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This thesis studies two important carbon structures, graphene and carbon nanotubes, with the purpose of understanding how their three-dimensional electron density distribution affects the way fast ions interact with them. <br /><br /> A brief introduction to research in pure carbon structures is made. We then use different models to calculate the equilibrium electron density distribution in graphene and carbon nanotubes. <br /><br /> In the second part of the thesis we investigate fast ions moving parallel to a graphene sheet and experiencing forces due to the dynamic polarization of carbon valence electrons. Using the three-dimensional electron density distribution of graphene, we calculate the force directly opposing the ion's motion (stopping force), as well as the force which bends the ion's trajectory towards the sheet (image force). It is our purpose to compare these results with those based on a two-dimensional hydrodynamic model of graphene, which approximates the electron distribution of graphene by a charged fluid confined to the two-dimensional plane of the sheet. <br /><br /> The results obtained for interactions of ions with a single graphene sheet should be useful for a further analysis of ion channeling through carbon nanostructures.

Background: Daily nutrient/energy intakes are typically evaluated as a total 24-hour intake rather than as the amounts consumed per eating opportunity. Evidence suggests that smaller, frequent meals containing persistent levels of energy and protein may be more beneficial for achieving a lower body fat and higher fat-free mass than equal intakes consumed in larger and less frequent amounts. This may be due to a better-maintained energy balance (EB) that is achieved with smaller and more frequent intakes. Objective: The objective of this study was to determine the relationship between hourly EB and protein intake with body composition. Methods: Using a software program that provides hourly and 24-hour energy and nutrient intakes and hourly energy expenditures, a secondary analysis of previously collected 3-day food diaries was used to examine the relationship between hourly EB and body composition. The food and activity diaries provided information on time of food/beverage consumption and hourly energy expenditure, enabling an hourly analysis of EB. Body composition, including fat mass, fat-free mass, and bone density were examined via dual-energy x-ray absorptiometry. SPSS was used for statistical analysis, and included descriptive statistics, correlational analyses, t-tests, and regression analyses. Results: Existing data from elite female gymnasts (N=40) were assessed using an IRB-approved protocol. Higher protein consumption was significantly associated with lower bone mineral density (BMD) in the gymnasts at the arms (r= -0.535; p< 0.001), legs (r= 0.0523; p= 0.001), trunk(r= -0.517; p=0.001), spine (r= -0.472; p=0.002), and pelvis (r= -0.539; p< 0.001). Other dietary factors assessing energy and protein intakes were not significantly associated with body composition. The assessed gymnasts spent the majority of the day in hourly energy balance deficits exceeding -400 kcal. A t-test comparing subjects with higher (n=22) vs. lower (n=18) fat-free mass (FFM), using the statistical mean as the cut point, found that higher protein intakes were significantly associated with lower FFM (p=.007). Subjects with more hours spent in an EB surplus had significantly higher FFM/kg (p=.008) and lower body fat % (p=.008). Conclusion: These findings suggest that higher protein intakes may compromise BMD, a finding likely exacerbated by the long periods of time spent in EB deficits. More hours in an EB surplus was associated with positive outcomes, including higher FFM/kg and lower body fat percent. These data suggest that higher protein intakes may be consumed by gymnasts with the greatest EB deficits, perhaps as a way of minimizing (unsuccessfully) weight and fat-mass. As virtually all hours of the assessed groups were in an EB deficit, it is possible that consumed protein was used to satisfy energy needs rather than being used anabolically to support or enlarge the muscle mass. Future studies should consider addressing this issue, perhaps by assessing more heterogeneous groups where at least a proportion of the population sustains a reasonably good EB during the assessment period.

