Heriot-Watt University
ROS: The Research Output Service. Heriot-Watt University EdinburghNot a member yet
4689 research outputs found
Sort by
Advanced flat panel antennas for satellite communication on-the-move
No full textAbstract unavailable. Please refer to PDF. Restricted access until 01.05.2031
Indenyl rhodium N-Heterocyclic carbene complexes for catalytic C-H borylation
Get PDFMetal-catalysed C-H activation offers the ability to access key synthetic targets in more
straightforward reactions than previously used methods. However, undirected activation
pathways face issues of selectivity and low rates of reaction that make substituting simple
hydrocarbons difficult. Indenyl (Ind) and fluorenyl ligands offer increased reactivity
compared to cyclopentadienyl groups, which have been used previously in C-H
borylation, and combining these donors with electron-donating NHC ligands was
investigated for the borylation of arenes and alkanes. Additionally, the effects of tethered
systems were explored to see whether the catalytic ability is enhanced.
[Rh(Ind)(SIPr)(C2H4)], [Rh(Ind)(SIPr)(COE)] and [Rh(Ind)(SIPr)(CO)] (SIPr = 1,3-
bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene, COE = cis-cyclooctene) were
synthesised and characterised by multinuclear NMR spectroscopy and X-ray diffraction.
Only the ethylene and cyclooctene complexes were found to be reactive under photolytic
conditions and towards silanes. Photolysis led to the loss of coordinated alkenes and the
formation of a cyclometallated species due to C-H activation of the NHC substituents.
With reducing silanes or hydrogen, a rhodium dihydride complex was observed, that is
hypothesised to form via the reaction of the cyclometallated species, while less reducing
silanes led to the formation of the oxidative addition product.
Both [Rh(Ind)(SIPr)(C2H4)] and [Rh(Ind)(SIPr)(COE)] were found to be catalytically
competent for the borylation of benzene, while the carbonyl complex was found to be
unreactive under these conditions. Borylation of a selection of arenes showed that the
selectivity was comparable to previously reported rhodium catalysts, which is dominated
by steric effects, however, the reactivity was lower compared to previously reported
catalysts such as [RhCp*(C6Me6)]. Borylation of decane and octane showed that the
cyclooctene complex was capable of borylating alkanes, albeit in low yields.
Stoichiometric experiments monitored by NMR spectroscopy provided evidence that the
catalysis proceeds via rhodium boryl hydride species, with the previously identified
cyclometallated species also likely to play a role.
The synthesis of fluorenyl-tethered saturated-NHC ligands required the development of
homobimetallic synergic bases in order to bring about a ring-opening deprotonation of a
spirocyclic intermediate. The structure of [Li2(μ2
‐Ph){μ2
‐N(SiMe3)2}] was
crystallographically characterised as a coordination polymer, and reaction with the spirocyclic compound led to the formation of dialkali metal complexes of a fluorenidetehered NHC ligand that incorporated a bridging amide group. The use of these bimetallic
complexes as ligand transfer reagents gave rhodium carbonyl and ethene complexes in
low yields. Initial testing of these complexes in the borylation of benzene found that the
carbonyl species was inactive while the ethene complex was less active than the related
monodentate species.
