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Porous silicon dioxide thin films were produced via dip-coating and doped with Ag+ by adding AgNO3 to the dipping solution. Nanoparticles were formed within the pores of these films by UV exposure. Nanoparticle formation was confirmed by UV-visible spectroscopy and Transmission Electron Microscopy (TEM). Conductive Atomic Force Microscopy (CAFM) showed that the conductivity of the films decreased upon exposure to UV. This decrease in the conductivity is most likely due to the clustering of charge carriers. Initially, Ag+ ions are attached to negatively charged pore walls in a dense packing network. Upon UV exposure (125 mW @ 266 nm), the Ag+ ions are reduced to Ag metal and agglomerate to form clusters. The agglomeration creates gaps in the film that decrease its conductivity. This ability to tune film conductivity was used to create insulating patterns within conducting films. A calibration mask was placed over the films during UV exposure, and exposed regions with a minimum width of ~2 μm were detected as depressions with insulating behavior. The fabrication of photonic and plasmonic devices is being explored using this method.

UV exposure via sunbathing and utilization of sun lamps and tanning beds are considered important risk factors for the development of skin cancer. Psychosocial models of UV exposure are often based on theories of health behavior, but theory from the body image field can be useful as well. The current study examines models that prospectively predict sunbathing and indoor tanning behaviors using constructs and interrelationships derived from the tripartite theory of body image, theory of reasoned action, health belief model, revised protection motivation theory, and a proposed integration of several health behavior models. The results generally support a model in which intentions mediate the relationship between appearance attitudes and tanning behaviors, appearance reasons to tan and intentions mediate the relationship between sociocultural influences and tanning behaviors, and appearance reasons not to tan and intentions mediate the role of perceived threat on behaviors. The implications of these findings are considered.

Background: Risk for skin cancer is increased by UV exposure and decreased by sun protection. Appearance reasons to tan and not tan have consistently been shown to be related to intentions and behaviors to UV exposure and protection. Purpose: This study was designed to determine the factor structure of appearance motives to tan and not tan, evaluate the extent to which this factor structure is gender invariant, test for mean differences in the identified factors, and evaluate internal consistency, temporal stability, and criterion-related validity. Method: Five-hundred eighty-nine females and 335 male college students were used to test confirmatory factor analysis models within and across gender groups, estimate latent mean differences, and use the correlation coefficient and Cronbach's alpha to further evaluate the reliability and validity of the identified factors. Results: A measurement invariant (i.e., factor-loading invariant) model was identified with three higher-order factors: sociocultural influences to tan (lower order factors: media, friends, family, significant others), appearance reasons to tan (general, acne, body shape), and appearance reasons not to tan (skin aging, immediate skin damage). Females had significantly higher means than males on all higher-order factors. All subscales had evidence of internal consistency, temporal stability, and criterion-related validity. Conclusions: This study offers a framework and measurement instrument that has evidence of validity and reliability for evaluating appearance-based motives to tan and not tan.

The present study examined theoretical mediators of a parent-based intervention on sunbathing tendencies and sunburn frequencies based on the work of Turrisi et al. [Turrisi, R., Hillhouse, J., Heavin, S., Robinson, J., Adams, M., & Berry, J. (2004). Journal of Behavioral Medicine, 27, 393-412.]. Three hundred and forty parents in two regions of the United States were educated about the dangers of risky sun behavior and how to convey information about skin cancer prevention to their children. Attitudes toward sunbathing, health beliefs, appearance beliefs, and social normative beliefs were examined and found to be significant mediators of program effects on sunbathing tendencies and sunburn frequencies. The findings are discussed with respect to maximizing the effectiveness of future skin cancer interventions with children.

