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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Isotope alpha irradiators for radiobiological research

Radiation absorption is considered for the case where the isotopic alpha source, in the form of a flat disk, and the axially located biological object, also in the form of a flat disk, are separated by a layer of gas. Frequently the biological object is covered by a polymer film with minimal thickness for protection against radioactive contaminants. The energy of the alpha particle is calculated at the place where the absorbed dose is determined, taking into account loss of energy in air, film and tissue. The level of energy is determined by the specific loss in energy of the alpha particle arriving from the point source to a point at the biological subject.

Drasher, V.↗
NASA NTRS1976

Space Telescope science program

The advantages of an orbiting astronomical observatory are discussed. The principal consequence of having the telescope in space is that more light will be concentrated in the images, which has two effects: (1) the ability to view more accurately complex sources, and (2) the ability to detect and measure extremely faint point sources. The fact that higher resolution will reveal complex and unexpected detail is demonstrated by comparing a well-known astronomical scene with an image artifically degraded. Five scientific functions are envisaged for the Space Telescope. The first flight will feature performance of four of these functions with these four pieces of equipment: the f24 field camera, the faint object spectrograph, the infrared photometer, and the faint object camera. Astrometry will be done not by any specialized scientific instrument but with the fine guidance and pointing system.

Odell, C. R.↗
NASA NTRS1973

Gamma-ray observations of the galactic centre.

Review of observation data obtained with a portable gas-Cerenkov gamma-ray telescope flown twice from Parana, Argentina (31.8 deg S), to search for gamma radiation from the galactic center. The angular resolution of this detector is not good enough to resolve the source structure controversy, i.e. whether the gamma radiation is coming from point sources or from a diffuse source along the galactic plane. Comparisons with observation data of other investigators are presented and discussed.

Helmken, H. F.↗
NASA NTRS1992

Compact radio sources near the Galactic plane

The results of the extension of the 20-cm Galactic-plane survey reported by Zoonematkermani to Galactic latitudes of +/- 1.8 deg over the central region of the Milky Way are reported. A total of 1457 discrete radio sources down to flux densities of less than about 5 mJy, and 95 percent completion is achieved at 20 mJy. A detailed comparison of all radio sources from the survey in this longitude range with the IRAS Point Source Catalog provides classification for 13 percent of the objects, including 159 compact H II regions, and nearly 100 planetary nebulae, over 70 of which are identified. The identity of the remaining radio sources is discussed.

Helfand, D. J.↗
NASA NTRS1994

Extreme Ultraviolet Explorer Bright Source List

Initial results from the analysis of the Extreme Ultraviolet Explorer (EUVE) all-sky survey (58-740 A) and deep survey (67-364 A) are presented through the EUVE Bright Source List (BSL). The BSL contains 356 confirmed extreme ultraviolet (EUV) point sources with supporting information, including positions, observed EUV count rates, and the identification of possible optical counterparts. One-hundred twenty-six sources have been detected longward of 200 A.

Malina, Roger F.↗
NASA NTRS1997

Spectral Models of Neutron Star Magnetospheres

We revisit the association of unidentified Galactic plane EGRET sources with tracers of recent massive star formation and death. Up-to-date catalogs of OB associations, SNR's, young pulsars, H2 regions and young open clusters were used in finding counterparts for a recent list of EGRET sources. It has been argued for some time that EGRET source positions are correlated with SNR's and OB associations as a class; we extend such analyses by finding additional counterparts and assessing the probability of individual source identifications. Among the several scenarios relating EGRET sources to massive stars, we focus on young neutron stars as the origin of the gamma-ray emission. The characteristics of the candidate identifications are compared to the known gamma-ray pulsar sample and to detailed Galactic population syntheses using our outer gap pulsar model of gamma-ray emission. Both the spatial distribution and luminosity function of the candidates are in good agreement with the model predictions; we infer that young pulsars can account for the bulk of the excess low latitude EGRET sources. We show that with this identification, the gamma-ray point sources provide an important new window into the history of recent massive star death in the solar neighborhood.

