Engineering & Physical Sciences
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Item Upscaling of two-phase flow in oil-gas systems(Engineering and Physical Sciences, 2000-04) Darman, Nasir B. Haji; Sorbie, Professor Kenneth S.; Pickup, Doctor Gillian E.Abstract unavailable please refer to PDF.Item Extending the measurement range of high-speed speckle pattern interferometry(Heriot-Watt University, 2009-09) Wu, Tao; Moore, Professor AndrewA digital speckle pattern interferometer based on a complementary metal-oxide semiconductor (CMOS) camera was developed. The temporal evolution of dynamic deformation was measured using inter-frame phase stepping. A numerical and analytical investigation showed that the maximum surface velocity that can be reliably measured with inter-frame phase stepping corresponds to ±0.3 times the surface velocity at which the interferogram is sampled at the Nyquist limit (vNyq). The flexibility of the CMOS detector readout was used to identify regions of interest with full-field time-averaged measurements and then to interrogate those regions with time-resolved measurements sampled at up to 70 kHz. To increase the surface velocity measurement range, spatial phase stepping was introduced to the high-speed CMOS system. A pair of binary phase gratings introduced double-channel sensing with a fixed phase step between the two channels. The maximum surface velocity was increased to ±1.0vNyq. Sub-Nyquist theory was implemented for the dynamic measurements and the measurement range with a continuous-wave laser illumination was increased by an order of magnitude with respect to inter-frame phase stepping to ±3.0vNyq. A numerical and analytical investigation showed that with a reduced exposure, for example from pulsed laser illumination, the maximum surface velocity that can be reliably measured is ±15.9vNyq and the surface acceleration is ±253.3vNyq with the current set-up. Due to spatial variations in speckle intensity, some low-modulating and saturated pixels within the small regions of interest interrogated at up to 70 kHz could not be analysed. The nonlinear LinlogTM response of the CMOS camera was used to increase the valid measurement area on the object surface by incorporating pixels that would be below a modulation threshold or saturated if recorded with a linear CCD detector.Item Computational studies on C-H activation reactions at Iridum, Rhodium and Ruthenium(Heriot-Watt University, 2009-12) Poblador-Bahamonde, Amalia I.; Macgregor, Professor StuartDensity Functional Theory (DFT) calculations have been carried out to study the factors that affect the cyclometallation reactions of the model system [Ir(-Cp)(dmba−H)(2- RCO2)]+ (R= CH3, CF3, CCl3, OH and Ph), as well as the triflate analogue. The limiting step is, in all cases, the dissociation of one arm of the chelating base and in most cases a 1-intermediate was located. The transition state for the subsequent C−H activation exhibits short MC−H and OH interactions which combine to allow an easy hydrogen transfer. The combination of these two factors leads to a new term Ambiphilic Metal Ligand Activation (AMLA) to describe these C−H activation processes. The above study was extended to [M(ring)(dmba−H)(2-OAc)] systems, (where M(ring) = {Rh(-Cp)}+, {Ru(-C6H6)}+ and {Ru(-Cp)}). Cationic systems have very similar activation energies (E‡), although small variations in the overall energy were computed. These effects were rationalized in terms of the strengths of the M−C and M−O bonds formed and broken in the reaction. The neutral systems gave a lower E‡ although the products were less stable. In addition, the substitution of the dmba−H ligand for related imine or amide substrates shows that these species also readily undergo facile cyclometallation. Finally, the intermolecular C−H activation of benzene by [Ir(-Cp)(PH3)(2-OAc)]+ and the incorporation of this step into a catalytic cycle for the hydroarylation of ethene was assessed. The rate-limiting step is associated with the alkene insertion step (E‡ = 16.7 kcal/mol), while the C−H activation is slightly more accessible. Therefore, this model appears to be a promising target for catalysis.Item Skeletal muscle microRNA's in human cancer cachexia and type 2 diabetes(Heriot-Watt University, 2009-09) McGregor, Robin A.MicroRNAs are powerful post-transcriptional regulators of gene expression and are biomarkers of chronic diseases such as cancer. This thesis explores the role of microRNAs in human cancer cachexia and Type 2 diabetes. MicroRNA expression was measured in skeletal muscle biopsies using RT-qPCR. In pancreatic cancer cachexia patients, expression of microRNA-1, microRNA-133a, microRNA-133b and microRNA-206 was negatively related to weight loss. In Type 2 diabetes skeletal muscle, microRNA-133a and microRNA-206 expression was down-regulated, but there was no evidence of altered microRNA transcription or processing and target expression was