The main aim of this thesis is to evaluate the effect of meridional blur, using refractive induced astigmatism, on visual performance at far and close distances. Visual performance was evaluated using letter discrimination tasks at distance and near (visual acuity, VA) and a reading task at near on subjects with pharmacologically blocked (young) or absent accommodation (presbyopic and pseudophakic). The effect of astigmatism was tested using positive cylindrical lenses oriented at 180 and 90 degrees, these simulating with- (WTR) and against-the-rule (ATR) astigmatism. Other refractive status were also evaluated, namely, in-focus and spherical defocus. The visual performance data were correlated with biometric measurements (pupil size, anterior chamber depth (ACD), corneal and ocular aberrations, corneal multifocality, patient age, axial length). Further, the functionality of meridional blur was evaluated for alphabets in addition to the standard Roman alphabet using a VA task. The results confirm that myopic astigmatism contributes to a better visual performance at closer distances, with ATR astigmatism providing higher performance for reading tasks compared to other forms of astigmatism. Anatomical factors such as pupil size, corneal multifocality and ACD were significantly correlated visual performance, while other ocular characteristics were not. Ray tracing modelling using wavefront data was a moderate predictor of VA and reading acuity. The results of the effect of meridional blur orientation on alphabets other than the Roman alphabet, suggest that visual performance is dependent on the interaction between blur orientation and letter's spatial characteristics. In conclusion, pseudoaccommodation is a multifactorial phenomenon with pupil size being the major contributor for the improvement in visual performance. Against-the-rule shows advantages over WTR astigmatism, by providing higher reading performance, however extending the present and previous findings for clinical application will require further investigation on the effect of meridional blur in common and socio-culturally adapted tasks.

A precise understanding of the fundamental correlation between synthesis, microstructure and physical properties is of vital importance towards rational design of improved functional epitaxial thin films. With the presence of heterogeneous interface and associated inhomogeneous lattice strain, film microstructure becomes sensitive to subtle interfacial perturbations and hence may exhibit intriguing physical properties. Control of the epitaxial film functionality requires accurate knowledge of the actual film chemistry, interfacial defects and associated strain field. This dissertation reports in-depth microstructural characterization of the intrinsic chemical inhomogeneity in selected epitaxial thin films including superconducting Fe1+yTe1-xSex/SrTiO3(STO) heterogeneous systems, the flux-pinning defects at both of conversional YBa2Cu3O7-δ (YBCO)/substrate lateral interfaces and vertical interfaces of YBCO&BaSnO3(BSO) nanocomposite films, and the misfit dislocation core configurations of STO/MgO and MgO/STO heterostructures pair, using the state-of-the-art aberration-corrected scanning transmission electron microscopy (CS-corrected STEM) in combination with geometric phase analysis (GPA). For the first time, the local atomic arrangement of Te and Se as well as interstitial Fe(2) has been clearly revealed in superconducting Fe1+yTe1-xSex/STO epitaxial films. We found that the film growth atmosphere can greatly affect the film stoichiometry, the homogeneity of Se/Te ordering and thus the overall film superconductivity. YBCO/substrate interface mismatch and YBCO&BSO vertical interface contact have been explored through substrate selection and doping-concentration variation. We observed a diverse nature of intrinsic defects in different YBCO/substrate heterosystems; thermal stable defects capable of maintaining individual strain field have been found effective in flux-pinning. Along the vertical heterointerface of YBCO/BSO, misfit dislocations were found throughout the film thickness. It adds another dimension to the flux-pinning landscape design. Four basic misfit dislocation core configurations of a STO/MgO heterosystem have been identified, and found strongly dependent on the actual interface disordering such as substrate atomic-height steps and interdiffussion. To precisely quantify the heterointerface lattice strain, we first conducted systematic investigations on the accuracy of STEM-based GPA. Follow our protocol, 1 pm accuracy has been proven in the STEM fast-scan direction with a spatial resolution less than 1 nm. The effectiveness and reliability of this optimized GPA strain profile were demonstrated in both applications of a relaxed STO/MgO and a partially strained LaAlO3/STO heterointerfaces, respectively.