Material jetting (MJ) is an additive manufacturing (AM) process that involves the selective jetting of a liquid material into the shape of a layer and subsequent solidification, often via ultraviolet (UV) irradiation, in a layer-wise fashion. The MJ process has the potential to emerge as a robust fabrication method: the inherent, facile, multi-material capability in a high-resolution process should distinguish the technology as a competitive, multi-functional, manufacturing process. However, it is mainly constrained to prototyping use, limited by both material and process constraints. This research expands material and process knowledge by characterizing the multi-material process-structure-property relationships in photopolymer-based MJ, which provides a basis for advancing the capability of MJ to fabricate accurate and consistent multi-material parts for functional applications. One of the challenges for advancing MJ is the general lack of processable materials. For example, MJ is increasingly being used for fabricating anatomic models for use as pre-procedural planning or medical student trainee tools, but commercial MJ elastomers are unable to mimic human tissues' mechanical properties, which limits the instructional value of printed anatomic models. By combining photo-curing and non-curing materials, a cardiac tissue-mimicking material was achieved and integrated into a fully-printed heart model used to practice the transseptal puncture procedure. Several mechanical properties of this multi-material combination were evaluated to facilitate quicker screening of future tissues that would be desired to be mimicked. Also impeding technological advancement of MJ systems is a lack of understanding the effects of indiscriminate UV exposure on material properties. Depending on factors such as part design and build layout, an indiscriminate UV toolpathing strategy poses the risk for providing inconsistent UV dosing to parts and causing unintended variations in mechanical performance. Experiments were conducted to quantify these effects, and an empirical model was developed to predict the accumulated exposure parts receive. A connection was then made between accumulated exposure received by material voxels and final part properties, where it was observed that overexposure effects exist, and are largely dependent on material, build layout, and toolpathing. This work will lead to improved design guidelines and process modifications to ensure consistency of UV dosing and achieve desired mechanical performance. This knowledge will enable future photopolymer AM systems to account for potential overcuring effects toward fabricating repeatable and reproducible functional products. Finally, documented in this work are efforts toward expanding the knowledge about the use of AM to safely produce personal protective equipment during the COVID-19 pandemic. Amid prospects of large-scale, distributed production of respirators via AM, the lack of filtration efficiency testing generated concerns about the respirators' effectiveness. The goal of this work was to measure particle transmission through respirators fabricated with powder bed fusion and fused filament fabrication processes and compare their performance to that of cloth masks and standardized N95 respirators. Through systematic post-processing, the connection between printed respirator deficiencies and changes in filtration efficiency were discerned. Identifying the system-level quality control challenges responsible for the respirator failure modes highlights some the current limitations in AM for fabricating functional parts. The findings will assist future efforts toward both creating enhanced designs and optimizing printer parameters, ultimately working toward qualifiable, end-use parts. / Doctor of Philosophy / The material jetting (MJ) additive manufacturing (AM) process operates in a similar fashion to inkjet printing. For MJ of photopolymer materials, liquid droplets are selectively deposited onto a build plate, and an ultraviolet (UV) light bulb provides the energy to solidify the droplets into a three-dimensional layer by curing the materials. Droplets are then deposited on top of these solidified droplets to fabricate a part layer by layer. Multiple materials and colors can be jetted simultaneously within a single part layer. If these materials exhibit different mechanical behavior, such as one material being rigid and another being flexible, a printed part could have regions with different material properties, as well as intermediate gradients of these properties. The MJ process offers high resolution, smooth surface finishing, a large build volume, and the opportunity to print multiple parts in one build. However, the process is mainly limited to prototypes and non-functional applications. One of the challenges for advancing MJ is the general lack of processable materials. In the medical field, surgeons