<p>Even though women make up over half the population in the United States, medical advancements in areas of women's health have typically lagged behind the rest of the medical field. Specifically, two major threats to women's reproductive health include human immunodeficiency virus (HIV), and cervical cancer with accompanying human papillomavirus (HPV) infection. This dissertation presents the development and application of two novel optical imaging technologies aimed at improving these aspects of women's reproductive health.</p><p>The presented work details the instrumentation development of a probe-based, dual-modality optical imaging instrument, which uses simultaneous imaging of fluorimetry and multiplexed low coherence interferometry (mLCI) to measure in vivo microbicide gel thickness distributions. The study explores the optical performance of the device and provides proof of concept measurements on a calibration socket, tissue phantom, and in vivo human data. Once the instrument is fully characterized, it is applied in a clinical trial in which in vivo human vaginal gel thickness distributions. The gel distribution data obtained by the modalities are compared in order to assess the ability of mLCI making accurate in vivo measurements. Differences between the fluorimetry and mLCI modalities are then exploited in order to show a methodology for calculating the extent of microbicide gel dilution with the dual-modality instrument data.</p><p>Limitations in cervical cancer screening are then addressed as angle-resolved low coherence interferometry (a/LCI) is used in an ex vivo pilot study to assess the feasibility of a/LCI in identifying dysplasia in cervical tissues. The study found that the average nuclear diameter found by a/LCI in the basal layer of ectocervical epithelium showed a statistically significant increase in size in dysplastic tissue. These results indicate that a/LCI is capable of identifying cervical dysplasia in ectocervical epithelium. The results of the work presented in this dissertation show that dual-modality optical imaging with fluorimetry and mLCI, and the a/LCI technique show promise in advancing technologies that are used in the field of women's reproductive health.</p> / Dissertation

The pseudo-spectral time domain (PSTD) and discrete dipole approximation (DDA) are two of the most popular methods to model the single-scattering properties of ice crystals and aerosols. Both methods solve for Maxwell’s equations. The PSTD method uses a Fourier pseudo-spectral method and a finite-difference method to compute the spatial and temporal derivatives of electromagnetic fields. The DDA method uses an electromagnetic integral equation in the frequency domain to calculate the single-scattering properties. We used a spherical model for this study because the analytical solution was given by the Lorenz-Mie theory. Previous studies have found that at refractive indices between 1.2 and 1.5, PSTD computed the single-scattering properties of spherical particles faster for large size parameters, while DDA was more computationally efficient at small size parameters; however, these previous studies did not consider absorptive cases. The purpose of this study was to expand the range of refractive indices to include absorptive cases and to determine which method was more efficient for computing the single-scattering properties of atmospheric particles within set criteria. The PSTD and DDA methods were systematically assessed in this study for 31 different realistic complex refractive indices. Similar to the previous studies, it was found that PSTD was more efficient than DDA for particles with large size parameters. The results in this study were consistent with the previous studies for non-absorptive to moderately absorptive particles. However, for strongly absorptive cases, DDA was more efficient than PSTD at all size parameters for the absorptive particles. It was also determined that the efficiencies of the two methods were dependent on both the real and imaginary parts of the complex refractive index. The significance of this study was to improve our understanding of the capabilities of the PSTD and DDA methods for computing single-scattering properties.

