The licentiate thesis explored the relationship between working conditions and wage income, and the relationship between working conditions and sense of coherence in relation to ill health, focusing on cardiovascular disease, musculoskeletal pain, and psychological distress among the working population in Sweden. The studies were based on cross-sectional and longitudinal survey data (ULF and LNU), and on the Swedish census (FoB90) linked to the national cause of death registry. The samples included employed men and women residing in Sweden, aged 18-64. The main results show that working conditions contributed to income differences in CVD prevalence as well as CVD mortality irrespective of study design or way of assessing working conditions. Further, sense of coherence moderated, yet not consistently, the impact of working conditions on musculoskeletal pain and psychological distress. The moderating role seemed to vary by work exposure, gender and health outcome. Hence, the results do not support the hypothesis that sense of coherence is a global health-protective factor. The findings stress that future research into working conditions and employees’ health would benefit from including income in the analyses since wages are closely related to working conditions and to people’s position on the labour market. In addition, focusing on individual resources such as sense of coherence increases our undertanding of how individual differences in coping with adverse working conditions may affect health. Since the results also revealed considerable gender differences, suggesting that the factors that determine future work-related health are different for men and women, it is important to study men and women separately.

Optical coherence tomography (OCT) is an innovative modern biomedical imaging technology that allows in-vivo, non-invasive imaging of biological tissues. At present, some of the major challenges in OCT include the need for fast data acquisition system for probing fast developing biochemical processes in biological tissue, for image processing algorithms to reduce speckle noise and to remove motion artefacts, and for dispersion compensation to improve axial resolution and image contrast. To address the need for fast data acquisition, a novel, high speed (47,000 A-scans/s), ultrahigh axial resolution (3.3μm) Fourier Domain Optical Coherence Tomography (FD-OCT) system in the 1060nm wavelength region has been built at the University of Waterloo. The system provides 3.3μm image resolution in biological tissue and maximum sensitivity of 110 dB. Retinal tomograms acquired in-vivo from a human volunteer and a rat animal model show clear visualization of all intra-retinal layers and increased penetration into the choroid. OCT is based on low-coherence light interferometry. Thus, image quality is dependent on the spatial and temporal coherence properties of the optical waves back-scattered from the imaged object. Due to the coherent nature of light, OCT images are contaminated with speckle noise. Two novel speckle noise reduction algorithms based on interval type II fuzzy sets has been developed to improve the quality of the OCT images. One algorithm is a combination of anisotropic diffusion and interval type II fuzzy system while the other algorithm is based on soft thresholding wavelet coefficients using interval type II fuzzy system. Application of these novel algorithms to Cameraman test image corrupted with speckle noise (variance=0.1) resulted in a root mean square error (RMSE) of 0.07 for both fuzzy anisotropic diffusion and fuzzy wavelet algorithms. This value is less compared to the results obtained for Wiener (RMSE=0.09), adaptive Lee (RMSE=0.09), and median (RMSE=0.12) filters. Applying the algorithms to optical coherence tomograms acquired in-vivo from a human finger-tip show reduction in the speckle noise and image SNR improvement of ~13dB for fuzzy anisotropic diffusion and ~11db for fuzzy wavelet. Comparison with the Wiener (SNR improvement of ~3dB), adaptive Lee (SNR improvement of ~5dB) and median (SNR improvement of ~5dB) filters, applied to the same images, demonstrates the better performance of the fuzzy type II algorithms in terms of image metrics improvement. Micrometer scale OCT image resolution is obtained via use of broad bandwidth light sources. However, the large spectral bandwidth of the imaging beam results in broadening of the OCT interferogram because of the dispersive properties of the imaged objects. This broadening causes deterioration of the axial resolution and as well as loss of contrast in OCT images. A novel even-order dispersion cancellation interferometry via a linear, classical interferometer has been developed which can be further expanded to dispersion canceled OCT.

