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At least 145 records · Page 8

All sources NASA NTRS DOE OSTI

NASA NTRS2014

Monitoring for Renal Stone Recurrence in Astronauts With History of Stone

After an initial stone episode persons are at increased risk for future stone formation. A systematic approach is required to monitor the efficacy of treatment and preventive measures, and to assess the risk of developing new stones. This is important for persons working in critical jobs or austere environments, such as astronauts. A literature review of the current standards of care for renal stone monitoring and imaging was done. Military and civil aviation standards were also reviewed, as well as the medical precedents from the space program. Additionally, a new, more effective, renal stone ultrasound protocol has been developed. Using this work, a monitoring algorithm was proposed that takes into consideration the unique mission and operational environment of spaceflight. The approach to imaging persons with history of renal stones varies widely in the literature. Imaging is often done yearly or biannually, which may be too long for mission critical personnel. In the proposed algorithm astronauts with a history of renal stone, who may be under consideration for assignment, are imaged by a detailed, physiciandriven, ultrasound protocol. Unassigned personnel are monitored by yearly ultrasound and urine studies. Any positive ultrasound study is then followed by low-dose renal computed tomography scan. Other criteria are also established. The proposed algorithm provides a balanced approach between efficacy and reduced radiation exposure for the monitoring of astronauts with a renal stone history. This may eventually allow a transition from a risk-averse, to a risk-modifying approach that can enable continued service of individuals with history of renal stone that have adequately controlled risk factors.

Reyes, David P.↗

NASA NTRS2013

Constraining Landscape History and Glacial Erosivity Using Paired Cosmogenic Nuclides in Upernavik, Northwest Greenland

High-latitude landscape evolution processes have the potential to preserve old, relict surfaces through burial by cold-based, nonerosive glacial ice. To investigate landscape history and age in the high Arctic, we analyzed in situ cosmogenic Be(sup 10) and Al (sup 26) in 33 rocks from Upernavik, northwest Greenland. We sampled adjacent bedrock-boulder pairs along a 100 km transect at elevations up to 1000 m above sea level. Bedrock samples gave significantly older apparent exposure ages than corresponding boulder samples, and minimum limiting ages increased with elevation. Two-isotope calculations Al(sup26)/B(sup 10) on 20 of the 33 samples yielded minimum limiting exposure durations up to 112 k.y., minimum limiting burial durations up to 900 k.y., and minimum limiting total histories up to 990 k.y. The prevalence of BE(sup 10) and Al(sup 26) inherited from previous periods of exposure, especially in bedrock samples at high elevation, indicates that these areas record long and complex surface exposure histories, including significant periods of burial with little subglacial erosion. The long total histories suggest that these high elevation surfaces were largely preserved beneath cold-based, nonerosive ice or snowfields for at least the latter half of the Quaternary. Because of high concentrations of inherited nuclides, only the six youngest boulder samples appear to record the timing of ice retreat. These six samples suggest deglaciation of the Upernavik coast at 11.3 +/- 0.5 ka (average +/- 1 standard deviation). There is no difference in deglaciation age along the 100 km sample transect, indicating that the ice-marginal position retreated rapidly at rates of approx.120 m yr(sup−1).

glacial↗

DOE OSTI2024

Enhancing predictive understanding and accuracy in geological carbon dioxide storage monitoring: Simulation and history matching of tracer transport dynamics

