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​​Electrical resistance tomography (ERT) and electrical impedance tomography (EIT) are imaging techniques reconstructing the internal conductivity distribution image of an object based on voltage measurements at the periphery of the object with a given applied current. ERT uses a direct current (DC), while EIT uses an alternating current (AC). However, for low frequencies both ERT and EIT have the same governing equation, which is often referred to as a non-linear and ill-posed inverse problem. Both methods have diverse applications in biology, biomedicine, and industry. ​This master’s degree project aims to create a low-cost imaging system for the ERT, which is the main focus, as well as for the EIT. The project includes three main components: 1) Simulations and reconstructions using EIDORS (Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software), 2) Developing an experimental workbench (a measurement system), and 3) developing a machine learning model for the ERT. ​EIDORS was used to simulate and reconstruct ERT and EIT images. It was also used to generate training data for the machine learning model to be developed. ​The measurement system includes a circular water tank with electrodes, power supplies, and measurement units. Tanks with 8 and 16 electrodes were designed using 3D printers. Initially, aluminium electrodes provided inconsistent measurements due to magnetization and electrolysis, later replaced by graphite electrodes, offering better but not yet accurate enough results. ​After implementing reconstruction algorithms in EIDORS, a machine learning model was developed for ERT. It involved: 1) generating a training set, containing over 5000 simulated data points, 2) preprocessing the generated data set which included PCA dimensionality reduction, 3) and lastly a linear regression model developed. The model struggled with small object detection and occasional inconclusive results, likely due to limited training dataset diversity. Additionally, images of two cases were reconstructed using EIT and comparing it to ERT it can be concluded that EIT performs better than ERT. ​

Mobile platforms for archaeological purposes have increased in use over the last 20 years with many of the developments coming from Continental Europe. Mobile platform developments have mainly focused on one type of instrumentation, offering multiple sensors, depths of detection or frequencies. This development of mobile platforms has focused on data acquisition rates but has not considered the physical impact on the soil. The Geoscan Research Mobile Sensor Platform (MSP40) was intended to improve survey efficiency and remain a lightweight system. The platform can collect two earth resistance configurations that show directional variation of the current flow through soil. Additional sensors were integrated on to the square frame of the hand-pulled cart to record simultaneous fluxgate gradiometer data and a microtopographic surveys. Ground based geophysical investigation will always have a physical impact on a site. The MSP40 is no exception but careful selection of wheel types and the lightweight frame limit the damage compared to many mobile arrays. The MSP40 has been tested on a number of different soils at various times of the year with encouraging results; however issues with overcoming the contact resistance of electrodes remain. The continuous collection rate and combination of techniques means a slight drop in data quality is inevitable. However the increased data density, multiple-sensors and improved rate of collection offset reductions in data quality. The research has shown that the MSP40 can perform low impact rapid site assessments on 'vulnerable' sites, whilst maximising the information gained from a single traverse.

Blood-brain barrier (BBB) is a unique membranous barrier, which segregates brain from the circulating blood. It works as a physical and metabolic barrier between the central nervous system (CNS) and periphery. In mammals, endothelial cells were shown to be of BBB and are characterized by the tight junctions along with efflux system which are responsible for the restriction of movement of molecules within the cells. Efflux system consists of multidrug resistance proteins such as P-glycoprotein (P-gp). P-gp removes substances out back from the brain to the blood before they reach to the brain. So the barrier is impermeable to many compounds such as amino acids, ions, small peptides and proteins, making it the most challenging factor for the development of new drugs for targeting CNS. Curcumin is a bioactive compound that has a number of health promoting benefits such as anti-inflammatory, anticancer, anti-oxidant agent; as well as a role in neurodegenerative diseases, but low oral bioavailability is the major limiting factor. Low water solubility and rapid metabolism are the two important factors responsible for poor bioavailability of curcumin. Galaxolide is a musk compound and previously known for the bioaccumulation of toxic components in the aquatic animals by interference with the activity of multidrug/multixenobiotic resistance efflux transporters (MDR/MXR). The bioavailability of curcumin can be enhanced when administered with galaxolide. This study was carried out to investigate the effect of galaxolide on the permeation of curcumin through the epithelial cell monolayers. MDCKII-MDR1 cell monolayer is used an in vitro blood-brain barrier model while Caco-2 monolayer is used as an in vitro intestinal model, which also expresses the P-glycoprotein. The curcumin and galaxolide were separately solubilised in the DMSO and used in combination to perform permeation study, to determine the effect of galaxolide on curcumin permeation through epithelial cell monolayers. The galaxolide shows an efflux protein inhibition activity and this activity was used to enhance permeation of curcumin through the Caco-2 monolayer. In summary, galaxolide is a novel permeation enhancer molecule, which can be used for the improvement of drug delivery of other bioactive compounds in future.

