The wettability of contact lenses has become an area of intense research, with the belief that the more "hydrophilic" or wettable the lens surface is, the more comfortable the lens may be, as the posterior surface of the eyelid will move more smoothly over it, hence increasing comfort. <br /><br /> There are many ways to assess the wettability of a given material, namely sessile drop,¹ captive bubble ² or Wilhelmy plate. ³ This thesis used the sessile drop method to determine the surface wettability of various hydrogel contact lens materials, by measuring the advancing contact angle made between the lens surface and a pre-determined volume of HPLC-grade water. This was followed by measuring the surface wettability following periods in which the lens materials were soaked in various contact lens care regimens. Further studies determined wettability of lens materials after various periods of in-eye wear and finally a study was undertaken to evaluate if a novel biological technique could be used to differentiate proteins that deposit on hydrogel lens materials that may affect wettability and cause discomfort. <br /><br /> A variety of hydrogel lenses, taken directly from their packaging and after soaking in various care regimens, were analyzed to determine their sessile drop advancing contact angles, in vitro. These studies indicated that poly-2-hydroxyethylmethacrylate (pHEMA)-based lenses are inherently more wettable than silicone-based lenses, unless they have a surface treatment that completely covers the hydrophobic siloxane groups. Additionally, certain combinations of lens materials and care regimens produce inherently more wettable surfaces when measured in vitro. <br /><br /> Suitable methods to assess contact lens wettability ex vivo, or after subjects had worn lenses for set periods of time, were developed. It was determined that using latex gloves to remove lenses had no impact upon the lens surface wettability and that rinsing of the lens surface after removal from the eye was required to determine the wettability of the underlying polymer. <br /><br /> The final wettability studies involved an analysis of various lens materials from clinical studies conducted within the Centre for Contact Lens Research (CCLR). These studies investigated differences in wettability between silicone hydrogel lenses manufactured from differing polymers and variations in ex vivo wettability of several combinations of lens materials and solutions, worn for varying periods of time. <br /><br /> A novel method to investigate proteins extracted from lenses using 2D-Difference in Gel Electrophoresis (DIGE) found that this technique could be used to analyze proteins extracted from contact lenses. The data obtained showed that there was no difference between a group of subjects who were symptomatic of lens-induced dryness or a control group, and that care solutions had a minimal influence on the pattern of deposition seen. <br /><br /> The overall conclusion of these studies is that hydrogel lens wettability is affected by the polymer composition and that care regimen components can modify the surface wettability.

The wettability of contact lenses has become an area of intense research, with the belief that the more "hydrophilic" or wettable the lens surface is, the more comfortable the lens may be, as the posterior surface of the eyelid will move more smoothly over it, hence increasing comfort. <br /><br /> There are many ways to assess the wettability of a given material, namely sessile drop,¹ captive bubble ² or Wilhelmy plate. ³ This thesis used the sessile drop method to determine the surface wettability of various hydrogel contact lens materials, by measuring the advancing contact angle made between the lens surface and a pre-determined volume of HPLC-grade water. This was followed by measuring the surface wettability following periods in which the lens materials were soaked in various contact lens care regimens. Further studies determined wettability of lens materials after various periods of in-eye wear and finally a study was undertaken to evaluate if a novel biological technique could be used to differentiate proteins that deposit on hydrogel lens materials that may affect wettability and cause discomfort. <br /><br /> A variety of hydrogel lenses, taken directly from their packaging and after soaking in various care regimens, were analyzed to determine their sessile drop advancing contact angles, in vitro. These studies indicated that poly-2-hydroxyethylmethacrylate (pHEMA)-based lenses are inherently more wettable than silicone-based lenses, unless they have a surface treatment that completely covers the hydrophobic siloxane groups. Additionally, certain combinations of lens materials and care regimens produce inherently more wettable surfaces when measured in vitro. <br /><br /> Suitable methods to assess contact lens wettability ex vivo, or after subjects had worn lenses for set periods of time, were developed. It was determined that using latex gloves to remove lenses had no impact upon the lens surface wettability and that rinsing of the lens surface after removal from the eye was required to determine the wettability of the underlying polymer. <br /><br /> The final wettability studies involved an analysis of various lens materials from clinical studies conducted within the Centre for Contact Lens Research (CCLR). These studies investigated differences in wettability between silicone hydrogel lenses manufactured from differing polymers and variations in ex vivo wettability of several combinations of lens materials and solutions, worn for varying periods of time. <br /><br /> A novel method to investigate proteins extracted from lenses using 2D-Difference in Gel Electrophoresis (DIGE) found that this technique could be used to analyze proteins extracted from contact lenses. The data obtained showed that there was no difference between a group of subjects who were symptomatic of lens-induced dryness or a control group, and that care solutions had a minimal influence on the pattern of deposition seen. <br /><br /> The overall conclusion of these studies is that hydrogel lens wettability is affected by the polymer composition and that care regimen components can modify the surface wettability.