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Many phenotypes are controlled by factors which include the genes, the environment, interactions between genes and interaction between the genotypes and the environment. Great strides have been made to understand how these various factors affect traits of agricultural, medical and environmental importance. The chicken is regarded as a model organism whose study would not only assist efforts towards increased agricultural productivity but also provide insight into the genetic determination of traits with potential application in understanding human health and disease. Detection of genomic regions or loci responsible for controlling quantitative traits (QTL) in poultry has focussed mainly on growth and production traits with limited information on reproductive traits. Most of the reported results have used additive-dominance models which are easy to implement because they ignore epistatic gene action despite indications that it may be important for traits with low heritability and high heterosis. The thesis presents results on the detection of loci and genetic mechanisms involved in sexual maturity traits through modelling both additive-dominance gene actions and epistasis. The study was conducted on an F2 broiler x White Leghorn layer cross for QTL detection for age, weight, abdominal fat, ovary weight, oviduct weight, comb weight, number of ovarian yellow follicles, a score for the persistence of the right oviduct and bone density. In addition, body weight QTL at 3, 6, 12, 24, 48 and 72 weeks of age, QTL for growth rate between the successive ages and QTL for the parameters of the growth curve were also detected. Most of the QTL for traits at sexual maturity acted additively. A few of the QTL explained a modest proportion of the phenotypic variation with most of the QTL explaining a small component of the cumulative proportion of the variation explained by the QTL. Body weight QTL were critical in determining the attainment of puberty. The broiler allele had positive effects on weight at first egg and negative effects on age at first egg. Most QTL affecting weight at first egg overlapped with QTL for age at first egg and for early growth rate (6-9 weeks) suggesting that growth rate QTL are intimately related to the onset of puberty. Specific QTL for early and adult growth were detected but most QTL had varying influence on growth throughout life. Chromosome 4 harboured most of QTL for the assessed traits which explained the highest proportion of the phenotypic variation in the traits confirming its critical role in influencing traits of economic importance. There was no evidence for epistasis for almost all the studied traits. Evidence for role of epistasis was significant for ovary weight and suggestive for both growth rate and abdominal fat.

The main aim of this thesis is to generate a deeper understanding of the mechanical behaviour of cellular materials, specifically for their use in aerospace applications. A closed-cell polymer foam material (Rohacell) of various foam densities was chosen for this investigation, and a comprehensive experimental study was conducted which generated significant findings that hitherto have not been reported in the literature. The research presented in this study revealed the following: The quasistatic response of Rohacell foam displays a compression/tension asymmetry in moduli and strength. In-situ experiments revealed that different macroscopic collapse mechanisms at different foam densities drove this behaviour. Improved experimental methods were developed to characterise the material response at various loading rates. Under compressive loading, as the relative density and loading rate increased, a transition in material behaviour from a ductile to brittle response at very high rates (~5x10^3 s^-1) was found, and tests conducted at different temperatures were used to validate and provide a better understanding of the causes for the observed rate dependency. The compression and tension properties of pre-crushed Rohacell foam loaded in different directions were measured, and with the use of three-point-bend tests it was shown that when the foams’ tension/compression asymmetry, or the changes in stiffness and strength due to pre-crushing (i.e. strain-induced anisotropy), are neglected, this leads to incorrect predictions of the foams’ structural response. Finally, a review of some existing Finite Element foam material models was conducted, and their ability to predict the foam response under complex loading was identified. The new data and understanding generated from this thesis will allow engineers and researchers, who are developing constitutive models for predicting the response of foam materials, specifically in aerospace applications, to account for more aspects of the mechanical behaviours in their Finite Element models.

Packaging industries widely use Low-Density Polyethylene (LDPE) in manufacturing different types of containers to store the food products. They are difficult to model numerically in order to have similar experimental response. This research deals with the study of numerical material model parameters of continuum LDPE. It is carried out with the help of experiments along with the numerical simulation of LDPE. Study of stress-strain distribution at crack tip and elements close to the tip is carried out in the LDPE material with the pre-existing center crack with varying lengths. By implementing an optimization algorithm and automating the simulation with the help of python code, we obtain a set of parameters. This obtained data for the material can be used directly for numerical simulation in the future without carrying out additional experimental studies. After implementing the optimization algorithm is also validated, against the results that were close to the experimental response.

