AIM: The overall aim of this thesis was to examine the associations between dental anxiety, experiences of dental care, psychosocial factors and oral health among 15-year-olds, and to analyse changes in the prevalence of dental anxiety over time. MATERIALS AND METHODS: The thesis was based on two cross-sectional epidemiological studies in Jönköping, Sweden. Papers I, II, and III were based on a random sample of 15-year-old individuals. The total sample consisted of 221 individuals. Six questionnaires were used, one included items of background data, while the others were psychometric instruments measuring dental anxiety, temperament, general anxiety and depression, general fearfulness and attitudes to dental care. Paper IV was based on the Jönköping studies, a series of epidemiological studies from 1973, 1983, 1993, and 2003 in which random samples of 15-year-old individuals were included. The total sample consisted of 405 individuals. Questionnaires including background data and dental anxiety were used and clinical data were collected. RESULTS: Of the 15-year-old individuals 6.5% were classified as dentally anxious with girls proportionally more fearful than boys (Papers I-III). Dental anxiety correlated significantly with three of the temperament dimensions; emotionality, activity and impulsivity. Reported pain or unpleasant experiences during dental care treatment were clear predictors concerning dental anxiety (Paper I). Both symptoms of general anxiety and depression were significantly correlated with dental anxiety after controlling for other potential risk factors (Paper II). Dental anxiety was associated with both general fearfulness and with attitudes to dental care, where the strongest predictor of dental anxiety was general fearfulness (Paper III). A trend analysis over the 30-year period showed a gradient of statistically significantly decreasing dental anxiety prevalence, from 38.1% in 1973 to 12.8% in 2003. Over the period the 15-year-old individuals with dental anxiety had significantly higher number of filled tooth-surfaces than those with no dental anxiety, and also more caries in 1973. There were no such differences concerning plaque and gingivitis (Paper IV). CONCLUSIONS: Dental anxiety in 15-year-olds correlated with experiences of dental care, psychosocial factors as well as to oral health. Specifically, pain experiences related to dental care, attitudes to dental care and general fearfulness seem to have the strongest impact on dental anxiety. Dental anxiety showed a clear declining change over time. More girls than boys reported dental anxiety. The thesis shows that dental care providers need paying attention on providing a supportive dental care situation, in which the patients should not experience pain. One part may be adequate local anaesthesia during operative dentistry or similar dental treatments. Another part may be a good oral health to prevent negative experiences of dental care. There is a need for the understanding of psychological factors associated with dental care procedures. / SYFTE: Det övergripande syftet med denna avhandling var att bland 15-åringar undersöka sambanden mellan tandvårdsrädsla, erfarenheter av tandvård, psykosociala faktorer och oral hälsa, samt att analysera förändringar i förekomsten av tandvårdsrädsla över tid. MATERIAL OCH METOD: Avhandlingen baseraspå två epidemiologiska tvärsnittsstudier i Jönköping. I arbete I, II och III redovisas studier av 221 slumpmässigt utvalda 15-åriga individer. Deltagarna besvarade frågor avseende bakgrundsdata, tandvårdsrädsla, temperament, ångest och depression, generell rädsla samt attityder till tandvård. Arbete IV bygger på Jönköpingsstudierna, från 1973, 1983, 1993, och 2003, där sammanlagt 405 slumpmässigt utvalda 15-åriga individer ingick. Datainsamling gjordes med hjälp av frågeformulär, bestående av bakgrundsdata och tandvårdsrädsla, samt kliniska data. RESULTAT: Resultatet i arbete I, II och III visade att 6,5% av ungdomarna rapporterade hög tandvårdsrädsla, där en övervägande andel var flickor. I arbete I visade tandvårdsrädsla samband med tre av temperamenten; emotionalitet, aktivitet och impulsivitet. Rapporterad smärta eller obehagliga upplevelser under tandbehandling var tydliga prediktorer avseende tandvårdsrädsla. I arbete II visade både symtom på ångest och depression samband med tandvårdsrädsla, sedan effekterna av andra potentiella riskfaktorer hade kontrollerats för statistiskt. I arbete III visade tandvårdsrädsla starkt samband med både generell rädsla och med attityder till tandvård, där den starkaste prediktorn för tandvårdsrädsla var generell rädsla. I arbete IV visade en trendanalys en statistiskt säkerställd minskning gällande förekomsten av tandvårdsrädsla, från 38,1% år 1973 till 12,8% år 2003. Ungdomarna med tandvårdsrädsla hade signifikant fler fyllda tandytor än ungdomarna utan tandvårdsrädsla under 30-årsperioden, och år 1973 även mer karies. Det fanns inga sådana skillnader avseende plack och gingivit. SLUTSATSER: Resultatet visar att tandvårdsrädsla är relaterat till smärtsamma erfarenheter av tandvård, generell rädsla, och oral hälsa. Resultatet visar också att tandvårdsrädsla hos 15-åringar har minskat över tid och är vanligare hos flickor. Resultaten pekar på att tandvårdspersonalen har en viktig uppgift i att unga tandvårdspatienter inte utsätts för smärtsam behandling. Framtida forskning av intresse kan vara hur olika sätt att administrera lokalbedövning kan förändra uppfattningen av smärta och nivåer av tandvårdsrädsla.

