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No description available.

No description available.

Nucleic acid analysis is one of the most important disease diagnostic approaches in medical practice, and has been commonly used in cancer biomarker detection, bacterial speciation and many other fields in laboratory. Currently, the application of powerful research methods for genetic analysis, including the polymerase chain reaction (PCR), DNA sequencing, and gene expression profiling using fluorescence microarrays, are not widely used in hospitals and extended-care units due to high-cost, long detection times, and extensive sample preparation. Bioassays, especially chip-based electrochemical sensors, may be suitable for the next generation of rapid, sensitive, and multiplexed detection tools. Herein, we report three different microelectrode platforms with capabilities enabled by nano- and microtechnology: nanoelectrode ensembles (NEEs), nanostructured microelectrodes (NMEs), and hierarchical nanostructured microelectrodes (HNMEs), all of which are able to directly detect unpurified RNA in clinical samples without enzymatic amplification. Biomarkers that are cancer and infectious disease relevant to clinical medicine were chosen to be the targets. Markers were successfully detected with clinically-relevant sensitivity. Using peptide nucleic acids (PNAs) as probes and an electrocatalytic reporter system, NEEs were able to detect prostate cancer-related gene fusions in tumor tissue samples with 100 ng of RNA. The development of NMEs improved the sensitivity of the assay further to 10 aM of DNA target, and multiplexed detection of RNA sequences of different prostate cancer-related gene fusion types was achieved on the chip-based NMEs platform. An HNMEs chip integrated with a bacterial lysis device was able to detect as few as 25 cfu bacteria in 30 minutes and monitor the detection in real time. Bacterial detection could also be performed in neat urine samples. The development of these versatile clinical diagnostic tools could be extended to the detection of various cancers, genetic, and infectious diseases.

Thesis (PhD)--University of South Australia, 1997

In this thesis, investigations into fabricating tin oxide hydrogen gas sensors from films assembled by the deposition of tin clusters are reported. The tin clusters were formed in a UHV compatible cluster apparatus by DC magnetron sputtering and inert gas aggregation. Through SEM imaging, it was found that the morphology of tin cluster assembled films deposited onto silicon nitride substrates was highly coalesced. The coalescence between the clusters was significantly reduced by reacting the clusters with nitrogen before they were deposited. This resulted in granular films with a grain size close to that of the deposited clusters. The coalesced and granular tin films were used to fabricate tin oxide conducti-metric gas sensors. This was done by depositing the tin films onto gold contacts and then oxidising them by baking them at 250°C for 24 hours. The sensors were tested using a purpose built gas test rig. It was found that the sensors with the granular film morphology were much more sensitive to 500 ppm, 1000 ppm, and 5000 ppm of hydrogen at 200°C in ambient air with zero humidity. This was attributed to the smaller grain size and the larger surface area of the granular films.

Experiments in the study of transient aerodynamics typically require pressure measurements with a high spatial and temporal resolution. Existing commercial pressure transducers are expensive and they provide a spatial resolution only on the order of millimetres. The full bandwidth of commercial devices (which extends to around 200 kHz) can only be utilised by exposing the transducer to the flow environment with very little thermal or mechanical protection. If insufficient protection is provided, the expensive commercial devices are likely to be damaged. Inexpensive pressure sensors based on extrinsic Fabry-Perot fibre optic interferometry are capable of measurement with a high spatial and temporal resolution. Thermal protection or isolation for these sensors is still required, but they can be exposed directly to the flow if the sensors are disposable (low cost). Excessive thermal or mechanical protection is not required for these sensors because the damaging heat transfer and particle impacts that may occur in transient aerodynamic facilities generally occur after the useful test flow. In this dissertation, a variety of construction techniques for diaphragm-based Fabry-Perot fibre optic pressure sensors were investigated and the advantages and disadvantages of all techniques are compared. The results indicate that using a zirconia ferrule as the substrate, a liquid adhesive as the bonding layer, and a polished copper foil as the diaphragm provide the best results. It is demonstrated that a spatial resolution on the order of 0.1 mm and a bandwidth to more than 100 kHz can be achieved with such constructions. A variety of problems such as hysteresis, response irregularity, low visibility and sensor non-repeatability were observed. By using a thinner bonding layer, a larger bonding area, longer cavity length, increased calibration period, and applying load cycling to the diaphragm, the hysteresis was minimized. Sensor response irregularity was also minimized using a polished diaphragm. Visibility increased to about 90% using active control of the cavity length during the construction process. Non-repeatability was found to be a consequence of adhesive viscoelasticity and this effect was minimized using a thin layer of adhesive to bond the diaphragm to the substrate. Due to the effects of adhesive viscoelasticity, the pressure sensors indicate an error of up to 10% of mean value for the reflected shock pressure. This error could not be further reduced in the current sensors configuration. Some new configurations are proposed to decrease the effect of sensor non-repeatability. The effect of pretensioning the diaphragm was investigated analytically but the results do not indicate any considerable advantage for the levels of pretension likely to be achieved in practice. However, the results do indicate that pretension effects caused by an environmental temperature change can damage the sensor during storage. The effect of the initial diaphragm deflection on the sensor performance and temperature sensitivity was modelled and the results show that an initial diaphragm deflection can improve the sensor performance. The effect of the thermal isolation layer on the sensor performance was also investigated and the results show that for a shock tube diaphragm bursting pressure ratio up to 5.7, heat transfer does not contribute to sensor errors for the first millisecond after shock reflection. However, it was found that the use of a thin layer of low viscosity grease can protect the sensor for about 20 ms while only decreasing its natural frequency by typically 17%. The grease layer was also found to decrease the settling time of a low damping ratio sensor by 40%. The sensor was successfully employed to identify an acoustic disturbance in a shock tube.

Thesis (M.S.)--University of Texas at El Paso, 2007. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (p. 105-114). Also available in electronic version.

Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2005. / Hesketh, Peter, Committee Chair ; Edmondson, Dale, Committee Member ; Frazier, Albert, Committee Member ; Hunt, William, Committee Member ; Janata, Jiri, Committee Member. Includes bibliographical references.