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The use of polarized light for characterization of biological tissues has received increased attention in recent years due to the wealth of information available in the interactions of polarized light with tissue and the noninvasive nature of optical radiation. While the depolarizing effects of multiple scattering complicate the use of polarimetry in tissue, many biological constituents affect the polarization of light such as collagen, muscle fibers, and glucose. Thus, if the effects of scattering can be accounted for⎯or utilized in the analysis⎯polarized light can potentially be used as a probe of tissue status. This thesis presents advancements in the techniques for the simulation of polarized light in tissue-simulating media, and explores two biomedical applications. Previous Monte Carlo models for simulation of polarized light propagation in tissue-simulating media do not include the effects of birefringence and optical activity, two polarizing effects of useful diagnostic potential. To overcome this limitation, our model was extended to include both these effects simultaneously, and then experimentally validated using a novel polarization phantom system. The use of polarized light for characterization of the myocardium, and specifically towards monitoring stem cell regenerative treatments of myocardial infarction, was investigated experimentally as a novel application for polarimetry. The potential for this technique is based on the changes in myocardial structure that occur with infarction and subsequent regeneration, and the associated changes in tissue birefringence. The use of polarized light for noninvasive tissue analyte monitoring, particularly glucose, was also investigated based on the optical activity exhibited by many tissue analytes due to their chiral structure. In this study, a novel combined optical polarization and intensity approach was developed and tested on Monte Carlo simulated data. The studies presented in thesis introduce new methods for polarization simulation and analysis in biological tissue and demonstrate potential for polarimetry in monitoring myocardial regeneration and noninvasive measurements of tissue analytes.

The use of polarized light for characterization of biological tissues has received increased attention in recent years due to the wealth of information available in the interactions of polarized light with tissue and the noninvasive nature of optical radiation. While the depolarizing effects of multiple scattering complicate the use of polarimetry in tissue, many biological constituents affect the polarization of light such as collagen, muscle fibers, and glucose. Thus, if the effects of scattering can be accounted for⎯or utilized in the analysis⎯polarized light can potentially be used as a probe of tissue status. This thesis presents advancements in the techniques for the simulation of polarized light in tissue-simulating media, and explores two biomedical applications. Previous Monte Carlo models for simulation of polarized light propagation in tissue-simulating media do not include the effects of birefringence and optical activity, two polarizing effects of useful diagnostic potential. To overcome this limitation, our model was extended to include both these effects simultaneously, and then experimentally validated using a novel polarization phantom system. The use of polarized light for characterization of the myocardium, and specifically towards monitoring stem cell regenerative treatments of myocardial infarction, was investigated experimentally as a novel application for polarimetry. The potential for this technique is based on the changes in myocardial structure that occur with infarction and subsequent regeneration, and the associated changes in tissue birefringence. The use of polarized light for noninvasive tissue analyte monitoring, particularly glucose, was also investigated based on the optical activity exhibited by many tissue analytes due to their chiral structure. In this study, a novel combined optical polarization and intensity approach was developed and tested on Monte Carlo simulated data. The studies presented in thesis introduce new methods for polarization simulation and analysis in biological tissue and demonstrate potential for polarimetry in monitoring myocardial regeneration and noninvasive measurements of tissue analytes.

Polarized hyphal growth dominates the life cycle of filamentous fungi and is essential to disease progression for many fungal pathogens. Despite its importance, much of the basic biology controlling the process remains to be elucidated. Protein Nmyristoylation is one process important to hyphal growth for which the direct mechanism for this connection is not understood. N-myristoylation is mediated by Nmyristoyltransferase (NMT), which links 14-carbon myristate to target proteins. In Aspergillus nidulans, a mutation in the NMT gene (swoF1) results in abnormal morphogenesis during spore germination and the establishment of hyphal polarity. I hypothesize that a protein or proteins downstream of NMT are important for polarized hyphal growth. Using a forward genetic approach, I obtained six suppressors of swoF1. I found that three were proteasome-related and a mutation in genes encoding 26S proteasome subunits by-passed the polarity defects of swoF1. Interestingly, N-myristoylation negatively regulated the activity of the 26S proteasome. This result was confirmed by treating with the proteasome inhibitor MG132. This is the first finding of a connection between N-myristoylation and proteasome function during polarized growth. To identify targets by reverse genetic analysis, I found that 41 proteins (of more that 10,000 encoded by the organism) were predicted to be myristoylated in silico. Three were ADP ribosylation factors (ARF), proteins known to be involved in vesicle formation and trafficking in other systems. I chose ArfA (AN1126.3), ArfB (AN5020.3), and ArlA (AN5912.3) for further characterization of polarization in this study. ArfA::GFP discretely localized to endomembrane likely to be Golgi bodies. ArfB::GFP localized to septa and plasma membrane. N-myristoylation determined the localization of both ArfA and ArfB. Disruption of the arfB gene resulted in loss of polarity establishment and endocytosis. Together these results suggest that endocytosis plays an important role in maintaining hyphal polarized growth and in shaping the cell apex.

