A proposition for a theater in Roanoke, Virginia is the vehicle for the exploration of architectural ideas on space, form, materiality, and atmosphere. The thesis developed through a series of models and drawings that studied oppositions in mass, scale, transparency, opacity, and most importantly, light vs. dark and day vs. night. / Master of Architecture

Yes / Contrast discrimination measures the smallest difference in contrast (the threshold) needed to successfully tell two stimuli apart. The contrast discrimination threshold typically increases with contrast. However, for low spatial frequency gratings the contrast threshold first increases, but then starts to decrease at contrasts above about 50%. This behaviour was originally observed in contrast discrimination experiments using dark spots as stimuli, suggesting that the contrast discrimination threshold for low spatial frequency gratings may be dominated by responses to the dark parts of the sinusoid. This study measures classification images for contrast discrimination experiments using a 1 cycle per degree sinusoidal grating at contrasts of 0, 25%, 50% and 75%. The classification images obtained clearly show that observers emphasize the darker parts of the sinusoidal grating (i.e. the troughs), and this emphasis increases with contrast. At 75% contrast, observers almost completely ignored the bright parts (peaks) of the sinusoid, and for some observers the emphasis on the troughs is already evident at contrasts as low as 25%. Analysis using a Hammerstein model suggests that the bias towards the dark parts of the stimulus is due to an early nonlinearity, perhaps similar to that proposed by Whittle.

This thesis is focused on the design, synthesis and characterization of magnetite-ionic copolymer complexes as nanocarriers for drug delivery and magnetic resonance imaging. The polymers included phosphonate and carboxylate-containing graft and block copolymers. Oleic-acid coated magnetite nanoparticles (8-nm and 16-nm diameters) were investigated. Cisplatin and carboplatin were used as sample drugs. The potentials of the magnetite-ionomer complexes as dual drug delivery carriers and magnetic resonance imaging agents were evaluated. An acrylate-functional poly(ethylene oxide) macromonomer and hexyl (and propyl) ammonium bisphosphonate methacrylate monomers were synthesized. Conventional free radical copolymerizations were conducted to synthesize the graft copolymers. The acrylate-functional poly(ethylene oxide) macromonomer was also used to form graft copolymers with tert-butyl acrylate. Block ionomers containing poly(tert-butyl acrylate) were synthesized via atom transfer radical polymerization, then the tert-butyl groups were removed to afford anions. All the monomers and polymers were characterized by 1H NMR to confirm their structures and assess their compositions. Phosphonate-containing polymers were also characterized by 31P NMR. Magnetite nanoparticles (8-nm diameter) were synthesized by reducing Fe(acac)3 with benzyl alcohol. The 16-nm diameter magnetite was synthesized by thermal decomposition of an iron oleate precursor in trioctylamine as a high-boiling solvent. The iron-oleate precursor was synthesized with iron (III) chloride hexahydrate and sodium oleate with mixed solvents. TEM images of the magnetite were obtained. Magnetite-ionomer complexes were synthesized by binding a portion of the anions (carboxylate or phosphonate) on the copolymers onto the surfaces the magnetite. The remainder of the anions was used to bind with cisplatin and carboplatin via chelation. Physicochemical properties of the complexes were measured by dynamic light scattering. All the complexes with different polymers and magnetite nanoparticles displayed relatively uniform sizes and good size distributions. The magnetite-ionomer complexes displayed good colloidal stabilities in simulated physiological conditions for at least 24 hours. Those graft and block copolymer-magnetite complexes may be good candidates as drug carriers for delivery applications. After cisplatin and carboplatin loading, the sizes of the complexes increased slightly and the zeta potential decreased slightly, which indicated that the loadings were successful. Minimal loss of iron was found, signaling that the binding strengths between the magnetite and the anions of the graft copolymers were strong. 8.7 wt% of platinum was found in the cisplatin loaded complexes and 6.9% in the carboplatin loaded complexes. The results indicated that the magnetite-graft ionomer complexes were capable of loading drugs. Drug release studies were performed at pH 4.6 and 7.4 to mimick endosomal conditions and the physiological environment. Sustained release of drugs was observed. This further indicated the potential for using the magnetite-ionomer complexes as drug carriers. Transverse relaxivities of the magnetite-ionomer complexes with and without drugs were measured and compared to a commercial T2-weighted iron MRI contrast agent-Feridex®. All the complexes had higher relaxivities compared to Feridex®. Thus, the magnetite-ionomer complexes are promising candidates for dual magnetic resonance imaging and drug delivery.Moreover, the aqueous dispersion of the complexes was found to heat upon exposure to an AC magnetic field, thus potentially allowing heat-induced drug release. / Master of Science

The harmonic generation due to the nonlinear behavior of Ultrasound Contrast Agents (UCAs) must be exploited for improved efficiency when imaging vascular targets in the neighborhood of highly echogenic tissue. One may even further improve the efficiency by focusing on the subharmonic generation of the UCAs, which is an even more exclusive property than the generation of higher harmonics, for improved Contrast-to-Tissue ratio (CTR). The aim of this work was first, the design of a set-up for nonlinear imaging of Poly-Vinyl Alcohol (PVA) based UCAs on The Verasonics Research System with special focus on nondestructive Subharmonic Imaging. The second part of the work addressed the evaluation of the subharmonic response provided by the agents in the developed setup. Six different imaging techniques were developed. These were Fundamental B-mode imaging (FB), Pulse Inversion imaging (PI), and a Contrast Pulse Sequence based on three pulses (CPS3), with and without a focus on the subharmonic component by the implementation of a Linear Bandpass Filter (LBF). Experiments were performed on a tissue mimicking flow phantom and the performance of the agents for each technique was determined in terms of CTR and CNR. The PVA agents provided a backscattering enhancement of the order of 23 dB through FB imaging. However, the performance of the FB technique was unsatisfactory in terms of CTR. The CPS3 sequence performed best of the six techniques with an improvement of 14 dB and 13 dB in CTR and CNR, respectively, compared with the FB technique. Combining the LBF around the subharmonic component with the multi-pulse techniques of PI and CPS3 resulted in a degraded CTR performance due to significant amount of signals from tissue around the subharmonic component and insufficient subharmonic detection from the PVA agents.

