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About MacSphere

MacSphere is McMaster University's Institutional Repository (IR). The purpose of an IR is to bring together all of a University's research under one umbrella, with an aim to preserve and provide access to that research. The research and scholarly output included in MacSphere has been selected and deposited by the individual university departments and centres on campus.

To contribute to McMaster's Institutional Repository, please sign on to MacSphere with your MAC ID.

If you have any questions, please contact the MacSphere Support Team.

Students wishing to deposit their PhD or Masters thesis, please follow the instructions outlined by the School of Graduate Studies.

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Recent Submissions

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    AN INVESTIGATION OF PARAMETERS AFFECTING THE SPURIOUS VARIATION OF PHOTON FLUENCE IN INTENSITY MODULATED RADIATION THERAPY
    (2003-12) FABIOLA VALLEJO-CASTANEDA
    The parameters that influence the amount of spurious variation in a set of optimized fluence maps (FMs) for intensity modulated radiation therapy (IMRT) were investigated. For this purpose, several simple geometries were used for testing various approaches. The FMs were characterized in term of the mean, standard deviation and first and second derivatives in the two cardinal directions. The peripheral and interior regions of the FMs were analyzed. The parameters tested and the results of the investigations were as follows. (1) The effect of the field margin: it was found that a margin of less than or equal to 0.5cm from the planning target volume (PTV) to the field edge increases the variation of a FM. (2) Incident beam direction: changing to a different but equivalent beam direction caused a small change in the variation of the FM. (3) Minimum transmission: small increases in the minimum transmission values reduce the amount of spurious variation. (4) Sequence of application of objectives: the sequence in which the objectives were applied influenced the smoothness of the fluence map to a small degree. (5) The influence of organ at risk separation from the PTV: the proximity of the PTV to organ at risk (OAR) affects the variation in a fluence map, independent of the thickness of the phantom or the beam direction. (6) The effect of different smoothing strategies on the optimized fluence maps: intelligent smoothing did not appreciably raise the composite objective value whereas a smooth-filter algorithm did. (7) The effect of different dose calculation grids: the amount of variation was reduced when the superior-inferior grid size was a factor of the pencil beam size. The factors that influenced the spurious variation the most were field margin size, ROI separation, minimum transmission and dose calculation grid dimensions. Strategic smoothing algorithms may reduce spurious variation while maintaining acceptable composite objective values. These results were applied to a very limited set of phantom geometries. In order to generalize this work, experiments will need to be done in clinically relevant geometries.
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    THE AGE OF NARCISSISM: A CULTURAL CRITIQUE OF THE NEW AGE MOVEMENT
    (1993-04) Lanna Nakoneshny
    The aim of this thesis is to show that the few theories surrounding the New Age movement are inaccurate, unfounded and even dangerous. By looking at the larger cultural contexts of advanced industrial societies, I argue that the New Age is a product of the culture of narcissism. The growing holistic healing practices, which New Age ideas and practices can best be understood, show the desperate need for us to make some sense of things. The search to unite body, mind and spirit emerges as a protective shield to guard off any unpleasant things that the world gives us. Even though the New Age movement has narcissistic tendencies, these leanings are solely brought about by survivalism: that self-awareness is the initial step to try to make a difference in the world. The result of this study is to dispel the myths that we, as participants of popular culture, have about the New Age movement and to judge it with sound facts, data and observation.
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    Approved Minutes: November 2025 Graduate Council
    (2025) School of Graduate Studies
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    Colorful photovoltaics using thickness-modulated thin film optical filters
    (2026) Bhattacharyya, Paramita
    Colorful photovoltaics have long been appealing to consumers for applications such as rooftop, building-integrated, and electric vehicle-integrated solar cells, among others. Achieving vibrant colors involves reflecting specific wavelengths of visible light. But energy capture in the visible range is crucial, as it often provides optimal external quantum efficiency. Therefore, it is essential to enhance the reflection of solar irradiance to achieve color while minimizing photocurrent loss. Researchers have explored various bottom-up approaches, such as modulating the thickness of single or dual-layer antireflective coatings (ARCs) or adding layers to existing standard ARCs. However, this often leads to broader reflection peaks and substantial photocurrent loss. While photonic crystal structures and metasurfaces show promise for color rendering, they require significant development before mass production. We explored various design strategies to develop two innovative methods for optical filter design that enhance both aesthetic appeal and photovoltaic efficiency while using fewer layers. Our first method employs a top-down strategy utilizing OptiLayer and MATLAB to design optical filters consisting of 2-6 layers. This approach results in narrower reflection peaks and achieves optimal colors (blue, green, red) while maintaining a photocurrent loss of only 5-10%, a notable improvement over previously proposed solutions. We investigated various combinations of materials to identify the optimal range of material pairs for this specific application. Our designs were validated through fabrication with three material pairs and two deposition techniques (CVD and PVD), and feedback from our experimental understanding was incorporated into our design method to make it robust. Our second approach uses a custom MATLAB code to design an optimal filter based on selected layer numbers and materials, specified by the manufacturers. The thesis includes details on design methods, deposition and characterization techniques, comparisons of spectral responses, and images of the colors produced by the fabricated filters.