and analyse the data.
The findings show that internal and external quality relations contribute to sustainability performance directly and indirectly, from management relations (MR) through employee relations (ER), customer relations (CR) and supplier relations (SR). Also, the results show that management relations (MR) supports other QM relations and is indirectly related to sustainability performance. The main effects were spread across the service and manufacturing sectors, and the results helped to identify the impact of different QM relations across different sustainability performance dimensions. The moderation results show mixed outcomes for QM relations and sustainability performance.
This study is relevant for academics and practitioners as it focuses on significant QM management relations that are beneficial for the triple bottom line (TBL) of firms. This research contributes to the streams of business relations research by examining the internal and external quality aspects related to management, employees, customers, and suppliers to explain the mechanisms through which those internal and external aspects could contribute to the firms’ sustainability performance. As firms adopt internal and external QM relations to sustain their competitive advantage and achieve operational performance, their social, environmental, and economic sustainability performance dimensions improve. The importance of this research is that it investigates the influence of specific QM relations on the three dimensions of sustainability by providing robust and generalisable simultaneous examinations of these sustainability dimensions, primarily the social one. The social dimension has been paid less attention than the other sustainability dimensions and examining this aspect will provide further knowledge that has thus far been neglected in sustainability studies.government of Oma