Surfactants are molecules that contain a water-soluble and afat-soluble part. They have important functions in productssuch as detergents, cosmetics, pharmaceuticals and foods aswell as in many industrial processes. Surfactants are used onvery large scale, which makes it important to decrease theirimpact on the environment. This can be done by starting withnatural materials, by improving the synthetic methods and byreducing the use of limited resources such as energy andorganic solvents. This thesis focuses on lipase-catalyzed synthesis ofsurfactants based on natural products. It also includesfunctional studies of the produced surfactants; as antioxidantsin oils, or as surfactants to solubilize pharmaceuticals. Unsaturated fatty acid esters of ascorbic acid weresynthesized with catalysis by Candida antarctica lipase B int-amyl alcohol and in ionic liquids. High yields ofascorbyl oleate were obtained in an ionic liquid that wasdesigned to improve the solubility of the fatty acid, when thereaction was performed under vacuum. Ascorbyl oleate wasamorphous and was a better antioxidant than ascorbyl palmitatein rapeseed oil. Polyethylene glycol (PEG) stearate, PEG 12-hydroxystearateand a series of PEG 12-acyloxy-stearates were synthesized in avacuum-driven, solvent-free system usingC. antarcticalipase B as catalyst. Critical micelleconcentration and solubilization capacity were determined forthe PEG 12-acyloxy-stearates. Their effects on living cellswere evaluated in studies of hemolysis and transepithelialelectrical resistance. Several PEG1500 12-acyloxy-stearateswere excellent solubilizers for pharmaceutical use and hadnegligible negative effects on living cells even at highconcentrations. Enzymatic and chemo-enzymatic methods offer uniquepossibilities to synthesize surfactants of high purity. Pureand well-defined surfactants enable new applications and areimportant for the understanding of surfactantstructure-function relationships.

Radio magnetotellurics (RMT), crosshole ground penetrating radar (GPR), and crosshole electrical resistance tomography (ERT) were applied in a range of hydrogeological applications where geophysical data could improve hydrogeological characterization. A profile of RMT data collected over highly resistive granite was used to map subhorizontal fracture zones below 300m depth, as well as a steeply dipping fracture zone, which was also observed on a coinciding seismic reflection profile. One-dimensional inverse modelling and 3D forward modelling with displacement currents included were necessary to test the reliability of features found in the 2D models, where the forward models did not include displacement currents and only lower frequencies were considered. An inversion code for RMT data was developed and applied to RMT data with azimuthal electrical anisotropy signature collected over a limestone formation. The results indicated that RMT is a faster and more reliable technique for studying electrical anisotropy than are azimuthal resistivity surveys. A new sequential inversion method to estimate hydraulic conductivity fields using crosshole GPR and tracer test data was applied to 2D synthetic examples. Given careful surveying, the results indicated that regularization of hydrogeological inverse problems using geophysical tomograms might improve models of hydraulic conductivity. A method to regularize geophysical inverse problems using geostatistical models was developed and applied to crosshole ERT and GPR data collected in unsaturated sandstone. The resulting models were geologically more reasonable than models where the regularization was based on traditional smoothness constraints. Electromagnetic geophysical techniques provide an inexpensive data source in estimating qualitative hydrogeological models, but hydrogeological data must be incorporated to make quantitative estimation of hydrogeological systems feasible.

<p>Surfactants are molecules that contain a water-soluble and afat-soluble part. They have important functions in productssuch as detergents, cosmetics, pharmaceuticals and foods aswell as in many industrial processes. Surfactants are used onvery large scale, which makes it important to decrease theirimpact on the environment. This can be done by starting withnatural materials, by improving the synthetic methods and byreducing the use of limited resources such as energy andorganic solvents.</p><p>This thesis focuses on lipase-catalyzed synthesis ofsurfactants based on natural products. It also includesfunctional studies of the produced surfactants; as antioxidantsin oils, or as surfactants to solubilize pharmaceuticals.</p><p>Unsaturated fatty acid esters of ascorbic acid weresynthesized with catalysis by Candida antarctica lipase B in<i>t</i>-amyl alcohol and in ionic liquids. High yields ofascorbyl oleate were obtained in an ionic liquid that wasdesigned to improve the solubility of the fatty acid, when thereaction was performed under vacuum. Ascorbyl oleate wasamorphous and was a better antioxidant than ascorbyl palmitatein rapeseed oil.</p><p>Polyethylene glycol (PEG) stearate, PEG 12-hydroxystearateand a series of PEG 12-acyloxy-stearates were synthesized in avacuum-driven, solvent-free system using<i>C. antarctica</i>lipase B as catalyst. Critical micelleconcentration and solubilization capacity were determined forthe PEG 12-acyloxy-stearates. Their effects on living cellswere evaluated in studies of hemolysis and transepithelialelectrical resistance. Several PEG1500 12-acyloxy-stearateswere excellent solubilizers for pharmaceutical use and hadnegligible negative effects on living cells even at highconcentrations.</p><p>Enzymatic and chemo-enzymatic methods offer uniquepossibilities to synthesize surfactants of high purity. Pureand well-defined surfactants enable new applications and areimportant for the understanding of surfactantstructure-function relationships.</p>

