Factors which affect iron bioavailability have been repeatedly and extensively investigated. A model, derived from these studies, has been developed for estimating available iron from meal data. However, many dietary surveys report only average daily intakes of iron, and do not report the iron present in single meals. No model to estimate available iron from daily iron intake has been presented in the literature. Dietary questionnaires were kept for two nonconsecutive weekdays by 355 male and 382 female Utah school children, mean age 7.5 years, assisted by their parents, and recorded by household measure. Data, first recorded as meals eaten, were used to develop three models for the estimation of available iron from total daily iron intake. It was concluded that available iron can be estimated from total iron intake by two of these models, as compared with the currently used model, which estimates available iron from data recorded by meal. Additionally, meal patterns of those factors involved with the estimation of available iron were investigated. The intake of dietary ascorbic acid and total iron was found to be evenly distributed among meals; approximately 10% of these nutrients was consumed as snacks. Of the meat, fish, poultry and the iron in those products consumed; 36% was taken at lunch, and 54% at dinner. Only 5% of the meat, fish, and poultry iron was consumed as snacks. The available iron distribution for breakfast, lunch, dinner, and snacks was 21.0%, 30.8%, 42.5% and 5.7%, respectively. Previous studies have investigated the characteristics of diets which provide 9 mg of iron per 1000 kcal of energy consumed. These diets have been shown to include larger portions of vegetables, fruits, and cereal products. In this study, these high-iron dense characteristics were studied as they pertain to total available iron intake. It was concluded that the high-iron dense diet receives more total available iron from the nonheme iron than from the heme iron consumed. Thus, it is conceivable that those dietary characteristics shown to provide a high-iron dense diet may also provide a high available iron intake.

Supersonic inlet starting by mass spillage is studied theoretically and numerically in the present thesis. A quasi-one-dimensional, quasi-steady theory is developed for the analysis of flow inside a perforated inlet. The theory results in closed-form relations applicable to flow starting by the mass spillage technique in supersonic and hypersonic inlets. / The theory involves three parameters to incorporate the multi-dimensional nature of mass spillage through a wall perforation. Mass spillage through an individual slot is studied to determine these parameters; analytical expressions for these parameters are derived for both subsonic and supersonic flow conditions. In the case of mass spillage from supersonic flows, the relations are exact. However, due to the complexity of flow field, the theory is an approximation for subsonic flows. Therefore, a correction factor is introduced which is determined from an empirical relation obtained from numerical simulations. / A methodology is also proposed to determine perforation size and distribution to achieve flow starting for a given inlet at a desired free-stream Mach number. The problem of shock stability inside a perforated inlet designed with the proposed method is also discussed. / The method is demonstrated for some test cases. Time-realistic CFD simulations and experimental results in the literature confirm the accuracy of the theory and the reliability of the proposed design methodology.

