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At least 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Extinction and scattering in the Orion Nebula - Comparison of optical and VLA 21 centimeter studies

We have compared VLA 21 cm continuum maps of M42 with extinction-corrected H-beta images and found that much of M42 has an excess of H-beta surface brightness. This is interpreted as reflection by particles lying close to the principal ionization front. Comparison of column densities of H I near M42 and extinction (C(H-beta)) indicates an excellent area-by-area correlation, establishing that most of the extinction in M42 arises in the neutral lid that lies on the near side of the nebula. A more quantitative comparison of (C(H-beta)) and N(H I), the column density, is consistent with this conclusion and indicates a dust scattering cross section per hydrogen atom that is similar to the value for the general interstellar medium. The usual model for extinction in the Trapezium region is that it occurs very near the stars and produces an anomalous reddening curve through modification of the nature or size distribution of the particles. These new results question the basic assumptions and conclusions of that model.

O'Dell, C. R.↗
NASA NTRS1992

COBE DMR results and implications

This lecture presents early results obtained from the first six months of measurements of the Cosmic Microwave Background (CMB) by Differential Microwave Radiometers (DMR) aboard COBE and discusses significant cosmological implications. The DMR maps show the dipole anisotropy and some galactic emission but otherwise a spatially smooth early universe. The measurements are sufficiently precise that we must pay careful attention to potential systematic errors. Maps of galactic and local emission such as those produced by the FIRAS and DIRBE instruments will be needed to identify foregrounds from extragalactic emission and thus to interpret the results in terms of events in the early universe. The current DMR results are significant for Cosmology.

Smoot, George F.↗
NASA NTRS1994

A Semantic Theory of Abstractions: A Preliminary Report

In this paper we present a semantic theory of abstractions based on viewing abstractions as interpretations between theories. This theory captures important aspects of abstractions not captured in the theory of abstractions presented by Giunchiglia and Walsh. Instead of viewing abstractions as syntactic mappings, we view abstractions as a two step process: the intended domain model is first abstracted and then a set of (abstract) formulas is constructed to capture the abstracted domain model. Viewing and justifying abstractions as model level transformations is both natural and insightful. We provide a precise characterization of the abstract theory that exactly implements the intended abstraction, and show that this theory, while being axiomatizable, is not always finitely axiomatizable. A simple corollary of the latter result disproves a conjecture made by Tenenberg that if a theory is finitely axiomatizable, then predicate abstraction of that theory leads to a finitely axiomatizable theory.

Nayak, P. Pandurang↗
NASA NTRS2020

Air Quality Monitoring Case Study Using Mobile Low-cost Sensors Mounted on Trash-Trucks: Methods Development and Lessons Learned

Air quality monitoring (AQM) is crucial for cities to develop management plans supporting population health. However, there is a dearth of measurements due to the high cost of standard reference instruments. Mobile AQM using low-cost sensors deployed on routine fleets of vehicles can enable the continuous detection of fine-scale pollutant variations in cities at a lower cost. New methods need to be developed to interpret these measurements. This paper presents three such methods. First, we propose a technique to identify aerosol hotspots. Second, we employ techniques published previously to assess the generalizable map of fine and coarse particle number concentrations, to understand qualitatively the contribution of local and regional sources across the region sampled. By using the raw number concentration of differently sized particles from the Optical Particle Counters (OPCs) instead of the noisier mass concentrations, we obtain more robust results. Third, in order to evaluate source signatures in cities, we propose another technique, in which we cluster the entire range of aerosol size-distribution measurements acquired. The properties of each cluster provide insight into the aerosol source characteristics in the sampling environment. We test these methods using a dataset we collected by mounting OPCs on two trash-trucks in Cambridge, Massachusetts.

