769 research outputs found
Electron microprobe study of lunar and planetary zoned plagioclase feldspars: An analytical and experimental study of zoning in plagioclase
Natural and experimentally grown zoned plagioclase feldspars were examined by electron microprobe. The analyses revealed discontinuous, sector, and oscillary chemical zoning superimposed on continuous normal or reverse zoning trends. Postulated mechanisms for the origin of zoning are based on either physical changes external to the magma (P, T, H2O saturation) or kinetic changes internal to the magma (diffusion, supersaturation, growth rate). Comparison of microprobe data on natural zoned plagioclase with zoned plagioclase grown in controlled experiments show that it may be possible to distinguish zonal development resulting from physio-chemical changes to the bulk magma from local kinetic control on the growth of individual crystals
An experimental study of trace element partitioning between perovskite, hibonite and melt: Equilibrium values
The presence of perovskite (CATiO3) and hibonite (Ca Al12O19) within different regions of Calcium-, Aluminum-rich Inclusions (CAI) and the trace element concentrations of these minerals in each circumstance, constrain models of precursor formation, nebular condensation, the thermal history of inclusions with relict perovskite and hibonite, and the formation of the Wark-Lovering rim. At present mineral/melt partition coefficient data for hibonite are limited to a few elements in simple experimental systems, or to those derived from hibonite-glass pairs in hibonite/glass microspherules. Similarly, there is only limited data on perovskite D that are applicable to meteorite compositions. Apart from the importance of partitioning studies to meteorite research, D values also are invaluable in the development of thermodynamic models, especially when data is available for a large number of elements that have different ionic charge and radii. In addition, study of the effect of rapid cooling on partitioning is crucial to our understanding of meteorite inclusions. To expand our knowledge of mineral/melt D for perovskite and hibonite, a study was instituted where D values are obtained in both equilibrium and dynamic cooling experiments. As an initial phase of this study mineral/melt D was measured for major elements (Ca, Mg, Al, Ti, and Si), 15 rare earth elements (La-Lu) and 8 other elements (Ba, Sr, U, Th, Nb, Zr, Hf, and Ge) in perovskite and hibonite grown under equilibrium conditions, in bulk compositions that are respectively similar to Compact Type A (CTA) CAI and to a hibonite/glass microspherule. Experimental mixes were doped with REE at 20-50x chondritic (ch) abundances, Ba at 50 ppm, Sr, Hf, Nb, and Zr at 100 ppm and, U and Th at 200 ppm. Trace element abundances were measured with the PANURGE ion microprobe. Major element compositions were obtained by electron microprobe analysis
Cattle Grubs and Their Control in South Dakota
The purposes of the research work carried on from 1947 to 1953 by the South Dakota Agricultural Experiment Station were: to study the distribution and seasonal abundance of cattle grubs in South Dakota; to measure effects of grub infestations and methods of control on rates of gain of feed lot cattle; to evaluate and improve methods of control; and to investigate the practicability of cattle grub control on an area or community-wide basis
Observations of Intercastes in Solenopsis Invicta Buren
The red imported fire ant, Solenopsis invicta Buren, exhibits classical polymorphism, which is defined as the coexistence of 2 or more functionally different castes of the same sex (Wilson 1971). The 2 basic castes are the worker and the female sexuals
Apollo Lunar Sample Photographs: Digitizing the Moon Rock Collection
The Acquisition and Curation Office at JSC has undertaken a 4-year data restoration project effort for the lunar science community funded by the LASER program (Lunar Advanced Science and Exploration Research) to digitize photographs of the Apollo lunar rock samples and create high resolution digital images. These sample photographs are not easily accessible outside of JSC, and currently exist only on degradable film in the Curation Data Storage Facilit
Acceptance and perception of digital health for managing nutrition in people with Parkinson\u27s disease and their caregivers and their digital competence in the United States: A mixed-methods study