Overall, this research has demonstrated that NHC ligands can be used to develop Rhcomplexes capable of C-H activation, the oxidative addition of silanes and the catalytic
borylation of hydrocarbons. This supports the idea that a [Rh(Ind)(NHC)] fragment (16
electron for η
5
-indenyl, or 14 electron with η
3
-indenyl) can mimic the reactivity of the
previously successful [Rh(Cp)(L)] and [Rh(Cp*)] fragments. Although the compounds
synthesised in this thesis were not better catalysts than literature examples, they hold
much promise because the incorporation of a tuneable NHC ligand on the metal centre
can lead to future improvements, especially considering the potential importance of
cyclometallated species in C-H activation reactivit
Microfluidics for waterborne pathogen separation and detection
Get PDFThere are millions of Cryptosporidium-attributable cases annually in children aged <24
months in the sub-Saharan Africa and India, Pakistan, Bangladesh, Nepal, Afghanistan
regions, respectively, and ~202,000 Cryptosporidium-attributable deaths”. Improved
monitoring is one solution to this challenge; however, detection of this pathogen is
particularly challenging, particularly in regard to determining viability information. This
thesis explores the development of novel protocols and devices for Cryptosporidium
parvum (C. parvum), through usage of nanoparticles (NPs) and microfluidic methods. NP
lysis approaches were developed as a low-cost, one-step rapid method with the possibility
to then integrate lysis and molecular detection into one microfluidic device. Different
materials, exposure times and concentrations were explored and ZnO NPs were found to
be as effective as the traditional freeze-thaw protocol.
Dielectrophoretic microfluidic devices were designed, prototyped and optimised for
viability-based separations. Fabrication was attempted via laser ablation for the purpose
of generating microchannels on PMMA sheets and Physical Vapour Deposition via an E-Beam system to investigate the deposition of electrodes; however, lift-off solvents were
incompatible with PMMA. Electrode design modifications were implemented to optimise
performance and efficacy of oocyst separation, based on viability, was assessed via an
excystation assay where at the outlet collecting non-viable oocysts viability was found to
be 5.9% and the other outlets showed a viability of 81.8% and 88.4%. The original
sample provided had a viability of 89.7%.
The work here adds to the growing number of studies investigating new ways of lysis and
detection for C. parvum. The lysis and detection of the oocyst is currently highly intensive
and a number of new methods of miniaturisation such as µPCR when integrated with a
lysing and filtration device to create a more precise method of finding the presence of C.
parvum in water samples. The DEP based separation device builds on the work of
previous studies such as Su et al. and others in order to separate C. parvum based on its
viability status in two different devices. This is a significant step showing that label-free
separation of oocysts of the same species can be separated based on their viability
Scalable techniques for multi-target tracking, sensor calibration, and multi-sensor fusion
Get PDFWith the increasing complexity of modern multi-target tracking scenarios comes
the need for efficient, scalable and robust solutions. The work performed in this
thesis focuses on providing such scalable solutions for multi-target tracking, parameter estimation and distributed fusion without the need for expensive computational
requirements. Gaussian mixtures have been proven to be an incredibly popular modelling tool for multi-target scenarios due to their straightforward nature and enabling
the use of exact solutions such as the Kalman filter. One of the main contributions
contained in this thesis is an optimised Gaussian mixture implementation that can
track one million targets in a cluttered environment in approximately one minute
per time step on a standard desktop computer, the fastest execution time yet for
any comparable solution. The Single Cluster filter, designed for joint parameter
estimation and tracking is also improved here through the use of a log-domain particle filter, allowing for a substantial increase in robustness and scalability. The final
contribution is a new distributed data fusion rule that enables a Gaussian mixture
based multi-target filter to incorporate target tracks from other tracking systems.