Nowadays plasmonics is rapidly developing areas from fundamental studies to more application driven research. This dissertation contains three different research topics on plasmonics. In the first research topic, by modulating the zone width of a plasmonic zone plate, we demonstrate that a beam focused by a proposed plasmonic zone plate lens can be achieved with higher intensity and smaller spot size than the diffraction-limited conventional zone plate lens. This sub-diffraction focusing capability is attributed to extraordinary optical transmission, which is explained by the complex propagation constant in the zone regions afforded by higher refractive index dielectric layer and surface plasmons. On the other hand, the resulted diffraction efficiency of this device is relatively low. By introducing a metal/dielectric multilayered zone plate, we present higher field enhancement at the focal point. This higher field enhancement originates not only from surface plasmon polaritons-assisted diffraction process along the propagation direction of the incident light (longitude mode), but also from multiple scattering and coupling of surface plasmons along the metal/dielectric interface (transverse mode). In the second research topic, we suggest a novel concept of SERS-active substrate applications. The surface-enhanced Raman scattering enhancement factor supported by gap surface plasmon polaritons is introduced. Due to higher effective refractive index induced by gap surface plasmon polaritons in the spacer region between two metal plates, incident light tends to localize itself mostly in the medium with higher refractive index than its adjacent ones and thereby the lights can confine with larger field enhancement. In the last research topic, we offer a simple structure in which a gold dipole antenna is formed on the SiC substrate. Surface phonon polaritons, counterparts of surface plasmon polaritons in the mid-infrared frequencies, are developed. Due to the synergistic action between the conventional dipole antenna coupling and the resonant excitation of surface phonon polaritons, strong field enhancement in the gap region of dipole antenna is attained. Most of research topics above are expected to find promising applications such as maskless nanolithography, high resolution scanning optical microscopy, optical data storage, optical antenna, SERS-active substrate, bio-molecular sensing and highly sensitive photo-detectors.

Not available

The cornea is the anterior most surface of the eye and plays a critical role in vision. A thin fluid layer, the tear film, coats the outer surface of the cornea and serves to protect, nourish, and lubricate the cornea. At the same time, the tear film is responsible for creating a smooth continuous surface where the majority of refraction takes place in the eye. A significant component of vision quality is determined by the shape of the cornea and stability of the tear film. It is desirable to possess an instrument that can measure the corneal shape and tear film surface with the same accuracy and resolution that is currently performed on common optical elements. A dual interferometer system for measuring the dynamic corneal topography is designed, built, and verified. The completed system is validated by testing on human subjects. The system consists of two co-aligned polarization splitting Twyman-Green interferometers designed to measure phase instantaneously. The primary interferometer measures the surface of the tear film while the secondary interferometer simultaneously tracks the absolute position of the cornea. Eye motion, ocular variation, and a dynamic tear film surface will result in a non-null configuration of the surface with respect to the interferometer system. A non-null test results in significant interferometer induced errors that add to the measured phase. New algorithms are developed to recover the absolute surface topography of the tear film and corneal surface from the simultaneous interferometer measurements. The results are high-resolution and high-accuracy surface topography measurements of the in vivo cornea that are captured at standard camera frame rates. This dissertation will cover the development and construction of an interferometer system for measuring the dynamic corneal topography of the human eye. The discussion starts with the completion of an interferometer for measuring the tear film. The tear film interferometer is part of an ongoing research project that has spanned multiple dissertations. For this research, the instrument was tested on human subjects and resulted in refinements to the interferometer design. The final configuration of the tear film interferometer and results from human subjects testing are presented. Feedback from this instrument was used to support the development and construction of the interferometric corneal topographer system. A calibration is performed on the instrument, and then verified against simulated eye surfaces. Finally, the instrument is validated by testing on human subjects. The result is an interferometer system that can non-invasively measure the dynamic corneal topography with greater accuracy and resolution than existing technologies.