Drive-by sensing↗
NASA NTRS2020

Air Quality Monitoring Case Study Using Mobile Low-cost Sensors mounted on Trash-Trucks: Methods Development and Lessons Learned

Air quality monitoring (AQM) is crucial for cities to develop management plans supporting population health. However, there is a dearth of measurements due to the high cost of standard reference instruments. Mobile AQM using low-cost sensors deployed on routine fleets of vehicles can enable the continuous detection of fine-scale pollutant variations in cities at a lower cost. New methods need to be developed to interpret these measurements. This paper presents three such methods. First, we propose a technique to identify aerosol hotspots. Second, we employ techniques published previously to assess the generalizable map of fine and coarse particle number concentrations, to understand qualitatively the contribution of local and regional sources across the region sampled. By using the raw number concentration of differently sized particles from the Optical Particle Counters (OPCs) instead of the noisier mass concentrations, we obtain more robust results. Third, in order to evaluate source signatures in cities, we propose another technique, in which we cluster the entire range of aerosol size-distribution measurements acquired. The properties of each cluster provide insight into the aerosol source characteristics in the sampling environment. We test these methods using a dataset we collected by mounting OPCs on two trash-trucks in Cambridge, Massachusetts.

Drive-by sensing↗
NASA NTRS1973

Ratio maps of iron ore deposits Atlantic City district, Wyoming

Preliminary results of a spectral rationing technique are shown for a region at the southern end of the Wind River Range, Wyoming. Digital ratio graymaps and analog ratio images have been produced for the test site, but ground truth is not yet available for thorough interpretation of these products. ERTS analog ratio images were found generally better than either ERTS single-channel images or high altitude aerial photos for the discrimination of vegetation from non-vegetation in the test site region. Some linear geological features smaller than the ERTS spatial resolution are seen as well in ERTS ratio and single-channel images as in high altitude aerial photography. Geochemical information appears to be extractable from ERTS data. Good preliminary quantitative agreement between ERTS-derived ratios and laboratory-derived reflectance ratios of rocks and minerals encourage plans to use lab data as training sets for a simple ratio gating logic approach to automatic recognition maps.

Vincent, R. K.↗
NASA NTRS1985

Geophysical interpretation of the magnetic anomalies of the Earth derived from MAGSAT data

The ambiguities about geophysical implications based on the correlation of scalar magnetic anomalies and geological features were investigated. A method was developed to convert scalar magnetic anomalies into a map of the lateral variations of magnetic susceptibility of the lithosphere. This map is directly correlated with the causative sources. The method is based on spherical harmonic analysis of lateral variations seen on the scalar magnetic anomaly map and those of the lithospheric magnetic susceptibility. The harmonic coefficients are related through the fundamental causality relationship governing a magnetized body and its associated scalar magnetic anomaly. The main features of the resulting magnetic susceptibility anomalies are outlined.

Arkani-Hamed, J.↗
NASA NTRS1973

Change in land use in the Phoenix (1:250,000) Quadrangle, Arizona between 1970 and 1972: Successful use of proposed land use classification system

Changes in land use in the Phoenix (1:250,000 scale) Quadrangle in Arizona have been mapped using only the images from ERTS-1, tending to verify the utility of a land use classification system proposed for use with ERTS images. The period of change investigated was from November 1970 to late summer or early fall, 1972. Seasonal changes also were studied using successive ERTS images. Types of equipment used to aid interpretation included a color additive viewer, a twenty-power magnifier, a density slicer, and a diazo copy machine for making ERTS color composites in hard copy. Types of changes detected have been: (1) cropland or rangeland developed for new residential areas; (2) rangeland converted to new cropland; and (3) possibly new areas of industrial or commercial development. A map of land use previously compiled from air photos was updated in this manner.