The performance of each of these algorithms is analysed through simulated experiments and suitable metrics alongside several case studies that highlight potential
applications
Mudrock microfabric and porosity : Sarawak and Sabah Basins, Malaysia
Get PDFMudrock microfabric is complex and heterogeneous and has a significant effect on
mudrock porosity and permeability characteristics. This study proposed the need for a
simplified representation of microfabric that has widespread application for sedimentary
mudrocks of all ages. One of the principal drivers is to develop an understanding of
mudrocks and mudrock microfabric that is useful in the exploration for and production
of shale gas and shale oil resources. Three different mudrock formations from the
Sarawak and Sabah Basins in Borneo, Malaysia: the Oligo-Miocene Setap Shale and
Sibuti Formations and the Miocene West Crocker Formation. New sedimentological data
presented here have established a marine shelf depositional environment for the Sibuti
Formation, an outer shelf to upper slope environment for the Setap Shale Formation, and
a deepwater turbidite-dominated environment for the West Crocker Formation. TOC
values are generally low (0.2-3.5%) and include both woody terrestrial and marine algal
organic material. The relative proportion of ductile minerals (clays and micas) and brittle
minerals (quartz, feldspar, carbonate, pyrite) in the sediment inorganic composition are
of key importance in the behaviour of the mudrocks during hydraulic stimulation. A new
composite microfacies model has been developed that links microstructure, microfabric
and microporosity. This is valid for all three study formations and is believed to be more
widely applicable to mudrocks in general. Microstructure and microfabric types have a
pronounced effect on microporosity style, distribution and network. An important aspect
of this model is the recognition that dispersed granular material (primary and diagenetic),
bioturbation traces, and disturbed microstructures all disrupt the original microfabric and
enhance microporosity. The integration of a multi-scale, multidisciplinary approach has
been applied in this study. Although the individual methods are not new, the application
of this kind of systematic approach is considered essential for the study of mudrocks and
unconventional hydrocarbon potential
Neutron and X-ray 3D and 4D imaging of fluid transport within natural and lab-deformed carbonate rocks
Get PDFCarbonate reservoir rocks are characterised by complexities in their void space caused by
various processes involved in deposition and diagenesis occurring through chemical
dissolution, reprecipitation, dolomitization, fracturing etc. These complexities affect the
transport properties of these rocks and hinder an accurate estimation, and therefore all ensuing
simulation, of their hydraulic behaviour. This PhD aims to deepen understanding of the
influence of core-scale complexities of the pore system of carbonate rocks on fluid transport
properties and processes. For this purpose, the complementary capabilities of X-ray and
Neutron imaging along with quantitative image analysis are employed to experimentally
investigate the miscible and immiscible fluid transport processes within carbonate rocks.
Different types of textural variations due to the depositional and mechanical deformational
features within four types of carbonate rocks, Coquina limestone, Biolithite, Travertine and
Oolitic limestone are first characterised by analysing X-ray micro-CT images acquired from
dry samples. Then, a series of High Speed Neutron Tomographies (HSNT) are acquired
during miscible and immiscible fluid flow experiments in the selected carbonate rock samples
(38mm diameter core) to explore different fluid transport processes affected by the
characterised core-scale features. Image analysis techniques are employed that allow the
extraction of quantitative data of pore system properties and fluid transport from the captured
X-ray micro-CT images and HSNTs. The analysis on X-ray micro CT images revealed the
significant influence of features like fractures, lamina or layering, layering orientation and
different types of textural variations on the pore network properties like porosity,
permeability, pore connectivity and tortuosity. The fluid transport processes and properties
including morphology of the flow patterns, fluid speed distribution, saturation/relative
concentration distribution of fluid phases, capillary heterogeneity trapping and fracture-matrix flow were resolved using the combination of HSNT and quantitative image analysis.
The results also provide important insight on miscible transport processes including
irregularity in the advancing fluid front and longitudinal dispersion.James-Watt scholarshi
Insights into climate-driven evolution of gas hydrate-bearing permafrost sediments
Get PDFMassive reserves of natural gas hydrates exist in permafrost and marine sediments.
Dissociation of natural gas hydrates could result in enhanced emissions of methane to the
atmosphere, aggravating global warming. It may also become a serious geohazard to the
geomechanical stability of gas hydrate deposits. The environmental and infrastructural
impacts due to climate-driven and human-induced dissociation of natural gas hydrates
cannot be well predicted unless we have an accurate estimation of hydrates deposited in
both marine and permafrost sediments. However, conventional seismic techniques cannot
give reliable estimations of gas hydrates in permafrost sediments as they are unable to
distinguish ice from hydrates due to their almost identical acoustic properties.
