Engineering & Physical Sciences
Permanent URI for this communityhttps://dspace-upgrade.is.ed.ac.uk/handle/10399/17
Browse
1002 results
Search Results
Item Unambiguous quantum measurements for quantum communication(Heriot-Watt University, 2018-05) Kleczkowska, Klaudia; Andersson, Professor ErikaAbstract and full text unavailable. Please refer to PDF.Item Large conductance Ca²+-activated potassium channels localisation and dynamics in living cells(Heriot-Watt University, 2019-02) Miguelez Crespo, Allende; Duncan, Rory; Brown, EuanLarge conductance Ca2+-activated K+ (BK) channels are expressed in a wide range of human tissues such as brain, thymus, muscle, adrenal gland, heart, lung or pancreas, where they regulate insulin secretion by closing N-type calcium channels. The study of BK channels activity, localisation and dynamics, would be useful not only for the achievement of a further understanding of BK channels properties in physiological conditions, but also in disease. Indeed, BK channel activity has been reported to be disrupted in a wide range of disorders, such as diabetes. Therefore, our study aims to determine whether components of the secretory machinery and BK-channels are localised in close proximity at the plasma membrane, as well as how the secretory machinery influences both BK channel localisation and activity. To carry out these experiments I was using super-resolution microscopy and electrophysiology. Previous electrophysiological studies have suggested that BK channels and components of secretory machinery must be in close proximity in the plasma membrane. Thus, we observed the dynamics and distribution of BK channels at the level of single molecules in cell membranes using super-resolution microscopy. We observed BK channel cluster organization of ~120 nm in diameter in cells expressing BKα-EGFP using gated-stimulated emission depletion (g-STED) microscopy. Moreover, to further examine these clusters we expressed a cDNA construct that encodes the BKα fused to a photoactivatable fluorescent protein mutant of mCherry (PAmCherry) and localised single channel molecules using photoactivatable localisation microscopy (PALM), which can localise where each single particle is within each cluster, and the distance respect to their closest secretory vesicles using Nearest Neighbour analysis. Further experiments in live cells using single particle tracking PALM (sptPALM) enabled us to track these single molecules over time showing different speeds of BK channels with and without the presence of the secretory machinery components. Additionally, the electrophysiological experiments with cells co-expressing BK channels and components of the secretory machinery suggest that BK channels current is not affected in the presence of these proteins. Moreover, to study the proximity of BK channels with the secretory machinery cells were transfected with our BKα-EGFP construct and Syntaxin-1A-mCherry, a plasma membrane protein involved in vesicle fusion, and analysed using Fluorescence Resonance Energy Transfer (FRET) and Fluorescence Lifetime Imaging (FLIM). Results suggested that both BKα and Syntaxin-1A interact in the plasma membrane.Item Ultrafast laser assisted etching of fibre optic probes for optical biopsy instruments(Heriot-Watt University, 2019-08) Ross, Calum Alexander; Thomson, Professor RobertAdvances in photonic techniques, instrumentation and computation is enabling the development of new tools for medical diagnosis. One such tool is a Raman-based “optical biopsy” where Raman spectroscopy is performed in the body to detect molecular level differences between healthy and malignant tissues to diagnose cancer and other diseases. Optical biopsies are less invasive than traditional surgical biopsies and can, in principle, provide highly specific, instantaneous feedback for the clinician. Raman spectroscopy can be performed in hard-to-reach regions of the body such as the oesophagus by utilising optical fibres and distal-end optics. Distal-end optical systems are small and complex and often require labour-intensive manual aligned and intricate bonding of components– a process which is time-consuming and expensive and not suitable for industrial manufacture. The lack of readily available distal-end optical systems has hampered progress in transferring fibre-based Raman biopsies from a research setting into the clinic. The aim of this work was to develop a miniaturised Raman probe, suitable for industrial manufacture, by employing an advanced three-dimensional laser-processing technique known as ultrafast laser assisted etching (ULAE). ULAE is a subtractive manufacturing process which relies on focused femtosecond laser pulses to locally enhance the chemical etchability of certain transparent materials, including fused silica. Material modification is confined to the laser focus and so freeform three-dimensional structures can be inscribed and subsequently removed by chemical etching. Several components can be written pre-aligned on a single substrate, making ULAE perfectly suited to the fabrication of distal-end optical systems (DOS). During the project, we developed a novel, confocal