Romani, Roger W.↗
NASA NTRS2016

2FHL- The Second Catalog of Hard Fermi-LAT Sources

We present a catalog of sources detected above 50 GeV by the Fermi-Large Area Telescope (LAT) in 80 months of data. The newly delivered Pass8 event-level analysis allows the detection and characterization of sources in the 50 GeV-2 TeV energy range. In this energy band, Fermi-LAT has detected 360 sources, which constitute the second catalog of hard Fermi-LAT sources (2FHL). The improved angular resolution enables the precise localization of point sources (1.7 radius at 68% C.L.) and the detection and characterization of spatially extended sources. We find that 86% of the sources can be associated with counterparts at other wavelengths, of which the majority (75%) are active galactic nuclei and the rest (11%) are Galactic sources. Only 25% of the 2FHLsources have been previously detected by Cherenkov telescopes, implying that the 2FHL provides a reservoir of candidates to be followed up at very high energies. This work closes the energy gap between the observations performed at GeV energies by Fermi-LAT on orbit and the observations performed at higher energies byCherenkov telescopes from the ground.

catalogs – gamma-rays: general↗
NASA NTRS1978

The infrared source associated with Sh 2-149

Observations at optical and infrared wavelengths of the bright infrared point source in the direction of Sh 2-149 are used to determine a spectral type (M1) and luminosity class (Ib-II) for the object. These observations contradict the suggestion of Bergeat et al. (1975) that the object is a highly reddened O star. The estimated visual extinction (approximately 5-7 magnitudes) and luminosity class derived from the present observations are used to estimate the distance (about 1-3 kpc) to the infrared source.

Russell, R. W.↗
NASA NTRS1978

Sound propagation through a subsonic jet due to a source near the duct exit

Matched asymptotic solutions are constructed for the acoustic potentials of a periodic point source located in a two-dimensional subsonic jet near the exit of the duct with the ratio of the duct thickness to the acoustic wave length as the small parameter. The leading term of the far field solution has the same directionality effect as that for an infinite jet without the duct and that when the plane at the duct exit is considered to be a plane of symmetry. However, the intensity is different because of the wave propagation into the duct and is dependent on the location of the source.

Ting, L.↗
DOE OSTI2020

The effects of earth model uncertainty on the inversion of seismic data for seismic source functions

SUMMARY We use Monte Carlo simulations to explore the effects of earth model uncertainty on the estimation of the seismic source time functions that correspond to the six independent components of the point source seismic moment tensor. Specifically, we invert synthetic data using Green’s functions estimated from a suite of earth models that contain stochastic density and seismic wave-speed heterogeneities. We find that the primary effect of earth model uncertainty on the data is that the amplitude of the first-arriving seismic energy is reduced, and that this amplitude reduction is proportional to the magnitude of the stochastic heterogeneities. Also, we find that the amplitude of the estimated seismic source functions can be under- or overestimated, depending on the stochastic earth model used to create the data. This effect is totally unpredictable, meaning that uncertainty in the earth model can lead to unpredictable biases in the amplitude of the estimated seismic source functions.

58 GEOSCIENCES↗
DOE OSTI2021

PNNL Sequim Campus Radionuclide Air Emissions Report for Calendar Year 2020

The U.S. Department of Energy Office of Science (DOE-SC) Pacific Northwest Site Office has oversight and stewardship duties associated with the Pacific Northwest National Laboratory Sequim Campus. Some research projects have the potential to emit low levels of radioactive materials. This report is prepared to document compliance with the Code of Federal Regulation, Title 40, Protection of the Environment, Part 61, National Emission Standards for Hazardous Air Pollutants, Subpart H, “National Emission Standards for Emissions of Radionuclides Other than Radon from Department of Energy Facilities” and Washington Administrative Code Chapter 246-247, "Radiation Protection–Air Emissions." Compliance is indicated by comparing the estimated effective dose equivalent (EDE) to the maximally exposed individual (MEI) member of the public with the 10 millirem per year (mrem/yr) U.S. Environmental Protection Agency (EPA) standard. The PNNL Sequim Campus has only fugitive emissions sources. Despite the fact that the regulations are intended for application to point source emissions, fugitive emissions are included with regard to complying with the EPA standard. The EDE to the Campus MEI due to routine operations in 2020 was 3.5E-05 mrem (3.5E-07 mSv). No non-routine emissions occurred in 2020. The Sequim Campus is in compliance with the federal and state 10 mrem/yr standard.