Co-injection of conservative tracers with carbon dioxide (CO 2 ) is a viable tool for monitoring subsurface processes during geological CO 2 storage (GCS). This research investigates the simulation and history-matching of a gas tracer (sulfur hexafluoride, SF 6 ) during CO 2 flooding, employing a core flooding result in Berea sandstone. Four extensively used saturation functions are assessed for their efficacy in history matching of CO 2 /SF 6 injection at the core scale. The history-matching process incorporates particle swarm optimization (PSO) to fine-tune constitutive relationships parameters. Next, employing transport models at the aquifer scale, we interrogate the impact on tracer transport and mixing of saturation function uncertainties, arising from the non-uniqueness of constitutive relationships parameters and saturation function types. To assess the effects of geological heterogeneity on behavior of tracer breakthrough curves (BTCs), we employ two normalized parameters assessing the degree of mixing and SF 6 breakthrough time. The aquifer-scale investigation encompasses both homogeneous and heterogeneous systems with and without capillary heterogeneity effects. Our findings underscore the critical importance of addressing saturation function uncertainties, emphasizing the significance of auxiliary experiments and innovative methodologies to enhance predictive accuracy. The findings highlight significant disparities in arrival times, BTC peaks, tails, and mixing levels, even under optimal conditions. Heterogeneity, with or without capillary heterogeneity, plays a crucial role in shaping BTC variations, resulting in accelerated SF 6 breakthrough times and reduced BTC peaks. Evaluation of monitoring points distant from the injector reveals a dampening effect on the SF6 BTC peak, particularly in heterogeneous systems with capillary heterogeneity, where the peak is halved. These insights underscore the challenges associated with tracer monitoring and the necessity for enhanced methodologies to improve predictive accuracy in subsurface processes during GCS.

58 GEOSCIENCES↗

DOE OSTI2025

Climate history modulates stress responses of common soil bacteria under experimental drought

Soil drying challenges microbial viability and survival, with bacteria employing various mechanisms to respond to shifts in osmolarity, including dormancy or metabolic upregulation of osmoprotectants. However, the extent to which these responses are shaped by an organism's phylogeny, or the climate history of a given environment is poorly understood. This study examines the responses of phylogenetically similar bacteria from semi-arid and humid tropical forest soils to osmotic and matric stress using synchrotron radiation-based Fourier Transform Infrared spectromicroscopy. This non-destructive approach depicts the biochemical phenotype for whole cells under control and stress conditions. We observed that, under osmotic stress, bacteria upregulated cell-signaling pathways, rapidly turned over lipid-storage compounds, and increased osmolyte production. In contrast, matric stress induced a more muted response, typically elevating the production of carbohydrate stress compounds, such as glycine betaine and trehalose. Whereas phylogenetically similar bacteria showed comparable biochemistry under control conditions, climate history played an important role in regulating responses to stress, whereby a stronger metabolic response was observed from semi-arid relative to tropical forest isolates. We conclude that bacterial stress response to drought can be more diverse than previously observed and regulated by both phylogeny and climate history.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2016

The changing role of mammal life histories in Late Quaternary extinction vulnerability on continents and islands

Understanding the drivers of extinction in a human dominated world is important if we are to preserve the remaining biodiversity. Here we compared extinction events on continents and islands after human arrival in prehistoric and historic times. We used regression trees to examine the role of life history in these extinctions. We found that all extinctions were significantly size-biased except for events on small islands in historic times. Further we found that life history traits associated with a lack of ability to respond quickly to perturbations were good predictors of prehistoric extinctions. In general life history traits were poor predictors of historic extinctions. Lastly, we conclude that these extinctions are part of one continuous extinction event, but that historic extinctions have multiple drivers, whereas prehistoric extinctions had fewer.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2014

Land-Use History and Contemporary Management Inform an Ecological Reference Model for Longleaf Pine Woodland Understory Plant Communities.

Ecological restoration is frequently guided by reference conditions describing a successfully restored ecosystem; however, the causes and magnitude of ecosystem degradation vary, making simple knowledge of reference conditions insufficient for prioritizing and guiding restoration. Ecological reference models provide further guidance by quantifying reference conditions, as well as conditions at degraded states that deviate from reference conditions. Many reference models remain qualitative, however, limiting their utility. We quantified and evaluated a reference model for southeastern U.S. longleaf pine woodland understory plant communities. We used regression trees to classify 232 longleaf pine woodland sites at three locations along the Atlantic coastal plain based on relationships between understory plant community composition, soils lol(which broadly structure these communities), and factors associated with understory degradation, including fire frequency, agricultural history, and tree basal area. To understand the spatial generality of this model, we classified all sites together. and for each of three study locations separately. Both the regional and location-specific models produced quantifiable degradation gradients–i.e., progressive deviation from conditions at 38 reference sites, based on understory species composition, diversity and total cover, litter depth, and other attributes. Regionally, fire suppression was the most important degrading factor, followed by agricultural history, but at individual locations, agricultural history or tree basal area was most important. At one location, the influence of a degrading factor depended on soil attributes. We suggest that our regional model can help prioritize longleaf pine woodland restoration across our study region; however, due to substantial landscape-to-landscape variation, local management decisions should take into account additional factors (e.g., soil attributes). Our study demonstrates the utility of quantifying degraded states and provides a series of hypotheses for future experimental restoration work. More broadly, our work provides a framework for developing and evaluating reference models that incorporate multiple, interactive anthropogenic drivers of ecosystem degradation.