Background and aims: This mixed-methods study examined participants\u27 acceptance and perception of using digital health for managing nutrition and participants\u27 digital competence. The results will be formative for making digital nutrition education more effective and acceptable for people with Parkinson\u27s disease (PwPD) and their informal caregivers. Methods: Qualitative data were collected through in-person semi-structured, dyadic interviews, and questionnaires from 20 dyads (20 PwPD and their caregivers) in the Northeastern United States and analyzed throughout the 2018 to 2019 academic year. Interview transcripts were deductively coded using the framework analysis method. Phrases related to acceptance of digital health were sub-coded into accept, neutral, or reject and those related to perceptions of digital health were sub-coded into perceived usefulness, perceived ease of use, and awareness of digital health. Quantitative data were analyzed using independent samples t tests and Fisher\u27s exact tests. Qualitative codes were transformed into variables and compared to digital competence scores to integrate the data. An average acceptance rate for digital health was calculated through examining the mean percent of phrases coded as accept from interview transcripts. Results: Twenty-five of 40 (62.5%) participants used the internet for at least 5 health-related purposes and the average acceptance rate was 54.4%. Dyads rejected digital health devices if they did not see the added benefit. The majority of participants reported digital health to be useful, but hard to use, and about half felt they needed education about existing digital health platforms. There was no difference in digital competence scores between PwPD and their caregivers (28.6 ± 12.6). Conclusion: Findings suggest that dyads accept and use technology but not to its full potential as technology can be perceived as hard to use. This finding, combined with digital competence scores, revealed that education is warranted prior to providing a digital nutrition intervention
'Mindless markers of the nation': The routine flagging of nationhood across the visual environment
The visual environment has increasingly been used as a lens with which to understand wider processes of social and economic change with studies employing in-depth qualitative approaches to focus on, for example, gentrification or trans-national networks. This exploratory paper offers an alternative perspective by using a novel method, quantitative photo mapping, to examine the extent to which a particular socio-cultural marker, the nation, is ‘flagged’ across three contrasting sites in Britain. As a multi-national state with an increasingly diverse population, Britain offers a particularly fruitful case study, drawing in debates around devolution, European integration and Commonwealth migration. In contributing to wider debates around banal nationalism, the paper notes the extent to which nations are increasingly articulated through commerce, consumption and market exchange and the overall significance of everyday markers (signs, objects, infrastructure) in naturalising a national view of the world
Healthy Sleep Leads to Improved Nutrition and Exercise in College Females
Diet, sleep quality, and exercise are important determinants of physical, mental, and emotional health. College students are particularly vulnerable to impaired health, as they experience multiple unique stressors associated with college life that impact their ability to engage in healthy sleep, diet, and exercise habits. Our results found that exercise significantly mediated the association between sleep quality and diet. Improved sleep habits may increase a young woman\u27s ability and desire to exercise, thus impacting her diet and nutrition. Findings suggest that clinicians can use a person\u27s motivation in any one domain, or multiple domains, to impact other health domains
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Contains reports on seven research projects.Lincoln Laboratory (Purchase Order DDL-B222
Transportability without positivity: a synthesis of statistical and simulation modeling
When estimating an effect of an action with a randomized or observational
study, that study is often not a random sample of the desired target
population. Instead, estimates from that study can be transported to the target
population. However, transportability methods generally rely on a positivity
assumption, such that all relevant covariate patterns in the target population
are also observed in the study sample. Strict eligibility criteria,
particularly in the context of randomized trials, may lead to violations of
this assumption. Two common approaches to address positivity violations are
restricting the target population and restricting the relevant covariate set.
As neither of these restrictions are ideal, we instead propose a synthesis of
statistical and simulation models to address positivity violations. We propose
corresponding g-computation and inverse probability weighting estimators. The
restriction and synthesis approaches to addressing positivity violations are
contrasted with a simulation experiment and an illustrative example in the
context of sexually transmitted infection testing uptake. In both cases, the
proposed synthesis approach accurately addressed the original research question
when paired with a thoughtfully selected simulation model. Neither of the
restriction approaches were able to accurately address the motivating question.
As public health decisions must often be made with imperfect target population
information, model synthesis is a viable approach given a combination of
empirical data and external information based on the best available knowledge
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