A longitudinal study of fat mass accrual from adolescence through to emerging adulthood and its impact on cardiometabolic risk later in life

Overweight and obesity (OWO), specifically abdominal obesity, are linked with cardiovascular and metabolic disease risk (CMR) at every stage of life. The prevalence of OWO nearly doubles in Canadians between childhood/adolescence and adulthood, suggesting that normal weight (NW) status is not stable through the life course and that there is a period in adulthood when fat mass (FM) increases. Emerging adulthood (EA; 18-25 years) has been identified as a potential critical period when FM accrues, the degree to which is potentially influenced by childhood and adolescence FM accrual. EA is also a period which favors trunk fat depots and when CMR likely commences or increases from child and adolescent levels. However, there is a paucity of longitudinal data describing the patterns and predictors of FM accrual during EA. Furthermore, there is also a lack of information showing how EA fat mass trajectories relate to adult cardiometabolic health. Thus, the primary purpose of this thesis is to describe patterns and predictors of total body fat (TBF) and trunk fat (TrF) mass accrual and OWO status in EA. The second purpose is to identify if trajectories of FM accrual in EA influence later adult CMR. The thesis will also explore sex differences. In study 1, 126 participants (59 male) were drawn from the Pediatric Bone Mineral Accrual Study (PBMAS) (1991-2011). Participants of the PBMAS were aged 8 to 15 years at the initial measurement. Serial measures of participants included chronological age (CA), biological age (BA - years from peak height velocity (PHV)), body mass index (BMI), and percent total body fat (%TBF). Study 1 is divided into two papers - 1a and 1b. The results from paper 1a based on this study indicated that fat mass increased from PHV into EA. At PHV, 9% of males and 14% of females were OWO by BMI, rising to 65% and 32%, respectively, 15 years after PHV (approximately 27 years in females, and 29 years in males). The prevalence of OWO by %TBF, increased from 29% to 45% in males, and from 33% to 59% in females over the same period. Differences in values of %TBF and BMI at PHV between those identified as NW had disappeared by 19-22 years (p>0.05) (i.e. fat mass between NW and OWO youth became more similar with age). OWO status at PHV did not predict OWO status during EA (p<0.05). These results indicate that EA appears to be a major period of transition from NW to OWO status. In addition, sex and FM metrics showed differences in ages when NW individuals became OWO. Study 1 also attempted to address the potential discrepancy in OWO identification and age at onset of OWO by different metrics in paper 1b, using the same PBMAS cohort. Longitudinal measures, including anthropometrics and dual x-ray absorptiometry from 1991-2017 were used to create hierarchical random effects models. Coefficients from the models were then used to develop growth curves, and these were compared to known cut-points. The age at onset of OWO was considered that age at which the predicted line crossed metric specific cut-offs. Age at onset of OWO in males was identified as 23.5 years by BMI and 21.5 years for % fat mass (%FM). Waist circumference (WC) cut-offs for OWO classification were not reached by 39 years. In females, onset was at 22.5 years by BMI, 15 years by %FM and 33.5 years by WC. Cut-points for BMI failed to identify 21.4% of OWO males and 56% of OWO females identified by %FM. The discrepancy in age at OWO between measures suggests that the most conservative indicator of age at onset is sex specific. BMI identifies OWO in males sooner than %FM. The opposite is true in females; however, BMI likely misses “over fatness” - more in females. WC may not be as appropriate for indicating risk in young adults and youth as in older adults. Using the same participants identified in study 1, study 2 created longitudinal models of fat accrual during EA and beyond (18 to 30 years of age) and identified concurrent and childhood/adolescent predictors of FM accrual, including measures of physical activity (PA) and energy intake (EI). It was found that childhood and adolescent TBF and TrF (0.30 ± 0.05, p<0.05) predicted EA accrual in both sexes and that concurrent PA (-0.06 ± 0.02, p<0.05) was significant in males only. These results underscored the importance of maintaining lower amounts of TBF and TrF mass during childhood and adolescence, and maintaining high level of PA in EA in order to mitigate TBF and TrF mass accrual and reduce the risk of transitioning from NW to OWO during EA. In study 3 (1991-2017) participants of the PBMAS, now aged 32 to 40 years of age, were invited back for reassessment. Blood analysis was used to create a Continuous Cardiometabolic Risk (conCMR) score for each participant. Multi-level models of TrF and TBF accrual were created looking at the same predictors as study 2, with the addition of cardiometabolic risk (CMR) group. Childhood TBF and TrF z-scores were again found to be the most significant predictor of TBF and TrF accrual, this time from 18-39 years. PA was also significant. CMR group did not influence the trajectory of TBF or TrF accrual, potentially due to the homogeneity of the group and the small sample size. In conclusion it was found that FM continues to increase steadily from late adolescence through EA leading to a marked increase in the prevalence of OWO in young adulthood. Greater trajectories during EA are related to higher levels of FM accrual in childhood and adolescence, and higher scores on individual CMR factors in later adulthood. The results suggest that maintaining high levels of PA throughout the life span is beneficial to adult health directly and through its mitigating effect on FM accrual in EA, and indirectly by limiting FM accumulation in childhood and adolescence