Yes / PURPOSE. Glaucoma raises contrast detection thresholds, but our natural visual environment is dominated by high contrast that may remain suprathreshold in early to moderate glaucoma. This study investigates the effect of glaucoma on the apparent contrast of visible stimuli. METHODS. Twenty participants with glaucoma with partial visual field defects (mean age, 72 ± 7 years) and 20 age-similar healthy controls (mean age, 70 ± 7 years) took part. Contrast detection thresholds for Gabor stimuli (SD, 0.75°) of four spatial frequencies (0.5, 1.0, 2.0, and 4.0 c/deg) were first measured at 10° eccentricity, both within and outside of visual field defects for participants with glaucoma. Subsequently, the contrast of a central Gabor was matched to that of a peripheral Gabor with contrast fixed at two times or four times the detection threshold. Data were analyzed by linear mixed modelling. RESULTS. Compared with controls, detection thresholds for participants with glaucoma were raised by 0.05 ± 0.025 (Michelson units, ± SE; P = 0.12) and by 0.141 ± 0.026 (P < 0.001) outside and within visual field defects, respectively. For reference stimuli at two times the detection contrast, matched contrast ratios (matched/reference contrast) were 0.16 ± 0.039 (P < 0.001) higher outside compared with within visual field defects in participants with glaucoma. Matched contrast ratios within visual field defects were similar to controls (mean 0.033 ± 0.066 lower; P = 0.87). For reference stimuli at four times the detection contrast, matched contrast ratios were similar across all three groups (P = 0.58). Spatial frequency had a minimal effect on matched contrast ratios. CONCLUSIONS. Despite decreased contrast sensitivity, people with glaucoma perceive the contrast of visible suprathreshold stimuli similarly to healthy controls. These results suggest possible compensation for sensitivity loss in the visual system. / Supported by a College of Optometrists PhD Scholarship. / Research Development Fund Publication Prize Award winner, June 2020

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<p>In this thesis, I experimentally investigate feeding selectivity in fallow deer (Dama dama), with respect to plant secondary compounds, especially tannins, which can decrease the quality of foods. I found that fallow deer avoided foods with higher amounts of tannic acid and Quebracho tannin, even though the deer ate some high-tannin food. The food choice was strongly dependent on the context in which the food was presented, so that the food choice in relation to tannin content was relative rather than absolute. When high-tannin food occurred at low frequency, the deer ate proportionally less from this type of food, at least when the difference in tannin content between the two foods was large. A basic implication is that an unpalatable plant type could benefit from its unpalatability, especially when occurring at low frequency. In experiments with two patches, the finding of a stronger within- than between-patch selectivity was mirrored in associational effects. First, low-tannin, palatable food was more eaten when occurring in a high-tannin patch, which corresponds to neighbour contrast susceptibility. Second, high-tannin, unpalatable food in a less defended patch was less eaten, which corresponds to neighbour contrast defence. A proximate cause of the associational effects can be the presence of a simultaneous negative contrast, which was experimentally demonstrated in an additional study. Individual differences in selectivity were present early in life and were consistent over five years, and selectivity was correlated with foraging exploratory behaviour. The results from this thesis suggest that fallow deer are selective in their food choice with respect to tannins from the beginning, and that the frequency of occurrence of different foods, but also the distance between foods and the complexity of presentation, influence the food choice. It is also suggested that a foraging behavioural syndrome is present in mammalian herbivores.</p>

In this thesis, I experimentally investigate feeding selectivity in fallow deer (Dama dama), with respect to plant secondary compounds, especially tannins, which can decrease the quality of foods. I found that fallow deer avoided foods with higher amounts of tannic acid and Quebracho tannin, even though the deer ate some high-tannin food. The food choice was strongly dependent on the context in which the food was presented, so that the food choice in relation to tannin content was relative rather than absolute. When high-tannin food occurred at low frequency, the deer ate proportionally less from this type of food, at least when the difference in tannin content between the two foods was large. A basic implication is that an unpalatable plant type could benefit from its unpalatability, especially when occurring at low frequency. In experiments with two patches, the finding of a stronger within- than between-patch selectivity was mirrored in associational effects. First, low-tannin, palatable food was more eaten when occurring in a high-tannin patch, which corresponds to neighbour contrast susceptibility. Second, high-tannin, unpalatable food in a less defended patch was less eaten, which corresponds to neighbour contrast defence. A proximate cause of the associational effects can be the presence of a simultaneous negative contrast, which was experimentally demonstrated in an additional study. Individual differences in selectivity were present early in life and were consistent over five years, and selectivity was correlated with foraging exploratory behaviour. The results from this thesis suggest that fallow deer are selective in their food choice with respect to tannins from the beginning, and that the frequency of occurrence of different foods, but also the distance between foods and the complexity of presentation, influence the food choice. It is also suggested that a foraging behavioural syndrome is present in mammalian herbivores.

Thesis (doctoral)--Technische Universiteit Eindhoven, 1999. / Originally published: Knegsel : HV Press, 1999. Includes bibliographical references and index.

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