This thesis is an investigation of methods to remediate methicillin-resistant Staphylococcus pseudintermedius (MRSP) biofilms through conventional and microfluidic-based in vitro assays. MRSP biofilm related infections are a major concern for veterinary clinicians as they may complicate remediation by the immune system or antimicrobials. Novel antimicrobials that have been found to reduce biofilm growth in other staphylococci were assessed in both mono- and combination therapy against MRSP biofilm. Quantitative assay results (p < 0.05) suggest fosfomycin alone and in combination with clarithromycin can significantly reduce biofilm formation. Morphological examination using scanning electron microscopy and atomic force microscopy further demonstrated the effectiveness of fosfomycin alone on biofilm formation on orthopaedic screws and mica sheets. Fabricated microfluidic assays were utilized to assess multiple concentrations of antimicrobial therapy against pre-formed biofilm under physiologically relevant conditions in a quick and repeatable manner. Results demonstrated the usefulness of microfluidic platforms in determining minimum biofilm eradication concentrations.

No description available.

Cement-based materials are of importance in the construction of geothermal wells and high-temperature oil and gas wells. These materials fill the annulus between the well casing and the rock forming a protective layer, known as sealant, which is used primarily to secure and support the casing inside the well. In addition it prevents entry of unwanted fluids into the well and communication between formation fluids at different levels. These cement based sealants need to perform for many years at high temperatures and in severe chemical environments; conditions which can cause the material of the well-casing to degrade resulting in reduced strength and increased permeability. The aim of this study is to develop new materials which will have the potential properties (high strength and low permeability) for use as sealants in geothermal and deep, hot oil wells. In order to do this special cement slurries, based on the CaO−Al2O3−SiO2−H2O (CASH) hydroceramic system, have been synthesised over the temperature range 200 to 350 °C (i.e. the typical working temperature of these wells). The additives used in these cement slurries are silica flour and alumina. A detailed description of a suite of novel hydroceramic compositions over the temperature range 200 to 350 °C is given. X-ray diffraction has been used to determine the mineralogical composition and Rietveld refinement to quantify the known phases present at different temperatures. In addition the chemistry of some of the major phases present has been examined using electron probe microanalysis. Scanning electron microprobe and simulation software have been employed to study the crystal shape of these major minerals. The engineering properties of the hydroceramic materials are very important. A study of the compressive strength and permeability has been carried out over a range of temperature (200 to 350 °C). In addition permeability has been calculated using simulation software and the results compared with experimental values. Hydroceramic formulations with excellent strength and permeability measurements have been found. Some of these formulations have been tested for durability under simulated well conditions. These materials have been immersed into different brines for a certain period of time at temperatures between 200 to 300 °C. Some preliminary results regarding the changes in mineralogy in these samples are presented in this thesis. These experiments have been carried out at the Synchrotron Radiation Source (SRS) using tomographic energy-dispersive diffraction imaging (TEDII).

This thesis work describes the fabrication and surface enhanced Raman spectroscopy (SERS) characterization of vertically aligned nitrogen (N) doped multi walled carbon nanotube (MWCNT) forests coated by silver (Ag) and gold (Au) nanoparticles. In the present work, the CNT forests were grown from a catalyst metal layer by the chemical vapor deposition (CVD) process at temperature of 800 oC and a physical vapor deposition (PVD) and annealing processes were applied subsequently for the evaporation and diffusion of noble metal nanoparticles on the forest. Transistor patterning of 20, 50 and 100 μm were made onto the silicon-oxide (SiO2) wafers through the photolithography process with and without depositing a thickness of 10 nm titanium (Ti) buffer layer on the Si-surfaces. Iron (Fe) and cobalt (Co) were used together to deposite a thickness of 5 nm catalyst layer onto the Single Side Polished (SSP) wafers. As carbon and nitrogen precursor for the CNT growth was used pyridine. Two different treatment times (20 and 60 minutes) in the CVD process determined the CNT forest height. Scanning Electron Microscopy (SEM) imaging was employed to characterize the CNT forest properties and Ag and Au nanoparticle distribution along the CNT walls. The existence of “hot spots” created by the Ag and Au nanoparticles through the surface roughness and plasmonic properties was demonstrated by the SERS measurements. Accordingly, the peak intensity at wave number of 1076 cm-1 was picked up from each SERS spectra to establish the Ag- and Au-trend curves with different concentrations of 4-ATP solution. The SERS mapping was also carried out to study the Ag- and Au-coated CNT surface homogeneity and “hot spots” distribution on the CNT surface. The SERS enhancement factors (EF) were calculated by applying an analyte solution of ethanolic 4-ATP on the CNT surface. The calculated values of EF from Ag- and Au-coated CNT forests were 9×106 and 2.7×105 respectively.