Approved for public release; distribution is unlimited / In this thesis a clutter voltage model for scattering from the sea surface is developed. A model for the scattering from a whitecap and a wave breaking occurrence model re combined to simulate the back scattered signal from one radar resolution cell. The simulation performed obtained the probability density function of sea clutter under different assumptions of wind velocities and wave breaking conditions. This model incorporates some measured quantities such as the mean clutter voltage and the correlation time as parameters. The probability density function depends on the parameters of this model. The obtained probability density functions do not confirm to any familiar simple density function. / http://archive.org/details/seaspikemodeling00kuoc / Lieutenant, Taiwan Navy

Given the rapid population decline and recent petition for listing of the monarch butterfly (Danaus plexippus L.) under the Endangered Species Act, an accurate estimate of the Eastern, migratory population size is needed. Because of difficulty in counting individual monarchs, the number of hectares occupied by monarchs in the overwintering area is commonly used as a proxy for population size, which is then multiplied by the density of individuals per hectare to estimate population size. There is, however, considerable variation in published estimates of overwintering density, ranging from 6.9-60.9 million ha(-1). We develop a probability distribution for overwinter density of monarch butterflies from six published density estimates. The mean density among the mixture of the six published estimates was similar to 27.9 million butterflies ha(-1) (95% CI [2.4-80.7] million ha(-1)); the mixture distribution is approximately log-normal, and as such is better represented by the median (21.1 million butterflies ha(-1)). Based upon assumptions regarding the number of milkweed needed to support monarchs, the amount of milkweed (Asciepias spp.) lost (0.86 billion stems) in the northern US plus the amount of milkweed remaining (1.34 billion stems), we estimate >1.8 billion stems is needed to return monarchs to an average population size of 6 ha. Considerable uncertainty exists in this required amount of milkweed because of the considerable uncertainty occurring in overwinter density estimates. Nevertheless, the estimate is on the same order as other published estimates, The studies included in our synthesis differ substantially by year, location, method, and measures of precision. A better understanding of the factors influencing overwintering density across space and time would be valuable for increasing the precision of conservation recommendations.

Background: Two-thirds of U.S. adult women are overweight or obese. High body mass index (BMI) and adult weight gain are risk factors for a number of chronic diseases, including postmenopausal breast cancer. The higher postmenopausal breast cancer risk in women with elevated BMI is likely to be attributable to related metabolic disturbances including altered circulating sex steroid hormones and adipokines, elevated pro-inflammatory cytokines, and insulin resistance. Metformin is a widely used antidiabetic drug that has demonstrated favorable effects on metabolic disturbances and as such may lead to lower breast cancer risk in obese women. Further, the anti-proliferative effects of metformin suggest it may decrease breast density, an accepted biomarker of breast cancer risk. Methods/design: This is a Phase II randomized, double-blind, placebo-controlled trial of metformin in overweight/obese premenopausal women who have elements of metabolic syndrome. Eligible participants will be randomized to receive metformin 850 mg BID (n=75) or placebo (n=75) for 12 months. The primary endpoint is change in breast density, based on magnetic resonance imaging (MRI) acquired fat-water features. Secondary outcomes include changes in serum insulin levels, serum insulin-like growth factor (IGF)-1 to insulin-like growth factor binding protein (IGFBP)-3 ratio, serum IGF-2 levels, serum testosterone levels, serum leptin to adiponectin ratio, body weight, and waist circumference. Exploratory outcomes include changes in metabolomic profiles in plasma and nipple aspirate fluid. Changes in tissue architecture as well as cellular and molecular targets in breast tissue collected in a subgroup of participants will also be explored. Discussion: The study will evaluate whether metformin can result in favorable changes in breast density, select proteins and hormones, products of body metabolism, and body weight and composition. The study should help determine the potential breast cancer preventive activity of metformin in a growing population at risk for multiple diseases.