The class of models which is studied in this paper, multi-unit longitudinal models, combines both the cross-sectional and the longitudinal aspects of observations. Many empirical investigations involve the analysis of data structures that are both cross-sectional (observations are taken on several units at a specific time period or at a specific location) and longitudinal (observations on the same unit are taken over time or space). Multi-unit longitudinal data structures arise in economics and business where panels of subjects are studied over time, biostatistics where groups of patients on different treatments are observed over time, and in situations where data are taken over time and space. Modelling issues in multi-unit longitudinal models with random coefficients and patterned correlation structure are illustrated in the context of two data sets. The first data set deals with short time series data on annual death rates and alcohol consumption for twenty-five European countries. The second data set deals with glaceologic time series data on snow temperature at 14 different locations within a small glacier in the Austrian Alps. A practical model building approach, consisting of model specification, estimation, and diagnostic checking, is outlined. (author's abstract) / Series: Forschungsberichte / Institut für Statistik

Abstract Objectives: To establish the prevalence of lower serum selenium status (<106 ng/ml) among the adult white American male population, to determine whether certain social, economic, geographic, physical, and dietary characteristics are risk factors for lower selenium status, and to identify a selenium augmentation strategy for white adult men deficient in this trace element. Design: An exploratory cross-sectional study using nationally representative data from the National Health and Nutrition Examination Survey III, 1988-1994 (NHANES III). Methods: 2989 white men, aged 20 or greater in the NHANES III dataset had recorded serum selenium values. These men were divided in two groups based on selenium status, those with values of less than 106 ng/ml (n=288) and those with a status greater than or equal to 106 ng/ml (n=2701). Various demographic, physical, and dietary variables were then compared between the two selenium status groups in a bivariate analysis. Multiple logistic regression was then performed to assess possible risk factors for lower selenium status. Results: This study estimated that 7.7% of white American adult men aged 20 years and older, a total of 4,751,618 individuals, had a selenium status less than 106 ng/ml. Several, of the more than forty, social, economic, geographic, physical and dietary characteristics examined were shown to be significantly associated with a lower selenium status. Risk factors for lower selenium status (<106 ng/ml) were, smoking, living in the Southern census region, being in either the 20-39 or the 60 years or older age groups, exercising less than their peers, having a lower income, and not consuming dark bread. Conclusion: It would appear that certain physical, geographic, dietary and demographic characteristics are significantly associated with lower selenium status. While, this work was unable to identify a suitable selenium fortification vehicle to reduce the prevalence of lower selenium status, it did identify risk factors that may contribute to this condition.

Experiments were conducted to investigate the shear behaviour of large deep beams subjected to uniform load. Six tests were performed on specimens with identical cross sections and reinforcing, but under different loading configurations. Variables included: span, degree of cracking prior to loading, proximity to a disturbed region near a reaction, and type of flexural stress on the loaded face. The findings indicate a specific set of variables resulting in unconservative predictions made using a strut-and-tie model for simply-supported beams subjected to uniform load, confirming and validating recent results by other researchers. A fanning strut model is proposed and is shown to provide more conservative results. The emerging trend of high capacity in continuous uniformly-loaded specimens is supported by the experimental results, as is the high capacity of specimens uniformly-loaded on their flexural tension face. Further, the high strength of specimens with suboptimal crack orientations supports recent experimental work.