Ecological Reference Models↗

DOE OSTI2011

Toward An Integrated History to Guide the Future

Abstract Many contemporary societal challenges manifest themselves in the domain of humanenvironment interactions. There is a growing recognition that responses to these challenges formulated within current disciplinary boundaries, in isolation from their wider contexts, cannot adequately address them. Here, we outline the need for an integrated, trans-disciplinary synthesis that allows for a holistic approach, and, above all, a much longer time perspective. We outline both the need for, and the fundamental characteristics of, what we call “integrated history.” This approach promises to yield new understandings of the relationship between the past, present and possible futures of our integrated human-environment system. We recommend a unique new focus of our historical efforts on the future, rather than the past, concentrated on learning about future possibilities from history. A growing worldwide community of trans-disciplinary scholars is forming around building this Integrated History and future of People on Earth (IHOPE). Building integrated models of past human societies and their interactions with their environments yields new insights into those interactions and can help to create a more sustainable and desirable future. The activity has become a major focus within the global change community.

99 GENERAL AND MISCELLANEOUS↗

DOE OSTI2022

National Renewable Energy Laboratory History: 1977-2016

Like the political and energy landscape at the time, the birth of the Solar Energy Research Institute (SERI) in 1977, which then became the National Renewable Energy Laboratory (NREL) in 1991, was at times tumultuous. Born from a need for better energy solutions, the newly formed U.S. Department of Energy realized that creating an organization solely dedicated to clean energy was crucial to our nation's ability to achieve energy independence. Forty-five years later, the "little lab in the hills" is at the forefront of clean energy innovation and is helping tackle our most daunting energy challenges. This book documents the creation of SERI and the politics and context of the times, from 1977 to 2016. It's the culmination of extensive independent research and formal oral history interviews - and it took more than a decade to complete. The "NREL History Project" was launched in 2009 to comprehensively record the birth and history of the laboratory to date. The project concluded in 2016 but was put on hold until 2021.

Adams↗

DOE OSTI2016

Measurements of Propanal Ignition Delay Times and Species Time Histories Using Shock Tube and Laser Absorption

Propanal is an aldehyde intermediate formed during the hydrocarbon combustion process. Potentially, the use of oxygenated biofuels reduces greenhouse gas emissions; however, it also results in increased toxic aldehyde by-products, mainly formaldehyde, acetaldehyde, acrolein, and propanal. These aldehydes are carcinogenic, and therefore it is important to understand their formation and destruction pathways in combustion systems. In this work, ignition delay times were measured behind reflected shock waves for stoichiometric (Φ = 1) mixtures of propanal (CH 3 CH 2 CHO) and oxygen (O 2 ) in argon bath gas at temperatures of 1129 K < T < 1696 K and pressures around 1 and 6 atm. Measurements were conducted using the kinetics shock tube facility at the University of Central Florida. Current results were compared to available data in the literature as well as to the predictions of three propanal combustion kinetic models: Politecnico di Milano (POLIMI), National University of Ireland at Galway, and McGill mechanisms. In addition, a continuous wave-distributed feedback interband cascade laser centered at 3403.4 nm was used for measuring methane (CH 4 ) and propanal time histories behind the reflected shock waves during propanal pyrolysis. Concentration time histories were obtained at temperatures between 1192 and 1388 K near 1 atm. Sensitivity analysis was carried for both ignition delay time and pyrolysis measurements to reveal the important reactions that were crucial to predicting the current experimental results. Adjustments to the POLIMI mechanism were adopted to better match the experimental data. Further research was suggested for the H abstraction reaction rates of propanal. Finally, in addition to extending the temperature and pressure region of literature ignition delay times, we provide the first high-temperature species concentration time histories during propanal pyrolysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

