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Vacuum field emission devices have become a promising candidate for emerging display technology due to their interesting properties compared to conventional thermionic emission devices that require high temperature and power to operate. Unlike thermionic emission, field emission devices can induce the electrons to emit at low temperature; sharp and thin emitters on the cathode are desired in order to increase the field emission. Many candidates from other research groups, such as Carbon Nanotubes (CNTs), SiC and ZnO, appear to have high field emission, but their complicated fabrication processes are the drawback. The silicon nanowhiskers produced by Geological & Nuclear Sciences (GNS) using Electron-Beam Rapid Thermal Annealing (EB-RTA) are an alternative material that is fast, inexpensive and uncomplicated to produce. They are based on the thermal desorption of silicon oxide, which forms silicon nanowhiskers on the silicon wafer in a short duration. Field emission diode structures on Silicon on Insulator (SOI) wafers were fabricated in order to investigate the field emission due to these GNS silicon nanowhiskers. An uncomplicated fabrication process using photolithography and etching process was developed. Electron beam lithography (EBL) was also used to create the different feature sizes directly onto the SOI wafer. The silicon nanowhiskers grown on these structures are as high as 35 nm with density distribution up to 30 µm⁻¹. The electrical characteristics of these devices are diode-like when the voltage range from -40 V to 40 V is applied. The best samples produced an emitted current as high as 2 mA, which is suitable for many applications, such as flat panel displays, x-ray sources and high frequency devices. However, in some cases, the diode structures failed to show the diode-like characteristics, perhaps as a result of bad contact connections or the emitters have been worn out after applying high voltage for some time. Device life time and stability were also considered and investigated via a number of electrical measurements for a period of time as long as one hour in this study. Even though these nanowhiskers have shown promising results, there are still many aspects to be considered to improve the experiments, such as the vacuum system and better contacts.

Antibody phage display technology mimics the natural immune system, and has been widely used for rapid isolation of single-domain antibodies (sdAbs) with various binding specificities and affinities in the micromolar to low nanomolar range. SdAbs are the variable regions of immunoglobulins (e.g., VH, VL, VHH) and serve as potential probes with therapeutic value. The small size, high solubility, high expression and stability, and high specificity and affinity for the cognate antigen, make sdAbs ideal in improving drug delivery and the overall therapeutic value of antibodies. The main objective of this thesis was to construct a large VL phage display library (~1010 diversity); analyze it via sequence analysis, and to subtractively pan the library for isolation of Neuropilin-1 (NRP1)-specific VLs. Neuropilin-1 (NRP1), a cell-surface receptor for both vascular endothelial growth factor (VEGF) and class 3 Semaphorins (Sema3A), contributes to neuron cell death through its interaction with Sema3A in stroke patients. Disruption of this NRP1-Sema3A interaction would allow for axonal outgrowth and neuron regeneration in the area of the brain affected by stroke. Construction of the synthetic phage antibody library utilized a single VL framework with selected positions in the complementarity-determining regions (CDRs) targeted for randomization in vitro using synthetic oligonucleotides that introduced sequence degeneracy. Specific VLs were then selected from the repertoire through subtractive panning against a cell line endogenously expressing NRP1 (PC12) as well as a negative cell line that does not express NRP1 (HEK293) with competitive elution carried out using a synthetic Sema3A-derived peptide. Fifteen VL clones were isolated, cloned in E. coli, expressed and purified, and of these, nine were determined to be non-aggregating by size exclusion chromatography. Further studies will determine the potential therapeutic use of these VL sdAbs as agents in recovery from stroke and neuron degeneration.

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

Many clinically important applications require measurements on a large portion of the human body surface that may not be visible from a single view. For example, a single view may be insufficient for the measurement of a complete facial surface for facial plastic surgery. And observing breast surfaces from multiple views is needed in accurate breast volume measurement. On the other hand most 3D vision systems only recover 3D data from a single viewpoint and the recovered 3D data are often incomplete due to the occlusion problem and thus cannot uniquely define the surface. A unique and more complete description of the surface is necessary for most applications such as measuring area or volume and finding the best 3D registration between corresponding surfaces. This thesis describes a structured light based system for fast and noncontact 3D measurement of the human body from multiple views. A particular application of our system is the study of human lactation through measuring the breast surface and volume. Fast, accurate, non-contact, and biologically safe measurement is the key requirement in our application. We use structured light to fulfill the requirement. Based on the SHAPE system [4,3], a single view structured light system developed at Monash University, our system for breast volume measurement generates more complete 3D information on object surfaces by observing the object from more than one viewpoint. The breast volume is computed using the integrated data from all views. We present a simple method that performs 3D measurement from multiple views simultaneously. Combined with a camera and a projector, a mirror is used in the method to create an additional viewpoint to recover the occluded regions that are illuminated by the light source but were previously invisible to the camera. Images from the two views one directly seen by the camera and the other seen via the mirror are taken simultaneously. We develop the method for the purpose of achieving more complete measurements without increasing image capture time, which is very useful in situations where both speed and accuracy are important. The complete 3D description of the surface of objects requires the acquisition of several images from different vantage viewpoints. Each image contains information on the part of the object that is visible from its viewpoint. A very important task consists in the integration of the information present in each view. We have developed a two view system to achieve a more complete breast volume measurement. The system uses a stationary sensor at each view. Our system can largely eliminate the occlusion regions produced by a single view system and all data from different views are integrated into an object centered coordinate system and resampled by a single parametric grid. The system has been used to accurately measure short term changes in breast volume for lactating mothers. Currently, the system is also used to observe the breast volume change of pregnant women over many weeks' time.