Optical coherence tomography (OCT) is an innovative modern biomedical imaging technology that allows in-vivo, non-invasive imaging of biological tissues. At present, some of the major challenges in OCT include the need for fast data acquisition system for probing fast developing biochemical processes in biological tissue, for image processing algorithms to reduce speckle noise and to remove motion artefacts, and for dispersion compensation to improve axial resolution and image contrast. To address the need for fast data acquisition, a novel, high speed (47,000 A-scans/s), ultrahigh axial resolution (3.3μm) Fourier Domain Optical Coherence Tomography (FD-OCT) system in the 1060nm wavelength region has been built at the University of Waterloo. The system provides 3.3μm image resolution in biological tissue and maximum sensitivity of 110 dB. Retinal tomograms acquired in-vivo from a human volunteer and a rat animal model show clear visualization of all intra-retinal layers and increased penetration into the choroid. OCT is based on low-coherence light interferometry. Thus, image quality is dependent on the spatial and temporal coherence properties of the optical waves back-scattered from the imaged object. Due to the coherent nature of light, OCT images are contaminated with speckle noise. Two novel speckle noise reduction algorithms based on interval type II fuzzy sets has been developed to improve the quality of the OCT images. One algorithm is a combination of anisotropic diffusion and interval type II fuzzy system while the other algorithm is based on soft thresholding wavelet coefficients using interval type II fuzzy system. Application of these novel algorithms to Cameraman test image corrupted with speckle noise (variance=0.1) resulted in a root mean square error (RMSE) of 0.07 for both fuzzy anisotropic diffusion and fuzzy wavelet algorithms. This value is less compared to the results obtained for Wiener (RMSE=0.09), adaptive Lee (RMSE=0.09), and median (RMSE=0.12) filters. Applying the algorithms to optical coherence tomograms acquired in-vivo from a human finger-tip show reduction in the speckle noise and image SNR improvement of ~13dB for fuzzy anisotropic diffusion and ~11db for fuzzy wavelet. Comparison with the Wiener (SNR improvement of ~3dB), adaptive Lee (SNR improvement of ~5dB) and median (SNR improvement of ~5dB) filters, applied to the same images, demonstrates the better performance of the fuzzy type II algorithms in terms of image metrics improvement. Micrometer scale OCT image resolution is obtained via use of broad bandwidth light sources. However, the large spectral bandwidth of the imaging beam results in broadening of the OCT interferogram because of the dispersive properties of the imaged objects. This broadening causes deterioration of the axial resolution and as well as loss of contrast in OCT images. A novel even-order dispersion cancellation interferometry via a linear, classical interferometer has been developed which can be further expanded to dispersion canceled OCT.