Place, J. L.↗
DOE OSTI2024

Relative State Counting for Semiclassical Black Holes

It has been shown that entropy differences between certain states of perturbative quantum gravity can be computed without specifying an ultraviolet completion. This is analogous to the situation in classical statistical mechanics, where entropy differences are defined but absolute entropy is not. Unlike in classical statistical mechanics, however, the entropy differences computed in perturbative quantum gravity do not have a clear physical interpretation. Here we construct a family of perturbative black hole states for which the entropy difference can be interpreted as a relative counting of states. Conceptually, this Letter begins with the algebra of mass fluctuations around a fixed black hole background, and points out that while this is a type I algebra, it is not a factor and therefore has no canonical definition of entropy. As in previous work, coupling the mass fluctuations to quantum matter embeds the mass algebra within a type II factor, in which entropy differences (but not absolute entropies) are well defined. It is then shown that for microcanonical wave functions of mass fluctuation, the type II entropy difference equals the logarithm of the dimension of the extra Hilbert space that is needed to map one microcanonical window to another using gauge-invariant unitaries. The Letter closes with comments on type II entropy difference in a more general class of states, where the von Neumann entropy difference does not have a physical interpretation, but “one-shot” entropy differences do. Published by the American Physical Society 2024

Akers, Chris (ORCID:0000000227929827)↗
DOE OSTI2016

Compressional residual stress in Bastogne boudins revealed by synchrotron X-ray microdiffraction

Lattice distortions in crystals can be mapped at the micron scale using synchrotron X-ray Laue microdiffraction (μXRD). From lattice distortions the shape and orientation of the elastic strain tensor can be derived and interpreted in terms of residual stress. We apply the new method to vein quartz from the original boudinage locality at Bastogne, Belgium. Furthermore, a long-standing debate surrounds the kinematics of the Bastogne boudins. The μXRD measurements reveal a shortening residual elastic strain, perpendicular to the vein wall, corroborating the model that the Bastogne boudins formed by layer-parallel shortening and not by layer-parallel extension, as is in the geological community generally inferred by the process of boudinage.

58 GEOSCIENCES↗
DOE OSTI2025

From subsidies to stressors: Positively skewed ecological gradients alter biological responses to nutrients in streams

Abstract Subsidy–stress gradients offer a useful framework for understanding ecological responses to perturbation and may help inform ecological metrics in highly modified systems. Historic, region‐wide shifts from bottomland hardwood forest to row crop agriculture can cause positively skewed impact gradients in alluvial plain ecoregions, resulting in tolerant organisms that typically exhibit a subsidy response (increased abundance in response to environmental stressors) shifting to a stress response (declining abundance at higher concentrations). As a result, observed biological tolerance in modified ecosystems may differ from less modified regions, creating significant challenges for detecting biological responses to restoration efforts. Using the agriculturally dominated Mississippi Alluvial Plain (MAP) ecoregion in Mississippi, USA, as a case study, we tested the hypothesis that macroinvertebrate taxa that typically display a subsidy response to nutrient enrichment in less modified ecoregions (i.e., nutrient‐tolerance) shift to a stress response to increasing nutrients in highly modified watersheds with elevated baseline nutrient conditions (i.e., nutrient intolerance). The abundance and diversity of MAP‐specific intolerant taxa identified with threshold indicator taxa analysis were either unresponsive or exhibited a subsidy response to increasing nutrients in less modified ecoregions in Mississippi with less land alteration and lower nutrient concentrations, but declined at higher concentrations, providing evidence for a stress response to elevated nutrients in the MAP. Additionally, MAP‐specific tolerant and intolerant taxa richness responded to increased nutrients predictably and consistently across space and time within the MAP. However, in MAP streams, elevated specific conductance was predicted to dampen the response of tolerant and intolerant taxa richness to increasing nutrient concentrations, highlighting the importance of considering multistressor interactions when interpreting biological data. Lastly, we demonstrate the efficacy of this approach with sediment bacterial communities characterized with amplicon sequencing, which lack sufficient life history characteristics necessary for the development of multimetric indices. Both macroinvertebrate and bacterial communities responded similarly to increasing nutrient concentrations, suggesting DNA‐based approaches may provide an efficient biological assessment tool for monitoring water quality improvements in highly modified watersheds.

