2,070 research outputs found
Mottling in the Meagher Limestone
The middle Cambrian Meagher limestone of southwest Montana is characterized by mottled members that are finely crystalline in the tan part and microcrystalline in the dark matrix. As seen in the literature, similar mottled limestones are thought to be an arrested stage in the dolomitization, or alteration of limestones
A Systems Approach to the Physiology of Weightlessness
A systems approach to the unraveling of the complex response pattern of the human subjected to weightlessness is presented. The major goal of this research is to obtain an understanding of the role that each of the major components of the human system plays following the transition to and from space. The cornerstone of this approach is the utilization of a variety of mathematical models in order to pose and test alternative hypotheses concerned with the adaptation process. An integrated hypothesis for the human physiological response to weightlessness is developed
Enhancing Manufacturing Planning and Control Systems Through Artificial Intelligence Techniques
Manufacturing planning and control systems are currently dominated by systems based upon Material Requirements Planning (MRP). MRP systems have a number of fundamental flaws. A potential alternative to MRP systems is suggested after research into the economic batch scheduling problem.
Based on the ideas of economic batch scheduling, and enhanced through artificial intelligence techniques, an alternative approach to manufacturing planning and control is developed. A framework for future research on this alternative to MRP is presented
Socioeconomic and Racial Disparities in Cancer Risk from Air Toxics in Maryland
We linked risk estimates from the U.S. Environmental Protection Agency’s National Air Toxics Assessment (NATA) to racial and socioeconomic characteristics of census tracts in Maryland (2000 Census) to evaluate disparities in estimated cancer risk from exposure to air toxics by emission source category. In Maryland, the average estimated cancer risk across census tracts was highest from on-road sources (50% of total risk from nonbackground sources), followed by nonroad (25%), area (23%), and major sources (< 1%). Census tracts in the highest quartile defined by the fraction of African-American residents were three times more likely to be high risk (> 90th percentile of risk) than those in the lowest quartile (95% confidence interval, 2.0–5.0). Conversely, risk decreased as the proportion of whites increased (p < 0.001). Census tracts in the lowest quartile of socioeconomic position, as measured by various indicators, were 10–100 times more likely to be high risk than those in the highest quartile. We observed substantial risk disparities for on-road, area, and nonroad sources by socioeconomic measure and on-road and area sources by race. There was considerably less evidence of risk disparities from major source emissions. We found a statistically significant interaction between race and income, suggesting a stronger relationship between race and risk at lower incomes. This research demonstrates the utility of NATA for assessing regional environmental justice, identifies an environmental justice concern in Maryland, and suggests that on-road sources may be appropriate targets for policies intended to reduce the disproportionate environmental health burden among economically disadvantaged and minority populations
Seawater Desalination for Municipal Water Production
This paper examines the optimal allocation of several inputs in the context of seawater desalination by reverse osmosis (RO) as a source of municipal (or commercial or industrial) water. A cost-minimization model is developed, a production function is estimated, and sensitivity analyses are conducted using the optimization model to investigate the effect of environmental conditions and economic factors on the optimal input portfolio and the cost of operating a modeled seawater desalination facility. The objectives of this paper are to better understand the effect on the seawater desalination facility’s costs and input portfolio from changes in water quality, membrane lifespan, daily operations schedule, and energy prices. Findings include that lower total facility costs are associated with warm-weather water quality parameters, longer membrane life, and mid-range daily operations schedule (14.265 hours/day). Under most conditions, an interruptible power supply regime reduces facility costs. Exceptions include when the interruptible power supply regime implies significant reductions in operating hours and the associated reduction in energy price is very small.water, production, seawater desalination, Resource /Energy Economics and Policy,
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Are the Public Rangelands Ailing?