unchanged. Importantly, microRNA-133a expression predicted fasting glucose, glucose tolerance and insulin resistance, and therefore may be a biomarker of Type 2 diabetes. Experimental validation of microRNA arrays was unsuccessful in identifying further novel cancer cachexia and Type 2 diabetes microRNA biomarkers. MicroRNA knockdown validated CDC42 and PTBP1 as microRNA-133a targets in myoblasts. In addition, muscle microRNA expression may be regulated by insulin and TNFa. In conclusion, microRNA-133a may be a skeletal muscle biomarker of Type 2 diabetes and cancer cachexia, microRNA-133a responds to extracellular insulin and TNFa, but it remains to be established whether microRNA-133a contributes to cancer cachexia or Type 2 diabetes pathogenesis.Item Towards the development of a novel colourimetric nucleic acid biosensor based on peptide nucleic acid-functionalised polydiacetylene liposomes(Heriot-Watt University, 2009-09) Goujon, Jennyfer; Howarth, Dr NicolaThe aim of the research project described here was to develop a novel colourimetric nucleic acids biosensor based on polydiacetylene liposomes containing lipophilic peptide nucleic acids. Preliminary investigations in this area have shown that PNA-containing PDA liposomes can be constructed and that they are blue in colour as expected. However, their poor water solubility and the resulting precipitation made it necessary to synthesise and evaluate a second generation. In these, the PNA head-group is separated from the lipid tail by an amino diethylene glycol-type spacer molecule. The first hydrophilic spacer synthesised was 8-(tert-butoxycarbonyl)amino-3,6- dioxaoctanoic acid. Three methods based on the O-alkylation of mono-Boc, di-Boc and dibenzyl 5-amino-3-oxapentanol were devised. The Boc strategy afforded the corresponding ether in low yield of 20% while in the case of the dibenzyl approach a suitable methodology to effectively cleave the protecting groups from the amino function could not be found. Moreover, the model reaction between dibenzyl 8-amino-3,6- dioxaoctanoic acid and thyminyl PNA monomer afforded the corresponding conjugates in only 6%. An alternative type of connection to link the spacer to the PNA headgroup was thus sought. A 1,4-disubstituted [1,2,3]-triazole moiety was obtained in 60% yield by reacting spacer, 8-(tert-butoxycarbonyl)amino-3,6-dioxaoctan-1-azide and N-alkynyl PNA monomers bearing thymine, Cbz protected adenine and Cbz protected cytosine according to the conditions of the ‘Click’ reaction. These ‘spacer-PNA monomer’ intermediates were then functionalised at their N-terminus using 10,12-pentacosadiynoyl fluoride, to afford ‘lipid-spacer-PNA monomer’ models. The saturated conjugates were obtained by first preparing the ‘lipid-spacer’ intermediate, N-(8-azido-3,6- dioxaoctanyl)stearamide which was then connected to the N-alkynyl PNA monomers using the ‘Click’ reaction. Following this last strategy, a homothymine PNA dimer, prepared in solution phase, was also functionalised with the saturated lipid chain. This second generation of lipid functionalised-PNA monomer models were incorporated into PDA-liposomes. Upon photo-polymerisation, the liposome solutions became blue. They were found to be stable in solution, at 4 oC over long period of time. Their colour changed to red upon environmental changes (i.e. pH and temperature).Item Characteristic and sensing properties of near- and mid-Infrared optical fibres(Heriot-Watt University, 2009-08) Li, Hongxia; Barton, Jim; MacPherson, BillThe work within this thesis investigates the characteristics and sensing properties of novel near- and mid-infrared tellurite and germanate glass fibres and their potential as sensing elements. An asymmetric splicing method for fusion-splicing tellurite and germanate glass fibres to standard silica fibre is demonstrated. The thermal and strain sensing properties of these glass fibres have been studied by analysing the properties of optical fibre Fabry-Perot cavities, which were formed when these high refractive index fibres were spliced to silica fibre, and fibre Bragg gratings. Using fibre F-P interferometer, the normalized thermal sensitivity of tellurite and germanate fibre was measured to be 10.76×10-6/°C and 15.56×10-6/°C respectively, and the normalized strain sensitivity of tellurite and germanate fibre was also measured with values of 0.676×10-6 /με and 0.817×10-6 /με respectively. These results show good agreement with measurements using fibre Bragg gratings in these fibres and are reasonably consistent with the values predicted using available published data for glasses of similar compositions. Tellurite and germanate glass fibres show potential as thermal sensing and load sensing elements compared with silica fibre. The design of an evanescent field gas sensor using tapered germanate fibre for methane gas species detection was investigated and modelled. This model shows the maximum gas cell