History of the Beer Game

This article describes the history of the Beer Game. By triangulating information from literature, archival analysis, and interviews with experts in the field, the main changes in the game over its almost 70-year history are identified. The article discusses three aspects of the game: 1) its structure (phases of its history, stocks and flows, parameters, etc.); 2) the process for playing the game; and 3) the game debrief. The structure of the Beer Game, and the process for running it, have stabilized over the years into what is now a de facto standard approach. Additional work is needed in the game debrief, specifically in the clarification of key insights and messages (depending on the context of the use of the game), in how to communicate such messages to different audiences, and in the development of support materials for its delivery. © 2024 UChicago Argonne, LLC. System Dynamics Review published by John Wiley & Sons Ltd on behalf of System Dynamics Society.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2016

History-Dependent Problems with Applications to Contact Models for Elastic Beams

We prove an existence and uniqueness result for a class of subdifferential inclusions which involve a history-dependent operator. Then we specialize this result in the study of a class of history-dependent hemivariational inequalities. Problems of such kind arise in a large number of mathematical models which describe quasistatic processes of contact. To provide an example we consider an elastic beam in contact with a reactive obstacle. The contact is modeled with a new and nonstandard condition which involves both the subdifferential of a nonconvex and nonsmooth function and a Volterra-type integral term. We derive a variational formulation of the problem which is in the form of a history-dependent hemivariational inequality for the displacement field. Then, we use our abstract result to prove its unique weak solvability. Finally, we consider a numerical approximation of the model, solve effectively the approximate problems and provide numerical simulations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2019

Differentiation of hepatic abscess from metastasis on contrast-enhanced dynamic computed tomography in patients with a history of extrahepatic malignancy: emphasis on dynamic change of arterial rim enhancement

Objectives: The objective of the study is to identify computed tomography (CT) findings that differentiate hepatic abscess from hepatic metastasis in a patient with a history of extrahepatic malignancy. Materials and methods: This retrospective study included 30 patients with 93 hepatic abscesses and 40 patients with 125 hepatic metastases who had a history of extrahepatic malignancy and underwent contrast-enhanced dynamic CT with arterial phase (AP) and portal venous phase (PVP). The diagnosis of hepatic abscess and hepatic metastasis was made using pathological confirmation or clinical diagnosis. Margin, patchy parenchymal enhancement, arterial rim enhancement, dynamic change of arterial rim enhancement, size discrepancy of lesions between arterial and portal phases, bile duct dilatation, perilesional hyperemia, and perilesional low density were evaluated by two radiologists independently. Significant findings for differentiating two groups were identified at univariate and multivariate analysis with nomogram for predicting hepatic abscess. Interobserver agreement was also analyzed for each variable. Results: Multivariate analysis revealed that patchy parenchymal enhancement (P < 0.001), arterial rim enhancement persistent through PVP (P < 0.001), and perilesional hyperemia (P = 0.013) were independent significant findings to predict hepatic abscess than metastasis. Among them, arterial rim enhancement persistent through PVP showed a highest odds ratio (OR 33.73) on multivariate analysis and a highest predictor point on a nomogram for predicting hepatic abscess. When two of these three criteria were combined, 80.7% (75/93) of hepatic abscess were correctly identified, with a specificity of 85.6% (107/125). When all three criteria were satisfied, specificity was up to 100% (125/125). Conclusions: At contrast-enhanced dynamic CT, patchy parenchymal enhancement, arterial rim enhancement persistent through PVP, perilesional hyperemia, and their combinations may be reliable CT features for differentiating hepatic abscess from metastasis in patients with a history of primary extrahepatic malignancy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2017

A Method to Alleviate the Long History Problem Encountered in Monte Carlo Simulations via Weight Window Variance Reduction

When the weight window is implemented in large and complex models, streaming path and deep penetration could lead to a long history problem that takes a disproportionate amount of time for the accomplishment of Monte Carlo simulations and exerts a detrimental effect on the efficiency of parallel computing. An approach set the limitation of weight window splitting was proposed for the alleviation of long history problem. Tests were conducted on a streaming dog-leg geometry model and a 3D model of the Chinese Fusion Engineering Testing Reactor. The results show that a suitable parameter in the alleviation method could optimize both the performance of variance reduction and the efficiency of parallel calculation, which makes long history problem tractable.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2018

