Molecular imaging using fluorescence spectroscopy-based techniques is generally inefficient due to the low quantum yield of most naturally occurring biomolecules. Current fluorescence imaging techniques tag these biomolecules chemically or through genetic manipulation, increasing the complexity of the system. A technique capable of imaging these biomolecules without modifying the chromophore and/or its environment could provide vital biometric parameters and unique insights into various biological processes at a molecular level. Pump probe spectroscopy has been used extensively to study the molecular properties of poorly fluorescing biomolecules, because it utilizes the known absorption spectrum of these chromophores. Optical Coherence Tomography (OCT) is an optical imaging modality that harnesses the power of low coherence interferometry to measure the 3-D spatially resolved reflectivity of a tissue sample. We plan to develop a new molecular imaging modality that combines these techniques to provide 3-D, highresolution molecular images of various important biomolecules. The system uses a Fourier domain OCT setup with a modified sample arm that combines the "pump" and "probe" beams. The pump beam drives the molecules from the ground state to excited state and the probe interrogates the population change due to the pump and is detected interferometrically. The pump and the probe beam wavelengths are optimized to maximize absorption at the pump wavelength and maximize the penetration depth at the probe wavelength. The pump-probe delay can be varied to measure the rate at which the excited state repopulates the ground state, i.e., the ground state recovery time. The ground state recovery time varies for different chromophores and can potentially be used to identify different biomolecules. The system was designed and optimized to increase the SNR of the PPOCT signals. It was tested by imaging hemoglobin and melanin samples and yielded encouraging results. Potential applications of imaging hemoglobin using this technique include the mapping of tissue microvasculature and measuring blood-oxygen saturation levels. These applications could be used to identify hypoxic areas in tissue. Melanin imaging can provide means of demarcation of melanoma in various organs such as skin, eye and intestines.

A detailed understanding of the corneal biomechanical response is an important prerequisite to understanding corneal diseases such as keratoconus and for placing the empirical equations used in refractive surgery on a physical basis. We have assembled a combined nonlinear optical microscopy (NLOM) and optical coherence microscopy (OCM) imaging system to simultaneously capture coregistered volumetric images of corneal morphology and biochemistry. Fudicial markers visible in the OCM volume enabled the calculation of strains for multiple depth layers in rabbit cornea. The results revealed a depth dependent strain distribution, with smaller strains in the anterior stroma and larger strains in the posterior stroma. The stress-strain curves can be grouped readily by depth into three groups: anterior (~20%), transitional mid (~40%), and posterior (~40%). Cross-sectional images of collagen lamellae, visible in NLOM, showed inhomogeneous collagen structure and its response to intraocular pressure along the anterior-posterior direction. The inhomogeneities correlate well with the noted heterogeneous corneal mechanical properties. The combined NLOM-OCM system can measure corneal microstructure and mechanical response uniquely, thus providing a microstructural understanding of corneal response to changes of collagen structure.

Coherence in written discourse has been a problematic concept for many English Language Teachers when teaching to write in English. It is considered as a crucial part of academic written discourse, which students are expected to master to be able to pursue their academic studies. This study aims to examine how much the coherence-related difficulties/problems of Turkish EFL students in writing English essays are related to writing Turkish essays. The subjects for this study were chosen from the upper-intermediate level students at the Preparatory Program of Istanbul Bilgi University. For a detailed understanding of the nature of the coherence-related difficulties/problems of students&rsquo / Turkish and English essays, this study suggests a pragmatic analysis, involving the use of Grice&rsquo / s Cooperative Principle and maxims and sub-maxims of Cooperation. This study was conducted in the middle of 2005-2006 Academic Year with the participation of 20 students who were chosen randomly. Each student was asked to write an essay in English on a given topic from their weekly program. Threeweeks later, the same students were asked to write essays on the same topic in Turkish. Thus, 20 English essays and 20 Turkish essays (i.e., Total 40 essays) were collected as data for this study. The essays were rated for coherence by three different raters. All English essays were analyzed by one monolingual Americanrater and one bilingual (Turkish and English) rater. Similarly, all Turkish essays were analyzed by one monolingual Turkish rater and the same bilingual (Turkish and English) rater. The coherence ratings showed that there is a positive significant correlation between the coherence judgments of monolingual raters and the bilingual rater, which means that both monolingual raters and the bilingual rater agree on the similar coherence judgments. Next, the essays were analyzed in light of the Gricean Maxims to find the violations of each maxim in each essay by the researcher. In the comparison of maxim violations and the coherence judgments of the raters, the maxim of Relation was found to be the most significant maxim that affected the coherence judgments of the raters both for Turkish and English essays. In addition, Manner maxim was significant for Turkish essays and Quantity maxim was significant for English essays. However, in the comparison of the violation of individual maxims in Turkish and English essays, the violation of Relation maxim in English essays was found to correlate with the violation of Relation, Quality and Quantity maxims in Turkish essays. Similarly, violation of Manner maxim in English essays was also found to correlate with the violation of Quantity and Relation maxims. On the other hand, the violation of Manner maxim in Turkish essays was found to correlate with the violation of Quantity maxim in English essays. In conclusion, by looking at these relationships between Turkish essays and English essays, it may be argued that students may have inadequacies in writing skills or may lack some writing skills in Turkish, which may cause inadequacies in English academic writing skills. However, this study suggests the same study be replicated in different contexts and with larger sample sizes, similar research studies be conducted in Turkish writing instruction in the contexts of Turkish Secondary Education, and further studies be conducted on the effect of Relation and Manner maxims on other maxims.