length (sensing fibre length), detectable gas concentration range, and required gas cell length range for the expected minimum detectable gas concentration of a fibre evanescent field sensor, which gives guidance for the effective gas cell length choosen according to different minimum detectable gas concentration requirement in practise. The investigation of tellurite and germanate glass fibre characteristics and sensing properties offer guidance for their applications in sensing areas.Item The development of a catalytic process for the hydrotreatment of haloarenes(Heriot-Watt University, 2009-09) Gomez-Quero, SantiagoThe abatement of halogenated compounds released from various processes into the environment is now recognized as a pressing environmental issue. Catalytic hydrodehalogenation (HDH) has emerged as a potential technology that can facilitate waste transformation and reuse. In this thesis, a comprehensive study of the critical reaction/catalyst variables is considered for the HDH of a range of haloarenes (chloroand bromo-phenols and chlorobenzenes) using (commercial) Pd/Al2O3 and (laboratory synthesised) Au supported on -Fe2O3 and Fe3O4. Aqueous phase (T = 303 K) HDH is demonstrated to be structure sensitive where smaller Pd particles are intrinsically more active and metal/support interactions have a major impact on reaction selectivity (notably at pH = 3). HDH follows an electrophilic aromatic substitution mechanism: the rate of C–Br bond(s) scission is an order of magnitude greater relative to C–Cl (due to the lower bond dissociation energy). The presence of a second halogen substituent has a deactivating effect (by lowering electron density in the aromatic ring). Solvent (water, organic and water/organic mixtures) effects have been established where, in absence of mass transport limitations, reaction in water delivers significantly higher HDH rates and selectivity is unaffected by solvent composition. A mathematical analysis demonstrates that these effects are principally (ca. 80 % contribution) the result of the variations in solvent dielectric constant where the molar volume represents a secondary consideration. The advantages of a shift from batch to continuous HDH are established in terms of: (i) more efficient gas to liquid H2 transfer; (ii) enhanced HDH rates; (iii) prolongued catalyst lifetime. The potential of HDH as a means of waste transformation to a commercial product is demonstrated in the gas phase (T = 423 K) hydroconversion of 2,4-dichlorophenol into cyclohexanone (over Pd) and 4- chlorophenol (over iron-oxide supported Au). In both cases, a contribution due to spillover hydrogen is established. A comprehensive programme of (Au) catalysts synthesis and characterization, in terms of TPR, H2 chemisorption/TPD, XRD, DRS UV-Vis, SEM/TEM and BET/pore volume measurements is provided and correlated with HDH kinetics. The results presented in this thesis demonstrate the feasibility and flexibility (in terms of operation, rate/selectivity control and product reuse) of catalytic HDH as a progressive means of haloarene waste treatment.Item The development of supported gold catalysts for selective hydrogenation applications(Heriot-Watt University, 2009-04) Cardenas-Lizana, Fernando; Keane, Professor Mark A.An alternative cleaner route for the production of aromatic amino-compounds under mild reaction conditions (P = 1 atm; 393 K ≤ T ≤ 573 K) via the continuous gas phase reduction of aromatic nitro derivates has been investigated over (oxide and/or carbon) supported Au, Ag, Pd, Ni, Ni-Pd, Au-Pd and Au-Ni catalysts. Taking the hydrogenation of p-chloronitrobenzene as a model reaction, Pd/Al2O3 promoted the exclusive production of nitrobenzene and aniline, i.e. hydrodechlorination with subsequent -NO2 group reduction prevailed. In contrast, p-chloroaniline was the only product detected over a series of supported Ni catalysts. This is the first time that such product exclusivity has been achieved in gas phase operation. The synthesis of bimetallic Pd-Ni/Al2O3 (prepared via co-impregnation) proved effective to enhance catalytic activity while maintaining 100% selective -NO2 reduction, a result ascribed to bimetallic particle formation as established by TPR, H2 chemisorption and XRD analyses. Nevertheless, the three systems (supported Pd, Ni and Pd-Ni) suffered a loss of activity with time-on-stream. Monometallic Au catalysts promoted the exclusive and time invariant formation of p-chloroaniline. The incorporation of Au (as a modifier) with Pd via reductive deposition to form Au-Pd/Al2O3 (Pd/Au=10 mol/mol) did not influence catalytic performance, which was equivalent to that delivered by Pd/Al2O3, i.e. aniline was the predominant product. On the other hand, the inclusion of Pd (as a promoter) with Au (at Au/Pd≥20) via co-impregnation and/or co-deposition precipitation resulted in increased hydrogenation rate while retaining exclusivity to pchloroaniline, an