Experiments were conducted to investigate the shear behaviour of large deep beams subjected to uniform load. Six tests were performed on specimens with identical cross sections and reinforcing, but under different loading configurations. Variables included: span, degree of cracking prior to loading, proximity to a disturbed region near a reaction, and type of flexural stress on the loaded face. The findings indicate a specific set of variables resulting in unconservative predictions made using a strut-and-tie model for simply-supported beams subjected to uniform load, confirming and validating recent results by other researchers. A fanning strut model is proposed and is shown to provide more conservative results. The emerging trend of high capacity in continuous uniformly-loaded specimens is supported by the experimental results, as is the high capacity of specimens uniformly-loaded on their flexural tension face. Further, the high strength of specimens with suboptimal crack orientations supports recent experimental work.

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SectionBuilder is an innovative finite element based tool, developed for analysis and design of composite beam cross-sections. The tool can handle the cross-sections with parametric shapes and arbitrary configurations. It can also handle arbitrary lay-ups for predefined beam cross-section geometries in a consistent manner. The material properties for each layer of the cross-section can be defined on the basis of the design requirements. This tool is capable of dealing with multi-cell composite cross-sections with arbitrary lay-ups. It has also the benefit of handling the variation of thickness of skin and D-spars for beams such as rotor blades. A typical cross-section is considered as a collection of interconnected walls. Walls with arbitrary lay-ups based on predefined geometries and material properties are generated first. The complex composite beam cross-sections are developed by connecting the walls using various types of connectors. These connectors are compatible with the walls, i.e., the thickness of the layers of the walls must match with those of the connectors at the place of connection. Cross-sections are often reinforced by core material for constructing realistic rotor blade cross-sections. The tool has the ability to integrate core materials into the cross-sections. A mapped mesh is considered for meshing parametric shapes, walls and various connectors, whereas a free mesh is considered for meshing the core materials. A new algorithm based on the Delaunay refinement algorithm is developed for creating the best possible free mesh for core materials. After meshing the cross-section, the tool determines the sectional properties using finite element analysis. This tool computes sectional properties including stiffness matrix, compliance matrix, mass matrix, and principal axes. A visualization environment is integrated with the tool for visualizing the stress and strain distributions over the cross-section.

This thesis describes the design, maintenance and statistical analysis involved in undertaking a Longitudinal Survey. A longitudinal survey (or study) obtains observations or responses from individuals over several times over a defined period. This enables the direct study of changes in an individual's response over time. In particular, it distinguishes an individual's change over time from the baseline differences among individuals within the initial panel (or cohort). This is not possible in a cross-sectional study. As such, longitudinal surveys give correlated responses within individuals. Longitudinal studies therefore require different considerations for sample design and selection and analysis from standard cross-sectional studies. This thesis looks at the methodology for analysing social surveys. Most social surveys comprise of variables described as categorical variables. This thesis outlines the process of sample design and selection, interviewing and analysis for a longitudinal study. Emphasis is given to categorical response data typical of a survey. Included in this thesis are examples relating to the Goodna Longitudinal Survey and the Longitudinal Survey of Immigrants to Australia (LSIA). Analysis in this thesis also utilises data collected from these surveys. The Goodna Longitudinal Survey was conducted by the Queensland Office of Economic and Statistical Research (a portfolio office within Queensland Treasury) and began in 2002. It ran for two years whereby two waves of responses were collected.

Dissertation (Ph.D.)--University of South Florida, 2008. / Title from PDF of title page. Document formatted into pages; contains 118 pages. Includes vita. Includes bibliographical references.

Thesis (Ph.D. in Analytic Health Sciences, Department of Preventive Medicine and Biometrics) -- University of Colorado Denver, 2007. / Typescript. Includes bibliographical references (leaves 75-77). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;