Parametric Modeling of AZ31-Mg Alloy Friction Stir Weld Temperature Histories

A parametric model of friction stir weld temperature histories is presented that uses constraint conditions, which are three-dimensional isothermal boundary conditions on the calculated temperature fields. This study describes further extension, with respect to formulation, of a parametric-modeling methodology, which is relatively optimal in terms of representation for application to friction stir welding and processing. These parametric representations of temperature histories can be used for modeling friction stir welds whose process conditions are similar to those in this study. Calculations of AZ31-Mg alloy friction stir weld temperature histories are presented, which use temperature-field constraint conditions based on measured weld cross sections and a model for the estimation of weld stir zone temperatures.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Multigroup Monte Carlo on GPUs: Comparison of history- and event-based algorithms

This article presents an investigation of the performance of different multigroup Monte Carlo transport algorithms on GPUs with a discussion of both history-based and event-based approaches. Several algorithmic improvements are introduced for both approaches. By modifying the history-based algorithm that is traditionally favored in CPU-based MC codes to occasionally filter out dead particles to reduce thread divergence, performance exceeds that of either the pure history-based or event-based approaches. The impacts of several algorithmic choices are discussed, including performance studies on Kepler and Pascal generation NVIDIA GPUs for fixed source and eigenvalue calculations. Single-device performance equivalent to 20–40 CPU cores on the K40 GPU and 60–80 CPU cores on the P100 GPU is achieved. Last, in addition, nearly perfect multi-device parallel weak scaling is demonstrated on more than 16,000 nodes of the Titan supercomputer.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2014

Generalized contexts and consistent histories in quantum mechanics

We analyze a restriction of the theory of consistent histories by imposing that a valid description of a physical system must include quantum histories which satisfy the consistency conditions for all states. We prove that these conditions are equivalent to imposing the compatibility conditions of our formalism of generalized contexts. Moreover, we show that the theory of consistent histories with the consistency conditions for all states and the formalism of generalized context are equally useful representing expressions which involve properties at different times.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2013

Influence of thermal history on the mechanical properties of carbon fiber-acrylate composites cured by electron beam and thermal processes

The mechanical properties of an acrylate resin and its carbon fiber composite, as well as the adhesion strength between them, were characterized in the case of thermal and electron beam curing. The thermal history during the cure was also recorded. It was shown that the properties of the matrix were similar but that the thermal history during the curing had a direct influence on the type of interactions that were generated at the interface, leading to different level of adhesion strength and level of performance for the associated composites. In the case of a thermal cure, the thermal profile allowed the generation of covalent bonding at the interface, leading to a high level of adhesion strength, which was not the case for electron beam curing. The thermal history during the cure appeared to be a determining parameter for the level of performance of composites cured by electron beam.

Vautard, Frederic↗

DOE OSTI2022

Disclination-dislocation based model for grain boundary stress field evolution due to slip transmission history and influence on subsequent dislocation transmission

This work demonstrates how the structure of a grain boundary (GB) and its evolution due to slip transmission history influences subsequent dislocation transmission. First, a model for the evolution of stress fields within grain boundaries that accounts for the effects of coherent dislocation transmission is introduced. Starting with a disclination-based construct of GBs at minimum energy (equilibrium), the model describes the evolution of the GB stress field to a state characteristic of excess energy (non-equilibrium) due to the incorporation of residual Burgers vector content following sequential slip transmission events. Several essential features of this model are verified via molecular dynamics simulations of lattice dislocation absorption. Second, this model is implemented into a discrete dislocation dynamics (DDD) code and simulations are performed to understand the influence of Non-equilibrium GB stress fields, conditioned by the slip transmission history, on subsequent dislocation transmission. DDD simulations reveal that the critical resolved stress necessary for slip propagation can be reduced by with continued absorption of residual dislocation content. Moreover, DDD simulations prove that a comprehensive consideration of both the binding and driving stresses, and the evolution of the transmission configuration is necessary to quantify the influence of the mechanical state of the GB on slip propagation. In general, this work provides important insights into the role of GB structure evolution, conditioned by prior deformation history, on intergranular plasticity.

42 ENGINEERING↗