DeVilbiss, Stephen E. [U.S. Geological Survey Lowe↗
DOE OSTI2019

Submicron Sodium Banding in Cultured Planktic Foraminifera Shells

The calcite shells, or tests, of foraminifera provide a window into Earth history because they are well preserved in marine sediments and contain useful geochemical proxies for paleoceanography. Previous observations of diurnal heterogeneity in proxies like Mg/Ca demonstrate a complex relationship between environmental conditions and test composition. The definitive causes for this diurnal banding and the potential impact for proxy interpretation in systems other than Mg/Ca have yet to be determined. Here we use time-of-flight secondary ion mass spectrometry (ToF-SIMS), a chemical and isotope mapping technique with a spatial resolution of 300 nm, to show that Na banding is a consistent feature in the tests of cultured Orbulina universa, a species of planktic foraminifer. This banding occurs in two distinct forms: (1) sharp Na bands associated with embedded organic sheets and (2) regular, thicker, but lower-amplitude Na bands that are found throughout the test. In Orbulina bilobata, a morphotype of O. universa that develops a second partial spherical chamber attached to the primary sphere, we use the first type of banding to show that a second organic sheet is used as a template to form this second chamber. Thus, sodium banding links test geochemistry with foraminiferal growth models, allowing us to explain the pattern and timing of chamber formation as well as a specific type of geochemical banding in foraminifera. Furthermore, the magnitude, timing, and coherency between Na and Mg bands can help constrain mechanistic explanations for geochemical banding in foraminifera in general.

paleoclimate, Foraminifera, biomineralization, pal↗
DOE OSTI2016

A new defect chemistry model for Nb-doped SrCoO 2.5+δ: The role of oxygen interstitials and delocalized-to-localized electron holes

Here a new defect chemistry model featuring oxygen interstitials ( O" I ) and delocalized-to-localized d-electron holes (Co' Co 2.5 reference framework to elucidate transport properties of Nb-doped SrCoO 2.5+δ (SCN) system over a range of partial pressure of oxygen (Po 2 ) and temperature (T). With this new defect chemistry model, the electronic conductivity behaviors with T and Po2 can be well interpreted by the change in concentration of d-electron holes migrating with a constant mobility. The important concentration contours of electron holes, excess electrons and oxygen interstitials are mapped out on the T-Po 2 domain, from which hole-concentration and conductivity under iso-stoichiometry are reconstructed. The partial/integral molar thermodynamic properties and thermodynamic factor of the SCN solid solution are also determined. A transitional delocalized-to-localized hole-transport mechanism with decreasing oxygen stoichiometry is discussed based on p=p(T) obtained under constant oxygen stoichiometry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Topological structure of complex predictions

Abstract Current complex prediction models are the result of fitting deep neural networks, graph convolutional networks or transducers to a set of training data. A key challenge with these models is that they are highly parameterized, which makes describing and interpreting the prediction strategies difficult. We use topological data analysis to transform these complex prediction models into a simplified topological view of the prediction landscape. The result is a map of the predictions that enables inspection of the model results with more specificity than dimensionality-reduction methods such as tSNE and UMAP. The methods scale up to large datasets across different domains. We present a case study of a transformer-based model previously designed to predict expression levels of a piece of DNA in thousands of genomic tracks. When the model is used to study mutations in the BRCA1 gene, our topological analysis shows that it is sensitive to the location of a mutation and the exon structure of BRCA1 in ways that cannot be found with tools based on dimensionality reduction. Moreover, the topological framework offers multiple ways to inspect results, including an error estimate that is more accurate than model uncertainty. Further studies show how these ideas produce useful results in graph-based learning and image classification.

