<p> This dissertation is concerned with establishing the conditions under which planar phase interfaces are morphologically unstable during phase transformations in isothermal ternary systems. First, linear perturbation methods are employed in a detailed treatment of precipitatematrix interface stability for dilute ternary systems. Following this, the stability of the planar interface in a two-phase ternary diffusion couple is examined with the aid of perturbation theory. An experimental investigation into the stability of <alpha>-<beta> phase interfaces in the Cu-Zn-Ni system at 775°C is described. The results of this experimental study are shown to be in good agreement with the earlier theoretical predictions. </p> / Thesis / Doctor of Philosophy (PhD)

<p dir="ltr">Nucleic acid testing has become a prominent method for rapid microbial detection. Unlike polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP) is a simple method of nucleic acid amplification where the reaction can be performed at a constant temperature and the output provided in a colorimetric format. A transparent water bath heater is a desirable instrument to perform the heating and observe the visual results of nucleic acid amplification. However, existing methods of heating the water are not convenient for loading and unloading the nucleic acid samples. Here, we developed a field-deployable water bath heating device—an isothermal heater called IsoHeat for short–which is solely dedicated to performing LAMP reactions and can heat the water up to 85 °C (if needed). Using 3D-printing and LASER-cutting technology, we fabricated different parts of the device and mechanically assembled the parts to develop the entire device. Users can commence the heating by pressing the start button on the screen after entering the target temperature. Subsequently, the device heats up the water bath and maintains the target temperature through a PID algorithm-based control system. We demonstrate that IsoHeat can operate in environmental temperatures ranging from 5-33 °C and it can conduct LAMP reactions in a liquid format as well as in paper-based devices. IsoHeat is more efficient and user-friendly compared to a commercially available immersion-heating device, which is often used to perform LAMP reactions. This newly developed device would be helpful to detect pathogens conveniently in the field (e.g., at the point-of-care for human applications, on farms for plant and animal applications, and in production facilities for food safety applications).</p>

No description available.

No description available.

No description available.

Concrete is the most widely used man-made material in the world. Its versatility, strength, and relative ease of construction allow it to be used in the majority of civil infrastructure. However, concrete production plays a significant role in greenhouse gas emissions, accounting for around 8% of CO2 emissions worldwide. This thesis aims to reduce the demand for cement in concrete construction, thus reducing the carbon footprint of the concrete, by focusing on classifying and determining the effectiveness of seven different quarry by-products as partial replacements of cement. Several methods were utilized in this study to characterize the quarry by-products: particle size distribution, helium pycnometry, X-Ray diffraction, X-Ray fluorescence, scanning electron microscopy, and a modified ASTM C1897 Method A that utilizes isothermal calorimetry and thermogravimetric analysis. These various methods allowed for the determination of the physical properties (e.g., gradation, specific gravity, and morphology) and the chemical properties (e.g., mineralogy and reactivity in a cementitious system). The quarry by-products were classified as four granites, two limestones, and one greenstone. These quarry by-products were found to be non-pozzolanic and non-hydraulic. However, there are indications that there may be reactions with the various clays and feldspars in the quarry by-products with calcium hydroxide, which suggests a degree of reactivity that is not necessarily pozzolanic or hydraulic. / Master of Science / Concrete is the most widely used man-made material in the world. Its versatility, strength, and relative ease of construction allow it to be used in the majority of civil infrastructure. However, concrete production plays a significant role in greenhouse gas emissions, accounting for around 8% of CO2 emissions worldwide. This thesis aims to reduce the demand for cement in concrete construction, thus reducing the carbon footprint of the concrete, by focusing on classifying and determining the effectiveness of seven different quarry by-products as partial replacements of cement. Several methods were utilized in this study to determine the physical properties (e.g., gradation, specific gravity, and morphology) and the chemical properties (e.g., mineralogy and reactivity in a cementitious solution) of the materials. The quarry by-products were classified as four granites, two limestones, and one greenstone. In general, these quarry by-products were not found to be reactive as a supplementary cementitious material, although the data may suggest some degree of reactivity between calcium hydroxide and the clays and/or feldspars in the quarry by-products.