Aberrationen in der DNA-Kopienzahl sind häufige genetische Veränderungen bei malignen Lymphomerkrankungen. Zugewinne sowie Deletionen stellen dabei Mechanismen zur Onkogen-Aktivierung sowie Tumorsuppressorgen-Inaktivierung dar und tragen somit zur Pathogenese der Erkrankung bei. Array-CGH und SNP-Array sind Messplattformen, die die genomweite Bestimmung von Kopienzahlaberrationen in einem Experiment ermöglichen. Die bei der Analyse entstehenden Datensätze sind komplex und erfordern automatische Methoden zur Unterstützung der Analyse und Interpretation der Messergebnisse. In dieser Promotionsarbeit wurden Methoden entwickelt, welche die Analyse von Array-CGH- und SNP-Array-Messungen ermöglichen. Diese Methoden wurden für die Auswertung umfangreicher Datensätze von malignen Non-Hodgkin-Lymphomen verwendet. Dabei wurden Lymphome der Entitäten Burkitt-Lymphom, diffus großzelliges B-Zell-Lymphom, Mantelzelllymphom, primäres ZNS-Lymphom und peripheres T-Zell-Lymphom – nicht anderweitig spezifiziert – analysiert. Für die untersuchten Lymphom-Entitäten konnten hierbei zahlreiche neue rekurrente Kopienzahlaberrationen sowie uniparentale Disomien gezeigt werden, die neue Einblicke in die Pathogenese der jeweiligen Erkrankungen erlauben. Darüber hinaus erfolgte ein Vergleich beider Messplattformen anhand eines Datensatzes mit gepaarten Array-CGH- und SNP-Array-Daten. Für die eingesetzten Plattformen (2800k-BAC-Array vs. Affymetrix 250k-Sty-SNP-Array) konnte eine circa zwölffach höhere effektive Auflösung der SNP-Array-Plattform gezeigt werden. Die wesentlichen Ergebnisse dieser Arbeit sind in sieben Publikationen eingeflossen.

Made available in DSpace on 2016-08-18T18:19:30Z (GMT). No. of bitstreams: 1 Dissertacao Girlane.pdf: 2233662 bytes, checksum: e187d35550c694d6e69d8bc6b2ca20db (MD5) Previous issue date: 2011-09-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Raman scattering phenomena has far been widely used as an experimental methodology for probing materials properties. In the last decade, the combination of microscopy and spectroscopy aspects has been largely used in the study of materials in low dimensions, especially carbon nanotubes and graphene. Graphene is a two-dimensional material that has one hexagonal structure. Due to its excellent crystalline quality, this material has shown great prospects of strategic applications in the near future. The majority of the studies reported on graphene are carried out by using confocal microscopes, which relies on the longitudinal chromatic aberration. This optical effect is related to intrinsic limitation of any lens to focus light with different wavelength at the same focal plane. In this work, we examine the effect of longitudinal chromatic aberration and also the effect of irradiance on the Raman spectra of graphene. Consistent with the results of literature, we found that the intensity of the Raman signal for the G mode increases linearly with the number of layers, up to the limit of six layers identified in our samples. We also found a strong dependence of the Raman intensity with longitudinal chromatic aberration. Owing to this effect, the intensity of the G peak was underestimated in about 20%, while the intensity of G peak appeared 56% below the real value. Measurement performed to confirm the effect of longitudinal chromatic aberration showed an aberration of 1,8 μm/eV for Raman scattering and 2,0 μm/eV by using pure reflectometry. Measurements in graphene with defects revealed a strong dependence of peak frequency with focal position and laser power as well. Changes of 6 cm-1 in G' mode was observed for laser power between 44 e 175 μW. / A microscopia Raman é uma das técnicas experimentais mais versáteis e tem sido muito utilizada no estudo das propriedades físicas de materiais. A microscopia confocal em combinação com a espectroscopia Raman tem levado a obtenção de imagens de estruturas em escala nanométrica. Estas ferramentas conjugadas têm sido amplamente utilizadas no estudo de propriedades de materiais em baixas dimensões, como nanotubos de carbono e grafeno. O grafeno é um material bidimensional que possui uma estrutura hexagonal. Devido à sua excelente qualidade cristalina, esse material tem apresentado grandes perspectivas de aplicações estratégicas no futuro próximo. Neste trabalho foram discutidos os efeitos da aberração cromática longitudinal e o efeito da irradiância sobre espectros Raman do grafeno obtidos por um microscópio Raman confocal. Consistente com os resultados da literatura, a intensidade do sinal Raman para o modo G aumentou linearmente com o número de camadas, até o limite de 6 camadas identificadas nas nossas amostras. Os resultados obtidos mostraram forte dependência da intensidade do sinal com a aberração cromática longitudinal. Por causa deste efeito, a intensidade do pico G foi subavaliada em cerca de 20%, enquanto a intensidade do pico G foi subavaliada em aproximadamente 56%. Medidas realizadas para confirmar o efeito da aberração cromática longitudinal mostraram uma aberração de 1,8 μm/eV para o espalhamento Raman e 2,0 μm/eV para o espalhamento Rayleigh. Medidas em grafeno com defeitos revelaram a grande dependência na posição dos picos com posição focal ou com a potência do laser. Mudanças de 6 cm-1 no modo G foram observadas para potências entre 44 e 175 μW.