are increasingly looking to MJ to fabricate physical, patient-specific models to assist in pre-surgical planning and to serve as practice models for medical student trainees. In particular, a printed cardiovascular model was sought to enable the practice of the transseptal puncture procedure; however, the available materials were not able to mimic the heart tissue. In this work, a non-curing liquid was patterned into an elastomer to soften the material and attain tissue-mimicking performance for a model to practice the transseptal puncture procedure. By characterizing this expanded material space, this work enables the potential for mimicking a broader spectrum of tissues in future anatomic models. Another aspect limiting widespread functional use for MJ is the lack of understanding how UV exposure affects material performance. For the MJ process, the UV light is on the same assembly as the printheads and remains on throughout the duration of a print, which means that the amount of administered energy is not consistent across the build plate. If, for example, parts have different heights, the shorter part will finish printing first and receive excess UV exposure, which has been shown to alter the mechanical performance for some materials. A model was developed to predict the accumulated exposure received by parts of different materials and build scenarios. Observed changes in mechanical properties could then be connected to specific instances of overexposure. With this knowledge, future strategies can be implemented to achieve consistency of UV exposure and thus better ensure reliable, functional parts. Additionally presented in this work is a study involving the use of AM to safely produce personal protective equipment for COVID-19 relief efforts. During the initial stages of the pandemic, AM was sought to address respirator shortages; however, there were no studies measuring printed respirators' effectiveness. By measuring particle transmission through respirators fabricated with a variety of AM processes, it was found that even when N95 filters were inserted, printed respirators were not able to consistently filter 95% of virus-sized particles, even with modifications. The quality control challenges for the AM processes identified in this study will assist future efforts in part design and printer parameter optimization to work toward accurate and qualifiable products.

This thesis looks at risk factors for multiple sclerosis (MS), a chronic, degenerative autoimmune disease which is usually diagnosed between the ages of 20 and 50 years. It is estimated to affect over 100,000 people in the UK. The research setting was Orkney and Shetland, two archipelagos situated north of mainland Scotland, and both of which have very high MS prevalence as do other countries at high latitudes. I examine genetic and environmental risk factors in Orkney and Shetland using multiple methods over four studies. I also review the vitamin D and UV exposure literatures as these are risk factors pertinent to MS in Orkney and Shetland. After devoting three chapters to introducing the purpose of the thesis, MS, and Orkney and Shetland, in the fourth chapter, I aim to establish whether the birthplace of cases show any spatial, temporal, or spatiotemporal clustering. Evidence of these kinds of clustering may indicate that there are environmental risk factors present in some areas or that were present over particular periods, which raise risk of developing MS. Although I find statistically significant temporal, spatial, and spatiotemporal clustering in Orkney, and a spatial cluster in Shetland, for multiple reasons these results need to be interpreted with caution. I conclude that the clusters are very likely to be artefacts. Furthermore, there are multiple possible alternative explanations for such clusters that could not be explored by the available data. Chapter 5 examines the heritability of MS in Orkney and Shetland to estimate the proportion of phenotypic variance attributable to additive genetic effects. I also look at the birthplaces of ancestors of cases and controls to see if any locations contribute a greater amount of ancestral DNA to the gene pool of modern MS cases, which I term ‘genetic clustering’. In Orkney I obtained a heritability estimate of 0.36 (95% CI -0.26, 0.98); in Shetland this estimate was 0.20 (95% CI -1.88, 2.28). These modest estimates are consistent with the heritability literature. The genetic clustering analyses highlight two Orkney registration districts, Kirkwall and Westray, which earlier studies identified as areas of MS clustering. I also identify three Shetland registration districts, however these locations had not shown any evidence of clustering in earlier studies. Again, I advise caution in interpreting results, particularly as all the error bars across registration districts overlap. Chapter 6 presents a scoping review to map