Many environmental compartments are acknowledged transmission routes for infectious diseases, antibiotic resistance, and anthropogenic pollution. The need for environmental sensing has consistently been stressed as a means to minimize public health threats caused by such contaminants. Many analytical detection techniques have been developed and applied for environmental sensing. However, these techniques are often reliant upon centralized facilities and require intensive resources. For these reasons their use can be challenging under resource-constrained conditions characterized by poor water, sanitation, and hygiene (WASH) services. In this dissertation, we developed biotechnology- and/or nanotechnology-advanced analytical tools for environmental sensing that have potential for future application in regions with poor WASH services. First, loop-mediated isothermal amplification (LAMP) and nanopore sequencing were applied to develop assays for the detection of SARS-CoV-2, the causative agent of COVID-19, in wastewater samples. Second, surface-enhanced Raman spectroscopy (SERS) was applied for environmental detection of a range of analytes. Gold nanoparticle (AuNP)-based SERS substrates were fabricated by droplet evaporation-induced aggregation on a hydrophobic substrate. These SERS substrates were then applied for the detection of antibiotic resistance genes (ARGs) and other environmental contaminants (e.g., dye or hydrophobic organic contaminants). In a separate study, Au nanostructured SERS substrates were fabricated and applied for pH sensing in a range of environmental media. Finally, the environmental impact of an AuNP-based colorimetric detection assay was assessed via life cycle assessment. / Doctor of Philosophy / Environmental sensing is an important means to intervene against public health threats of infectious diseases and environmental contaminants. However, currently available analytical tools for environmental samples often require intensive resources that are not available in low- and middle-income countries. In this dissertation, we developed biotechnology and/or nanotechnology advanced analytical tools for environmental sensing that have potential future application applied under resource-constrained conditions. First, we applied loop-mediated isothermal amplification (LAMP) and nanopore sequencing to develop detection assays for SARS-CoV-2, the causative agent of COVID-19, in wastewater samples. Second, we applied surface-enhanced Raman spectroscopy (SERS) to develop assays for environmental analytes. We fabricated SERS substrates by evaporation-induced aggregation of gold nanoparticles (AuNPs) on a hydrophobic substrate and applied these for the detection of antibiotic resistance genes (ARGs) and other environmental contaminants. In addition, Au nanostructured SERS substrates were fabricated and applied for pH sensing in a range of environmental media. Finally, we used life cycle assessment to quantitatively evaluate the environmental impacts of an AuNP-based sensing applications.

No / Rheological characterisation of hydroxyapatite -high density polyethylene (HA-HDPE) composites has been performed in terms of isothermal compressibility and wall slip. Addition of HA to the polymer melt decreases the compressibility of the melt. The unfilled HDPE was found to exhibit wall slip at shear stresses as low as 0.10 MPa. The flow curves of the composites showed three distinct regions: a gradient at low shear rates; a plateau region; and a gradient at higher shear rate. An increase in rheometer pressure seems to suppress the slip in composites. The 40 vol.-% HA-HDPE composite exhibited two critical shear stresses, one corresponding to wall slip, which occurs in the lower shear rate region of the flow curve, and the other corresponding to a plateau, which is identified with the stick-slip behaviour of unfilled HDPE reported in the literature. The plateau shear stress increased with filler volume fraction and this effect is attributed to the decreased compressibility of the melt. A good correlation with a negative correlation coefficient was found to exist between compressibility and shear stress in the plateau region. The slip observed in unfilled HDPE and at low shear rates in the 40 vol.-% HA- HDPE systems has been explained in terms of a low molecular weight polymer layer formed at the melt/wall interface. The large interfacial slip observed in the plateau region is attributed to complete disentanglement of adsorbed chains from free chains at the melt/wall interface at and beyond the plateau region.