Raman probe with a sub-millimetre diameter and a collection efficiency of 52.1% over a numerical aperture of 0.8. To enable highly repeatable fabrication, we conducted a thorough investigation into how several laser irradiation parameters affect the etching enhancement and achieved an etching selectivity of 955. The Raman probe was used to measure the Raman spectra of healthy and tumorous colorectal mouse tissue and successfully identified molecular peaks associated with relevant cancer biomarkers.Item A critical review of the non-destructive evaluation of thermal barrier coatings prior to failure(Heriot-Watt University, 2018-08) Etieve, DannyA critical review of literature on thermal barrier coatings (TBC) with an emphasis on the stochastic nature of TBC failure data is undertaken. The Characteristic Life Equation, first proposed by Professor John R Nicholls in modelling the influence thermally grown oxides have on TBC spallation is devised. The works of A.G Evans and co-workers on the mechanics of failure of thin, brittle layers on ductile substrates during thermal cycling was applied to the thermally grown oxide layer within a TBC system where plate theory is used to analytically derive forces acting on initial defects allowing to analytically determine the critical height required for an induced delamination to cause buckling leading to spallation failure. The probabilistic models proposed as part of the ‘Characteristic Life Equation’ allows for the coefficients of Weibull Stochastic models of TBC spallation failure to be related in strain-energy and material property terms through modelling the mechanics of crack propagation within the thermally grown oxide of a TBC system. X-Ray Diffraction (XRD), Raman spectroscopy, Digital Image Correlation (DIC) and THz radiation in the form of a reflection based polariscope were reviewed to investigate whether these NDE techniques have the potential to evaluate TBC ‘performance’ using the characteristic life equation. A preliminary sensitivity analysis of the characteristic life equation was carried out. DIC was assessed for its suitability to non-destructively evaluate both in and out-of-plane displacements on a TBCs surface. The observed range in DIC data for the range of speckle patterns and system parameter settings explored was found to be able to reliably resolve out of-plane measurements of 0.03069mm with an associated error of 2.87𝑥10−7𝑚𝑚. XRD, Raman, DIC and THz radiation, potentially in combination with other non-destructive evaluation techniques as well as the characteristic life equation may ultimately aid develop a methodology by which the remaining life of a TBC may be non-destructively assessed. Should this goal be achieved - probing the Characteristic Life Equation non-destructively may prove invaluable as a tool in the improvement and development of TBCs.Item Design, manufacturing and characterisation of a wireless flexible pressure sensor system for the monitoring of the gastro-intestinal tract(Engineering and Physical Sciences, 2019-04) Mitrakos, Vasileios; Desmulliez, Professor Marc; Macintyre, Doctor LisaIngestible motility capsule (IMC) endoscopy holds a strong potential in providing advanced diagnostic capabilities within the small intestine with higher patient tolerance for pathologies such as irritable bowel syndrome, gastroparesis and chronic abdominal amongst others. Currently state-of-the art IMCs are limited by the use of obstructive off-the-shelf sensing modules that are unable to provide multi-site tactile monitoring of the Gastro-Intestinal tract. In this work a novel 12 mm in diameter by 30 mm in length IMC is presented that utilises custom-built flexible, thin-film, biocompatible, wireless and highly sensitive tactile pressure sensors arrays functionalising the capsule shell. The 150 μm thick, microstructured, PDMS flexible passive pressure sensors are wirelessly powered and interrogated, and are capable of detecting pressure values ranging from 0.1 kPa up to 30 kPa with a 0.1 kPa resolution. A novel bottom-up wafer-scale microfabrication process is presented which enables the development of these ultra-dense, self-aligned, scalable and uniquely addressable flexible wireless sensors with high yield (>80%). This thesis also presents an innovative metallisation microfabrication process on soft-elastomeric substrates capable to withstand without failure of the tracks 180o bending, folding and iterative deformation such as to allow conformable mapping of these sensors. A custom-built and low-cost reflectometer system was also designed, built and tested within the capsule that can provide a fast (100 ms) and accurate extraction (±0.1 kPa) of their response. In vitro and in vivo characterisation of the developed IMC device is also presented, facilitated respectively via the use of a biomimetic phantom gut and via live porcine subjects. The capsule device was found to successfully capture respiration, low-amplitude and peristaltic motility of the GI tract from multiple sites of the capsule.Item Precision laser micromachining of hollow core negative curvature fibres(Heriot-Watt University, 2019-02) Novo, Catarina