the literature and identify evidence of an association between vitamin D and UV exposure with MS. In methodically searching the literature, I identify a large and heterogeneous evidence base comprising multiple observational, intervention, and genetic studies. Overall, many studies support an association between vitamin D deficiency and MS. There is also evidence for an association between UV exposure and MS, although UV exposure is considerably less explored than vitamin D. I finally identify gaps in the literature and make suggestions for future research. In Chapter 7 I aim to compare vitamin D levels in Orkney and mainland Scotland, and establish the determinants of vitamin D status in Orkney. I firstly compare mean vitamin D and prevalence of deficiency in cross-sectional data from studies in Orkney and mainland Scotland. I secondly use multivariable regression to identify factors associated with vitamin D levels in Orkney. I find that mean (standard deviation) vitamin D is significantly higher in Orkney compared to mainland Scotland (35.3 (18.0) and 31.7 (21.2), respectively), and prevalence of severe deficiency is lower in Orkney (6.6% to 16.2% p = 1.1 x 10-15). Factors associated with higher vitamin D in Orkney include older age, farming occupations and foreign holidays. I conclude that although mean vitamin D levels are higher in Orkney compared to mainland Scotland, there is substantial variation within the Orkney population which may influence MS risk. Chapter 8 examines the correlates and determinants of UVB exposure in Shetland. I firstly construct correlation matrices to visualise how 1) personal characteristics such as sex, occupation, and skin type, 2) physical activity, and 3) body weight and fat, correlate with UVB exposure. I then use multivariable regression to identify factors associated with UVB exposure in Shetland. I run two multivariable models. The first includes the full sample size where activity data were measured by questionnaires. The second includes both questionnaire physical activity data and step-count data from pedometers, however as only a subset of participants had been supplied with pedometers, this analysis comprises a smaller sample size. I find that the amount of skin exposed was most strongly correlated with UVB exposure. Step count and activity minutes were also moderately positively correlated, and indoor occupations moderately negatively correlated, with UVB exposure. The regression analysis using the full sample with questionnaire activity data found that factors associated with greater UVB exposure were age and ambient UVB, while working indoors was significantly associated with lower UVB exposure. The model including the pedometer data found that found that age, total steps, and the amount of ambient UVB were significantly associated with greater UVB exposure. I conclude that atmospheric conditions, working outdoors and older age are important factors in UVB exposure in Shetland. It remains to be seen how UVB exposure translates to vitamin D levels in Shetland. I found evidence for environmental and genetic risk factors for MS in Orkney and Shetland. The two environmental risk factors, vitamin D deficiency and reduced UV exposure, are more likely to affect the younger population who are still within their lifetime risk of developing MS.

Submitted by JOSIANE SANTOS DE OLIVEIRA (josianeso) on 2019-03-13T15:52:53Z No. of bitstreams: 1 José Maurício de Moura Leitão_.pdf: 2775602 bytes, checksum: b3838f30f897415be8b7b629885f3a15 (MD5) / Made available in DSpace on 2019-03-13T15:52:53Z (GMT). No. of bitstreams: 1 José Maurício de Moura Leitão_.pdf: 2775602 bytes, checksum: b3838f30f897415be8b7b629885f3a15 (MD5) Previous issue date: 2018-11-21 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Eficiência e economia na produção de energia são fatores-chave no desenvolvimento social e econômico de um país. A energia solar é uma fonte de energia limpa e renovável, utilizada em sua maior parte para o aquecimento de água por meio de coletores solares. Nos últimos 15 anos, os coletores solares planos vêm, devido ao apelo mundial para o uso de materiais mais facilmente recicláveis e ao baixo custo, utilizando cada vez mais materiais poliméricos, substituindo os convencionais. Para analisar quais materiais poliméricos podem ser usados em coletores solares planos, este trabalho realizou um teste de intemperismo acelerado nos materiais polissulfona (PSU), polietileno (PE) e policarbonato (PC). Destacam-se o PSU e o PE. O PSU tem o melhor resultado em relação ao nível de degradação, pois sua cadeia polimérica é composta por anéis aromáticos e fortes ligações de carbono, enxofre e oxigênio dentro da espinha dorsal do polímero. Adicionalmente, foram realizadas análises do infravermelho nos materiais envelhecidos na câmara de intemperismo acelerado pelo método ATR ou refletância total atenuada. Eles apresentaram, na