Marine protected areas for spatially structured exploited stocks

Copyright © 2000 Inter-ResearchMany harvested marine and terrestrial populations have segments of their range protected in areas free from exploitation. Reasons for areas being protected from harvesting include conservation, tourism, research, protection of breeding grounds, stock recovery, harvest regulation, or habitat that is uneconomical to exploit. In this paper we consider the problem of optimally exploiting a single species local population that is connected by dispersing larvae to an unharvested local population. We define a spatially-explicit population dynamics model and apply dynamic optimization techniques to determine policies for harvesting the exploited patch. We then consider how reservation affects yield and spawning stock abundance when compared to policies that have not recognised the spatial structure of the metapopulation. Comparisons of harvest strategies between an exploited metapopulation with and without a harvest refuge are also made. Results show that in a 2 local population metapopulation with unidirectional larval transfer, the optimal exploitation of the harvested population should be conducted as if it were independent of the reserved population. Numerical examples suggest that relative source populations should be exploited if the objective is to maximise spawning stock abundance within a harvested metapopulation that includes a protected local population. However, this strategy can markedly reduce yield over a sink harvested reserve system and may require strict regulation for conservation goals to be realised. If exchange rates are high, results indicate that spawning stock abundance can be less in a reserve system than in a fully exploited metapopulation. In order to maximise economic gain in the reserve system, results indicate that relative sink populations should be harvested. Depending on transfer levels, loss in harvest through reservation can be minimal, and is likely to be compensated by the potential environmental and economic benefits of the reserve.G. N. Tuck and H. P. Possingha

Exact and semiclassical approach to a class of singular integral operators arising in fluid mechanics and quantum field theory

A class of singular integral operators, encompassing two physically relevant cases arising in perturbative QCD and in classical fluid dynamics, is presented and analyzed. It is shown that three special values of the parameters allow for an exact eigenfunction expansion; these can be associated to Riemannian symmetric spaces of rank one with positive, negative or vanishing curvature. For all other cases an accurate semiclassical approximation is derived, based on the identification of the operators with a peculiar Schroedinger-like operator.Comment: 12 pages, 1 figure, amslatex, bibtex (added missing label eq.11

