Computational Materials Techniques for Thermal Protection Solutions: Materials and Process Design

Integrated computational materials techniques that span the atomistic and continuum scales have the potential to aid the design and manufacturing of thermal protection materials. Two cases demonstrating the practical application of these methods are discussed. Case one examines the selection of a high temperature coating for carbon/carbon, with the target application being a solar thermal propulsion heat exchanger. The performance of various refractory metal and metal-carbide coatings is characterized considering extreme thermal (3500 K) and chemical (hydrogen flows) conditions. The recession rate, hydrogen leakage, and likelihood of mechanical failure are characterized and provide directions for further experimental investigation. Case two examines the process optimization of a heat shield material composed of a woven silica fiber preform and cyanate ester resin. Frequently, internal voids were found to be present in this composite after the resin infusion and curing stages of manufacturing. Using the manufacturing conditions, computations indicate that both water adsorption and resin cure shrinkage are contributing factors to void formation. The results suggest an alternative process configuration for curing that would mitigate voids

Molecular Dynamics Simulations of Liquid and Polymer Electrolytes for Energy Storage Devices

Advancing beyond current lithium-ion technology is necessary in order to enable energy storage devices for electric airplanes. Electrolyte stability is a key limiting factor, yet the design of improved electrolytes remains a formidable challenge. Molecular dynamics (MD) simulations are a powerful tool for studying electrolytes, since they can be used to evaluate structural, thermodynamic, and transport properties, and can provide molecular-level detail often inaccessible to experimental techniques. Our computational materials groups at the NASA Ames Research Center has developed models and methods to accurately simulate both liquid and polymer electrolytes.We report the results from atomistic MD simulations of several electrolyte materials, with lithium salts dissolved in ionic liquids, dimethoxyethane (DME), and polyethylene oxide (PEO). For improved accuracy, we employ polarizable models, where each atom is given an environment-dependent atomic dipole. The simulations accurately predict bulk transport properties, including viscosity, diffusion, and ionic conductivity, in quantitative agreement with available experimental data. Moreover, the simulations provide important insights into the solvation structure of the lithium ions.We also report the results from coarse-grained MD simulations of polyanion electrolytes. In order to more efficiently capture the longer length- and time-scales of these systems, we employ a generic bead-spring model. These simulations provide important insight into how the polymer chain architecture and ionic interaction strengths affect the ionic aggregation behavior and cation dynamics. Despite the simplicity of the model, the simulations yield qualitative agreement with experimental data for similar systems

A case for revising the strength of the relationship between childhood asthma and atopy in the developing world

Introduction. Asthma is the commonest chronic condition of children. Diagnosis remains difficult and many surrogate markers are used, such as documenting evidence of atopy.Method. Two studies investigated the role of atopy in childhood asthma. The first documented the prevalence and nature of allergy sensitivities in a group of asthmatic children compared with non-asthmatic children in Pretoria, South Africa. The second enrolled a random sample of asthmatic children and their mothers attending the Children’s Chest and Allergy Clinic at Steve Biko Academic Hospital, Pretoria. Children were classified as having atopic or non-atopic asthma. Mothers completed a questionnaire to reveal atopic features.Results. In the first study, only 45.0% of asthmatic children had a positive skin-prick test (SPT), as opposed to 16.2% of control children. This is a lower proportion than in many reported international studies. In the second study, 64 children with atopic asthma and 36 with non-atopic asthma were studied, along with their mothers. The proportion of children with atopic asthma did not differ for mothers with and without a positive SPT (p=0.836), a history of asthma (p=0.045) or symptoms suggestive of an allergic disease (p=1.000), or who were considered to be allergic (p=0.806). The odds ratio (OR) of a child having atopic asthma when he or she had a mother with a doctor-diagnosed history of asthma was 4.76, but the sensitivity was low (21.9%).Conclusion. The data demonstrate that fewer asthmatic children in South Africa are atopic than was previously thought. Also, all maternal allergic or asthmatic associations are poor predictors of childhood atopic asthma. Despite the increased risk of atopic asthma in a child of a mother who has a doctor diagnosis of asthma (OR 4.76; p=0.045), this is a poor predictor of atopic asthma (sensitivity 21.9%