Ocean ambient noise is one of factors that can affect the performance of sonar and underwater communication system, it can degrade the performance of sonar system on listening or active detection, and also can affect the quality of underwater communication. Due to the variation of temperature and density in the ocean which make ambient noise has directionality. Beamforming can analyze the directionality of noise energy. Conventional beamforming is based on the assumption of plane wave sound field, so the energy from each angle is obtained by linear accumulation of every element. However plane wave assumption may not be satisfied because of the boundary interactions of sound propagation and energy attenuation of water column, therefore conventional beamforming may have poor beam resolution and SNR in applications. This research is to study of the influence of spatial coherence of ambient noise on beam resolution, and to improve the beam resolution by using the adaptive algorithm from the communication system theory. Firstly, simulations were performed to study spatial coherence between plane wave and non-plane wave in ambient noise, and the results were compared with beam resolution. This research also analyzes the influence of different conditions of noise spatial coherence on beamforming with ASIAEX data. The results showed that ambient noise has lower spatial coherence at high frequency, and the beamforming has poor beam resolution because of the lower spatial coherence in noise. Therefore, the adaptive beamforming were performed to improve the beam resolution, and compared with the conventional beamforming. The results showed that the highest improvement on beam resolution is 42.9 %, and increased SNR by 6 dB. On the other hand, the application of ASIAEX data show that, the highest improvement on beam resolution is 40.0 %, and increased SNR by 8 dB. The noise notch of ambient noise became more significant by increasing in beam resolution, and it also promoted the accuracy of analysis on noise directionality.

Low frequency mechanical vibrations (<100 Hz) are naturally generated by skeletal muscles during voluntary contractions. Recording of these vibrations at the muscle surface are called surface mechanomyograms (S-MMGs). In this study, S-MMGs were recorded over a 3 x 5 grid of skin mounted accelerometers on the biceps brachii muscle during submaximal voluntary isometric contractions with the arm in a pronated position for ten healthy and young male subjects with no overt sign of neuromuscular diseases. For a given pair of accelerometers, the spatial coherence of S-MMG is a measure of the similarity of the S-MMG signals propagating between those two sensors. Two common techniques to estimate the spatial coherence for narrowband S-MMG signals, namely the magnitude squared coherence function and the maximum of the time-domain cross-correlation function, were found to yield similar results. In particular, high spatial coherence values were measured for sensor pairs aligned along the proximal to distal ends of the biceps, i.e. the longitudinal direction. On the other hand, the spatial coherence values for sensor pairs oriented perpendicular to the muscle fiber, i.e. along the transverse direction, were found to be significantly lower. This finding indicates that coherent S-MMGs were mainly propagating along the muscle fibers direction (longitudinal) of the biceps brachii within a frequency band varying between 10Hz to 50Hz. Additionally, the spatial coherence of S-MMGs along the longitudinal direction was found to decrease with increasing frequency and increasing sensor separation distance and to increase with contraction level varying between 20% to 60% of the maximum contraction level.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 157-163). Available also in a digital version from Dissertation Abstracts.

Semiconductor quantum dots tightly confine excited electron-hole pairs, called excitons, resulting in discrete energy levels similar to those of single atoms. Transition energies in the visible or near-infrared make quantum dots suitable for many applications in quantum optics and quantum information science, but to take advantage of all the properties of quantum dot emission, it is necessary to excite them coherently which has been a great challenge due to background scattering of the excitation laser. This dissertation presents the first coherent control of a single quantum dot with observation of its resonance fluorescence and decoherence phenomena. Strong continuous-wave excitation causes the dot to undergo several Rabi oscillations before emitting. These are visible as oscillations in the first- and second-order correlation functions of the emission, and the quantum dot states are "dressed", resulting in a Mollow triplet in the emission spectrum. Some resonantly excited dots, in addition to resonance fluorescence, also emit light from excited states several meV higher in energy. Such up-conversion fits existing theories of decoherence but has never been directly observed before. The up-conversion intensity is shown to be described well by a fairly simple three-level model with single-phonon absorption. The coherent phenomena of resonance fluorescence and the decoherence due to up-conversion paint a dual picture of single quantum dots wherein they can sometimes be treated as an ideal two-level system, but their interactions with the host crystal can lead to many complex behaviors. / text