LIDAR, an acronym for LIght Detection And Ranging, is a system used for studying the scattering of laser light incident on a parcel of air. This thesis investigates the atmosphere above the Durban region using two atmospheric LIDARs, referred to, in this study, as the "old LIDAR" and the "new LIDAR". The old LIDAR was used in a campaign of observation from July to October 1997 in a study of aerosol concentrations over Durban. This thesis will focus on, among other things, the local aerosol profiles for low altitude (0 to 10 km) and high altitude (10 to 35 km). In particular, the focus will shift on any long persistence in this region (it was found that the aerosol layer observed by M. Kuppen (1996) on June 1994 at 25 km may have moved to the higher altitude of 28 km in October 1997. This may be explained by stratospheric upwelling, carrying the layer to higher altitude. These aerosols are known to influence the local climate). This investigation will give some useful insight into the local atmospheric dynamics. The new LIDAR system (Rayleigh-Mie LIDAR) has been used to measure atmospheric temperatures from 20 to 60 km as well as aerosol extinction coefficients from 15 to 40 km. Height profiles of temperature have been measured by assuming that the LIDAR returns are solely due to Rayleigh scattering by molecular species and that the atmosphere obeys the perfect gas law and is in hydrostatic equilibrium (Hauchecorne and Chanin 1980). Since its installation in April 1999, the new LIDAR has been used to monitor stratospheric temperatures and aerosol concentrations from 10 to 40 km. In this study, we discuss in chapter 7 the results of a validation campaign conducted during the period of April 1999 to December 2000. Average monthly LIDAR temperatures are computed from April 1999 to December 1999 and compared with radiosonde temperatures obtained from the South African Weather Service (SAWS) at Durban. The monthly LIDAR temperature profiles over two years (1999 and 2000) were also computed and compared with the climatological model Cospar International Reference Atmosphere (CIRA)-1986 and with the average monthly European Centre for Medium Range Weather Forecast (ECMWF) temperatures . The results show that there is good agreement between LIDAR and SAWS radiosonde temperatures in the 20 and 30 km altitude range. Between 20 and 40 km, the monthly LIDAR temperatures agree closely with the CIRA-86 and ECMWF profiles. However, during winter, in the altitude range 40 to 60 km, LIDAR temperatures are warmer than CIRA-1986 and ECMWF temperatures, and they show large variability. These variations could be due to relatively fast transient phenomena like gravity waves or planetary waves propagating vertically in the stratosphere. As part of the validation process, the aerosol extinction coefficients retrieved from the LIDAR data have also been compared with the extinction coefficients measured by Stratospheric Aerosol and Gas Experiment (SAGE) II close to the LIDAR location and on coincident days. Appendix E of this thesis also investigates the concept of refraction by atmospheric gases as applied to gas lenses. A simple spinning pipe gas lens (SPGL) has been used as the objective lens of a camera to take pictures of the moon and sun spots. The SPGL is a varifocal length lens which depends on the temperature of the pipe and the angular velocity at which it spins. For our purpose a focal length of 8 m has been used. The moon pictures are compared with a lunar map so as to identify the maria. / Thesis (Ph.D.)-University of Natal, Durban, 2002.

No description available.

This dissertation describes two independent studies related to charged aerosols. The first study examines the role of electrical conductivity on the amounts of charge and mass emitted during the break-up of charged droplets via Coulombic fission. The second study examines the hygroscopic behavior of mixed particles. The results from both studies are presented here in detail along with an in-depth discussion of pertinent literature and applications in modern technologies. Charged droplets break-up via a process termed Coulombic fission when their charge density reaches a certain level during which they emit a portion of their charge and mass in the form of progeny microdroplets. Although Rayleigh theory can be used to predict the charge level at which break-ups occur, no equivocal theory exists to predict the amounts of charge or mass emitted or the characteristics of the progenies. Previous investigations have indicated that the electrical conductivity of a charged droplet may determine how much charge and mass are emitted during its break-up via Coulombic fission. To further examine this supposition, charged droplets having known electrical conductivities were observed through multiple break-ups while individually levitated in an electrodynamic balance. The amounts of charge and mass emitted during break-ups were determined using a light scattering technique and changes in the DC null point levitation potentials of the charged droplets. Here, electrical conductivity was found to increase and decrease the amounts of charge and mass emitted, respectively, while having no effect on the charge level at which break-ups occurred. The findings of this investigation have significant bearing in nanoparticle generation and electrospray applications. The hygroscopic behavior of atmospherically relevant inorganic salts is essential to the chemical and radiative processes that occur in Earth’s atmosphere. Furthermore, studies have shown that an immense variety of chemical species exist in the atmosphere which inherently mix to form complex heterogeneous particles with differing morphologies. However, how such materials and particle morphologies affect the hygroscopic behavior of atmospherically relevant inorganic salts remains mostly unknown. Therefore, the effects of water insoluble materials, such as black carbon, on the hygroscopic behavior of inorganic salts were examined. Here, water insoluble solids were found to increase the crystallization relative humidities of atmospherically relevant inorganic salts when internally mixed. Water insoluble liquids however, were found to have no effect on the hygroscopic behavior of atmospherically relevant inorganic salts. The findings of this investigation have significant bearing in atmospheric modeling.