The objective of this thesis is to present the fabrication of a multiphoton microscope and the underlying theory responsible for its proper functioning. A basic introduction to nonlinear optics will give the necessary knowledge to the reader to understand the optical effects involved. Femtosecond laser pulses will be presented and characterized. Each part of the microscope, their integration and the design of the microscope will be discussed. The basic concepts of laser scanning microscopy are also required to explain the design of the scanning optics. Fast scanning problems and their solutions are also briefly viewed. As a working proof, the first images taken with the microscope will be presented. Fluorescent beads, rat tail tendon, gold nanoparticles and pollen grain images using various nonlinear effects will be shown and discussed.

Human bone is considered one of the most direct and insightful sources of information on peoples of the past. As a result, curation protocols have been developed to ensure that the integrity of human skeletal collections is maintained. Although collections are generally considered safe when these protocols are followed, the results of this investigation show that the Tell Leilan skeletal collection from Syria (circa 2900 – 1900 BCE) was contaminated by microbial growth (also known as biodeterioration) during curation. This biodeterioration was evaluated by light microscopy (LM), by the application of a histological preservation index (HPI), and by scanning electron microscopy (SEM). All samples (n=192) were found to be biodeteriorated by LM and the HPI. SEM confirmed that the Tell Leilan skeletal material had been contaminated by a complex microbial aggregate known as a biofilm. Amycolatopsis sp. and Penicillium chrysogenum, along with species of Aspergillus, Chaetomium, and Cladosporium were isolated and cultured from several contaminated bones and were identified based on morphology and DNA sequences. The results of this research suggest that we must focus on new techniques to examine bone as well as on new conservation protocols designed to limit the growth of biofilms in human skeletal collections in the future.

Coronary artery disease is a leading cause of morbidity and mortality in developed countries. Percutaneous transluminal coronary angioplasty (PTCA) is an important treatment option when intervention is required; namely for patients with relatively severe occlusions. However, adverse events including recurrence of angina pectoris and restenosis of the treated artery limit patient prognosis, with subsequent re-vascularisation often necessary. Platelet activation accompanies PTCA, with platelet adhesion and aggregation involved in thrombus formation during restenosis. During platelet activation, highly coagulant platelet-derived microparticles (PMPs) are formed, and it is likely that these PMPs will also be produced during PTCA. While platelet aggregation inhibitors used during PTCA limit platelet aggregation and decrease the incidence of restenosis, they do not prevent PMPs being formed. PMPs are capable of adhesion and aggregation, and adhere to PTCA treated arteries in an animal model. Therefore, in order to understand the phenomenon of restenosis and its improved limitation, it is necessary to investigate PMP formation during PTCA. The field of PMP study is in its infancy, with conflicting results from the substantial inequities in methods of PMP measurement, which may be exacerbated by PMP heterogeneity. The current literature on this topic is reviewed in Chapter 2, where the PMP surface and possible functions are considered, and the PMP size and morphology examined. To conclude, the relationship between PMPs and PTCA is explored, with a focus on the potential role of PMPs in restenosis. The knowledge deficiencies in this field are highlighted at the conclusion of this chapter. Very little is known regarding the production of PMPs with PTCA. The level of PMPs during PTCA was monitored in paired arterial blood samples obtained from seventy-five patients undergoing the procedure (Chapter 3). A significant increase in PMPs from baseline to completion of PTCA was clearly demonstrated for the first time. This indicated that procoagulant PMPs are produced during PTCA and may contribute to subsequent restenosis. Furthermore, administration of the platelet aggregation inhibitor abciximab to a group of thirty-eight high risk patients limited PMP formation; given that abciximab patients required more rigorous PTCA, the protective benefit of this medication for PMP production is underlined. Although few patients in this study experienced restenosis, it is interesting to note that of those treated with abciximab, all patients suffering subsequent restenosis were revascularised using PTCA. This demonstrates that their occlusions were comparatively mild as the need for coronary artery bypass grafting was avoided, and suggests that minimisation of PMP levels may assist in limiting the progression of severe restenosis. The increased peripheral level of PMPs predicated investigation of the coronary circulation to determine local events. Although the level of PMPs increased significantly within the coronary arteries of PTCA patients, there was no corresponding increase in the coronary sinus (Chapter 4). This important finding indicated that significant levels of PMPs remained within the coronary circulation, where their ability to adhere, aggregate and accelerate haemostasis may allow them to contribute directly to restenosis. During the time when increased levels of PMPs were being formed, there was no evidence of platelet lysis, which refuted the hypothesis that PMPs are merely membrane fragments of lysed platelets. A wide variation in reported PMP sizes has contributed to the hypothesis that PMPs are heterogeneous. As morphological information can assist in understanding physiology, the final study was designed to investigate platelet morphology from PTCA patients (Chapter 5). Most platelets were activated prior to and following PTCA, with a slight decrease in body size occurring due to PTCA, presumably due to loss of cytoplasm in PMPs being shed as reported in the previous chapter. Importantly, platelet distal pseudopod buds were observed, and these did not alter significantly with PTCA. These buds were probably unformed PMPs, although the exact mechanism of PMP formation remains undetermined. The platelet pseudopods were longer and significantly thinner distally with PTCA, which may be due to movement of cytoplasm into these terminal swellings. In addition, buds or swellings directly on the platelet body were smaller following PTCA, and it is likely these may also be PMPs prior to detachment from the parent platelet. This work has contributed substantially to knowledge of PMPs produced during PTCA. The level of PMPs increased significantly in peripheral arterial samples, with the platelet aggregation inhibitor abciximab preventing this occurrence. This may indicate that functional aggregation receptors are an essential requirement for PMP formation under these conditions. However, it is possible for PMPs to be formed when aggregation is inhibited, and therefore the molecular mechanisms of PMP formation remain unconfirmed. The examination of PMPs from the coronary circulation provided valuable data indicating that PMPs are produced during PTCA but remain within the coronary circulation. As PMPs are capable of adhesion and aggregation, this strongly suggests that PMPs within the coronary circulation would contribute directly to pathogenesis of restenosis, although further investigation on PMPs with PTCA is necessary to confirm this association. The examination of platelet morphology during PTCA indicated that platelets possessed terminal pseudopod swellings, and cell surface swellings. Importantly, the terminal swellings, which are likely to be unformed PMPs, were observed for the first time during PTCA.

