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A spectrally integrated response method is proposed for analyzing transmission data from nanohole array sensors. This method increases the sensitivity by reducing noise and taking more information from the spectrum for bulk and surface sensing. Results from both real experiments and idealized simulations are presented. Comparison with two other methods- peak transmission wavelength shift and a normalized difference integrated response method are shown. This method shows improved sensing performance which can be exploited in future. Further improvement in sensing using nanohole arrays is explored by improving the instrumentation of the sensor system. Design parameters of the nanohole arrays for transmission at two different operating wavelengths were examined by using finite difference time domain simulations. Focused ion beam milling was used to fabricate chosen arrays. A microfluidic chip with the embedded nanohole array sensor was used to introduce different solutions for bulk chemical sensing. Intensity measurements were taken with a high speed CMOS camera. Sensing results using this system with possible improvements shows promise for future sensing applications. / Graduate

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The plasma membrane, which separates intracellular contents from extra cellular milieu, consists of a lipid bilayer comprising mainly phospholipids and cholesterol together with various functional proteins, which control the interaction of the cell with its environment. Cells are killed at elevated temperatures and previous work suggests that the plasma membrane may be a primary target in this hyperthermic cell death. The present study set out to test this hypothesis using a rat liver tumour cell hue (Hepatoma Tissue Culture cells). Several different experimental approaches were adopted. Supplementation of these cells with linoleic acid (18 : 2) for a 36 hour period increased the thermal sensitivity of cells at 43 C, though increased sensitivity was not evident at other times. Plasma membrane-enriched fractions were obtained from control cells and from cells supplemented with linoleic acid for a 36 hour period, then lipids were extracted and characterised. Whilst there was little difference in the cholesterol : phospholipid ratio, the phospholipid fatty acid composition of membranes from supplemented cells showed elevated levels of 18 : 2 and decreased levels of oleic acid (18 : 1) relative to control cell membranes. DPH fluorescence polarisation studies indicated that plasma membranes from supplemented cells were less 'ordered' than control membranes. Alkaline phosphodiesterase I, a plasma membrane-bound enzyme, appeared to be more thermolabile in supplemented cells suggesting that plasma membrane 'fluidity' may be an important factor in determining the thermal sensitivity of this membrane-bound enzyme. Hyperthermic cell death was potentiated by the presence of local anaesthetics, two of which, dibucaine and tetracaine, also produced less 'ordered' membranes. Morphological studies conducted on cells in the presence and absence of local anaesthetic at elevated temperatures indicated changes in cellular surface morphology on heating which were accelerated in the presence of the anaesthetic. The intermediate filament network of these cells did not appear to be a primary target of hyperthermic treatment. These studies suggest that the lipid composition and physical state of the plasma membrane are critical features involved in the expression of cell death, possibly through a modulation of membrane protein thermal sensitivity.

This thesis investigated the behaviour and physiology of the visual system of Sepia officinalis by studying systematically its visual sensitivity and its spatial resolution. The cephalopod retina is composed of only photoreceptors and supporting cells, thereby providing a unique opportunity to study the interactions between photoreceptors, without the influence of other neurons, such as those typically found in the vertebrate retina. The minimum separable angle (MSA), a measure of spatial resolution, of S. officinalis was determined from behavioural experiments to be 42' for animals of 8 cm mantle length at 15 µW/cm² light intensity. As the animals grew in size and as the ambient light intensity was increased, S. officinalis showed improved visual acuity. Through these experiments, it was revealed that each tested size of animal adapted to light with similar efficiencies, and that factors other than retinal growth were involved in the improvement of behavioural MSA with increasing size. The minimum light intensity to which the retina of S. officinalis responded was 0.1 µW /cm2 , which was slightly higher than that to which individual photoreceptor cells responded. Retinal sensitivity decreased with increasing animal size. This was unexpected, as previous theoretical and behavioural studies in other species have shown sensitivity to increase with increasing animal size. Possible reasons for the decrease in sensitivity were a reciprocal decrease in cell resistance or an increase in dark noise. The visual sensitivity of S. officinalis was also affected by the stimulus flash wavelength and duration. Its retina adapted to background light in a way similar to vertebrate photoreceptors and the extracellular calcium concentration of the solution perfusing the retina affected this process. Finally, two series of experiments provided some evidence that functioning gap junctions exist in the retina of S. officinalis. By completing a study of the visual sensitivity of S. officinalis at the three levels of single cell, retina and whole animal, the visual processing that occurs between these physiological levels was investigated. From the work presented in this thesis, it is concluded that, although S. officinalis did not prove comparable in every aspect to other species on an intracellular level, it would be a useful model of behavioural and extracellular visual processes for both invertebrate and vertebrate species.

This research presents new physics-based methods to estimate predictive uncertainty stemming from uncertainty in the material opacities in radiative transfer computations of key quantities of interest (QOIs). New methods are needed because it is infeasible to apply standard uncertainty-propagation techniques to the O(105) uncertain opacities in a realistic simulation. The new approach toward uncertainty quantification applies the uncertainty analysis to the physical parameters in the underlying model used to calculate the opacities. This set of uncertain parameters is much smaller (O(102)) than the number of opacities. To further reduce the dimension of the set of parameters to be rigorously explored, we use additional screening applied at two different levels of the calculational hierarchy: first, physics-based screening eliminates the physical parameters that are unimportant from underlying physics models a priori; then, sensitivity analysis in simplified versions of the complex problem of interest screens out parameters that are not important to the QOIs. We employ a Bayesian Multivariate Adaptive Regression Spline (BMARS) emulator for this sensitivity analysis. The high dimension of the input space and large number of samples test the efficacy of these methods on larger problems. Ultimately, we want to perform uncertainty quantification on the large, complex problem with the reduced set of parameters. Results of this research demonstrate that the QOIs for target problems agree at for different parameter screening criteria and varying sample sizes. Since the QOIs agree, we have gained confidence in our results using the multiple screening criteria and sample sizes.

Thesis (Ph.D.)--University of Southern Mississippi, 2000. / Includes bibliographical references (leaves 216-229).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 39-45). Also available via the Internet.