With the rapid development of the industry all over the world, the consumption of fossil fuel of human activities has reached an extremely high level which result in an incredible dust emission level nowadays. As one of the major environment challenges today, dust pollution has become a vital issue that the human beings have to face and resolve.    To tackle the dust pollution problem, a reliable measurement of the dust concentration level is essential. In recent years, methods with different principles are used to detect the dust concentration have been developed. The methods developed based on the scattering principle and the extinction principle for dust concentration measurement have a series of virtues such as high measurement speed, excellent precision and can be useful for real time monitoring.    This thesis reviewed the popular theories that are applied in the field which are light scattering (Mie theory) and light extinction (Lambert-beer theory). Matlab simulation is used to verify the possibility of the determined physical quantities related to the concentration measurement in the theory analysis. A new method using the ratio of scattering intensity and extinction intensity is discussed in this thesis providing a more accurate result eliminating the drawbacks of the scattering method and the extinction method.

Polytetrafluoroethylene (PTFE) is a highly scattering material and has been used as diffuse reflectors. In the present study, the ranges of the scattering coefficient, absorption coefficient, and the asymmetric parameter of the Henyey-Greenstein scattering phase function are assessed for semitransparent PTFE films whose thicknesses range from 0.11 mm to 10 mm. The bidirectional reflectance distribution function (BRDF) and bidirectional transmittance distribution function (BTDF) of these PTFE films were measured using a laser scatterometer at a wavelength of 635 nm, and the directional-hemispherical reflectance and transmittance were obtained by integrating BRDF and BTDF at normal incidence. The scattering coefficient of PTFE is estimated to exceed 1200 (1/cm). On the other hand, the absorption coefficient should be less than 0.01 (1/cm). A Monte Carlo simulation was employed to predict the BRDF and BTDF of PTFE films, and the calculations were compared with measurements at various incidence angles.

Background.The extracellular matrix surrounds all cells within our bodies. The glycosaminoglycan hyaluronan is a major component in the extracellular matrix. Despite its structural simplicity it has been shown to be involved in several important functions. It is a lubricant and shock absorber, as well as an important player in inflammation and tumor invasion. Many of its functions are closely related to its size and concentration in tissues. Therefore methods for measuring these properties are of great importance to properly understand the role that hyaluronan play in different events. Proteins are found both inside and outside cells, and they have a wide variety of functions. The protein structure and function is determined by the properties of their building blocks, the amino acids. Several diseases have been linked to changes in the amino acid sequence of certain proteins by mutations, causing the proteins to form extracellular deposits of structures called amyloid aggregates. The aim of this thesis is to investigate the function of hyaluronan in cell cultures, develop new methods for size determination hyaluronan and to use multivariate methods to provide prediction and better understanding of factors driving protein amyloid aggregation. Methods.Cardiomyocytes and fibroblast were cultured and stimulated by different growth factors. Hyaluronan was purified and its size and concentration were measured. Crosstalk between cardiomyocytes and fibroblast were investigated and gene expression of hyaluronan synthases was determined. A new method for size measurement of hyaluronan was developed. The amyloid aggregation rate of different mutants of acylphosphatase was predicted by multivariate analysis. Results. Cardiomyocytes stimulated by PDGF-BB produced hyaluronan. Cardiomyocytes could induce fibroblast to increase its hyaluronan production, through an unknown soluble factor. The cardiomyocyte gene expression changed when stimulated by hyaluronan. GEMMA was presented as a new method for size determination of hyaluronan. Amyloid aggregation of different acylphosphatase mutants could be predicted using a multivariate regression model of the physicochemical and structural properties of the amino acid sequence. Conclusion. It was shown that cardiomyocytes are not only able to produce hyaluronan, but also induce an increased hyaluronan production in other cells. GEMMA was proven suitable for size determination of hyaluronan at very low concentrations. Multivariate analysis showed that hydrophobic patterns and charge where the most important factors for amyloid aggregation of acylphosphatase.