Is level of implementation linked with intervention outcomes? Process evaluation of the TransformUs intervention to increase children's physical activity and reduce sedentary behaviour

Background TransformUs was a four-arm school-based intervention to increase physical activity and reduce sedentary behaviour among primary school children. Pedagogical and environmental strategies targeted the classroom, school grounds and family setting. The aims of this study were to evaluate program fidelity, dose, appropriateness, satisfaction and sustainability, and associations between implementation level and outcomes among the three intervention arms. Methods At baseline, 18-months (mid-intervention) and 30-months (post-intervention), teachers, parents and children completed surveys, and children wore GT3X ActiGraph accelerometers for 8 days at each time point to determine physical activity and sedentary time. Implementation data were pooled across the three intervention groups and teachers were categorised by level of implementation: (i) ‘Low’ ( 67% delivered). Linear and logistic mixed models examined between group differences in implementation, and the association with children’s physical activity and sedentary time outcomes. Qualitative survey data were analysed thematically. Results Among intervention recipients, 52% (n = 85) of teachers, 29% (n = 331) of parents and 92% (n = 407) of children completed baseline evaluation surveys. At 18-months, teachers delivered on average 70% of the key messages, 65% set active/standing homework, 30% reported delivering > 1 standing lesson/day, and 56% delivered active breaks per day. The majority of teachers (96%) made activity/sports equipment available during recess and lunch, and also used this equipment in class (81%). Fidelity and dose of key messages and active homework reduced over time, whilst fidelity of standing lessons, active breaks and equipment use increased. TransformUs was deemed appropriate for the school setting and positively received. Implementation level and child behavioural outcomes were not associated. Integration of TransformUs into existing practices, children’s enjoyment, and teachers’ awareness of program benefits all facilitated delivery and sustainability. Conclusions This study demonstrated that intervention dose and fidelity increased over time, and that children’s enjoyment, senior school leadership and effective integration of interventions into school practices facilitated improved intervention delivery and sustainability. Teacher implementation level and child behavioural outcomes were unrelated, suggesting intervention efficacy was achieved irrespective of implementation variability. The potential translatability of TransformUs into practice contexts may therefore be increased. Findings have informed scale-up of TransformUs across Victoria, Australia. Trial registration International Standard Randomized Controlled Trial Number ISRCTN83725066; Australian New Zealand Clinical Trials Registry Number ACTRN12609000715279. Registered 19 August 2009. Available at: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=308387&isReview=tru

In-groups, out-groups, and their contrasting perceptions of values among generational cohorts of Australians

Objective: Personal values guide, and are used to justify, behaviours both within and beyond organisational contexts. Baby Boomers, Generation X, and Generation Y are purported to vary in the values they espouse and hence their behaviours. The aim of this research was to examine and compare self-ratings and out-group perceptions of the importance of the four overarching clusters of values in Schwartz's circumplex model by generation. Method: A convenience sample of 157 participants (49 Baby Boomers, 47 Generation X, and 61 Generation Y) completed an online survey of self-rated values and perceptions of another generation's values. Results: Multivariate analyses identified that self-ratings of self-enhancement, openness to change, and conservation value clusters varied between generations (medium effect size), but self-transcendence did not. Out-group perceptions of generations varied across all four value clusters (very large effect size). We then compared each generation's self-ratings of value importance with perceptions of value importance provided by other generations (in-group/out-group comparisons). There were significant variations between self-ratings and perceived importance ratings provided by other generations for all three generations (large effect). Conclusions: Larger differences in other-ascribed than self-ascribed value importance across generations highlights the need to avoid actions based on generation value stereotypes, both within and beyond the workplace. Further research on a representative sample of the Australian population using a mixed-methods approach is recommended

Association of Preoperative Risk Factors With Malignancy in Pancreatic Mucinous Cystic Neoplasms: A Multicenter Study