MODISTools - downloading and processing MODIS remotely sensed data in R

Remotely sensed data – available at medium to high resolution across global spatial and temporal scales – are a valuable resource for ecologists. In particular, products from NASA's MODerate-resolution Imaging Spectroradiometer (MODIS), providing twice-daily global coverage, have been widely used for ecological applications. We present MODISTools, an R package designed to improve the accessing, downloading, and processing of remotely sensed MODIS data. MODISTools automates the process of data downloading and processing from any number of locations, time periods, and MODIS products. This automation reduces the risk of human error, and the researcher effort required compared to manual per-location downloads. The package will be particularly useful for ecological studies that include multiple sites, such as meta-analyses, observation networks, and globally distributed experiments. We give examples of the simple, reproducible workflow that MODISTools provides and of the checks that are carried out in the process. The end product is in a format that is amenable to statistical modeling. We analyzed the relationship between species richness across multiple higher taxa observed at 526 sites in temperate forests and vegetation indices, measures of aboveground net primary productivity. We downloaded MODIS derived vegetation index time series for each location where the species richness had been sampled, and summarized the data into three measures: maximum time-series value, temporal mean, and temporal variability. On average, species richness covaried positively with our vegetation index measures. Different higher taxa show different positive relationships with vegetation indices. Models had high R2 values, suggesting higher taxon identity and a gradient of vegetation index together explain most of the variation in species richness in our data. MODISTools can be used on Windows, Mac, and Linux platforms, and is available from CRAN and GitHub (https://github.com/seantuck12/MODISTools)

Predictor Equations for Beach Processes and Responses

A stepwise (linear) multiple regression procedure is applied to 11 environmental variables (or predictors) in the beach-ocean-atmosphersey stema t Virginia Beach, Virginia, for the following five predictands: mean longshore current velocity, mean bottom slope in the shoaling-wave zone, average mean grain size in the shoaling-wave zone, and beach deposition and beach erosion on the lower foreshore. Predictors consist of variables related to beach geometry, local water properties, local wind conditions, tidal fluctuations, and wave characteristics The resultant equations are tested against a set of independent data and, with one exception, agree reasonably. It is believed that if the data set were increased to include at least one year\u27s continuous measurements the procedure outlined would yield valid equations for all but stormy-weather conditions.It is presupposed that some provision will have to be made for preconditioning the data, as \u27storm\u27 and \u27nonstorm\u27 data will probably have to be analyzed separately

Dynamics of water evaporation from porous asphalt

The dynamics of water evaporation from porous asphalt mixture, with porosity ranging from 15% to 12 29%, have been investigated in this article. In order to test the same samples under different conditions, the pore structure of asphalt was quantified using X-ray Computed Tomography (CT) scans and 3D printed in transparent resin blocks. 3D printed transparent resin samples were tested under controlled laboratory conditions to understand the effect of pore space topology on the water retention and drying dynamics. The macroporosity, pore size distribution, air void tortuosity, water conductivity, and water retention curves of the 3D printed porous asphalt samples were quantified by means of image analysis. Moreover, a model was developed and tested experimentally to estimate the evaporation rates from porous asphalt materials under a wide range of porosities. Within the range of asphalt mixtures studied in the present work, the evaporation rate is related predominantly to the porosity, pore size distribution and tortuosity. It was found that the period over which water evaporation occurs at the surface is relatively short during drying of porous asphalt materials due to their relatively large pores weakening the capillary forces. This results in significantly shortening the so-called stage-1 evaporation (when the drying rate is controlled by liquid vaporisation at the surface) and early onset of the transition period (when both surface water evaporation and vapour diffusion inside porous asphalt play a comparable role in supplying the 26 evaporative demand). The transition period is followed by the stage-2 evaporation when the process is limited by the vapour diffusion inside the porous asphalt. Our results illustrate that the beginning of the stage-2 evaporation depends on the porosity and tortuosity of the porous asphalt material among other parameters. Our results and analysis provide new insights into the dynamics of water evaporation from asphalt materials

Dynamics of water evaporation from porous asphalt

The dynamics of water evaporation from porous asphalt mixture, with porosity ranging from 15% to 29%, have been investigated in this article. In order to test the same samples under different conditions, the pore structure of asphalt was quantified using X-ray Computed Tomography (CT) scans and 3D printed in transparent resin blocks. 3D printed transparent resin samples were tested under controlled laboratory conditions to understand the effect of pore space topology on the water retention and drying dynamics. The macroporosity, pore size distribution, air void tortuosity, water conductivity, and water retention curves of the 3D printed porous asphalt samples were quantified by means of image analysis. Moreover, a model was developed and tested experimentally to estimate the evaporation rates from porous asphalt materials under a wide range of porosities. Within the range of asphalt mixtures studied in the present work, the evaporation rate is related predominantly to the porosity, pore size distribution and tortuosity. It was found that the period over which water evaporation occurs at the surface is relatively short during drying of porous asphalt materials due to their relatively large pores weakening the capillary forces. This results in significantly shortening the so-called stage-1 evaporation (when the drying rate is controlled by liquid vaporisation at the surface) and early onset of the transition period (when both surface water evaporation and vapour diffusion inside porous asphalt play a comparable role in supplying the evaporative demand). The transition period is followed by the stage-2 evaporation when the process is limited by the vapour diffusion inside the porous asphalt. Our results illustrate that the beginning of the stage-2 evaporation depends on the porosity and tortuosity of the porous asphalt material among other parameters. Our results and analysis provide new insights into the dynamics of water evaporation from asphalt materials