Cardoso; Shephard, Doctor Jonathan D.; Thomson, Professor Robert R.The principal aim of this work was to develop a novel micromachining strategy for a new class of hollow core silica optical fibre, the Negative Curvature Fibre (NCF). Processing techniques were investigated to increase the physical access to the hollow core (along the length of the fibre) in order to enhance the interaction of chemical species with the light and hence enable practical sensing devices. Because of the unique internal structure of these NCFs, consisting of a fine (sub-micron) silica webbing, a highly precise and controllable machining process was required. Due to the well-known advantages of femtosecond laser machining such as the ability for inscription in any material, small volume removal and the non-thermal nature of the process, resulting in machined structures with an almost negligible heat-affected zone, a new femtosecond laser micromachining process was developed. A methodology was successfully demonstrated which gives the capability to precisely machine away the solid outer cladding fibre and then controllably remove the silica webbing and expose the hollow core of the fibre. This single step process provides a more direct way of machining a fibre (compared to previously reported hybrid techniques such as laser machining plus chemical etching). Parameter optimisation allowed control of the removal depth, minimisation of re-deposited material and avoidance of damage to the remaining silica web which is very important for NCF due to its guidance mechanism. An NCF, which was machined through to the hollow core, exhibited no significant disruption to the guidance preserving the confinement of light to the hollow core. Hence the laser micromachining strategy presented in this work paves the way to develop new optical sensing devices exploiting the unique properties of these novel fibre geometries.Item Towards scalable and efficient single photon sources(Heriot-Watt University, 2019-12) Ballesteros Garcia, Guillem; Gerardot, Professor Brian D.This thesis investigates the development of techniques to enable the creation of brighter and easier to scale single photon emitters. This is possible with the use of a novel nanoantenna design paired with a redesigned confocal microscope capable of addressing multiple sources in parallel. The nanoantenna design is based on a hemishperical cavity which is typically used in the design of lasers. These are the source of their very high directivity. The design is adapted to allow its integration with solid state sources such as quantum dots and defect centres in diamond. By modifying the properties of the mirror enclosing the cavity it is possible to precisely control the quality factor and the Purcell enhancement of the emission. Additionally, due to its monolithic nature the design is highly stable and permits the incorporation of additional contacting layers to tune the emitters. The new microscope design makes use of multicore fibres on its excitation and collection arms in order to have multiple independent focii on the sample. The design is demonstrated on a nanowire sample were two single photon streams from two separate nanowires are collected simultaneously. The new design also makes use of a quasi-4F lens configuration to minimize beam displacement and optical aberrations. Finally, a new open source tool is developed to facilitate the analysis of time correlated single photon experiments. All the algorithms are optimized to make adequate use of modern computer’s memory hierarchy and multicore nature.Item Picosecond laser micro-machining of glass for optics manufacture(Heriot-Watt University, 2019-02) Amiel Adrian, Lopes; Hand, Professor Duncan P.Glass-based aspheric optics are attractive for compact optical setups. In addition, custom optics are useful for the correction of pointing errors of High Power Diode Lasers (HPDL). The machining of fused silica (Corning HPFS® 7980), Schott N-BK7®, Schott N-LaF21 and Ohara S-TiH53 using a Trumpf TruMicro 5X50 laser which provides a 6 picosecond pulse duration with a maximum pulse repetition rate of 400 kHz and maximum average power of 50 W has been explored in this thesis. The machining of these glass materials was carried out using laser wavelengths λ = 1030 nm, 515 nm and 343 nm at different pulse spatial overlap and fluence values. Two scan strategies were used, namely the sequential raster scan strategy and the novel interlaced scan strategy. In this thesis, we show the differences in the machining outcome. The sequential scan strategy is similar to the standard raster scan technique and is limited to lower pulse repetition rates of 20 kHz due to a thermal build-up effect manifesting itself in the formation of fibres and fused debris on the surface. On the other hand, given the same conditions of total pulse energy deposited on the surface, the interlaced scan strategy is found to provide up to 3 times larger ablation depths. Furthermore, as the interlaced scan strategy has been found to suppress the effects of thermal accumulation, higher repetition rates up to 400 kHz could be used providing higher