No description available.

Šiame darbe yra sudaryta ir analiziškai išspręsta spindulių eigos idealiuose lęšiuose, diferencialinė lygtis. Rastas paviršius, į kurį kritę spinduliai po lūžimo eina lygiagrečiai simetrijos ašiai. Aprašyta, kaip sklinda perėję per idealųjį lęšį iš idealaus ir ne iš idealaus taškinio šaltinio išėję šviesos spinduliai. / In the present work, the differential equation is being structured and solved by analysis of beams motion in ideal lenses. There was a surface on witch motioned beams, after the refraction, come in parallel with symmetric axis. Also it includes how to gleams spread after passing through the ideal lens from ideal and non-ideal spot source witch they came from.

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.

Šiame darbe analizuojami didesnio lūžio rodiklio lęšių įtaka, akinių lęšių nešiotojams. Išnagrinėta mokslinės literatūros lęšių ir jų esamų aberacijų klausimais. Išanalizuota didesnio lūžio rodiklio plonintų lęšių, sferinių ir asferinių optinės charakteristikos. Išsiaiškinta kokių refrakcijos ydų turintys klientai netoleruoja labiausiai didesnio lūžio rodiklio plonintų lęšių. Pateikti tyrimo grafikai ir jų analizė bei išvados. Tyrime dalyvavo 90 respondentų. Tiriamieji suskirstyti pagal amžių, išsilavinimą, refrakcijos ydas bei nešiojamus akinių lęšius (plonintus ar neplonintus, sferinius ar asferinius). Analizuojant šio darbo temą, pastebėta, kad ši problema susijusi su akinių lęšių nepageidaujamais efektais, analizuojama mažai. Gauti tyrimo rezultatai rodo, kad didesnio lūžio rodiklio ploninti lęšiai, ypač asferiniai sukelia nepageidaujamus efektus. Tuos vaizdo iškraipymus labiau pajaučia tie klientai, kurie turi toliaregystės (hipermetropijos) refrakcijos ydas. Esant vidutinio laipsnio (nuo ±3.0 D iki ±6.0 D) ir didesnio laipsnio miopijai (nuo ±6.0 D ir daugiau), klientai nori lengvesnių ir plonesnių akinių lęšių. Todėl užsisako didesnio lūžio rodiklio asferinius akinių lęšius, kurie esant didesnėms dioptrijoms nedidina akių ir yra žymiai plonesni bei lengvesni. Tačiau tokie akinių lęšiai ne visada pateisina laukiamus lūkesčius. Asferinius lęšius užsisakė 30 respondentų: 22 žmonės buvo su trumparegystės (miopijos) refrakcijos yda, iš kurių nepageidaujamus vaizdo efektus... [toliau žr. visą tekstą] / In this work, effect of lenses with higher refractive index for glasses wearers is analysed. Scientific literature in field of lenses and current aberration in them is examined. Optical characteristics of thin lenses with higher refractive index both spherical and aspherical are investigated. It has been find out what kind of refractive defects have clients who do not tolerate thin lenses with higher refractive index. Graphs of the research, their analysis and conclusions are presented. The research involved 90 respondents. Participants of the research were divided according to age, education, refractive defects and eyeglass lenses worn (thin or non-thin, spherical or aspherical). While analysing the topic of the work, it was noticed that this problem, related with adverse effect of glasses, is analysed a little. The results of research shows that thin lenses with higher refractive index and especially aspherical ones cause adverse effects. Image distortions are felt by these clients who have refraction defects of long-sightedness (hypermetropia). At moderate (from ± 3.0 to ± 6.0 D D) and higher degree of myopia (from ± 6.0 D, and more), clients want lighter, thinner eyeglass lenses. Therefore, they order aspherical eyeglass lenses with higher refractive index, which consisting higher dioptres do not increase eye and are much thinner and lighter. Unfortunately these kind of eyeglass lenses do not always justify expectations. Aspherical lenses was ordered by 30 respondents:... [to full text]

