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Adolescence proves to be one of the most vulnerable development stages in the life of humans and therefore dietary assessment of this group is important, but complex. This is due to rapid growth during puberty and the development of new eating patterns that influence dietary intake. Adequate dietary intake in this age group is crucial, since adverse effects such as iron deficiency anemia, inadequate growth and dental caries can occur. Furthermore, dietary imbalance is a significant risk factor that can lay the groundwork for developing preventable complications in late adolescence and adult life such as non-communicable chronic diseases including obesity and diabetes mellitus type II and certain cancers, all leading causes of morbidity and mortality. Given the vulnerability of adolescents in terms of dietary intake, understanding their dietary intake is crucial. Dietary assessment of adolescents is influenced by social, physiological and psychological changes making accurate measurement of this group difficult. Hence, it is of fundamental importance to find a golden standard in terms of a dietary assessment method to use in this group. Several international studies investigated validity and reproducibility of the dietary intake of adolescents, measured with different dietary assessment methods. However, in South Africa only three validity and reproducibility studies have been published and none of them focused exclusively on adolescents. Since the validity of the results of dietary assessment methods of international studies cannot be extrapolated to South African black adolescents, this study emanated from the need to investigate whether multiple 24-hour recalls are valid and reproducible when used to assess the dietary intakes of black adolescents in a convenience sample of grade eight learners from a high school in a township in the North West Province. The study was nested in the multidisciplinary "Physical, Activity in the Young" (PLAY) study. Firstly, the optimal number of 24-hour recalls was determined by calculation of reproducibility coefficients for energy, selected nutrients and food groups. Results showed that four repeated 24-hour recalls provided the optimal reproducibility for black peri-urban South African adolescents. Secondly, the search for a reference method to compare energy intake against energy expenditure led to an investigation into basal metabolic rate equations and physical activity factors with the intention of estimating the energy expenditure. Validity of reported energy intake assessed by multiple 24-hour recalls and estimated energy expenditure was tested using the Pearson correlation coefficient and the dependent t-test. The Pearson correlation test revealed low associations between energy intake and energy expenditure for boys (0.32) and girls (0.17), while the dependent t-test of the energy intake between the different measured occasions showed little difference, which could be explained by the high within participant variation and lower variation between the different participants. The low correlation coefficients showed that there was no association between reported energy intake and mean estimated energy expenditure; thus also no agreement. As a result, multiple 24-hour recalls measured over two years with only five 24-hour recalls did not give a valid measurement of the energy intake of black peri-urban adolescents. Lastly, the ratio of reported energy intake over energy expenditure was evaluated against the energy cut-off points, specifically calculated for age and ethnic group. It indicated that 85% of the participants underreported their energy intake. These results could have been influenced by the estimated basal metabolic rate equations that could have estimated the basal metabolic rate of this group incorrectly or could be due to the inability of the group to recall their physical activity levels correctly. Therefore it is recommended that further validity studies regarding dietary intake need to be performed on adolescents. It is suggested that energy expenditure as a reference method should be measured by using a calorimeter or the doubly labeled water method and then compared with the reported energy intake. Analysing different biochemical determinants of nutritional intake could also be used as an objective reference method to assess the validity of dietary data obtained from questionnaires. / Thesis (Ph.D. (Dietetics)--North-West University, Potchefstroom Campus, 2009.

Adolescence proves to be one of the most vulnerable development stages in the life of humans and therefore dietary assessment of this group is important, but complex. This is due to rapid growth during puberty and the development of new eating patterns that influence dietary intake. Adequate dietary intake in this age group is crucial, since adverse effects such as iron deficiency anemia, inadequate growth and dental caries can occur. Furthermore, dietary imbalance is a significant risk factor that can lay the groundwork for developing preventable complications in late adolescence and adult life such as non-communicable chronic diseases including obesity and diabetes mellitus type II and certain cancers, all leading causes of morbidity and mortality. Given the vulnerability of adolescents in terms of dietary intake, understanding their dietary intake is crucial. Dietary assessment of adolescents is influenced by social, physiological and psychological changes making accurate measurement of this group difficult. Hence, it is of fundamental importance to find a golden standard in terms of a dietary assessment method to use in this group. Several international studies investigated validity and reproducibility of the dietary intake of adolescents, measured with different dietary assessment methods. However, in South Africa only three validity and reproducibility studies have been published and none of them focused exclusively on adolescents. Since the validity of the results of dietary assessment methods of international studies cannot be extrapolated to South African black adolescents, this study emanated from the need to investigate whether multiple 24-hour recalls are valid and reproducible when used to assess the dietary intakes of black adolescents in a convenience sample of grade eight learners from a high school in a township in the North West Province. The study was nested in the multidisciplinary "Physical, Activity in the Young" (PLAY) study. Firstly, the optimal number of 24-hour recalls was determined by calculation of reproducibility coefficients for energy, selected nutrients and food groups. Results showed that four repeated 24-hour recalls provided the optimal reproducibility for black peri-urban South African adolescents. Secondly, the search for a reference method to compare energy intake against energy expenditure led to an investigation into basal metabolic rate equations and physical activity factors with the intention of estimating the energy expenditure. Validity of reported energy intake assessed by multiple 24-hour recalls and estimated energy expenditure was tested using the Pearson correlation coefficient and the dependent t-test. The Pearson correlation test revealed low associations between energy intake and energy expenditure for boys (0.32) and girls (0.17), while the dependent t-test of the energy intake between the different measured occasions showed little difference, which could be explained by the high within participant variation and lower variation between the different participants. The low correlation coefficients showed that there was no association between reported energy intake and mean estimated energy expenditure; thus also no agreement. As a result, multiple 24-hour recalls measured over two years with only five 24-hour recalls did not give a valid measurement of the energy intake of black peri-urban adolescents. Lastly, the ratio of reported energy intake over energy expenditure was evaluated against the energy cut-off points, specifically calculated for age and ethnic group. It indicated that 85% of the participants underreported their energy intake. These results could have been influenced by the estimated basal metabolic rate equations that could have estimated the basal metabolic rate of this group incorrectly or could be due to the inability of the group to recall their physical activity levels correctly. Therefore it is recommended that further validity studies regarding dietary intake need to be performed on adolescents. It is suggested that energy expenditure as a reference method should be measured by using a calorimeter or the doubly labeled water method and then compared with the reported energy intake. Analysing different biochemical determinants of nutritional intake could also be used as an objective reference method to assess the validity of dietary data obtained from questionnaires. / Thesis (Ph.D. (Dietetics)--North-West University, Potchefstroom Campus, 2009.