ablation rates up to 60 times more than the sequential scan strategy on the laser used. A high-speed camera was used to observe the mechanism of material removal for the two scan strategies providing insight into the cause of the higher ablation efficiency of the interlaced scan strategy. We demonstrate the capability of this process by machining cylindrical lenses. One batch of the picosecond laser machined lenses was shipped to Fraunhofer ILT while another similar batch of lenses was shipped to PowerPhotonic Ltd. for polishing using their CO2 laser polishing techniques. The polished lenses were tested for their performance, and the accuracy of the process was measured. Finally, the future scope of this technology along with its applications is discussed.Item An investigation of continuous hydrogenation(Heriot-Watt University, 2019-10) Navarro Fuentes, Francisca; Ni, Professor Xiong-WeiHeterogeneous catalysis is one of the key processes for the synthesis of pharmaceuticals, fine chemicals, petrochemicals, polymers, agrochemicals, among others and often involves three phases where a gaseous reactant needs to diffuse through the solvent (liquid) onto the surfaces of catalyst particles (solid) in order for catalytic reaction to take place. Traditionally stirred tank and packed bed reactors are the workhorse for heterogeneous catalysis, as such, interphase mass transfer limits the overall efficiency for this type of operation. This PhD project focuses on the study of a multiphase catalytic hydrogenation in an alternative reactor platform, i.e. oscillatory baffled reactor (OBR), due to its reported uniform mixing and enhanced mass transfer rate. The chosen model reaction is the hydrogenation of 3-butyn-2-ol over Pd/Al2O3. A comprehensive and systematic comparable evaluation of the OBR vs a commercial stirred tank PARR reactor was for the first time undertaken in this project by assessing reactor efficiency (power consumption), hydrogen feed mode and hydrogen utilization (H2 efficiency). Our investigation demonstrates • enhanced reaction performance is obtained when hydrogen-on-demand is operated; • H2 efficiency is significantly improved and the residence time reduced in the OBR in comparison to the PARR reactor at both ambient and pressurized conditions due to its enhanced and uniform mixing; • the OBR has also displayed better reactor efficiency than the PARR reactor. One of the objectives of this PhD work was to investigate the possibility of performing heterogeneous catalysis continuously in the OBR, this has been achieved. The model hydrogenation reaction was successfully run for 8 hrs continuously, the catalyst stability and usability were consistent for the 8 hrs achieving the target conversion of 95 % and selectivity > 97%. This work is again the first of its kind in this field.Item Bayesian methods for inverse problems with point clouds : applications to single-photon lidar(Heriot-Watt University, 2019-11) Tachella, Julian Andres; McLaughlin, Professor Stephen; Altmann, Doctor Yoann; Tourneret, Professor Jean-YvesSingle-photon light detection and ranging (lidar) has emerged as a prime candidate technology for depth imaging through challenging environments. This modality relies on constructing, for each pixel, a histogram of time delays between emitted light pulses and detected photon arrivals. The problem of estimating the number of imaged surfaces, their reflectivity and position becomes very challenging in the low-photon regime (which equates to short acquisition times) or relatively high background levels (i.e., strong ambient illumination). In a general setting, a variable number of surfaces can be observed per imaged pixel. The majority of existing methods assume exactly one surface per pixel, simplifying the reconstruction problem so that standard image processing techniques can be easily applied. However, this assumption hinders practical three-dimensional (3D) imaging applications, being restricted to controlled indoor scenarios. Moreover, other existing methods that relax this assumption achieve worse reconstructions, suffering from long execution times and large memory requirements. This thesis presents novel approaches to 3D reconstruction from single-photon lidar data, which are capable of identifying multiple surfaces in each pixel. The resulting algorithms obtain new state-of-the-art reconstructions without strong assumptions about the sensed scene. The models proposed here differ from standard image processing tools, being designed to capture correlations of manifold-like structures. Until now, a major limitation has been the significant amount of time required for the analysis of the recorded data. By combining statistical models with highly scalable computational tools from the computer graphics community, we demonstrate 3D reconstruction of complex outdoor scenes with processing times of the order of 20 ms, where the lidar data was acquired in broad daylight from distances up to 320 m. This has enabled robust, real-time target reconstruction of complex moving scenes, paving the way for single-photon lidar at video rates for practical 3D imaging applications.