Successful integration of daylighting systems requires the ability to predict their performance for given climates. In this dissertation, a bottom-up approach is applied to evaluate the optical performance of a selection of daylighting systems. The evaluations are based on the optical properties of the included materials, and part of the dissertation focuses on developing new optical characterization methods. The work on characterization techniques uses an integrating sphere method to characterize the transmittance of light scattering samples more accurately. The method's principle is to reduce the discrepancy in light distribution between the reference and the sample scans by using an entry port beam diffuser. For samples exhibiting distinct light scattering patterns, the benefits of improved uniformity outweigh the errors introduced by the diffusing material. The method is applicable to any integrating sphere instrument, and its simplicity makes it suitable for standard measurements. In addition to normal-hemispherical properties, many daylighting applications require knowledge of the system's spatial light distribution. This dissertation presents a method combining experimental techniques and ray tracing simulations to assess the light distribution from a Venetian blind system. The method indicates that ray tracing based on simplified optical data is inadequate to predict the light distribution for slat materials exhibiting both specular and diffuse properties. Ray tracing is a promising complement to experimental methods used to characterize light guiding or light redirecting systems. Here, spectrophotometric measurements of a scaled mirror light pipe validate a ray tracing model. The model shows excellent agreement with experimental results for both direct and diffuse incident light. The spectral evaluation shows no dramatic color changes for the transmitted light. The ray tracing model is used to evaluate four daylighting systems for a selection of Swedish locations. The percentage of occupied time when the studied systems achieve full design illuminance is relatively low, but the systems provide a valuable contribution to the required illuminance. Additionally, this dissertation provides an overview of available energy efficient windows and illustrates the importance of including the solar energy transmittance when evaluating window energy performance. Overall, this dissertation presents optical characterization techniques for improved performance evaluations of daylighting systems.

Optical tweezers using highly focussed laser beams can be used to exert forces and torques and thus drive micromachines. This opens up a new field of microengineering, whose potential has yet to be fully realized. Until now, methods that have been used for modelling optical tweezers are limited to scatterers that are homogeneous or that have simple geometry. To aid in designing more general micromachines, I developed and implemented two main methods for modelling the micromachines that we use. These methods can be used for further proposed structures to be fabricated. The first is a FDFD/T-matrix hybrid method that incorporates the finite difference frequency domain (FDFD) method, which is used for inhomogeneous and anisotropic media, with vector spherical wave functions (VSWF) to formulate the T-matrix. The T-matrix is then used to calculate the torque of the trapped vaterite sphere, which is apparently composed of birefringent unit crystals but the bulk structure appears to be arranged in a sheaf-of-wheat fashion. The second method is formulating the T-matrix via discrete dipole approximation (DDA) of complex arbitrarily shaped mesoscale objects and implementing symmetry optimizations to allow calculations to be performed on high-end desktop PCs that are otherwise impractical due to memory requirements and calculation time. This method was applied to modelling microrotors. The T-matrix represents the scattering properties of an object for a given wavelength. Once it is calculated, subsequent calculations with different illumination conditions can be performed rapidly. This thesis also deals with studies of other light scattering phenomena including the modelling of scattered fields from protein molecules subsequently used to model FRET resonance, determining the limits of trappability, interferometric Brownian motion and the comparison between integral transforms by direct numerical integration and overdetermined point-matching.