Pancreatic mucinous cystic neoplasms (MCNs) harbor malignant potential, and current guidelines recommend resection. However, data are limited on preoperative risk factors for malignancy (adenocarcinoma or high-grade dysplasia) occurring in the setting of an MCN

The diagnosis of pancreatic mucinous cystic neoplasm and associated adenocarcinoma in males: An eight‐institution study of 349 patients over 15 years

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137278/1/jso24582_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137278/2/jso24582.pd

Who needs bereavement support? A population based survey of bereavement risk and support need

This study identifies and describes the profiles of bereavement risk and support needs of a community sample in Australia and tests the fit of the data with the three-tiered public health model for bereavement support. Family members who were bereaved 6-24 months prior to the survey and who were clients of four funeral providers participated (May-July 2013). A postal survey was used to collect information about bereaved people's experience of caring and perceived satisfaction with any bereavement support provided. The questionnaire included a validated risk assessment screening measure for Prolonged Grief Disorder (PG-13). A total of 678 bereaved people responded. The model predicted that 60% of the sample would be low risk, 30% moderate risk, and 10% high risk. Actual figures were very close at 58.4%, 35.2%and 6.4% respectively. The analysis of the demographic characteristics, experience and impact of caring and bereavement, and satisfaction with support received from a variety of sources revealed differential experiences and needs that align with the expectation of low, moderate, and high bereavement support need, as articulated in the public health model. This is the first empirical test of the public health model of bereavement support. As there is a lack of clear evidence to guide development and allocation of bereavement support programs, the findings have the potential to inform the ability of services, community organizations and informal networks to prioritize care according to each level of bereavement need. This is essential to achieve cost-effective and equitable resource allocation

National and subnational short-term forecasting of COVID-19 in Germany and Poland during early 2021

We compare forecasts of weekly case and death numbers for COVID-19 in Germany and Poland based on 15 different modelling approaches. These cover the period from January to April 2021 and address numbers of cases and deaths one and two weeks into the future, along with the respective uncertainties. We find that combining different forecasts into one forecast can enable better predictions. However, case numbers over longer periods were challenging to predict. Additional data sources, such as information about different versions of the SARS-CoV-2 virus present in the population, might improve forecasts in the future

Salted roads lead to oedema and reduced locomotor function in amphibian populations

Human activities have caused massive losses of natural populations across the globe. Like many groups, amphibians have experienced substantial declines worldwide, driven by environmental changes such as habitat conversion, pollution, and disease emergence. Each of these drivers is often found in close association with the presence of roads. Here we report a novel consequence of roads affecting an amphibian native to much of North America, the wood frog (Rana sylvatica). Across 38 populations distributed from southern to central New England, we found that adult wood frogs living adjacent to roads had higher incidence and severity of oedema (indicated by obvious bloating caused by subcutaneous fluid accumulation) during the breeding season than frogs living away from the influence of roads. This effect was best explained by increased conductivity of breeding ponds, prob-ably caused by runoff pollution from road salt used for de-icing. Oedema severity was negatively correlated with locomotor performance in more northerly populations. Interestingly, northern populations experience more intense winters, which tends to result in more de-icing salt runoff and increased energetic demands associated with overwintering cryoprotection needs. Thus, this emerging consequence of roads appears to impose potential fitness costs associated with locomotion, and these effects might be most impactful on populations living in regions where de-icing is most intense.Together, our findings reveal a novel set of impacts of roads and runoff pollution on wood frog physiology and performance, which seem likely to contribute to population decline. Given the global prevalence of roads and increasing salinisation of freshwater habitats, oedema and related impacts could be widespread consequences faced by amphibian populations across much of the planet's temperate zonesThis work was supported by Mianus River Gorge Preserve, Elm City Innovation Collaborative, Yale Institute for Biospheric Studies, EEES Graduate fellowship and Cramer funds, Guarini School of Graduate and Advanced Studies McCulloch Fellowship, CAPES graduate fellowship (SwB 13442/13-9), the Margarita Salas Fellowship, and the National Science Foundation (DEB #1011335, DEB #1655092).Peer reviewe