Purpose To examine soft contact lens fitting characteristics using anterior segment imaging techniques and comfort. The specific aims of each chapter are as follows: Chapter 2: To calibrate the new ZEISS VisanteTM anterior segment optical coherence tomographer (OCT) using references with known physical thickness and refractive index equal to the human cornea and to compare the Visante measures to those from a previous generation OCT (Zeiss-Humphrey OCT II). Chapter 3: The first purpose of this study was to measure the repeatability of the Visante TM OCT in a normal sample. The second was to compare corneal thickness measured with the Visante TM OCT to the Zeiss-Humphrey OCT II (model II, Carl Zeiss Meditec, Jena Germany) adapted for anterior segment imaging and to the Orbscan II TM (Bausch and Lomb, Rochester New York). Chapter 4: Conjunctival displacement observed with the edges of the contact lens, when imaged may be real or may be an artefact of all OCT imagers. A continuous surface appears displaced when the refractive index of the leading medium changes at the edge of a contact lens. To examine this effect, edges of the contact lenses were imaged on a continuous surface using the UHR-OCT. Contact lens edges on the human conjunctival tissue were also imaged to see if the lens indentation on the conjunctival tissue is real or an artefact at the edge of the lens. Chapter 5: The main purpose of this study was to determine if we can predict end of the day discomfort and dryness using clinical predictive variables. The second purpose of the study was to determine if there was any relationship between lens fitting characteristics and clinical complications and especially to the superior cornea and conjunctiva with a dispensing clinical trial. Methods Chapter 2: Twenty two semi-rigid lenses of specified thicknesses were manufactured using a material with refractive index of 1.376. Central thickness of these lenses was measured using VisanteTM OCT and Zeiss-Humphrey OCT II (Zeiss, Germany). Two data sets consisting of nominal measures (with a standard pachymeter of the lenses and one obtained using a digital micrometer) were used as references. Regression equations between the physical and optical (OCT) measures were derived to calibrate the devices. Chapter 3: Fifteen healthy participants were recruited. At the Day 1 visit the epithelial and total corneal thickness, across the central 10mm of the horizontal meridian were measured using the OCT II and the Visante TM OCT. Only total corneal thickness across the central 10mm of the horizontal meridian was measured using the Orbscan II. The order of these measurements was randomized. These measurements were repeated on Day 2. Each individual measurement was repeated three times and averaged to give a single result. Chapter 4: (2-D) Images of the edges of marketed silicone hydrogel and hydrogel lenses with refractive indices (n) ranging from 1.41-1.51 were taken placing them concave side down on a continuous surface. Five images for each lens were taken using a UHR-OCT system, operating at 1060 nm with ~3.2um (axial) and 10μm (lateral) resolution at the rate of 75,000 A-scans/s. The displacement of the glass slide beneath the lens edge was measured using Image J. Chapter 5: Thirty participants (neophytes) were included in the study and the four lenses (Acuvue Advance 8.3, Acuvue Advance 8.7, Pure Vision 8.3, and Pure Vision 8.6) were randomly assigned for each eye. The lenses were worn for a period of two weeks on a daily wear basis for 8 to 10hrs per day. Lens performance was monitored over the 2week period. Assessment of subjective comfort was made using visual analogue scales. Total corneal and epithelium thickness was measured using the Visante OCT, the lens edge profiles of the contact lenses were observed using the ultra-high resolution OCT and the conjunctival epithelial thinning was measured using the RTVue OCT. Conjunctival blood velocity was measured at the baseline and 2 week visit using a high magnification camera. Results Chapter 2: Before calibration, repeated measures ANOVA showed that there were significant differences between the mean lens thicknesses from each of the measurement methods (p<0.05), where Visante measurements were significantly different from the other three (OCT II, MG and OP) methods (p<0.05). Visante thickness was significantly higher than the microgauge measures (453±37.6 µm compared to 445.1±38.2 µm) and the OCT II was significantly lower (424.5±36.1 µm both, p<0.05). After calibration using the regression equations between the physical and optical measurements, there were no differences between OCT II and Visante OCT (p<0.05). Chapter 3: Mean central corneal and epithelial thickness using the Visante™ OCT after calibration at the apex of the cornea was 536± 27 µm (range, 563-509 µm) and 55± 2.3 µm (range, 57.3-52.7 µm), respectively. The mean corneal and epithelial thickness using OCT II at the apex was 520±25µm and 56±4.9 µm, respectively. The mean of total corneal thickness measured with the Orbscan II was 609±29µm. Visante OCT was the most repeatable for test-retest at the apex, nasal and temporal quadrants of the cornea compared to OCT II and Orbscan II. COR’s of Visante OCT ranged from ±7.71µm to ±8.98µm for total corneal thickness and ± 8.72 µm to ± 9.92 µm for epithelial thickness. CCC’s with Visante OCT were high for total corneal thickness for test-retest differences ranging from 0.97 to 0.99, CCC’s for epithelial thickness showed moderate concordance for both the instruments. Chapter 4: Results showed that artefactual displacement of the contact lens edge was observed when the lenses were imaged on the glass reference sphere, custom made rigid contact lenses (1.376) and on the conjunctival tissue. The displacement measured on the conjunctival tissue ranged from 7.0±0.86 µm for the Air Optix Night and Day to 17.4±0.22 µm for the Acuvue Advance contact lenses. The range of displacement with the soft lens edges imaged on the rigid contact lens was from 5.51±0.03 µm to 9.72±0.12 µm. Chapter 5: The lenses with the steepest sag (Acuvue Advance 8.3, Pure Vision 8.3) resulted not only with the tightest fit, but with compromise to the superior conjunctiva. This was especially seen with the Acuvue Advance lenses. The steeper lenses caused more total corneal swelling, superior epithelial thinning, mechanical compression of conjunctiva, conjunctival staining, bulbar hyperemia, conjunctival indentation and reduced blood flow at the lens edge. Not many associations were observed between baseline clinical and 2 weeks sensory variables. However, significant associations were observed when comparing the baseline clinical variables to end of the day sensory variables. Baseline clinical variables compared to 2 week clinical variables also showed significant correlations. Conclusions Chapter 2: Using reference lenses with refractive index of the cornea (1.376) allows rapid and simple calibration and cross calibration of instruments for measuring the corneal thickness. The Visante and OCT II do not produce measurements that are equal to physical references with refractive index equal to the human cornea. Chapter 3: There is good repeatability of corneal and epithelial thickness using each OCT for test-retest differences compared to the between instruments repeatability. Measurements of epithelial thickness are less repeatable compared to the total corneal thickness for the instruments used in the study. Chapter 4: When contact lenses are imaged in-situ using UHR-OCT the conjunctival tissue appeared displaced. This experiment indicates that this displacement is an artefact of all OCT imagers since a continuous surface (glass slide) was optically displaced indicating that the displacement that is observed is a function of the refractive index change and also the thickness of the contact lens edges. Chapter 5: Discomfort is a complex issue to resolve since it appears to be related to ocular factors such as the corneal and conjunctival topography and sagittal depth; to lens factors that is 1) how the sag depth of the lenses relate to the corneal/conjunctival shape and depth and therefore how well it moves on the eye. 2) Also with the lens material; whether they are high or low modulus, low or high water content, dehydration properties, wetting agents used and its resistance to deposits, lens edge profile and thickness and its interaction with the upper eyelid.