In situ thermal treatment (ISTT) applications require successful gas capture for the effective remediation of chlorinated solvent dense non-aqueous phase liquid (DNAPL) source zones. Gas production and transport mechanisms during bench-scale electrical resistance heating (ERH) experiments were examined in this study using a quantitative light transmission visualization method. Processed images during water boiling indicated that gas bubble nucleation, growth and coalescence into a connected steam phase occurred at critical gas saturations of Sgc = 0.233 ± 0.017, which allowed for continuous gas transport out of the heated zone. Critical gas saturations were lower than air-water emergence gas saturations of Sgm = 0.285 ± 0.025, derived from the inflection point of ambient temperature capillary pressure-saturation curves. Coupled electrical current and temperature measurements were identified as a metric to assess gas phase development. Processed images during co-boiling of pooled trichloroethene (TCE) DNAPL and water indicated that discontinuous gas transport occurred above the DNAPL pool. When colder zones were introduced, condensation prevented the development of continuous steam channels and caused redistribution of DNAPL along the vapour front. These results suggest that water boiling temperatures should be targeted throughout the subsurface (i.e., from specific locations of DNAPL to extraction points) during ERH applications. Because convective heat loss and non-uniform power distributions have the potential to prevent the achievement of boiling temperatures, a thermal enhancement was developed where dissolved gas delivered to the target heated zone liberates from solution at elevated temperatures and increases gas production. Processed images of ERH-activated carbon dioxide (CO2) exsolution indicated that discontinuous gas transport occurred above saturations of Sg = 0.070 ± 0.022. Maximum exsolved gas saturations of Sg = 0.118 ± 0.005 were sustained during continuous injection of the saturated CO2 solution into the heated zone. Estimated groundwater relative permeabilities of krw = 0.642 ± 0.009 at these saturations are expected to decrease convective heat loss. Discontinuous transport of exsolved gas at sub-boiling temperatures also demonstrated the potential of the enhancement to bridge vertical gas transport through colder zones. In conclusion, sustained gas saturations and transport mechanisms were dependent on the mechanism of gas production and effects of condensation. / Thesis (Master, Civil Engineering) -- Queen's University, 2014-03-27 15:26:30.683

A dissertation submitted to the Faculty of Engineering, Cape Peninsula University of Technology, Cape Town, in partial fulfilment of the requirements for the MTech Degree in Mechanical Engineering 2012 / Flow features provide considerable guidance for the rational selection of techniques to predict hydraulic behaviour and for suitable operating conditions for pipelines. Traditionally, water was used to transport coarse particles, and it was necessary to operate at velocities at which the flow was turbulent in order to avoid blockage. Consequently the friction losses were too high for economic operation. In addition, wear on pipes, fittings and pumps presented serious problems. Nowadays, it is well established that it is possible to operate at very high solids concentration in a heavy vehicle (carrier fluid). Similar solids throughputs may be achieved at very much lower velocities by operating in the laminar flow regime. This results not only in lower power requirement, but it also reduces wear and water consumption. In spite of these potential benefits, only a few studies dealing with the transport of coarse particles in heavy media have been reported. Since the distinction between different flow patterns is of paramount importance for modelling purposes, as equations are flow pattern dependent, and given the importance of avoiding excessive wear of pipes at low and high velocities, the present work was carried out in the context of dense or non-Newtonian carrier fluid. This project comprised analysis of existing data acquired at the Flow Process and Rheology Centre of the Cape Peninsula University of Technology. Kaolin in the range of 6% to 15% volumetric concentration was used as a carrier fluid and coarse material in the range of 10% to 30% volumetric concentration was simulated by silica sand ranging in size from 1 mm to 3 mm. For the purpose of this study flow patterns derived from resistance curves for various mixtures, particle concentrations, particle grading and flow conditions were compared with “concentration profiles” and images obtained from electrical resistance tomography (ERT). It appeared from this work that the sand concentration does not change the flow pattern but increases or reduces the pressure gradients depending on the case. The concentration of kaolin carrier can change the flow patterns from layered to homogeneous flow, inducing an increase in total pressure gradients as it increases. Flow patterns obtained from ERT compared reasonably well with those derived from pressure gradients profiles. The transition velocities from layered to heterogeneous flow obtained from both methods were similar, especially for low and moderate carrier concentrations. As the kaolin carrier concentration or as the sand concentration increased it became more difficult to distinguish the transition velocity between heterogeneous and layered flow. More work is still needed to improve the ERT instrument and its image reconstruction software.