<p dir="ltr">Since the beginning of the HIV/AIDS epidemic, 85.6 million people worldwide have become infected with HIV; more than half of whom have died from AIDS-related complications.[1] Sustained viral suppression below the clinically relevant threshold (1000 copies per mL) with highly active antiretroviral therapy (HAART) has proven effective at managing and prolonging the life expectancy of people living with HIV (PLHIV). However, in 2022, 11.3 million PLHIV had still not achieved viral suppression and may become susceptible to both HIV transmission and a variety of opportunistic infections. Of particular importance is the complex issue of patient non-compliance in global HIV management due to social, economic, behavioral, and healthcare access barriers, potentially disconnecting many PLHIV from the HIV care continuum. Therefore, to boost patient engagement in clinical care and to improve overall patient outcomes, new approaches to viral load monitoring practices need to be developed to increase access, particularly in regions of high HIV prevalence.</p><p dir="ltr">Nucleic acid amplification tests (NAATs) have emerged as potent tools for monitoring viral load, with reverse transcription quantitative polymerase chain reaction (RT-qPCR) being recognized as the benchmark due to its sensitivity and ability for real-time quantification enabled by fluorescence signal emission. Nevertheless, RT-qPCR is burdened by drawbacks including extended processing times, high operational costs, and the requirement for specialized laboratory facilities. In this study, we propose a novel method for HIV-1 viral load monitoring by integrating reverse-transcriptase loop-mediated isothermal amplification (RT-LAMP) with real-time particle diffusometry (PD). This approach allows for the continuous monitoring of changes in the diffusion of 400 nm fluorescent particles during RT-LAMP amplification, targeting the <i>p24</i> gene region of HIV-1 RNA. This enables the real-time detection of amplification curves, achieving a detection sensitivity in water samples as low as 25 virus particles per μL within a short duration of 30 minutes. Additionally, to address challenges related to amplification inhibition in complex human specimens, we developed a power-free sample processing system specifically designed for extracting HIV-1 RNA from both whole blood and plasma.Top of FormBottom of FormThis system modifies a commercially available spin-column protocol by integrating a syringe device and handheld bulb dryer, thus eliminating the requirement for a centrifuge. The adaptation allows for the completion of the entire extraction procedure, encompassing viral lysis, RNA capture, washing, and elution of purified HIV-1 RNA, within a timeframe of less than 16 minutes. Subsequent analyses, including RT-LAMP and RT-qPCR, demonstrate a limit of detection of 100 copies per μL and an average RNA recovery of 32% (for blood) and 70% (for plasma) in the elution fraction. Further investigations emphasize the significant presence of purified RNA in the spin column volume (termed as dead volume), and the cumulative recovered RNA copies align with those obtained using the gold standard centrifugation extraction method. Ultimately, we incorporated the real-time quantitative PD-RT-LAMP assay onto a field-compatible handheld portable platform suitable for field use, featuring built-in quality control measures. This platform enables sample-to-answer viral load testing near the point of care (POC). Subsequently, we undertook essential preparatory steps, such as reagent drying to obviate the need for cold storage, initial device calibration, and hands-on training of laboratory personnel regarding device operation, to validate device performance within a cohort of individuals living with HIV (PLHIV). These innovations facilitate quick and comprehensive viral load determination, offering promise for enhanced HIV management and patient care</p>

A new method of in situ extraction of alcohols from fermentation broth was investigated. The extraction method exploited the latent advantages of the non-equilibrium phase interaction of the fluid system in the flash tank to effectively recover the alcohol. Carbon dioxide gas ranging from 4.2L/min to 12.6L/min was used to continuously strip 2 and 12% (v/v) ethanol solution in a fermentor with a recycle. Ethanol and water in the stripped gas was recovered by compressing and then flashing into a flash tank that was maintained at 5 to 70bar and 5 to 55oC where two immiscible phases comprising CO2-rich phase (top layer) and H2O-rich phase (bottom layer) were formed. The H2O-rich bottom layer was collected as the Bottoms. The CO2-rich phase was continuously throttled producing a condensate (Tops) as a result of the Joule-Thompson cooling effect. The total ethanol recovered from the extraction scheme was 46.0 to 80% for the fermentor containing 2% (v/v) ethanol and 57 to 89% for the fermentor containing 12% (v/v) ethanol. The concentration of ethanol in the Bottoms ranged from 8.0 to 14.9 %(v/v) for the extraction from the 2 %(v/v) ethanol solution and 40.0 to 53.8 %(v/v) for the 12% (v/v) fermentor ethanol extraction. The Bottoms concentration showed a fourfold increase compared to the feed. The ethanol concentration of the Tops were much higher with the highest at approx. 90% (v/v) ethanol, however the yields were extremely low. Compression work required ranged from 6.4 to 20.1 MJ/kg ethanol recovered from the gas stream in the case of 12% (v/v) ethanol in fermentor. The energy requirement for the 2% (v/v) extraction was 84MJ/kg recovered ethanol. The measured Joule-Thompson cooling effect for the extraction scheme was in the range of 10 to 20% the work of compressing the gas. The lowest measured throttle valve temperature was -47oC at the flash tank conditions of 70bar and 25oC. Optimization of the extraction scheme showed that increasing the temperature of the flash tank reduced the amount of ethanol recovered. Increasing the pressure of the flash tank increased the total ethanol recovered but beyond 45bar it appeared to reduce the yield. The 12.6L/min carbon dioxide flow rate favored the high pressure(70bar) extraction whiles 4.2L/min appeared to favor the low pressure(40bar) extraction. The studies showed that the extraction method could potentially be used to recover ethanol and other fermentation products. / Master of Science