This material was digitized as part of a cooperative project between the Society for Range Management, the National Agricultural Library, and the University of Arizona Libraries.The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform March 202
Determining cross sections from transport coefficients using deep neural networks
We present a neural network for the solution of the inverse swarm problem of
deriving cross sections from swarm transport data. To account for the
uncertainty inherent to this somewhat ill-posed inverse problem, we train the
neural network using cross sections from the LXCat project, paired with
associated transport coefficients found by the numerical solution of
Boltzmann's equation. The use of experimentally measured and theoretically
calculated cross sections for training encourages the network to avoid
unphysical solutions, such as those containing spurious energy-dependent
oscillations. We successfully apply this machine learning approach to simulated
swarm data for electron transport in helium, separately determining its elastic
momentum transfer and ionisation cross sections to within an accuracy of
over the range of energies considered. Our attempt to extend our method to
argon was less successful, although the reason for that observation is
well-understood. Finally, we explore the feasibility of simultaneously
determining cross sections of helium using this approach. We have some success
here, determining elastic, total excitation and ionisation cross sections
to , and accuracy, respectively. We are unsuccessful in
properly unfolding the separate singlet and triplet excitation cross
sections of helium, but this is as expected given their similar threshold
energies.Comment: 20 pages, 9 figures, submitted to Plasma Sources Science and
Technolog
Proton-coupled dynamics in lactose permease
Lactose permease of Escherichia coli (LacY) catalyzes symport of a
galactopyranoside and an H+ via an alternating access mechanism. The
transition from an inward- to an outward-facing conformation of LacY involves
sugar-release followed by deprotonation. Because the transition depends
intimately upon the dynamics of LacY in a bilayer environment, molecular
dynamics (MD) simulations may be the only means of following the accompanying
structural changes in atomic detail. Here, we describe MD simulations of wild-
type apo LacY in phosphatidylethanolamine (POPE) lipids that features two
protonation states of the critical Glu325. While the protonated system
displays configurational stability, deprotonation of Glu325 causes significant
structural rearrangements that bring into proximity side chains important for
H+ translocation and sugar binding and closes the internal cavity. Moreover,
protonated LacY in phosphatidylcholine (DMPC) lipids shows that the observed
dynamics are lipid-dependent. Together, the simulations describe early
dynamics of the inward-to-outward transition of LacY that agree well with
experimental data
Is the observed high-frequency radio luminosity distribution of QSOs bimodal?
The distribution of QSO radio luminosities has long been debated in the
literature. Some argue that it is a bimodal distribution, implying that there
are two separate QSO populations (normally referred to as 'radio-loud' and
'radio-quiet'), while others claim it forms a more continuous distribution
characteristic of a single population. We use deep observations at 20 GHz to
investigate whether the distribution is bimodal at high radio frequencies.
Carrying out this study at high radio frequencies has an advantage over
previous studies as the radio emission comes predominantly from the core of the
AGN, hence probes the most recent activity. Studies carried out at lower
frequencies are dominated by the large scale lobes where the emission is built
up over longer timescales (10^7-10^8 yrs), thereby confusing the sample. Our
sample comprises 874 X-ray selected QSOs that were observed as part of the 6dF
Galaxy Survey. Of these, 40% were detected down to a 3 sigma detection limit of
0.2-0.5 mJy.
No evidence of bimodality is seen in either the 20 GHz luminosity
distribution or in the distribution of the R_20 parameter: the ratio of the
radio to optical luminosities traditionally used to classify objects as being
either radio-loud or radio-quiet. Previous results have claimed that at low
radio luminosities, star formation processes can dominate the radio emission
observed in QSOs. We attempt to investigate these claims by stacking the
undetected sources at 20 GHz and discuss the limitations in carrying out this
analysis. However, if the radio emission was solely due to star formation
processes, we calculate that this corresponds to star formation rates ranging
from ~10 solar masses/yr to ~2300 solar masses/yr.Comment: 13 pages, 11 figures. Accepted for publication in Ap
A More Generalizable Method to Evaluate Changes in Health Care Costs with Changes in Health Risks Among Employers of All Sizes
The objective of this study was to estimate the association between changes in health care expenditures relative to changes in health risk status for employers of all sizes. Repeat health risk assessments (HRAs) were obtained from 50,005 employees and spouses with 2 years of health plan enrollment, and from 37,559 employees and spouses with 3 years of enrollment in employer-sponsored medical coverage. Changes in health care expenditures were measured from the year before completion of the first HRA to the years before and after the completion of the second HRA. Propensity score weighting was used to adjust for those who did not repeat the HRA so results could be extrapolated to the larger population. Propensity score weighted multiple regression analyses were used to estimate the relationship between changes in health care expenditures with changes in risk status for 9 risk categories. Significantly higher health care expenditures were associated with those who moved from low risk to medium or high risk, compared to those who remained low risk. Expenditure reductions estimated for those who improved their health status from high risk to medium or low risk were not statistically significant. This study is unique because of its large sample size, its use of data from a wide range of employer sizes, and its efforts to extend generalizability to those who did not complete both HRAs. These results demonstrate that the potential for short-term health care savings may be greater for programs that help maintain low risk than for programs focused on risk reduction. (Population Health Management 2014;17:297?305)Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140183/1/pop.2013.0103.pd
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