The long term degradation of polyethersulfone (PES) based ultrafiltration membranes used in the dairy industry has been investigated. The main aim of the study was to identify characterisation techniques which could give an indication of the condition and performance of ultrafiltration membranes after long term exposure to sodium hypochlorite solution. Membranes were degraded using sodium hypochlorite solution at pH 9, 10, 11 and 12, and with 5000 ppm-days to 25,000 ppm-days of exposure at 55°C. The degraded membranes were studied using the following characterisation techniques: dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), tensile testing, field emission scanning electron microscopy with energy dispersive x-ray spectroscopy (FESEM-EDS), Fourier transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR), contact angle, drop absorption, zeta potential, liquid-liquid displacement porosimetery (LLDP), protein separation, and colour measurement. The protein separation test included membrane throughput measurements (using casein-whey as feed), with size exclusion chromatography and gel electrophoresis to analyse the feed, permeate and retentate. Also a membrane disinfection experiment was performed to study the effect of sodium hypochlorite pH on disinfection of mixed dairy culture.

In this thesis, I analyze the potential for a REDD+ program to succeed in Uganda at this time, and I explore why this may or may not be possible. REDD+, which stands for Reducing Deforestation and Forest Degradation, aims to enhance carbon stocks while also conserving and sustainably managing forests. In doing so, REDD+ not only works to offset carbon emission levels and conserve forests and forest biodiversity, but also provides financial benefits to REDD+ participant countries, thus improving the livelihoods of local people living adjacent to forests. This program is widely regarded as the most effective and least risky solution to deforestation and forest degradation in developing countries, however, I argue that this may not be the case. Government documents reveal a rather simplistic and idealistic view of the policy, its implementation process, and desired outcomes, while specific case studies in countries outside of Uganda in which the REDD+ program has been implemented or is in the process of being implemented reveal unaddressed concerns with the mechanism itself and within the surrounding communities. Based on my research, I believe that if the recommendations that I propose are not included in the REDD+ preparation and implementation phases, the REDD+ mechanism is not only predestined to fail, but also to harm the most at-risk stakeholders that it is meant to benefit.

Spinal cord injury (SCI) leads to axonal damage and limits the ability of the brain to communicate with the rest of the body. Several bioengineered approaches have been developed for the recovery of SCI. Among these techniques, degradable guidance tubes have shown promising results. However, design of nerve guide tubes requires several design considerations and has been a significant challenge. To assess the efficacy of a prototypical implanted nerve guide tubes, it is essential to perform continuous monitoring. In this respect, magnetic resonance imaging (MRI) is one of the most reliable imaging techniques as it offers the ability to achieve extraordinary high temporal and spatial resolution in addition to its non-invasive features. In spite of the excellent image quality of non-enhanced MRI various types of contrast agents have been developed to further enhance the contrast and allow improved visualization. The MRI contrast agents principally work by shortening the T1 or T2 relaxation times of protons located nearby. The presented study was intended to evaluate the in vitro degradation of the nerve guide tubes made of poly (lactic-co-glycolic acid) (PLGA). PLGA tubes incorporated with different concentrations of superparamagnetic iron oxide (SPIO) were scanned by MRI 3T on weekly basis during the degradation period. Spin-echo (SE) sequence with various echo times (TEs) ranged from 13.3 to 314.4 msec was applied. T2 mapping was computed using in-house algorithm developed in Matlab. Least square fit was used to find the slope of the decay curve by plotting log intensity on the y-axis and echo time on the x-axis. The average T2 values were calculated. Mass loss and water uptake of the degrading tubes were also measured weekly. Moreover, the micro-structural changes of the tubes were investigated using the scanning electron microscope (SEM). The MRI results showed that the concentration of SPIO affects the signal intensity of the T2 weighted images reducing the T2 relaxation time value. Accordingly, a linear correlation between SPIO concentration and T2 relaxation time was found. At the beginning of degradation, the SPIO nanoparticles were trapped within the polymeric network. Therefore, water penetration was the predominant factor affecting the T2 relaxation times. At week 5, a significant mass loss was observed. From this stage onwards, the trapped SPIO were released from the polymeric network increasing T2 relaxation time dramatically. According to SEM images, the size of the pores in PLGA guide tubes was increased with the degradation. Approaching the end of degradation, shrinkage of the tubes was observed and the degraded nerve guide tubes were shown to be collapsed. Similar shape variation was observed in T2 weighted MR images. In summary, this study provided an approach to non-invasive monitoring of degradation behavior of nerve guide tubes using contrast enhancement. The developed technique is of great importance since it opened an insight to non-invasive monitoring of tissue engineered scaffolds for in vivo studies.

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No description available.