The influence of steel metallurgy on rock bolt SCC was studied using a series of commercial carbon and low-alloyed steels. The chemical composition, their mechanical properties and the microstructures of these steels varied considerably in order to gather information for the discussion of the metallurgical influences under Hydrogen Embrittlement (HE) and Stress Corrosion Cracking (SCC) conditions. In order to understand the metallurgical influences on Rock Bolt SCC, an evaluation was carried out to fifteen commercial steels. The experiments reproduced the Stress Corrosion Cracking condition at which commercial rock bolts had failed in Australians mines. Due to the selected materials, stress and electrolyte condition it is expected that Hydrogen Embrittlement (HE) will affect the steel failure. The approach was to use the Linearly Increasing Stress Test (LIST) and exposing the sample to a dilute pH 2.1-sulphate solution, in accordance with prior studies. Stress Corrosion Cracking was evaluated by analysing the decrease in tensile strength, loss of ductility and fractography observed using Scanning Electron Microscopy (SEM). The initial series of test to the fifteen steels were performed at the free corrosion potential (f.c.p.) vs. Ag/AgCl. From this initial test only five steels (AISI 1008, AISI 4140, AISI 4145H, pipeline X-65 and X-70) did not show Stress Corrosion Cracking features. These five steel were tested in accordance with the Linearly Increased Stress Test (LIST) in the dilute pH 2.1 sulphate solution at different electronegative applied potential to minimum value of -1500mV. The experimental procedure tried to reproduce the Stress Corrosion Cracking condition to identify the most aggressive condition the steel is able to support before failing due to Stress Corrosion Cracking to then compare the theory of SCC and HE in low carbon and low alloy steel with the obtained experimental results. The investigation compared the well-known theory of SCC and HE in low carbon and low alloy steel with the obtained experimental results. Surprisingly, the experimental result did not always agree with the theory.