Glaucoma is the second leading cause of blindness worldwide after cataract. Retinal nerve fiber layer thickness (RNFLT), phase retardation, and birefringence measured by Polarization Sensitive Optical Coherence Tomography (PS-OCT) have been used for glaucoma diagnosis. We first investigated two different image registration algorithms, a mutual information (MI) based algorithm and a log-polar transform cross-correlation (LPCC) based algorithm, on both human and non-human primate models. We evaluated the effects of image registration on longitudinal analysis of RNFLT in non-human primates using PS-OCT. Then, we investigated thickness, phase retardation, birefringence, and reflectance of the retinal nerve fiber layer as measured by PS-OCT in normal and glaucomatous non-human primates in a longitudinal study. We defined a new Reflectance Index (RI) and demonstrated that it might be an earlier indicator of glaucoma onset than RNFLT, phase retardation, or birefringence. Finally, we validated this finding on cross-sectional clinical study on human eyes measured by PS-OCT and RTVue OCT. For the data measured by PS-OCT, we showed that for distinguishing between glaucomatous and healthy eyes, as well as for distinguishing between glaucoma suspect and healthy eyes, our new normalized RNFL reflectance index (NRRI) performs significantly better than phase retardation and birefringence. The performances of NRRI and RNFL thickness in both conditions were statistically indistinguishable in this study, which is likely due to the limited sample size. For the data measured by RTVue OCT, the performances of NRRI and RNFL thickness were statistically indistinguishable for distinguishing between glaucomatous and healthy eyes. NRRI performs significantly better than RNFL thickness for distinguishing between glaucoma suspect and healthy eyes. NRRI also performs significantly better than temporal, superior, nasal, inferior and temporal (TSNIT) average and nerve fiber indicator (NFI) from GDx VCC for distinguishing between glaucoma suspect and healthy eyes. NRRI is a promising parameter for distinguishing glaucoma suspect and healthy eyes and may indicate disease in the pre-perimetric stage. / text

In 1946 the World Health Organization (WHO) stated that in order to promote overall health in a given population, it is necessary to identify factors that contribute to health and well-being, and not to solely focus on methods to reduce vulnerability to distress. Over 50 years later the WHO (2006) identified the Lesbian, Gay, Bisexual, Transgender, and Questioning (LGBTQ) community as a specific sub-population that requires particular investment in finding ways to reduce their observed higher rates of distress and suicidality. During this same half-century, U.S. colleges and universities transitioned from being fundamentally mono-cultural student bodies to becoming more multicultural in nature. In essence, each college’s student body is now a population of populations. One prominent population among the larger student body is the LGBTQ college student community. Furthermore, the LGB portion of this college sub-population has been identified as an under-researched subset of the larger LGBTQ population (Russell et al., 2011). This is because past research has been limited by drawing primarily upon non-college adolescent LGBTQ samples and has over generalized its findings by the inclusion of the Transgender and Questioning populations, which have been observed to report even higher rates of distress and suicidality than the LGB community (Clements-Nolle et al. 2006; Goldblum et al. 2012). This study is designed to refine our understanding of the LGB college sub-population by first examining if trends of increased acquired vulnerability for distress and suicidality found in studies of the adolescent LGBTQ population (Garofalo, Wolf, Kessel, Palfrey, & DuRant, 1998; Russell & Toomey, 2010; Haas et al., 2011; King et al., 2008) also exist in the LGB college sub-population. Second, in line with the World Health Organization’s goal of identifying protective qualities capable of enhancing and preserving one’s state of well-being and resilience, this study will be the first to examine if Sense of Coherence (SOC) serves as a moderating factor on LGB college students’ vulnerability to distress and suicidality, and thereby, contributes to overall well-being and health. Through this study, we hope to achieve a better understanding of LGB students’ vulnerability to distress and suicidality during the college years, as well as to examine the applicability of the SOC construct for health promoting interventions in the college population. / text

Abstract Cardiovascular disease is one of the leading causes of death in Canada. Atherosclerosis is considered the primary cause for cardiovascular disease. Optical coherence tomography (OCT) provides a means to minimally invasive imaging and assessment of textural features of atherosclerotic plaque. However, detecting atherosclerotic plaque by visual inspection from Optical Coherence Tomography (OCT) images is usually difficult. Therefore we developed unsupervised segmentation algorithms to automatically detect atherosclerosis plaque from OCT images. We used three different clustering methods to identify atherosclerotic plaque automatically from OCT images. Our method involves data preprocessing of raw OCT images, feature selection and texture feature extraction using the Spatial Gray Level Dependence Matrix method (SGLDM), and the application of three different clustering techniques: K-means, Fuzzy C-means and Gustafson-Kessel algorithms to segment the plaque regions from OCT images and to map the cluster regions (background, vascular tissue, OCT degraded signal region and Atherosclerosis plaque) from the feature-space back to the original preprocessed OCT image. We validated our results by comparing our segmented OCT images with actual photographic images of vascular tissue with plaque. / October 2015