Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 92-95). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Hong Kong, 1987.

published_or_final_version / abstract / toc / Mathematics / Doctoral / Doctor of Philosophy

published_or_final_version / Mathematics / Master / Master of Philosophy

published_or_final_version / Mathematics / Master / Master of Philosophy

In this work we have made use of a geometric approach which quantifies robustness and performance and we finally combine them using a cost function. In particular, we calculate the robustness of the estimate of standard deviation of nominally Laplacian distribution. As this distribution is imperfectly known, we employ a more general family, the generalized Gaussian; Laplacian distribution, is one of the members of this family. We compute parameter estimates and present a classical algorithm which is then analyzed for distribution from the generalized Gaussian family. We calculate the mean squared error according to the censoring height k. We measure performance as a function of (1/MSE) and combine it with robustness using a cost criterion and design a robust estimator which optimizes a mix of performance and robustness specified by the user.

The aim of this research is to study the work function (Фm) tuning of the HfxSiyNz metal films through the incorporation of nitrogen. The Hf and the Si targets were co-sputtered in nitrogen (N2) and argon (Ar) plasma at 12mTorr. The gas flow ratio, RN = N2/ (N2+Ar), was adjusted to vary the nitrogen concentration in HfSiN films. The work function (Фm) of HfSiN gate extracted from the capacitance-voltage (CV) and the internal photoemission (IPE) measurements was found to decrease (from ~ 4.64eV to ~ 4.42eV) for increasing gas flow ratios (from 10% to 30%). X-ray photoelectron spectroscopy (XPS) was used for material characterization. During XPS analysis, the nitrogen (N 1s) peak intensity was observed to increase with increasing gas flow ratios. The results indicate that adjusting the nitrogen concentration in HfSiN films can be used to tune the HfSiN gate work function over ~ 0.2 eV tuning window.

The proportion of elderly individuals in society is increasing dramatically, leading to an increase in the prevalence of age-related neurological disorders that affect the function of the frontal lobes and overall movement control. This thesis aims to evaluate ‘executive control’ and the underlying brain changes in normal versus abnormal aging processes using saccadic eye movement tasks. Tasks performed by subjects that probe executive control consist of antisaccades (generate a voluntary eye movement after inhibiting an automatic movement to a visual stimulus), and memory-guided saccades (generate eye movements to three previous remembered visual stimuli in the same sequence they were presented). Both of these types of saccades require good functioning behavioural control, which is subserved by areas in the prefrontal cortex. This thesis specifically characterizes the changes in oculomotor control related to aging, Huntington’s disease, mild cognitive impairment (amnestic), and Alzheimer’s disease. We also specifically examine the neural mechanisms related to behavioural control in the antisaccade task in aging. Together, the conclusions drawn from this thesis reveal that specific areas in the prefrontal cortex are involved in executive dysfunction in both normal and abnormal aging, but the patient groups studied have provided new understanding that different underlying brain substrates may be altering function in the frontal cortical areas, such as the basal ganglia and the hippocampus. / Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2011-04-28 13:44:32.25

The aim of this research is to study the work function (Фm) tuning of the HfxSiyNz metal films through the incorporation of nitrogen. The Hf and the Si targets were co-sputtered in nitrogen (N2) and argon (Ar) plasma at 12mTorr. The gas flow ratio, RN = N2/ (N2+Ar), was adjusted to vary the nitrogen concentration in HfSiN films. The work function (Фm) of HfSiN gate extracted from the capacitance-voltage (CV) and the internal photoemission (IPE) measurements was found to decrease (from ~ 4.64eV to ~ 4.42eV) for increasing gas flow ratios (from 10% to 30%). X-ray photoelectron spectroscopy (XPS) was used for material characterization. During XPS analysis, the nitrogen (N 1s) peak intensity was observed to increase with increasing gas flow ratios. The results indicate that adjusting the nitrogen concentration in HfSiN films can be used to tune the HfSiN gate work function over ~ 0.2 eV tuning window.

The sodium-calcium exchanger (NCX) is a countertransporter of Na+ and Ca2+ across most cell membranes. It has been identified as an essential component of Ca2+ homeostasis in physiological and disease conditions in both cardiovascular and neurological settings. The exchanger not only transports Na+ and Ca2+, but is also regulated by these ions. Although ionic regulatory profiles differ between NCX isoforms, similar regulatory domains have been identified. Previous structure-function studies have determined key residues within these domains, particularly in the eXchanger Inhibitory Peptide region (XIP) and the Ca2+ binding domains (CBD1/2), which have a direct impact on ionic regulation of the outward exchange currents. Recent structural studies of the Ca2+ binding domains of NCX1 suggest a mechanism by which Ca2+ binding would not only be essential for activation of current but may also influence Na+-dependent inactivation. The alternative splice region is located within the Ca2+ binding domain and may play a role in mediating these regulatory phenotypes. Previous studies have demonstrated that specific combinations of the mutually-exclusive and cassette exons are associated with profound effects on ionic regulation in NCX1. This study focuses on examining the mechanisms by which the alternative splice region, in combination with specific regulatory domains, modulates exchange activity in two isoforms, NCX1 and NCX2. Chimaeric and mutant constructs in the alternative splice region were expressed in Xenopus oocytes and outward Na+-Ca2+ exchange activity was assessed using the giant, excised patch clamp technique. Substitution of the region corresponding to the mutually exclusive exon in either exchanger greatly reduced the extent of Na+-dependent inactivation, independently of intracellular Ca2+ concentrations. However, replacement of both the region corresponding to the mutually exclusive exon A and the XIP region reestablishes a wild-type profile in NCX2. The first mutually exclusive exon is therefore critical in determining Na+ and Ca2+-dependent regulatory properties. Furthermore, non-conserved residues within the XIP region may be essential in maintaining the structural stability of the Na+-dependent inactive state of NCX1, and by interacting with the mutually exclusive exon, may contribute to the structure-function relationship and the distinct regulatory phenotype of each Na+-Ca2+ exchanger variant and isoform.