Endurance athletes have long benefited from ingesting carbohydrates prior to, and during endurance events. Fatigue during endurance exercise has repeatedly been associated with the depletion, or reduction, of bodily carbohydrate reserves. The improved endurance capability observed after aerobic training has, however, been attributed to the increased oxidation of fat relative to carbohydrate, thereby having a 'carbohydrate sparing" effect and thus delaying the point at which reduced carbohydrate reserves will cause fatigue. This study was therefore designed to investigate the effects of medium-chain triglyceride (MCT) and carbohydrate (CHO) supplementation, on the performance and metabolic parameters of nine male marathon athletes. These results were then statistically compared to the effects of adding L-carnitine to the MCT and CHO supplement, on the same parameters. Metabolic parameters included nutritional status evaluations, serum organic acid profiles (non-esterified fatty acid and L-lactate profiles), and plasma carnitine determinations. Performance was measured in terms of peak treadmill running speed, V02 max, respiratory exchange ratios, heart rates, vco2 and vo2 data during progressive treadmill exercise tests. Nutrition and energy intakes were recorded during the study, as well as record kept of the athlete's training programmes. At the end of each supplementation period, a standard marathon was included in the experimental design, in order to practically validate controlled laboratory results. The main findings of this study included the identification of two athletes as 'fat burners'~ Non-esterified fatty acid (NEFA) profiles indicated that they predominantly relied on fatty acid oxidation during exercise, after MCT supplementation. The latter presumably because of adaptive changes in their metabolism, enabling them to benefit from MCT supplementation. In spite of the majority of athletes relying on carbohydrate metabolism during exercise, the addition of L-carnitine to the MCT and CHO supplement, induced a shift towards lipid metabolism; evident from RER and VC02 data, as well as the majority of athletes improving their performance. The observed shift was slight; the latter being ascribed to the relatively small dose of L-carnitine (compared to previous studies) included in the supplement. However, L-carnitine was incorporated into a palatable, liquid MCT and CHO supplement, and not merely administered in the form of a pharmacological dose. A major, and extremely unexpected finding, was the presumed effect that the winter, and continuous cold exposure, had on plasma carnitine levels. Plasma carnitine levels decreased significantly, without any intervention, prior to the start of the second trial period, which stretched over the middle of winter. Despite carnitine supplementation, plasma carnitine levels still decreased. This occurrence most certainly influenced results; the shift towards lipid metabolism would presumably have been more pronounced, had the 'Winter factor' not come into play. / Dissertation (MSc)--University of Pretoria, 2012. / Physiology / unrestricted

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In this thesis, a simple moving boundary technique has been suggested, implemented and verified. The technique may be considered as a generalization of the well-known "ghost" cell approach for boundary condition implementation. According to the proposed idea, the moving body does not appear on the computational grid and is allowed to move over the grid. The impermeable wall boundary condition is enforced by assigning proper gasdynamic values at the grid nodes located inside the moving body close to its boundaries (ghost nodes). The reflection principle taking into account the velocity of the boundaries assigns values at the ghost nodes. The new method does not impose any particular restrictions on the geometry, deformation and law of motion of the moving body. / The developed technique is rather general and can be used with virtually any finite-volume or finite-difference scheme, since the modifications of the schemes themselves are not required. In the present study the proposed technique has been incorporated into a one-dimensional non-adaptive Euler code and a two-dimensional locally adaptive unstructured Euler code. / It is shown that the new approach is conservative with the order of approximation near the moving boundaries. To reduce the conservation error, it is beneficial to use the method in conjunction with local grid adaptation. / The technique is verified for a number of one and two dimensional test cases with analytical solutions. It is applied to the problem of supersonic inlet starting via variable geometry approach. At first, a classical starting technique of changing exit area by a moving wedge is numerically simulated. Then, the feasibility of some novel ideas such as a collapsing frontal body and "tractor-rocket" are explored.

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"This thesis presents a series of physical experiments and numerical simulations intended to determine whether the use of commercially available computational fluid dynamics (CFD) software may provide a viable alternative to the use of physical models for predicting the occurrence of vortices and swirl in pump intakes. The physical experiments were set up at Alden Research Laboratories, Inc. (ARL) of Holden, Massachusetts, using a simple pump intake model donated by ARL for use in this study. Swirl and velocity measurements and dye injections were used to characterize the flow in the physical model. Three flow conditions were chosen for the physical experiments because they demonstrated swirl and vortices developing at the pump intake. Once the physical experiments were performed, FIDAP, a general-purpose finite-element CFD package, was used to simulate the circulation patterns in the vicinity of a pump intake. The model configuration and scale were selected to simulate experimental conditions in the physical pump intake model. Some similarities were also identified in the locations of the models predicted vortex characteristics and the vortex characteristics that were observed in the experimental facility. However, the characteristics of swirl within the pump intake differed from experimental observations. Therefore, additional simulations were conducted to analyze the sensitivity of simulations to model assumptions. These additional simulations showed that the assumptions related to these model parameters have minor affects on the general nature of the predicted vortices, but do affect the predicted vortex strength. This thesis represents a first step in addressing the discrepancies between numerical and experimental results. Additional investigations are recommended to clarify the applicability of CFD to address pump intake problems."