Deformable mirrors are the standard adaptive optical elements for aberration correction in confocal microscopy. Their usage leads to increased contrast and resolution. However, these improvements are achieved at the cost of bulky optical setups. Since spherical aberrations are the dominating aberrations in confocal microscopy, it is not required to employ all degrees of freedom commonly offered by deformable mirrors. In this contribution, we present an alternative approach for aberration correction in confocal microscopy based on a novel adaptive lens with two degrees of freedom. These lenses enable both axial scanning and aberration correction, keeping the setup simple and compact. Using digital holography, we characterize the tuning range of the focal length and the spherical aberration correction ability of the adaptive lens. The operation at fixed trajectories in terms of focal length and spherical aberrations is demonstrated and investigated in terms of reproducibility. First results indicate that such adaptive lenses are a promising approach towards high-resolution, high-speed three-dimensional microscopy.

The main aim of this thesis is to evaluate the effect of meridional blur, using refractive induced astigmatism, on visual performance at far and close distances. Visual performance was evaluated using letter discrimination tasks at distance and near (visual acuity, VA) and a reading task at near on subjects with pharmacologically blocked (young) or absent accommodation (presbyopic and pseudophakic). The effect of astigmatism was tested using positive cylindrical lenses oriented at 180 and 90 degrees, these simulating with- (WTR) and against-the-rule (ATR) astigmatism. Other refractive status were also evaluated, namely, in-focus and spherical defocus. The visual performance data were correlated with biometric measurements (pupil size, anterior chamber depth (ACD), corneal and ocular aberrations, corneal multifocality, patient age, axial length). Further, the functionality of meridional blur was evaluated for alphabets in addition to the standard Roman alphabet using a VA task. The results confirm that myopic astigmatism contributes to a better visual performance at closer distances, with ATR astigmatism providing higher performance for reading tasks compared to other forms of astigmatism. Anatomical factors such as pupil size, corneal multifocality and ACD were significantly correlated visual performance, while other ocular characteristics were not. Ray tracing modelling using wavefront data was a moderate predictor of VA and reading acuity. The results of the effect of meridional blur orientation on alphabets other than the Roman alphabet, suggest that visual performance is dependent on the interaction between blur orientation and letter¿s spatial characteristics. In conclusion, pseudoaccommodation is a multifactorial phenomenon with pupil size being the major contributor for the improvement in visual performance. Against-the-rule shows advantages over WTR astigmatism, by providing higher reading performance, however extending the present and previous findings for clinical application will require further investigation on the effect of meridional blur in common and socio-culturally adapted tasks. / Bradford School of Optometry and Vision Sciences

No description available.