The main objective of this thesis is to address the above challenge via shedding light on
the influence of the hydrates presence on the evolution of gas hydrate-bearing permafrost
sediments, and developing a coupled geophysical-geothermal scheme, for the first time,
for estimation of hydrates saturation in these sediments. To achieve this, magnetic
resonance imaging (MRI) was employed to investigate the kinetics of formation and
spatial characteristics of methane hydrate in synthetic and natural sediment samples. The
analysis of the images acquired during three consecutive thermally-induced hydrate
formation/dissociation cycles indicated that in addition to the kinetics of formation, pore-scale distribution of hydrates is affected by the thermal history of the system and the host
sediment type, characteristics, and particle size distribution. The results also showed that
different hydrate pore-scale habits may co-exist in the system, which is essential to be
considered in the models developed for the estimation of the physical properties of gas
hydrate-bearing sediments. Having the above fundamental insights, the geophysical and
geothermal responses of hydrate-free and hydrate-bearing sediments were characterised
by measuring their elastic wave velocities and effective thermal conductivity (ETC) at
different hydrate saturations (up to 55%) and effective overburden pressures (up to 6.89
MPa) at both unfrozen and frozen conditions. The results confirmed that the evolution of
the elastic wave velocities as well as ETC depends on the saturation and pore-scale habit
of hydrates; and ETC could interestingly assist with distinguishing ice from hydrates. The
ETC measurements also revealed that the presence of hydrates in porous media is
associated with three key pore-scale phenomena contributing to the efficiency of the heat
transfer: the saturation and pore-scale habit of hydrates, hydrate/ice-forced heave, and
unfrozen water saturation at frozen conditions. Moreover, a new physical model was
developed for the prediction of ETC of hydrate-free sediments using the Free-energy
Lattice Boltzmann Model (LBM) and a space renormalisation technique, and modified
according to the insights from the ETC measurements to account for the effect of the
above-mentioned key pore-scale phenomena. Ultimately, the coupled geophysical-geothermal scheme was developed by using the modified ETC model as the geothermal
part and Ecker’s rock-physics models as the geophysical part, and its performance was
validated using the measured geophysical and geothermal properties. It was demonstrated
that the proposed coupled scheme is able to quantify the saturation of the co-existing
phases in a wide range of hydrate saturations and at different effective overburden
pressures, particularly at frozen conditions where the co-existence of hydrates, ice, and
unfrozen water is essential to be captured. This scheme makes it possible to distinguish
ice from gas hydrates in frozen sediments hence it could be employed for not only
quantification of gas hydrates in permafrost but also further development of large-scale
permafrost monitoring systems for monitoring the dynamic response of gas hydrate-bearing permafrost sediments to climate warming in cold regions.James Watt Scholarshi
Metric algebroids, para-Hermitian structures and T-duality
Get PDFThe geometry of para-Hermitian vector bundles is introduced and generalised metrics are defined on such vector bundles. In particular, the properties of Born metrics
are demonstrated. Their application to classical Lagrangian dynamics is highlighted.
Metric algebroids are presented and their existence problem is addressed together with their compatibility with para-Hermitian structures. The example of
pre-Courant algebroids is thoroughly discussed and applied to the special case of
Courant algebroids. In this setting the notion of Dirac structure is recalled in order
to introduce Dirac-Riemannian foliations.
Para-Hermitian manifolds endowed with a Born metric and their compatible
metric algebroid structure are used to define sigma-models in a duality-symmetric
formulation. Their Lie algebroid gauging is studied and the geometric interpretation
of the gauging conditions as Dirac-Riemannian structures is presented. In particular,
a detailed analysis of gauged sigma-models for regularly foliated manifolds is given.