The capability to map anthropogenic aerosol quantities and properties over land can provide significant insights for climate and environmental studies on global and regional scales. One of the primary challenges in aerosol information monitoring is separating two signals measured by downward-viewing airborne or spaceborne instruments: the light scattered from the aerosols and light reflected from the Earth's surface. In order to study the aerosols independently, the surface signal needs to be subtracted out from the measurements. Some observational modalities, such as multispectral and multiangle, do not provide enough information to uniquely define the Earth's directional reflectance properties for this task due to the high magnitude and inhomogeneity of albedo for land surface types. Polarization, however, can provide additional information to define surface reflection. To improve upon current measurement capabilities of aerosols over urban areas, Jet Propulsion Laboratory developed the Multiangle SpectroPolarimetric Imager (MSPI) that can accurately measure the Degree of Linear Polarization to 0.5%. In particular, data acquired by the ground-based prototype, GroundMSPI, is used for directional reflectance studies of outdoor surfaces in this dissertation. This work expands upon an existing model, the microfacet model, to characterize the polarized bidirectional reflectance distribution function (pBRDF) of surfaces and validate an assumption, the Spectral Invariance Hypothesis, on the surface pBRDF that is used in aerosol retrieval algorithms. The microfacet model is commonly used to represent the pBRDF of Earth's surface types, such as ocean and land. It represents a roughened surface comprised of randomly oriented facets that specularly reflect incoming light into the upward hemisphere. The analytic form of the pBRDF for this model assumes only a single reflection of light from the microfaceted surface. If the incoming illumination is unpolarized, as it is with natural light from the Sun, the reflected light is linearly polarized perpendicular to the plane that contains the illumination and view directions, the scattering plane. However, previous work has shown that manmade objects, such as asphalt and brick, show a polarization signature that differs from the single reflection microfacet model. Using the polarization ray-tracing (PRT) program POLARIS-M, a numerical calculation for the pBRDF is made for a roughened surface to account for multiple reflections that light can experience between microfacets. Results from this numerical PRT method shows rays that experience two or more reflections with the microfacet surface can be polarized at an orientation that differs from the analytical single reflection microfacet model. This PRT method is compared against GroundMSPI data of manmade surfaces. An assumption made regarding the pBRDF for this microfacet model is verified with GroundMSPI data of urban areas. This is known as the Spectral Invariance Hypothesis and asserts that the magnitude and shape of the polarized bidirectional reflectance factor (pBRF) is the same for all wavelengths. This simplifies the microfacet model by assuming some surface parameters such as the index of refraction are spectrally neutral. GroundMSPI acquires the pBRF for five prominent region types, asphalt, brick, cement, dirt, and grass, for day-long measurements on clear sky conditions. Over the course of each day, changing solar position in the sky provides a large range of scattering angles for this study. The pBRF is measured for the three polarimetric wavelengths of GroundMSPI, 470, 660, and 865nm, and the best fit slope of the spectral correlation is reported. This investigation shows agreement to the Spectral Invariance Hypothesis within 10% for all region types excluding grass. Grass measurements show a large mean deviation of 31.1%. This motivated an angle of linear polarization (AoLP) analysis of cotton crops to isolate single reflection cases, or specular reflections, from multiple scattering cases of light in vegetation. Results from this AoLP method show that specular reflections off the top surface of leaves follow the Spectral Invariance Hypothesis.

Novel broadband designs of microstrip antennas have been proposed in this dissertation, including bandwidth enhancement using integrated reactive loading, broadband circularly polarized designs, broadband dual-frequency design, bandwidth enhancement using a slotted ground plane and practical applications. First, bandwidth enhancement of microstrip antennas using integrated reactive loading is proposed and experimentally studied. Results show that the proposed antennas can have an operating bandwidth more than 2.0 times that of a conventional one at a given operating frequency. Second, by selecting a thick air substrate, a wideband circularly polarized microstrip antenna with improved CP quality has been implemented. In addition to the improved CP quality obtained, a 2-dB axial-ratio bandwidth as large as about 38% is also achieved. Third, by bending a planar rectangular patch into an inverted L-shaped patch, a dual-frequency planar antenna has been obtained. Experimental results show that the proposed antenna has a tunable frequency ratio of about 1.66-2.29. Fourth, by embedding meandering slots or slits in the antenna¡¦s ground plane, it is observed that the impedance bandwidth of the microstrip antenna is twice larger than the conventional one. The experimental results show that the resonant frequency is significantly lower, which can lead to a large antenna size reduction for a fixed frequency operation. In addition, enhanced antenna gain is also obtained. Finally, a shorted patch antenna suitable for applications in DCS (1710-1880 MHz) base station is presented.

No / It is shown that a conical beam 5.2-GHz antenna suitable for HIPERLAN application, but working in horizontal polarization, can be realized as a group of microstrip patch radiators in a ring formation. Layouts with three and four patches are described, and radiation patterns are found to agree well with predictions from a simple array model. The three-patch form is smaller and gives a closer approximation to an azimuth-independent pattern. Patterns are very similar to those achieved in vertical polarization with previously reported disk antenna realizations, giving peak radiation at about 50 elevation. Two methods of impedance matching are found to give satisfactory results. A dual-polarized conical-beam microstrip antenna, with a strictly uniplanar conductor pattern, is also presented and realized as an array of three square patches whose corners meet a central feed point. For the second polarization, the antenna functions as a series fed array. Fairly good conical beam patterns have been obtained, though only moderate polarization purity appears to be obtainable from threeelement arrays.

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Design of the circularly polarized ceramic antenna, suitable for GPS system, on an asymmetric ground plane is presented in this thesis. Firstly, to obtain two isolated ground planes, we insert an L slit on an asymmetric ground plane, making the antenna with a symmetric ground plane. Then, we isolate the excited surface current between the two ground planes by using a quarter-wavelength mini-coaxial cable. The surface current can distribute uniformly on the ground plane when the proposed antenna is in operation, which makes possible a good circularly polarized radiation pattern in the operation band.