A method to measure the mixed-mode fatigue behavior of environmentally degraded adhesive joints was developed. Firstly, the absorption and desorption of water in two different rubber-toughened epoxy adhesives was measured gravimetrically. The water absorption in both adhesives showed anomalous behavior that was fitted to a new “sequential dual Fickian” (SDF) model. The water desorption in both adhesives was modelled accurately using Fick’s law, and there was a significant difference in the amount of retained water after drying in the two adhesives. The effects of long-term aging were studied using open-faced specimens made with two different rubber-toughened epoxy adhesives. The contrasting results illustrated the effects of environmental degradation on the matrix and toughener. Furthermore, the differences in the degradation behavior of both adhesives, combined with gravimetric and dynamic mechanical thermal analysis (DMTA) results, were used to illustrate the role of retained water in degrading the toughening mechanisms. The measured fatigue results invalidated the environmental index (EI) hypothesis for fatigue behavior, at least for the relatively short aging times studied here. Compared with aging under constant humidity, the fatigue performance of joints was found to be superior after aging in a cyclic salt-spray environment due to the lower water concentrations in the adhesive. The effects of test environment humidity and temperature on the fatigue behavior were also studied using closed, un-aged specimens. Both individual and combined effects of temperature and humidity on fatigue behavior were studied. In elevated temperature and humidity environment, joint performance at higher crack growth rates was degraded solely due to the effect of the increased temperature, whereas fatigue performance at low crack growth rates degraded predominantly because of elevated moisture. Finally, to generalise the techniques developed to automotive aluminum sheets, a reinforced specimen was developed that avoids yielding of thin aluminum sheet adherends while loading. Fatigue testing with these reinforced specimens revealed that the fatigue behavior was sensitive to the loading phase angle and the orientation of rolling lines on the sheet. These reinforced specimens were also used to study the effects of long-term aging and the effects of test environment.

A method to measure the mixed-mode fatigue behavior of environmentally degraded adhesive joints was developed. Firstly, the absorption and desorption of water in two different rubber-toughened epoxy adhesives was measured gravimetrically. The water absorption in both adhesives showed anomalous behavior that was fitted to a new “sequential dual Fickian” (SDF) model. The water desorption in both adhesives was modelled accurately using Fick’s law, and there was a significant difference in the amount of retained water after drying in the two adhesives. The effects of long-term aging were studied using open-faced specimens made with two different rubber-toughened epoxy adhesives. The contrasting results illustrated the effects of environmental degradation on the matrix and toughener. Furthermore, the differences in the degradation behavior of both adhesives, combined with gravimetric and dynamic mechanical thermal analysis (DMTA) results, were used to illustrate the role of retained water in degrading the toughening mechanisms. The measured fatigue results invalidated the environmental index (EI) hypothesis for fatigue behavior, at least for the relatively short aging times studied here. Compared with aging under constant humidity, the fatigue performance of joints was found to be superior after aging in a cyclic salt-spray environment due to the lower water concentrations in the adhesive. The effects of test environment humidity and temperature on the fatigue behavior were also studied using closed, un-aged specimens. Both individual and combined effects of temperature and humidity on fatigue behavior were studied. In elevated temperature and humidity environment, joint performance at higher crack growth rates was degraded solely due to the effect of the increased temperature, whereas fatigue performance at low crack growth rates degraded predominantly because of elevated moisture. Finally, to generalise the techniques developed to automotive aluminum sheets, a reinforced specimen was developed that avoids yielding of thin aluminum sheet adherends while loading. Fatigue testing with these reinforced specimens revealed that the fatigue behavior was sensitive to the loading phase angle and the orientation of rolling lines on the sheet. These reinforced specimens were also used to study the effects of long-term aging and the effects of test environment.

The mechanisms underlying the effect of alterations in Type I collagen on bone mechanical properties are not well defined. Clinical tools for evaluating fracture risk, such as dual energy x-ray absorptiometry (DXA) and quantitative ultrasound (QUS) focus on bone mineral and cannot detect changes in the collagen matrix. The mechanical response tissue analyzer (MRTA) is a potential tool for evaluating fracture risk. Thus, the focus of this work was to investigate the effects of collagen degradation on bone mechanical properties and examine whether clinical tools can detect these changes. Female and male emu tibiae were endocortically treated with 1 M potassium hydroxide (KOH) solution for 1-14 days and then either mechanically tested in three-point bending, fatigued to failure or fatigued to induce stiffness loss. Computed Tomography scans, DXA, QUS, MRTA and three-point bend testing in the elastic region were performed on emu tibiae before and after either KOH treatment or fatigue to induce stiffness loss. Fracture surfaces were examined to determine failure mechanisms. Bone mineral and bone collagen were characterized using appropriate techniques. Bone mineral-collagen interface was investigated using Raman spectroscopy and atomic force microscopy (AFM). Endocortical KOH treatment does not affect bone mineral however, it causes in situ collagen degradation, rather than removal and may be weakening the mineral-collagen interface. These changes result in significantly compromised mechanical properties. Emu tibiae show significant decreases in failure stress and increased failure strain and toughness, with increasing KOH treatment time. The significant increase in toughness of KOH treated bones is due to structural alterations that enhance the ability of the microstructure to dissipate energy during the failure process, thereby slowing crack propagation, as shown by fracture surface analysis. KOH treated samples exhibit a lower fatigue resistance compared to untreated samples at high stresses only for both sexes. Partial fatigue testing results in similar decreases in modulus for all groups and sexes. The MRTA detected these changes whereas DXA and QUS did not. MRTA detects changes in bone mechanical properties induced by changes in collagen quality and fatigue and could be a more effective tool for predicting fracture risk.