Mn Interstitial Diffusion in (Ga,Mn)As

We present a combined theoretical and experimental study of the ferromagnetic semiconductor (Ga,Mn)As which explains the remarkably large changes observed on low temperature annealing. Careful control of the annealing conditions allows us to obtain samples with ferromagnetic transition temperatures up to 159 K. Ab initio calculations, and resistivity measurements during annealing, show that the observed changes are due to out-diffusion of Mn interstitials towards the surface, governed by an energy barrier of about 0.7-0.8 eV. The Mn interstitial is a double donor resulting in compensation of charge carriers and suppression of ferromagnetism. Electric fields induced by high concentrations of substitutional Mn acceptors have a significant effect on the diffusion.Comment: 5 pages, 4 figures, submitted to Physical Review Letter

Fractal scan strategies for selective laser melting of ‘unweldable’ nickel superalloys

The high thermal gradients experienced during manufacture via selective laser melting commonly result in cracking of high γ/γ′ Nickel based superalloys. Such defects cannot be tolerated in applications where component integrity is of paramount importance. To overcome this, many industrial practitioners make use of hot isostatic pressing to ‘heal’ these defects. The possibility of such defects re-opening during the component life necessitates optimisation of SLM processing parameters in order to produce the highest bulk density and integrity in the as-built state. In this paper, novel fractal scanning strategies based upon mathematical fill curves, namely the Hilbert and Peano-Gosper curve, are explored in which the use of short vector length scans, in the order of 100 μm, is used as a method of reducing residual stresses. The effect on cracking observed in CM247LC superalloy samples was analysed using image processing, comparing the novel fractal scan strategies to more conventional ‘island’ scans. Scanning electron microscopy and energy dispersive X-ray spectroscopy was utilised to determine the cracking mechanisms. Results show that cracking occurs via two mechanisms, solidification and liquation, with a strong dependence on the laser scan vectors. Through the use of fractal scan strategies, bulk density can be increased by 2 ± 0.7% when compared to the ‘island’ scanning, demonstrating the potential of fractal scan strategies in the manufacture of typically ‘unweldable’ nickel superalloys

The Capaciousness of No: Affective Refusals as Literacy Practices

© 2020 The Authors. Reading Research Quarterly published by Wiley Periodicals, Inc. on behalf of International Literacy Association The authors considered the capacious feeling that emerges from saying no to literacy practices, and the affective potential of saying no as a literacy practice. The authors highlight the affective possibilities of saying no to normative understandings of literacy, thinking with a series of vignettes in which children, young people, and teachers refused literacy practices in different ways. The authors use the term capacious to signal possibilities that are as yet unthought: a sense of broadening and opening out through enacting no. The authors examined how attention to affect ruptures humanist logics that inform normative approaches to literacy. Through attention to nonconscious, noncognitive, and transindividual bodily forces and capacities, affect deprivileges the human as the sole agent in an interaction, thus disrupting measurements of who counts as a literate subject and what counts as a literacy event. No is an affective moment. It can signal a pushback, an absence, or a silence. As a theoretical and methodological way of thinking/feeling with literacy, affect proposes problems rather than solutions, countering solution-focused research in which the resistance is to be overcome, co-opted, or solved. Affect operates as a crack or a chink, a tiny ripple, a barely perceivable gesture, that can persist and, in doing so, hold open the possibility for alternative futures