Social cohesion among peers profoundly influences decision making during adolescence. Despite this, the current research is very limited concerning the association of social cohesion and intimacy among rural adolescent peers with dietary intake and weight outcomes. This is problematic because social cohesion could be an unknown contributing factor in obesity among rural adolescents. The purpose of this study was to investigate how social cohesion and intimacy among rural adolescents in Kentucky and North Carolina affects the outcomes of a text message intervention aimed at improving fruit, vegetable, fast food and sugar sweetened beverage intake. Additionally, to determine if social cohesion is an independent contributing factor to dietary intakes and weight outcomes among rural adolescents. It was found that the intervention had no effect on fruit and vegetable consumption and purchases and sugar sweetened beverage calories. However, the intervention did have a modest effect on the amount of times fast food was consumed per week.

La consommation d’aliments biologiques et sa part relative dans le régime alimentaire n’ont été que peu étudiées. De même, les profils nutritionnels et de santé, les motivations et les pratiques de tels consommateurs ne sont que rarement décrits. L’objectif de cette thèse était d’étudier et de caractériser les profils des consommateurs de produits issus de l’agriculture biologique sur le plan nutritionnel, de la santé et des pratiques. Les données de la cohorte NutriNet-Santé incluant des adultes français ont été exploitées. Les résultats de cette thèse ont montré qu’une forte consommation de produits bio était associée à une meilleure qualité nutritionnelle globale du régime. Le régime des très forts consommateurs de bio était ainsi souvent caractérisé par une place importante donnée aux produits végétaux et aux produits complets en particulier. La mise en oeuvre d'une analyse typologique a mis en évidence une diversité de profils des consommateurs sur le plan nutritionnel d'une part et sur les modes de production d'autre part. Ces différents profils de consommateurs étaient marqués par des différences sur le plan des caractéristiques sociodémographiques, des modes de vie, des pratiques d’achat et des motivations d’achat. Par ailleurs, la probabilité de présenter le syndrome métabolique était plus faible chez les forts consommateurs de bio comparés aux faibles consommateurs. L’étude cas-témoins a montré chez les forts consommateurs de bio une teneur significativement plus faible de certains résidus de pesticides dans les urines (2-(diethylamino)-6-méthylpyrimidin-4-ol/one total, en DETP et DMTP et en 3-PBA). Les conclusions des premières analyses transversales sur les marqueurs de santé restent à confirmer dans des études prospectives. L’ensemble de ces travaux souligne la nécessité de considérer toutes les dimensions de l’alimentation (structure du régime et mode de production bio ou conventionnel) dans les futures études sur les potentiels effets de la consommation de bio sur la santé. Ces résultats plaident également pour l’intégration d’une diversité de profils de consommateurs lors de l’élaboration de stratégies visant à encourager les consommations alimentaires durables. / Few data are available regarding the contribution of organic foods to the diet. In addition, dietary patterns, nutritional and health status of organic food consumers have rarely been described. The objective of this thesis was to study the characteristics of different groups of organic food consumers in terms of nutritional intakes, health status and practices. Data of the cohort NutriNet-Santé including French adults were analysed. The results showed strong dietary behaviour correlates associated with high organic food consumption. Higher levels of organic food consumption were related to healthier dietary patterns. Dietary patterns of high organic food consumers were characterised by high consumption of plant-based products, and wholegrain products in particular. A cluster analysis has underlined a diversity of profiles of consumers in terms of dietary patterns and mode of food production. Disparities in sociodemographic and lifestyle patterns were observed across clusters. Furthermore, the probability of having the metabolic syndrome was lower among high organic food consumers. The case-control study showed significantly lower levels of some pesticide residues (2-(diethylamino)-6-methylpyrimidin-4-ol/one total, DETP, DMTP and 3-PBA) among high organic food consumers compared to low organic food consumers. Prospective studies are needed to confirm these findings. To accurately assess potential effects of consumption of organic products, future etiological studies need to take into consideration all components of the diet (dietary patterns as well as level of organic food consumption in the diet). These results highlight the importance of the integration of a diversity of consumers’ profiles when developing strategies aimed at promoting sustainable food practices.