This thesis presents a study of antioxidant depletion in water containing chlorinated species (water containing 10 ppm either Cl2 or ClO2, buffered to pH = 6.8), the degradation products in the aqueous phase, and polyethylene pipe degradation scenarios. A low molecular weight hydrocarbon analogue (squalane) was used instead of solid polyethylene as the host material for the antioxidants, and the depletion of antioxidants has been studied. The phenolic antioxidant Irganox 1010 was consumed ca. 4 times faster in water containing 10 ppm ClO2 than in water containing 10 ppm Cl2. The different degradation products in extracts from the aqueous phase identified by infrared, liquid chromatography and mass spectrometry revealed the different degradation mechanisms between ClO2 (" cleavage) and Cl2 (hydrogen substitution). The squalane test shows no energy barrier between 30 and 70 °C, and the activation energy of the antioxidant in solid PE was found to be ca. 21 kJ mol-1. A linear relationship has been established between the time to reach antioxidant depletion in the polyethylene tape samples and the time to reach depletion in samples based on squalane containing the same antioxidants. The surface oxidation and surface embrittlement of PE tape on long time exposure have been studied by IR and SEM. Pressure testing on medium density PE pipes with a controlled pH aqueous media (6.8 ± 0.2) containing 4 ppm either ClO2 or at 90 °C showed that the stabilizers were rapidly consumed towards the inner pipe wall and the rate of consumption in ClO2 was 4 times greater than in Cl2 solution. The subsequent polymer degradation was an immediate surface reaction. It was confirmed by differential scanning calorimetry, infrared spectroscopy and size exclusion chromatography that, in the surface layer which came into contact with the oxidizing medium, the amorphous component of the polymer was heavily oxidized leaving a highly crystalline powder with many carboxylic acid chain ends in extended and once-folded chains. / <p>QC 20130122</p>

This research study represents an important contribution towards fulfilling the long-term objective of the research program in terms of assessing and controlling seismic risks of building structures in low and moderate seismic regions such as Australia. The research outcome enables the existing building stock to be assessed in an inexpensive way. Post-disaster agencies and insurance agencies could then better assess risk exposure. The displacement controlled phenomenon associated with conditions in low and moderate seismic regions has become the basis of a new performance assessment methodology for strength degraded structures. / In low and moderate seismic regions the kinetic energy demand generated by a small or medium magnitude earthquake (M<7) (at an epicentral distance consistence with Peak Ground Velocity (PGV) of up to 80 mm/s on rock) will generally subside when the structure has been displaced to the maximum limit. Current design guidelines in seismic design and assessment of structures has been based on trading-off strength with ductility demand to accommodate large displacement without significant strength degradation to ensure that structures have sufficient energy dissipation capacity. The drift capacity recommended for strength degraded structures is quite low as per the current guidelines which are developed for high seismic regions and it is considered that a structure is deemed unsafe when the lateral strength has degraded by more than 20%. An important investigation has been undertaken to determine if such structures are actually unsafe, should the displacement controlled phenomenon be taken into account. / Therefore, the research described in this thesis is aimed at capitalizing the displacement controlled concept (not to be confused with the displacement based design methods) which is particularly relevant for low and moderate seismic regions for investigating the seismic performance of strength degraded structures. If the peak displacement demand (PDD) and the displacement capacity of the structure are known then the displacement based approach can be applied directly for assessing the performance of the structure. The seismic displacement demand is then simply compared with the displacement capacity to ensure that its gravity load carrying capacity is not compromised in the projected earthquake scenario. / A full scale testing was carried out under quasi-static conditions on a soft-storey building which was representative of existing building stock in low-moderate seismic regions to investigate the force-deformation relationship and drift capacity of soft-storey buildings. Data obtained from the full-scale experimental field studies on the force displacement behaviour of the building has been used as input into the nonlinear time history analyses to study the seismic response behavioral trends of soft-storey buildings. / A new simple methodology for estimating the peak displacement demand of inelastic nonlinear systems, which is based on the elastic displacement response spectra, was introduced. The major findings from the parametric studies shows that highest point on the elastic displacement response spectra can provide a conservative prediction of the maximum displacement demand of non-linear inelastic systems.