Walking and bicycling to work, active commuting, can contribute to sustainable mobility and provide regular health-enhancing physical activity for individuals. Our knowledge of active commuting behaviours in general and in different mode and gender groups in particular is limited. Moreover, the validity and reproducibility of the methods to measure the key variables of the behaviours are uncertain. The aims of this thesis is to explore gender and mode choice differences in commuting behaviours in terms of distance, duration, velocity and trip frequency, of a group of adult commuters in Greater Stockholm, Sweden, and furthermore to develop a criterion method for distance measurements and to assess the validity of four other distance measurement methods. We used one sample of active commuters recruited by advertisements, n = 1872, and one street-recruited sample, n = 140. Participants received a questionnaire and a map to draw their commuting route on. The main findings of the thesis were, firstly, that the map-based method could function as a criterion method for active commuting distance measurements and, secondly, that four assessed distance measurement methods – straight-line distance, GIS, GPS and self-report – differed significantly from the criterion method. Therefore, we recommend the use of correction factors to compensate for the systematic over- and underestimations. We also found three distinctly different modality groups in both men and women with different behaviours in commuting distance, duration and trip frequency. These groups were commuters who exclusively walk or bicycle the whole way to work, and dual mode commuters who switch between walking and cycling. These mode groups accrued different amounts of activity time for commuting. Through active commuting per se, the median pedestrian and dual mode commuters met or were close to the recommended physical activity level of 150 minutes per week during most months of the year, whereas the single mode cyclists did so only during the summer half of the year.

Licentiatavhandling (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 2 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2002. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Thesis (M.S.)--University of Michigan, 1973.

Thesis (M.S.)--University of Michigan, 1973.

Orientador: Eduardo Paciência Godoy / Banca: Ivando Severino Diniz / Banca: Dennis Brandão / Resumo: A alta complexidade atrelada às necessidades de segurança e confiabilidade dos processos industriais têm demandado a implantação de sistemas automáticos de segurança. Esse sistema, conhecido como Sistema Instrumentado de Segurança (SIS), é responsável pela segurança operacional do processo dentro de limites seguros através da monitoração de valores e parâmetros quando houver condições de risco. Os SISs são concebidos com diferentes Níveis de Integridade de Segurança (SIL) de acordo com o risco do processo. O desafio na implantação de um SIS é que seu procedimento de projeto é complexo e pouco difundido, além de existirem diversos métodos de cálculo e análise de riscos aceitos pelas normas de segurança. A motivação para este trabalho foi automatizar e auxiliar o projeto de SIS no que diz respeito à redução da quantidade de pessoas envolvidas e de tarefas manuais que podem causar erros, à padronização e simplificação dos procedimentos e cálculos necessários e também à diminuição do tempo de projeto, promovendo um aumento na eficiência e redução dos custos envolvidos. O objetivo é desenvolver uma ferramenta de análise e projeto de SIS, com programação voltada para Web, capaz realizar um estudo de riscos e falhas de um processo industrial e calcular um valor adequado para a seleção do SIL requerido para implantação de um sistema de segurança. A ferramenta é composta de quatro módulos: o Estudo de riscos e falhas usando a técnica HAZOP, a Quantificação dos riscos e criação de árvo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The high complexity tied to the reliability and security requirements of industrial processes has demanded the deployment of automatic safety systems. This system is known as Safety Instrumented Systems (SIS) and is responsible for the process operational safety within safe limits through the monitoring of values and parameters when there are conditions of risk. The SIS is designed with different Safety Integrity Levels (SIL) according to the process risk. The challenge in the deployment of SIS is that the design procedure is complex and not well known, and there are many calculation and risk analysis methods accepted by the safety standards. The motivation was automating and assisting in the design of SIS with regard to the reduction of people involved and manual tasks that may cause errors, the standardization and simplification of procedures and calculations needed and the reduction in project time, promoting an increase in efficiency and reducing the costs. The objective was developing an analysis and design tool for SIS, with web-based programming, capable of performing a study of the risks and failures of an industrial process and calculating an adequate value for the selection of the Safety Integrity Level (SIL) required for the implementation of the safety system. The tool is comprised of four modules: the Study of risks and failures using the HAZOP technique, the Quantification of risks and creation of fault trees; the SIL calculation through the Fault Tree Analysis ... (Complete abstract click electronic access below) / Mestre