effect resulting from a surface Pd-Au synergism demonstrated by DRIFTS analysis. With the goal of elevating the catalytic activity of Au, the possible role of the oxide (Al2O3 vs. TiO2) support to modify catalytic response was considered. Au/TiO2 delivered a higher specific rate that was attributed to a combination of smaller Au particle size (with higher number of defects) and possible p-chloronitrobenzene activation via interaction(s) with TiO2 surface oxygen vacancies. This work was extended to decouple the individual contribution of each factor by (i) considering a series of oxide supports that exhibited a range of acid-base and redox surface properties, i.e. Al2O3, TiO2, Fe2O3 and CeO2 and (ii) controlling the Au particle size using two synthesis methods (deposition-precipitation and impregnation). The results demonstrated that specific activity increased with decreasing particle size (from 9 to 3 nm), regardless of the nature of the support. Furthermore, in the case of Au/Fe2O3, XRD and TPR analyses have established that Au can promote the partial reduction of the iii support (from α-Fe2O3 to Fe3O4), an effect more pronounced for smaller Au particles (< 5 nm) where H2-TPD suggests the participation of spillover hydrogen in this reduction step. A similar effect was also found for the TiO2 allotropic phase transition (from anatase to rutile), which can occur at lower temperatures due to the presence of Au, as demonstrated by DRS UV-vis, XRD and BET measurements. Having established that supported Au is effective in promoting the exclusive reduction of p-chloronitrobenzene to p-chloroaniline, hydrogenation selectivity was proved further by considering the reduction of m-dinitrobenzene. The reaction products, i.e. m-nitroanline (partial -NO2 reduction) and m-phenylenediamine (complete -NO2 reduction) are both high value intermediates in the fine chemical industry but existing routes can not achieve high selectivity to either product. It is shown that the nature of the oxide support (for TiO2-rutile, TiO2-anatase, Al2O3, CeO2, Fe2O3) does not have a direct effect on the rate of nitro-group reduction, which is controlled by Au particle size where a mean size of 5 nm was found to be critical in that with larger particles, nitrogroup reduction rate was structure insensitive. In contrast, the nature of the support has a direct effect on the selectivity response. Au/TiO2 and Au/Fe2O3 promoted the exclusive hydrogenation of m-dinitrobenzene to m-nitroaniline, Au/CeO2 delivered mphenylenediamine as the sole product and Au/Al2O3 generated a mixture of both products. This response can be accounted for on the basis of a modification to the electronic character of the Au nanoclusters induced by the acid-base Lewis properties of the support that impacts on the adsorption/activation of m-dinitrobenzene. A similar alteration of the electronic nature of Au can also be induced by alteration of the Au particle size or the introduction of a second metal (Ni). Taking the same reaction over Au/Al2O3, Ni/Al2O3 and Au-Ni/Al2O3, it is established that it is possible to control product composition in terms of partial (over Au) or complete nitro-group reduction (over Ni) or a combination of both (over Au-Ni), which can be attributed to a surface Au-Ni synergism as suggested by XPS and EDX mapping measurements. In order to assess the impact of annealing treatment on catalytic response, the analysis was extended to the preparation and application of an Au-Ni/Al2O3 alloy, formation of which is demonstrated by XRD, DRS UV-Vis and HRTEM. While alumina supported bimetallic and alloy both promoted the formation of both m-nitroaniline and mphenylenediamine via a predominantly stepwise reduction mechanism, the annealed (alloy) system delivered rate constants up to two orders of magnitude lower. In the final section of this thesis, the catalytic behaviour of supported (TiO2) Au and Ag is iv compared in the selective hydrogenation of a series of para-substituted nitroarenes. While both catalysts promoted the exclusive nitro-group reduction, Ag/TiO2 delivered lower reaction rates. The reaction mechanism has been probed by adopting the Hammett approach, where the linear correlation and positive slopes (higher for Au than Ag) associated with the Hammett plots are consistent with an electron withdrawing substituent activation effect, i.e. nucleophilic attack and a more effective reactant activation over Au/TiO2. The results presented in this thesis demonstrate, for the first time, that catalytic hydrogenation over gold-based catalysts in continuous flow gas operation is a viable, clean high throughput route to aromatic amines. The findings of this thesis show that Au on reducible supports with dAu < 5 nm is the optimum monometallic formulation while -NO2 group reduction rate and/or selectivity can be controlled (or tuned) by (i) changing the acid-base Lewis character of the support, (ii) modifying Au