Computer Science↗
DOE OSTI2021

A HPC Theory-Guided Machine Learning Cyberinfrastructure for Communicating Hydrometeorological Data Across Scales

High-resolution predictions of hydrometeorological variables are critical for supporting hydropower generation decisions and flood control at hydroelectric power plants. Traditional climate and hydrologic models rely on the numerical simulation of detailed physical processes. Therefore, running these simulations is time-, labor-, and computation-intensive. Improving the spatial and temporal resolution in these modeling outputs could lead to cubic increases in both the simulation time and computational demands, rendering high-resolution hydrometeorological predictions expensive and impractical. Many past studies apply the super resolution (SR) technique to downscale climate models using deep learners. However, deep learners are deemed “black-boxes,” as their derivation processes from low-resolution outputs to high-resolution outputs are often hidden. Their results are difficult for domain scientists to interpret and validate. Thus, there is a need for an exploratory machine learning approach that can partially integrate domain-specific theory and knowledge into the data-driven mapping process between simulation outputs of different spatial scales. The domain-specific theory and knowledge can be incorporated into the data model through an inductive approach in which process-related environmental variables are used and analyzed as key drivers (i.e., environmental surrogates) to reflect the complex physical processes. Many of these variables, such as land use land cover, soil types, topography, digital elevation, air temperature, and various watershed characteristics, can be directly measured through sensors or remote sensing techniques. Additionally, SR applications that can downscale hydrological and hydrodynamics models to efficiently produce high-resolution (1 m) flood depth grids are still rare. Since the flood depth grid can be used to support critical decisions for flood control operation at hydroelectric power plants, it is crucial to enable an SR-based capability for interpolating high-resolution flood inundation maps.

13 HYDRO ENERGY↗
NASA NTRS1973

An evaluation of acquired data as a tool for management of wildlife habitat in Alaska

The author has identified the following significant results. Density sliced and digitized imagery of the Kuskokwin/Yukon Delta were analyzed. Color coded images of the isodensity displays were compared with existing vegetation maps of the ERTS-1 frames for the Yukon/Kuskokwin area. A high degree of positive correlation was found to exist between the ERTS-1 image and the conventionally prepared maps. Hydrologic phenomena were also analyzed. Digitization on South Dakota State Remote Sensing Center's SADE system provide some discrimination among several large lakes in the subject area. However, interpretation must await ground observations and depth measurements. An attempt will be made to classify large water bodies by depth classes.

Vantries, B. J.↗
NASA NTRS1975

A scheme for the uniform mapping and monitoring of earth resources and environmental complexes: An assessment of natural vegetation, environmental, and crop analogs

The author has identified the following significant results. A study was performed to develop and test a procedure for the uniform mapping and monitoring of natural ecosystems in the semi-arid and wood regions of the Sierra-Lahontan and Colorado Plateau areas, and for the estimating of rice crop production in the Northern Great Valley (Ca.) and the Louisiana Coastal Plain. ERTS-1 and high flight and low flight aerial photos were used in a visual photointerpretation scheme to identify vegetation complexes, map acreages, and evaluate crop vigor and stress. Results indicated that the vegetation analog concept is valid; that depending on the kind of vegetation and its density, analogs are interpretable at different levels in the hierarchical classification from second to the fourth level. The second level uses physiognomic growth form-structural criteria, and the fourth level uses floristic or taxonomic criteria, usually at generic level. It is recommended that analog comparisons should be made in relatively small test areas where large homogeneous examples can be found of each analog.

Poulton, C. E.↗
NASA NTRS1976

Two-Point Correlations of Sound Pressure in the Far Field of a Jet: Experiment

Correlations of sound pressure between two microphones yield substantially more information than single microphone data; hence, they provide useful information about the nature and behavior of jet noise sources as a basis for theory development. The mapping of the space-time correlations of the pressure over a distant sphere enclosing a subsonic jet revealed a number of previously unaccounted for features essential for the interpretation of the radiation field and for the modeling of the flow field.

Maestrello, L.↗