cadeia molecular, pequenas mudanças nos espectros na região do infravermelho à medida que o tempo exposto na câmara de envelhecimento aumentava. Por fim, foi desenvolvida uma simulação numérica de um coletor solar plano na plataforma ESS (Engineering Equation Solver) em que foi simulado o efeito do número de tubos no absorvedor com diferentes materiais e foi simulada uma geometria de tubos de sessão quadrada no absorvedor. A simulação apresentou o melhor resultado com um absorvedor construído com 100 tubos de sessão quadrada de polissulfona, no qual a eficiência teoricamente pode chegar a 81,62%. / Efficiency and economy in energy production are key factors in the social and economic development of a country. Solar energy is a source of clean and renewable energy used for heating water through solar collectors. Over the past 15 years, due to the worldwide appeal for the use of more readily recyclable materials and their low cost, flat solar collectors have increasingly used polymeric materials to replace conventional ones. In order to assess which polymeric materials can be used in flat-plate solar collectors, an accelerated temperature test has been conducted on polysulfone (PSU), polyethylene (PE), and polycarbonate (PC). PSU and EP have stood out. PSU had the best result for degradation because its polymeric chain is composed of aromatic rings and strong bonds of carbon, sulfur and oxygen within the backbone of the polymer. Additionally, infrared analyses have been made of the materials aged in the accelerated temperature chamber according to the ATR method or attenuated total reflectance. They presented small molecular chain changes in the spectra in the infrared region as exposure time in the UV chamber increased. Finally, a numerical simulation of a flat solar collector was developed in the ESS (Engineering Equation Solver) platform in which the effect of the number of tubes in the absorber with different materials was simulated as well a geometry of square session tubes in the absorber. The simulation presented the best result with an absorber built with 100 polysulfone square session tubes, in which efficiency can theoretically reach 81.62%.

This dissertation aims to develop methods for statistical predictions based on various types of data from different areas. We focus on applications from reliability and spatial epidemiology. Chapter 1 gives a general introduction of statistical predictions. Chapters 2 and 3 investigate the photodegradation of an organic coating, which is mainly caused by ultraviolet (UV) radiation but also affected by environmental factors, including temperature and humidity. In Chapter 2, we identify a physically motivated nonlinear mixed-effects model, including the effects of environmental variables, to describe the degradation path. Unit-to-unit variabilities are modeled as random effects. The maximum likelihood approach is used to estimate parameters based on the accelerated test data from laboratory. The developed model is then extended to allow for time-varying covariates and is used to predict outdoor degradation where the explanatory variables are time-varying. Chapter 3 introduces a class of models for analyzing degradation data with dynamic covariate information. We use a general path model with random effects to describe the degradation paths and a vector time series model to describe the covariate process. Shape restricted splines are used to estimate the effects of dynamic covariates on the degradation process. The unknown parameters of these models are estimated by using the maximum likelihood method. Algorithms for computing the estimated lifetime distribution are also described. The proposed methods are applied to predict the photodegradation path of an organic coating in a complicated dynamic environment. Chapter 4 investigates the Lyme disease emergency in Virginia at census tract level. Based on areal (census tract level) count data of Lyme disease cases in Virginia from 1998 to 2011, we analyze the spatial patterns of the disease using statistical smoothing techniques. We also use the space and space-time scan statistics to reveal the presence of clusters in the spatial and spatial/temporal distribution of Lyme disease. Chapter 5 builds a predictive model for Lyme disease based on historical data and environmental/demographical information of each census tract. We propose a Divide-Recombine method to take advantage of parallel computing. We compare prediction results through simulation studies, which show our method can provide comparable fitting and predicting accuracy but can achieve much more computational efficiency. We also apply the proposed method to analyze Virginia Lyme disease spatio-temporal data. Our method makes large-scale spatio-temporal predictions possible. Chapter 6 gives a general review on the contributions of this dissertation, and discusses directions for future research. / Ph. D.