This construction is applied to describing a geometric picture of generalised Tduality, where the para-Hermitian manifold is supposed to admit different maximally
isotropic foliations so that T-dual sigma models are recovered on their leaf spaces,
which represent the physical space-times. The main examples presented in this
work are given by Lie groups endowed with invariant para-Hermitian structures and
the doubled twisted torus. In particular, for the latter its full T-duality chain is
recovered by using these techniques.UK Science and Technology Facilities Council (STFC). Doctoral Training Grant ST/R504774/
Spectroscopy of two-dimensional quantum light sources incorporated into functional devices
Get PDFTwo-dimensional materials are promising building blocks for photonic-based quantum technologies. Single-photon emitters – the required quantum light sources for
such applications – can be induced in some of these layered materials, with the prevalent example of tungsten diselenide WSe2 monolayer. They can be incorporated into
electronic and photonic devices, being combined with other atomically thin materials into tailored heterostructures and transferred onto patterned substrates. Ow ing to their intrinsic nature, these novel two-dimensional quantum systems present
a promising potential to overcome challenges such as collection efficiency limitation due to total internal reflection encountered in other solide-state sources like
semiconductor quantum dots or colour centres in diamond. This thesis undertakes
the nanofabrication and optical characterisation of two-dimensional quantum light
sources incorporated into devices.
Four projects were achieved during the PhD. They are described and discussed
in this thesis. A chapter is dedicated to an argon atmosphere glovebox system I
developed for the nanofabrication, monitoring, and characterisation of pristine two-dimensional samples is described. Second, a dichromatic pulsed laser excitation
regime is employed to coherently drive WSe2 monolayer quantum emitters incorporated into planar cavities, with a successful observation of π-pulses. Third, these
emitters are excited out-of-resonance with a continuous wave laser, and their coherence time is estimated from a Hong-Ou-Mandel interferometry experiment. A short
time of ∼ 10 ps – as compared to their ∼ ns lifetimes – is obtained; it is due to
the emitters inhomogeneous broadening. Finally, cw resonant excitation of WSe2
monolayer quantum emitters coupled to a Si3N4 waveguide is successfully achieved
Thermochemical conversion of textile waste to useful commodities and fuel
Get PDFThe quantity of textile waste has been increased significantly in the recent years and a considerable
portion of this waste has been sent to landfills, causing environmental issues. This research has been
carried out to address this issue and propose a method for textile waste conversion to useful
commodities such as chemicals or biofuels with potential of application in a commercial scale.
Wool was selected as feedstock while gasification and pyrolysis were selected as the technologies
with potential to facilitate the achievement of the objectives. Pyrolysis and gasification were carried
out in bench-scale fixed bed reactor to check the feasibility of the pyrolysis for textile waste
conversion. Furthermore, model compounds representing textile waste were pyrolysed with and
without catalysts to evaluate if the properties of products could be modified.
5 different catalysts were used for pyrolysis of lignin, cellulose, and phenylalanine. The results
indicated that Al-KIL2 and 20-ZSM5 had the potential to modify the properties of wool pyrolysis
by-products and were used in wool pyrolysis in fixed bed. This decision was based on the increase
in quantity of aromatics obtained in the oil products in based on the GC-MS analysis results.
High CO content of gas, char product properties and marketable products such as phenols in the
oil obtained in pyrolysisand gasification using fixed bed reactor proved that these technologies were
promising. Therefore, a novel scaled-up system (auger reactor) for textile waste pyrolysis was
designed, built, and modified.
Comparing the findings of the gasification/pyrolysis of wool in the fixed bed and auger reactor, the
conversion of feedstock to volatiles seemed to be more efficient in fixed bed while the properties
of the char did not vary significantly. Regarding the oil products, while phenols and indoles were
the prominent product in the fixed bed, ketones, nitriles and quinolines were the main products in
the auger reactor.
Overall, the results indicated that up to 2 kg/h of textile waste feedstock on its own (without
mixing with other material) can be pyrolysed/gasified in this system and by-products could be
collected successfully. Furthermore, it was observed that residence time, heating rate and product
collection method have been the main contributor for the difference between the small scale and
scaled-up tests
Access Repository Dashboard
Do you manage ROS: The Research Output Service. Heriot-Watt University Edinburgh ? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!