The work in this thesis is a study of excimer laser induced damage in optical materials. This includes characterization of the focused laser radiation, development of sensitive techniques for the early detection of laser damage and finally laser damage studies at 193 nm and 248 nm in crystalline materials, metal mirrors and dielectric coatings. Characterization of the focused laser radiation involved pulse energy, temporal pulse profile and spatial profile measurements. This was assisted by development of a laser attenuator using a variable length liquid cell with a dynamic range of 25 dB. Non-linear absorption phenomena were observed in liquids at high intensities. Beam profiling methods were used to show the intensity distribution in the focal region of a lens was reproducible and approximated to a 2-D Gaussian function [continued]…

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Effective planning and management of transportation infrastructure requires adequate geospatial data. Existing geospatial data acquisition techniques based on conventional route surveys are very time consuming, labor intensive, and costly. Mobile laser scanning (MLS) technology enables a rapid collection of enormous volumes of highly dense, irregularly distributed, accurate geo-referenced point cloud data in the format of three-dimensional (3D) point clouds. Today, more and more commercial MLS systems are available for transportation applications. However, many transportation engineers have neither interest in the 3D point cloud data nor know how to transform such data into their computer-aided model (CAD) formatted geometric road information. Therefore, automated methods and software tools for rapid and accurate extraction of 2D/3D road information from the MLS data are urgently needed. This doctoral dissertation deals with the development and implementation aspects of a novel strategy for the automated extraction of road information from the MLS data. The main features of this strategy include: (1) the extraction of road surfaces from large volumes of MLS point clouds, (2) the generation of 2D geo-referenced feature (GRF) images from the road-surface data, (3) the exploration of point density and intensity of MLS data for road-marking extraction, and (4) the extension of tensor voting (TV) for curvilinear pavement crack extraction. In accordance with this strategy, a RoadModeler prototype with three computerized algorithms was developed. They are: (1) road-surface extraction, (2) road-marking extraction, and (3) pavement-crack extraction. Four main contributions of this development can be summarized as follows. Firstly, a curb-based approach to road surface extraction with assistance of the vehicle???s trajectory is proposed and implemented. The vehicle???s trajectory and the function of curbs that separate road surfaces from sidewalks are used to efficiently separate road-surface points from large volume of MLS data. The accuracy of extracted road surfaces is validated with manually selected reference points. Secondly, the extracted road enables accurate detection of road markings and cracks for transportation-related applications in road traffic safety. To further improve computational efficiency, the extracted 3D road data are converted into 2D image data, termed as a GRF image. The GRF image of the extracted road enables an automated road-marking extraction algorithm and an automated crack detection algorithm, respectively. Thirdly, the automated road-marking extraction algorithm applies a point-density-dependent, multi-thresholding segmentation to the GRF image to overcome unevenly distributed intensity caused by the scanning range, the incidence angle, and the surface characteristics of an illuminated object. The morphological operation is then implemented to deal with the presence of noise and incompleteness of the extracted road markings. Fourthly, the automated crack extraction algorithm applies an iterative tensor voting (ITV) algorithm to the GRF image for crack enhancement. The tensor voting, a perceptual organization method that is capable of extracting curvilinear structures from the noisy and corrupted background, is explored and extended into the field of crack detection. The successful development of three algorithms suggests that the RoadModeler strategy offers a solution to the automated extraction of road information from the MLS data. Recommendations are given for future research and development to be conducted to ensure that this progress goes beyond the prototype stage and towards everyday use.

Laser processing of NiTi shape memory alloys (SMA) has been identified as having great potential in surface treatment, welding, and novel performance requirement applications. However, discrepancies arise regarding whether laser processing improves or degrades the corrosion performance of NiTi-based SMAs. This is a cause for concern over the reliability of the laser processed surfaces. Prior to full scale implementation, a better understanding of oxide evolution during laser processing is required. The first part of this study concerned a systematic investigation of the surface of Ni-44.2 wt.% Ti SMA after the application of differing amounts of laser pulsing and thus energy input. Specific focus was directed on characterizing local changes in the surface oxide adjacent to laser spots. The sample local electrochemical characteristics were investigated by scanning electrochemical microscopy (SECM). The effect of laser processing on the regeneration kinetics of the redox-active mediator was analyzed through microelectrode current maps and approach curves in the feedback mode. Raman spectroscopy was used to determine the crystallinity of the oxide and potentiodynamic cyclic polarization was used to determine oxide stability. Results showed that for a small number of pulses (i.e. low total energy input) corrosion performance was determined primarily by topographical effects. However, increasing the number of pulses (i.e. higher total energy input) had a significant impact on the stability of the oxide in the heat-affected zone (HAZ) region due to the increase in crystallinity, which dictated where the corrosion initiated. In the second part of this study, post-process surface treatments that could be applied to NiTi SMA after laser processing were systematically investigated. Specific focus was directed at characterizing the crystallinity of the newly formed oxides and the stability across the entire surface (containing laser-processed regions and retained base material). Raman spectroscopy and potentiodynamic cyclic polarization were used for this analysis. Results showed that the post-process surface treatments successfully restored the corrosion performance to pre-laser-processing conditions by eliminating crystallinity in the surface oxide and reducing inhomogeneity across the surface.

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The work described in this thesis is concerned with the development of new applications of the photo-CIDNP (photochemically induced dynamic nuclear polarization) technique to aspects of protein structure and folding. Chapters 1 and 2 are introductory chapters; Chapter 1 describes the theoretical basis of the CIDNP phenomenon in terms of the underlying spin chemistry of the radical pair mechanism, while Chapter 2 presents the apparatus, photosensitizer and pulse sequences used, along with some important experimental considerations. Chapter 3 describes how ¹⁵N CIDNP can be used to probe the accessibility of tryptophan side-chains in both native and denatured states of proteins. The polarization of indole nitrogens in uniformly ¹⁵N labeled protein is detected in a two-dimensional ¹⁵N-¹ H NMR heteronuclear correlation experiment. Chapter 4 describes two new techniques offering considerable improvements in the quality of photo-CIDNP spectra of proteins. Both focus on the problem of progressive photo-degradation of the flavin dye and in both cases a larger number of scans can be accumulated before the flavin is exhausted than would otherwise be possible. In Chapter 5, the potential of stopped-flow photo-CIDNP spectroscopy for the study of protein folding is explored. Rapid dilution of denatured protein into a buffer solution is used to initiate a refolding process which is followed using short laser pulses to generate ¹H CIDNP in the side-chains of exposed aromatic residues. In Chapter 6, the field dependence of amino acid photo-CIDNP intensities is investigated using a stopped-flow CIDNP device that allows sample irradiation over a range of magnetic fields (0.1-7 T) within the bore of a 9.4 T NMR magnet and rapid transfer into the NMR tube for detection. Finally, in Chapter 7 two photo-CIDNP techniques that probe the exposure of aromatic residues in partially folded states are described. Both involve transfer of polarization to the native state for detection. One approach achieves this kinetically by rapid refolding, and the other involves monitoring exchange cross peaks in a two-dimensional CIDNP spectrum under conditions where the two states are interconverting.

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