The aim of the study was to investigate the sense of coherence among students in Zambia. Sense of coherence was assessed with the questionnaire SOC-29. The respondents were 102 students, aged 15 to 20 years, in three schools in Livingstone. A secondary aim was to examine the relationship between sense of coherence, gender and age. The mean score on SOC-29 was 131 for the Zambian students, which is lower than SOC measured for Swedish adolescents (m=138,5) as well as the Swedish population (m=146). There were no significant correlations between sense of coherence and gender, nor between sense of coherence and age.

<p>Liposomes are excellent chemotherapy drug delivery agents, on the cutting edge of cancer treatment technology. Since liposomes are already used to deploy cancer drugs in patients, imaging capacity would make them dual-purpose "theranostic" vesicles. Intermolecular double quantum coherence (iDQC) MRI is uniquely suited to this application, as its contrast does not require any additional chemicals. Adding contrast agents to liposomes can be time-consuming, add to toxicity, interfere with membrane function, or adversely affect drug loading. Furthermore, iDQC contrast measures diffusion and thus directly depends on membrane permeability and related properties. In this set of experiments, it has been shown that iDQC signal from intra-liposomal water can be distinguished from that of bulk water, and that the T2 dynamics of intra-liposomal water are predictable and dependent on the percent of water encapsulated. These techniques to distinguish between water molecules based on their current physical circumstances lead to many novel possibilities in MRI, as nearly all the signal in conventional MRI is from water protons. Based on the signal to noise ratio in the aforementioned iDQC experiments, we predict that iDQC contrast from liposomes will be visible in vivo, and propose to prove this in a murine model. By examining intra-liposomal water, iDQC can be used to improve chemotherapy delivery via real time monitoring of liposome location and drug release.</p> / Thesis