40 CFR 61 Subpart H↗
DOE OSTI2022

PNNL Sequim Campus Radionuclide Air Emissions Report for Calendar Year 2021

The U.S. Department of Energy Office of Science (DOE-SC) Pacific Northwest Site Office has oversight and stewardship duties associated with the Pacific Northwest National Laboratory Sequim Campus. Some research projects have the potential to emit low levels of radioactive materials. This report is prepared to document compliance with the Code of Federal Regulation, Title 40, Protection of the Environment, Part 61, National Emission Standards for Hazardous Air Pollutants, Subpart H, “National Emission Standards for Emissions of Radionuclides Other than Radon from Department of Energy Facilities” and Washington Administrative Code Chapter 246-247, "Radiation Protection–Air Emissions." Compliance is indicated by comparing the estimated effective dose equivalent (EDE) to the maximally exposed individual (MEI) member of the public with the 10 millirem per year (mrem/yr) U.S. Environmental Protection Agency (EPA) standard. The PNNL Sequim Campus has only fugitive emissions sources. Despite the fact that the regulations are intended for application to point source emissions, fugitive emissions are included with regard to complying with the EPA standard. The EDE to the Campus MEI due to routine operations in 2021 was 5.4E-05 mrem (5.4E-07 mSv). No non-routine emissions occurred in 2021. The Sequim Campus is in compliance with the federal and state 10 mrem/yr standard.

40 CFR 61 Subpart H↗
DOE OSTI2023

PNNL-Sequim Campus Radionuclide Air Emissions Report for Calendar Year 2022

The U.S. Department of Energy Office of Science (DOE-SC) Pacific Northwest Site Office has oversight and stewardship duties associated with the Pacific Northwest National Laboratory Sequim Campus. Some research projects have the potential to emit low levels of radioactive materials. This report is prepared to document compliance with the Code of Federal Regulation, Title 40, Protection of the Environment, Part 61, National Emission Standards for Hazardous Air Pollutants, Subpart H, “National Emission Standards for Emissions of Radionuclides Other than Radon from Department of Energy Facilities” and Washington Administrative Code Chapter 246-247, "Radiation Protection–Air Emissions." Compliance is indicated by comparing the estimated effective dose equivalent (EDE) to the maximally exposed individual (MEI) member of the public with the 10 millirem per year (mrem/yr) U.S. Environmental Protection Agency (EPA) standard. The PNNL-Sequim Campus has only fugitive emissions sources. Despite the fact that the regulations are intended for application to point source emissions, fugitive emissions are included with regard to complying with the EPA standard. The EDE to the Campus MEI due to routine operations in 2022 was 7.5E-07 mrem (7.5E-09 mSv). No non-routine emissions occurred in 2022. The PNNL-Sequim Campus is in compliance with the federal and state 10 mrem/yr standard.

