Record sections from partially reversed refraction lines in northern British Columbia show that the amplitudes of upper mantle arrivals vary smoothly with distance. The pattern of crustal arrival amplitudes is not smooth. Normalization of the seismograms to remove the amplification caused by shot size and instrument response show the effects of recording sites on Pn amplitudes are minimal. Models derived from ray theory indicate a crust which thins from about 40 km in the Omineca Crystalline Belt to about 25 km in the Insular Trough. The average Pn velocity is 8.06 km/s. The average crustal velocity is 6.4 km/s. The secondary energy would indicate the models are greatly simplified. A time-term profile between the Omineca Crystalline Belt and the Coast Mountains suggests a Mohorovicic transition which is characterized by two significant topographic wavelengths. The shorter (200 km) wavelength correlates roughly with the Cordilleran structural elements of Wheeler et al. (1972). The larger (800 km) wavelength may have tectonic significance. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

M.Phil. / The primary purpose of this study was to investigate in different age groups the various relationships between autorefraction and subjective refraction, between autorefraction and retinoscopy and between retinoscopy and subjective refraction. Multivariate statistical methods are used to explore the nature of the relationships between these three different methods of evaluating refractive state. This is the first occasion in which these statistical approaches have been used to address these relationships within a sample of black South Africans. The short-term variation of measurements of the autorefractor used in this study was evaluated by means of an artificial or model eye. Here samples of fifty measurements each were obtained every two hours over a period of one day. Scatter plots, meridional profiles and hypothesis tests of equality of variance-covariance and of equality of mean autorefraction are used for analysis of the measurements obtained. Such analysis suggests that the variability in autorefraction across the day was of small magnitude and less than that typically found with human eyes. The implication is that many other factors besides the instrument itself are responsible for the variation found when using an autorefractor on a human eye. These factors include changes in accommodation, ocular fixation, the blinking process and attention. The environment within which the autorefractor is placed is important and changes in, for example, temperatur may have subtle but significant influences. The major part of this dissertation describes a study performed over a period of about seven months during which a sample of 240 male and female subjects were chosen randomly from a larger group of about 2800 patients who came to have their eyes examined in a clinical practice. A questionnaire was completed by each subject and retinoscopy was performed followed by subjective refraction and then autorefraction. Ocular health was assessed and visual acuities were measured. The study subjects were further divided into six smaller subgroups according to their ages and the analysis of results obtained with retinoscopy, subjective refraction and autorefraction included both qualitative and quantitative multivariate methods such as stereo-pair scatter plots, trajectories of change of dioptric power, meridional profiles, confidence and distribution ellipsoids, and testing of hypotheses of equality of variance-covariance and of equality of means. All of these methods help in understanding the nature of the various relationships between the different refractive methods, and they also are important when considering concepts such as mean refractive state and variation of refraction in human eyes. They also are used to develop an understanding of the distribution or spread of the population of refractive states from which the 'sample was obtained. For the three refractive methods . (retinoscopy, subjective refraction and autorefraction) the spread or distribution of measurements in the six age groups suggests that generally the refractive behaviour of right and left eyes was similar. A possible shift towards hyperopia and more astigmatism with increasing age is apparent. For example, mean autorefraction for the right and left eyes in the youngest and oldest age groups (Groups 1 and 6 respectively) is -0.41/-0.06 x 148 and -0.32/-0.07 x 177 and 0.41/-0.57 x 102 and 0.57/-0.32 x 75. Similarly mean subjective refraction for the right and left eyes of Group 1 is 0.10/-0.14 x 97 and 0.30/-0.17 x 81 and is 0.78/-0.70 x 95 and 0.89/-0.47 x 82 for the right and left eyes of Group 6 respectively. Again mean retinoscopy for the iv right and left eyes of Group 1 and Group 6 respectively is 0.69/-0.05 x 91 and 0.65/-0.21 x 82 and 1.72/-0.88 x 89

In this article, the author dissects and refracts a single, defining moment in his life using autoethnography and the lenses of specific communication and social theories. The author mines the moment in first, second, and third person to uncover the different responses to overwhelming emotions ranging from the noble to the shameful in response to his father’s “coming out of the closet.” A torrent of emotion took the author by surprise and is the total moment of his analysis in this article. The author scrutinizes the multiple ways in which this moment was a release, a turning point, an ending, a beginning, bittersweet, hateful and hate filled, selfish, guilt ridden, and loving. Through multiple retellings of the event, like the film Groundhog Day, the author presents the moment in different narrative formats, from multiple perspectives, with relevant quotations and passages to thoroughly dissect the emotional layers.

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No / In this paper, the seasonal variations of vertical refractivity gradients and statistics of anomalous Refractive Conditions in the United Arab Emirates (UAE) have been analyzed. Nine years of local radiosonde meteorological data, from 1997 to 2005, for the lowest atmospheric layer above the ground surface have been used. Monthly variations and cumulative distributions of refractivity gradients in the first 100 meters of the atmosphere are presented.

Thesis advisor: John E. Ebel / Degradation within an earth embankment structure is often unobservable from the surface. In order to evaluate the structural integrity of earth embankment dams and levees and identify subsurface zones of weakness that may result in future failures, various geophysical methods have been proposed as effective subsurface imaging tools. This study presents the results of using the horizontal-to-vertical spectral ratio (HVSR), seismic refraction analysis, and multi-channel analysis of surface waves (MASW) methods to estimate subsurface seismic structures for two earth embankment dams located in Chestnut Hill, MA, and Franklin Falls, NH. The estimated seismic velocity structures from the seismic refraction analysis and MASW performed in this study confirm the HVSR method is able to effectively estimate depth to bedrock at sites atop earth embankments using estimated fundamental frequencies. The MASW was found to resolve a low-velocity zone in the subsurface at the Chestnut Hill reservoir embankment that the seismic refraction method was unable to image, and this low-velocity zone is required to best fit a theoretical HVSR to an observed spectrum. Furthermore, the variation and uncertainty in fundamental frequency estimation were investigated by making repeated HVSR measurements at the Chestnut Hill embankment. / Thesis (BS) — Boston College, 2023. / Submitted to: Boston College. College of Arts and Sciences.. / Discipline: Departmental Honors. / Discipline: Earth and Environmental Sciences.

A description of several experiments carried out to investigate the behaviour of 3.2 cm. microwaves on passing through a dielectric prism is given in this thesis. Chapter I contains a description of the experimental apparatus used to generate electromagnetic radiation and to measure the field intensity in a plane perpendicular to the refracting edge of the prism. Particular emphasis is placed on a description of the receiver amplifier, and on the construction of the wax prism. In Chapter II are given the results of several preliminary investigations of the field close to, and polarized parallel to the retracting edge of the prism. Fresnel interference fringes were observed with the prism oriented as a biprism. Diffraction fringes of a 45˚ wedge, both dielectric and metallic, were observed incidentally. Evidence of the evanescent wave predicted for total internal reflection was obtained directly in this experiment where earlier evidence of such waves in the optical and microwave regions has been indirect. / Thesis / Master of Science (MSc)

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Yes / In this communication, nine years of local radiosonde meteorological data, from 1997 to 2005, have been used to calculate the vertical refractivity gradient, ΔN, in the lowest atmospheric layer above the ground surface. The values obtained are used to estimate the parameter β0, which represents the probability of non-standard propagation. Hourly, monthly and yearly distributions of ΔN in the first 100 meters above the ground are given. Monthly and yearly variations of the mean of ΔN and β0 are provided and the β0 values are compared with the ITU maps.