Coherent effects are studied in a dense atomic vapor driven by laser fields. With optical properties dramatically modified by these effects, the medium can be used to manipulate some of the properties of laser field. Our experiments demonstrate the coherent control over transmission, spatial distribution and noise feature of the laser field interacting with coherent media. The results have potential applications in the field such as precision metrology, precision spectroscopy, optical imaging and lithography. We develop an experiment to investigate the atomic excitation by few-cycle radio frequency (RF) pulses interacting with Zeeman sublevels. The system provides the flexibility to fully control all parameters of RF pulses. Such a flexibility can not be achieved in optical domain. Based on this system, experiments can be conducted to simulate processes in ultra-short laser physics. In particular, we study the carrier-envelope effect of few-cycle pulses and the strong off-resonant excitation by short pulses. We also discuss the selective reflection spectrum on a highly dense atomic vapor in which the dipole-dipole interaction can not be neglected. The spectrum broadening due to dipole-dipole interaction is much broader than the Doppler broadening. Our experiments show that the excitation by a pump laser can reduce the dipole-dipole interaction, thus reduce the broadening and improve the spectral resolution. The excitation dependence is studied at various atomic densities.

The coherence of a semiconductor laser subjected to a coherent optical feedback of greater than -30 dB will collapse, causing the laser¡¦s performance in many applications to be severely degraded. This research investigated the feasibility of suppression the coherence collapse with orthogonal-polarization optical feedback. In the experiments, we first studied the characteristics of coherence collapse state of semiconductor laser. Under an operational condition of 63.9 mA, 21.9¢J and -11 dB of coherent optical feedback, a Hitachi HLP 7806G semiconductor laser would be conducted from its solitary single-mode state into a multimode oscillation state with a very broad linewidth. At the same time, the relative intensity noise measured from the RF spectrum analyzer drastically raised about 15 dB. When a -16 dB and a -23 dB orthogonal-polarization optical feedback were fed back into the laser¡¦s cavity. The coherence collapse could be effectively suppressed, while the laser was conducted back to its solitary single-mode state stably. This result will greatly increase the application of the laser. Some experiments were also reported to explore the interaction between the laser and the orthogonal-polarization feedback light.

The statistics of the phase dependent optical time-domain reflectometer have been analyzed. The optical fiber is modeled by the use of a discrete set of reflectors positioned randomly along the fiber. The statistics of the reflected light from a traveling pulse are derived. The statistics of the signal are used to calculate the characteristics of shot noise in the photodetector, and the probability that noise of certain intensity will occur. An estimation of the backscattered power is made by calculating the fraction of the backscattered power that is captured in a guiding mode. Upper power limits are calculated by considering nonlinear optical effects. An estimation of noise from thermally excited sound waves, amplified by Brillouin scattering, is derived. This noise considers the parameters of a photodetector, giving a model for the noise in the measurable photocurrent. Two models are used to describe the fading probability of the signal. The first model, based on the Fabry-Perot interferometer with a random phase perturbation in the middle, is used to calculate the probability that the whole signal vanishes for any value of phase perturbation. The second model, by calculating the correlation between two signals, one perturbed and one unperturbed, predicts the fading of the signal of interest. The present work gives the theoretical basis for the phase dependant Optical Time Domain Reflectometry, allowing its optimization and setting the fundamental limitations to the performance of the system.

<p>The aim of the study was to investigate the sense of coherence among students in Zambia. Sense of coherence was assessed with the questionnaire SOC-29. The respondents were 102 students, aged 15 to 20 years, in three schools in Livingstone. A secondary aim was to examine the relationship between sense of coherence, gender and age. The mean score on SOC-29 was 131 for the Zambian students, which is lower than SOC measured for Swedish adolescents (m=138,5) as well as the Swedish population (m=146). There were no significant correlations between sense of coherence and gender, nor between sense of coherence and age.</p>