40 CFR 61 Subpart H↗
DOE OSTI2023

Identification of Galaxy–Galaxy Strong Lens Candidates in the DECam Local Volume Exploration Survey Using Machine Learning

We perform a search for galaxy–galaxy strong lens systems using a convolutional neural network (CNN) applied to imaging data from the first public data release of the DECam Local Volume Exploration Survey, which contains ~520 million astronomical sources covering ~4000 deg 2 of the southern sky to a 5σ point–source depth of g = 24.3, r= 23.9, i = 23.3, and z = 22.8 mag. Following the methodology of similar searches using Dark Energy Camera data, we apply color and magnitude cuts to select a catalog of ~11 million extended astronomical sources. After scoring with our CNN, the highest-scoring 50,000 images were visually inspected and assigned a score on a scale from 0 (not a lens) to 3 (very probable lens). We present a list of 581 strong lens candidates, 562 of which are previously unreported. We categorize our candidates using their human-assigned scores, resulting in 55 Grade A candidates, 149 Grade B candidates, and 377 Grade C candidates. We additionally highlight eight potential quadruply lensed quasars from this sample. Due to the location of our search footprint in the northern Galactic cap (b > 10 deg) and southern celestial hemisphere (decl. < 0 deg), our candidate list has little overlap with other existing ground-based searches. Where our search footprint does overlap with other searches, we find a significant number of high-quality candidates that were previously unidentified, indicating a degree of orthogonality in our methodology. We report properties of our candidates including apparent magnitude and Einstein radius estimated from the image separation.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1976

Electron transport and the magnetic field in the Crab Nebula

Observational data obtained at radio, optical, and X-ray frequencies on the size of the emission region in the Crab Nebula are used to examine various energy-transport models. It is shown that the data cannot be fitted by diffusion models, even when the energy-injection region is extended. A more favorable comparison is made with an extended source model in which bulk motion is the transport mechanism. Assuming a point source of electrons and a uniform nebular magnetic field, a perpendicular magnetic-field component of less than 0.0008 gauss is determined. Combining this with the lower limit obtained from gamma-ray observations, a perpendicular field component of between 0.0005 and 0.0008 gauss is obtained. A break in the size dependence is predicted at about 12 microns and 45 keV. Above 45 keV, the size should decrease as the inverse square root of proton energy.

Wolff, R. S.↗
NASA NTRS1992

Underground muons from the direction of Cygnus X-3

The flux of underground muons from the direction of the binary Cygnus X-3 was measured by the Soudan 2 proton decay detector. This time-projection calorimeter is located at a depth of 2200 m (water equivalent) in northern Minnesota at latitude 48 deg N, longitude 92 deg W. An analysis was then performed that compared both the total observed flux and the observed flux per transit with the number of events expected in the absence of a source. This expected number of events was determined by combining the detector acceptance as a function of time with detector acceptance as a function of the local spatial coordinates. These functions were evaluated by use of off-source events. The direction of Cygnus X-3 was defined as a 2 deg half-angle cone, centered on the nominal source coordinates. This definition is consistent with the expected appearance of a point source in the Soudan 2 detector after consideration of track reconstruction errors, multiple scattering in the rock, and possible systematic effects. Details of the analysis and the results are presented.

Marshak, M. L.↗
NASA NTRS1994

Estimates of ozone response to various combinations of NO(x) and VOC emission reductions in the eastern United States

There is increasing recognition that controls on NO(x) emissions may be necessary, in addition to existing and future Volatile Organic Compounds (VOC) controls, for the abatement of ozone (O3) over portions of the United States. This study compares various combinations of anthropogenic NO(x) and VOC emission reductions through a series of model simulations. A total of 6 simulations were performed with the Regional Oxidant Model (ROM) for a 9-day period in July 1988. Each simulation reduced anthropogenic NO(x) and VOC emissions across-the-board by different amounts. Maximum O3 concentrations for the period were compared between the simulations. Comparison of the simulations suggests that: (1) NO(x) controls may be more effective than VOC controls in reducing peak O3 over most of the eastern United States; (2) VOC controls are most effective in urban areas having large sources of emissions; (3) NO(x) controls may increase O3 near large point sources; and (4) the benefit gained from increasing the amount of VOC controls may lessen as the amount of NO(x) control is increased. This paper has been reviewed in accordance with the U.S. Environmental Protection Agency's peer and administrative review policies and approved for presentation and publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

Roselle, Shawn J.↗