Le télescope de l'Observatoire du Mont-Mégantic est utilisé depuis la fin des années 70. La grande variété d'instruments qui y est disponible en fait un télescope très polyvalent. Cependant, très peu de données existent par rapport à ses aberrations optiques. Il est important de connaître ces aberrations si on désire améliorer la performance optique du télescope. Pour évaluer ces aberrations, deux méthodes de reconstruction de front d'onde ont été utilisées : le senseur de front d'onde de type Shack-Hartmann et le senseur de courbure. L'analyse des fronts d'ondes reconstruits permet d'identifier les aberrations dominantes ainsi que plusieurs paramètres influençant ces aberrations. De plus, les méthodes sont comparées afin de vérifier si elles peuvent permettre un alignement des miroirs primaire et secondaire.

During recent years, new types of materials have been discovered with unique properties. One family of such materials are two-dimensional materials, which include graphene and MXene. These materials are stronger, more flexible, and have higher conductivity than other materials. As such they are highly interesting for new applications, e.g. specialized in vivo drug delivery systems, hydrogen storage, or as replacements of common materials in e.g. batteries, bulletproof clothing, and sensors. The list of potential applications is long for these new materials. As these materials are almost entirely made up of surfaces, their properties are strongly influenced by interaction between their surfaces, as well as with molecules or adatoms attached to the surfaces (surface groups). This interaction can change the materials and their properties, and it is therefore imperative to understand the underlying mechanisms. Surface groups on two-dimensional materials can be studied by Transmission Electron Microscopy (TEM), where high energy electrons are transmitted through a sample and the resulting image is recorded. However, the high energy needed to get enough resolution to observe single atoms damages the sample and limits the type of materials which can be analyzed. Lowering the electron energy decreases the damage, but the image resolution at such conditions is severely limited by inherent imperfections (aberrations) in the TEM. During the last years, new TEM models have been developed which employ a low acceleration voltage together with aberration correction, enabling imaging at the atomic scale without damaging the samples. These aberration-corrected TEMs are important tools in understanding the structure and chemistry of two-dimensional materials. In this thesis the two-dimensional materials graphene and Ti3C2Tx MXene have been investigated by low-voltage, aberration-corrected (scanning) TEM. High temperature annealing of graphene covered by residues from the synthesis is studied, as well as the structure and surface groups on single and double Ti3C2Tx MXene. These results are important contributions to the understanding of this class of materials and how their properties can be controlled.

Chromosomal aberrations are common causes of abnormal development of fetuses leading to the birth of malformed indvidual or to the intrauterine death. Half of miscarriages in the first trimester and a third in the second trimester are caused by fetal chromosomal abnormalities, mainly aneuploidies. If fetus is abnormally developed, invasive prenatal cytogenetic diagnosis should be recommended. Positive cytogenetic finding can be reason for induced abortion till the end of 24th week of gestation. We investigated 81 miscarriages, 46 fetuses from induced abortions and 80 fetuses with abnormal development from ongoing pregnancies. G-banding analysis was used as the main method for investigating miscarriages. Genomic DNA isolated from abnormally developed fetuses was screened by array CGH technique. We found 43,75 % chromosomal abnormal miscarried fetuses, majority of them with numerical aberrations (91,4 %). In group of induced abortions, 25,71 % fetuses carried chromosomal abnormality. The lowest rate 11,67 % of chromosoal aberrations was detected in group of prenatally diagnosed fetuses from ongoing pregnancies. Array CGH detected submicroscopic aberrations in 13,41 % fetuses with ultrasound findings. All together 25,74 % microscopic and causal submicroscopic chromosomal abnormalities were found to be...