This thesis presents the study of four aspects of high energy astronomy.The first part of my thesis is dedicated to an aspect of instrument development for imaging atmospheric Cherenkov telescopes, namely the Level 2 trigger system of the High Energy Stereoscopic System (H.E.S.S.). My work on the project focused on the algorithm development and the Monte Carlo simulations of the trigger system and overall instrument (Moudden, Barnacka, Glicenstein et al. 2011a; Moudden, Venault, Barnacka et al. 2011b). The hardware implementation of the system is described andits expected performances are then evaluated. The H.E.S.S. array has been used to observe the blazar PKS 1510-089.The second part of my thesis deals with the data analysis and modeling of broad-band emission of this particular blazar. In part II of my thesis, I am presenting the analysis of the H.E.S.S. data: the light curve and spectrum of PKS 1510-089, together with the FERMI data and a collection of multi-wavelength data obtained with various instruments. I am presenting the model of PKS 1510-089 observations carried out during a flare recorded by H.E.S.S.. The model is based on a single zone internal shock scenario.The third part of my thesis deals with blazars observed by the FERMI-LAT, but from the point of view of other phenomena: a strong gravitational lensing. This part of my thesis shows the first evidence for gravitational lensing phenomena in high energy gamma-rays. This evidence comes from the observation of a gravitational lens system induced echo in the light curve of the distant blazar PKS 1830-211. Traditionalmethods for the estimation of time delays in gravitational lensing systems rely on the cross-correlation of the light curves from individual images. In my thesis, I used 300 MeV-30 GeV photons detected by the Fermi-LAT instrument. The FERMI-LAT instrument cannot separate the images of known lenses. The observed light curve is thus the superposition of individual image light curves. The FERMI-LAT instrument has the advantage of providing long, evenly spaced, time series with very low photonnoise. This allows to use directly Fourier transform methods. A time delay between the two compact images of PKS 1830-211 has been searchedfor both by the autocorrelation method and a new method: the "double power spectrum". The double power spectrum shows a 4.2 σ evidence for a time delay of 27.1±0.6 days (Barnacka et al. 2011), consistent with the results from Lovell et al. (1998) and Wiklind & Combes (2001).The last part of my thesis concentrates on another lensing phenomena called "femtolensing". The search for femtolensing effects has been used to derive limits on the primordial black holes abundance. The abundance of primordial black holes is currently significantly constrained in a wide range of masses. The weakest limits are established for the small mass objects, where the small intensity of the associated physical phenomenon provides a challenge for current experiments. I have usedgamma-ray bursts with known redshifts detected by the FERMI Gamma-ray Burst Monitor (GBM) to search for the femtolensing effects caused by compact objects. The lack of femtolensing detection in the GBM data provides new evidence that primordial black holes in the mass range 5 × 10^17 - 10^20 g do not constitute a major fraction of dark matter (Barnacka et al. 2012). My Ph.D. studies have been carried out jointly between the Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences, in Warsaw in Poland and the IRFU institute of the Commissariat à l'énergie atomique et aux énergies alternatives(CEA) Saclay in France.