dispersion or (iii) incorporation of Pd or Ni as promotors. This work represents a critical advancement in the sustainable production of high value fine chemicals.Item A tunable microcavity for semiconductor quantum dots(Heriot-Watt University, 2009-07) Barbour, Russell James; Warburton, Professor RichardSemiconductor optical microcavities that combine high Q-factors with a small mode volume play a vital role in modifying the interaction between light and matter. Several interesting phenomena arise when an emitter is introduced into such a cavity. These include enhancement or suppression of the spontaneous emission rate (weak coupling) and normal mode splitting (strong coupling). In order to fully exploit the high Q and low mode volume of current microcavities, it is crucial for the emitter to be resonant with the cavity mode. Furthermore the emitter must be located at the exact antinode of the cavity electric eld. Wavelength tuning in semiconductor monolithic microcavities is challenging and is traditionally achieved by altering the temperature or using the Stark shift to alter the emitter's wavelength. Spatially matching the emitter to the electric eld antinode in monolithic cavities is even more challenging. The work in this thesis addresses these challenges. The realisation of a miniaturised, fully tunable Fabry-P erot type microcavity for semiconductor quantum dot experiments is presented. The cavity has a high Q-factor and low mode volume. The cavity wavelength is tuned by altering the air gap between the mirrors to vary the cavity length. This allows a much broader tuning range than is possible using monolithic cavities. In this work the cavity modes are characterised using a xed wavelength laser technique and varying the cavity length. A high nesse is obtained by using a miniaturised concave mirror which laterally con nes the optical mode. Unprecedented in situ control over a single InAs/GaAs quantum dot within the cavity mode is demonstrated at 4 K. The Purcell e ect is demonstrated for a single quantum dot, spatially positioned at the exact antinode of the electric eld. The cavity beam waist at the dot layer is experimentally measured and shown to be in good agreement with the theoretical value. The cavity mode volume is calculated from the measured beam waist. The e ect of weakly coupling a single dot to the cavity transverse modes is also investigated. Photoluminesence data from a high dot density sample within the cavity is presented. An anti-crossing behaviour between an ensemble of dots and the cavity mode is demonstrated. Finally, a dot dependent Fano e ect in the absorption lineshapes in a chargetunable sample is presented. A subtle interaction with an electronic continuum is revealed. The Fano e ect is shown to become more pronounced with increasing excitation power.Item Human retinal oximetry using hyperspectral imaging(Heriot-Watt University, 2009-12) Alabboud, Ied; Harvey, Professor AndyThe aim of the work reported in this thesis was to investigate the possibility of measuring human retinal oxygen saturation using hyperspectral imaging. A direct non-invasive quantitative mapping of retinal oxygen saturation is enabled by hyperspectral imaging whereby the absorption spectra of oxygenated and deoxygenated haemoglobin are recorded and analysed. Implementation of spectral retinal imaging thus requires ophthalmic instrumentation capable of efficiently recording the requisite spectral data cube. For this purpose, a spectral retinal imager was developed for the first time by integrating a liquid crystal tuneable filter into the illumination system of a conventional fundus camera to enable the recording of narrow-band spectral images in time sequence from 400nm to 700nm. Postprocessing algorithms were developed to enable accurate exploitation of spectral retinal images and overcome the confounding problems associated with this technique due to the erratic eye motion and illumination variation. Several algorithms were developed to provide semi-quantitative and quantitative oxygen saturation measurements. Accurate quantitative measurements necessitated an optical model of light propagation into the retina that takes into account the absorption and scattering of light by red blood cells. To validate the oxygen saturation measurements and algorithms, a model eye was constructed and measurements were compared with gold-standard measurements obtained by a Co-Oximeter. The accuracy of the oxygen saturation measurements was (3.31%± 2.19) for oxygenated blood samples. Clinical trials from healthy and diseased subjects were analysed and oxygen saturation measurements were compared to establish a merit of certain retinal diseases. Oxygen saturation measurements were in agreement with clinician expectations in both veins (48%±9) and arteries (96%±5). We also present in this thesis the development of novel clinical instrument based on IRIS to perform retinal oximetry.