Copper-alumina composites were developed for testing in abrasive wear applications. The composites featured a porous continuous ceramic-preform network infiltrated by a liquid metal to form the final consolidated composite. The liquid metal phase was pure copper. Six different ceramic preform variants were tested. Ceramic volume fractions of 40, 50 and 60% were used, of two preform types; one pure-alumina, and one with additional 2wt% copper(I) oxide (CU20), functioning as an infiltration aid, the effects of which were determined in a previous study; the copper-oxide reduced infiltration pressure and allowed the use of higher ceramic phase volume fraction in the final composite. Abrasive wear tests against two automotive braking system materials were conducted. Grey cast iron of alloy type GG15 was used to establish a baseline for behaviour of the six different composite samples and compare them. Following this, the three volume fraction variants of samples using the copper-oxide infiltration aid were trialled against a commercially-available European passenger vehicle brake pad friction material; ABEX 6091. Wear tests were conducted on a pin-on-disc tribometer. Hemispherical-headed pins were made from the composite and tested against rotating discs of the grey cast iron and the ABEX friction material. Contact velocity was kept constant at Ims-?? at room temperature in air, and contact loads up to 15N were used. Test loads of 1-4N were used against grey cast iron, and 15N against the ABEX friction material. Optical micrography was used to monitor the wear rate of samples tested against grey cast iron. Scanning electron microscopy (SEM) was used to characterise bulk microstructures and evaluate surface wear features. Transmission electron microscopy (TEM) was used for further microstructural investigation of the sintering and interfacial features of the undamaged pin samples, as well as damage zones and tribofilm compositions. Focussed ion beam (FIB) milling was used to create subsurface cross-sections of wear regions and prepare TEM samples. The wear performance of the different sample types was compared by ceramic content and preform additives. It was found that the wear resistance of pure-alumina preform composites was dependent on ceramic volume fraction. Increasing ceramic content lead to increased wear resistance. The lower sinter temperature of the samples with the copper oxide additive led to reduced wear resistance compared with the monolithic alumina preforms and changes in ceramic volume fractions were not discernable in wear resistance against grey cast iron. This could be further supported by qualitative micrographic observations. All tests against grey cast iron were dominated by tribochemical film formation, which was determined to be oxidation of the iron which formed at the composite pin contact surface. Further testing of the copper-oxide containing samples against the ABEX friction material revealed a mixed result; the 50 and 60% ceramic volume samples produced near-identical wear performance, while the 40% sample suffered poor wear resistance. The dominant wear mechanism of composite pins tested against the ABEX friction material was abrasive wear. Sub-surface analysis of wear pins revealed a prominent damage layer forming at the contact surface of all pin samples which progressively grew into the bulk material. This layer was believed to have an important effect on the wear behaviour of the materials.

Copper-alumina composites were developed for testing in abrasive wear applications. The composites featured a porous continuous ceramic-preform network infiltrated by a liquid metal to form the final consolidated composite. The liquid metal phase was pure copper. Six different ceramic preform variants were tested. Ceramic volume fractions of 40, 50 and 60% were used, of two preform types; one pure-alumina, and one with additional 2wt% copper(I) oxide (CU20), functioning as an infiltration aid, the effects of which were determined in a previous study; the copper-oxide reduced infiltration pressure and allowed the use of higher ceramic phase volume fraction in the final composite. Abrasive wear tests against two automotive braking system materials were conducted. Grey cast iron of alloy type GG15 was used to establish a baseline for behaviour of the six different composite samples and compare them. Following this, the three volume fraction variants of samples using the copper-oxide infiltration aid were trialled against a commercially-available European passenger vehicle brake pad friction material; ABEX 6091. Wear tests were conducted on a pin-on-disc tribometer. Hemispherical-headed pins were made from the composite and tested against rotating discs of the grey cast iron and the ABEX friction material. Contact velocity was kept constant at Ims-?? at room temperature in air, and contact loads up to 15N were used. Test loads of 1-4N were used against grey cast iron, and 15N against the ABEX friction material. Optical micrography was used to monitor the wear rate of samples tested against grey cast iron. Scanning electron microscopy (SEM) was used to characterise bulk microstructures and evaluate surface wear features. Transmission electron microscopy (TEM) was used for further microstructural investigation of the sintering and interfacial features of the undamaged pin samples, as well as damage zones and tribofilm compositions. Focussed ion beam (FIB) milling was used to create subsurface cross-sections of wear regions and prepare TEM samples. The wear performance of the different sample types was compared by ceramic content and preform additives. It was found that the wear resistance of pure-alumina preform composites was dependent on ceramic volume fraction. Increasing ceramic content lead to increased wear resistance. The lower sinter temperature of the samples with the copper oxide additive led to reduced wear resistance compared with the monolithic alumina preforms and changes in ceramic volume fractions were not discernable in wear resistance against grey cast iron. This could be further supported by qualitative micrographic observations. All tests against grey cast iron were dominated by tribochemical film formation, which was determined to be oxidation of the iron which formed at the composite pin contact surface. Further testing of the copper-oxide containing samples against the ABEX friction material revealed a mixed result; the 50 and 60% ceramic volume samples produced near-identical wear performance, while the 40% sample suffered poor wear resistance. The dominant wear mechanism of composite pins tested against the ABEX friction material was abrasive wear. Sub-surface analysis of wear pins revealed a prominent damage layer forming at the contact surface of all pin samples which progressively grew into the bulk material. This layer was believed to have an important effect on the wear behaviour of the materials.