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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Multifrequency Studies

The present report concerns the following projects 'Multifrequency observations of the BL Lacertae object MK 421"; "EUVE and multifrequency observations of the quasars 3C 273 and 3C 279"; "EUVE observations of the symbiotic star RAquarii"; and "Morphology of the local HI void and ionization of He in the local ISM". The common theme of the above projects is UV observations and analysis of a wide range of astrophysical classes or objects, from the diffuse interstellar medium, to symbiotic stars (R Aqr), to active galactic nuclei (AGNs). Understanding the local (primarily neutral hydrogen or HI) interstellar medium is of great importance to detecting nearby EUV sources. Specifically, the ionization of helium is strongly influencing the extinction in the extreme ultraviolet (EUV) and the optical depth can vary almost by an order of magnitude depending on the degree of ionization of various species including neutral helium Vel ) and singly ionized helium (Hell). The local interstellar medium (ISM) contains a giant void. Understanding the local ISM and the extent of the HI void engulfing the Sun is crucial to our understanding of the EUV emission from nearby strongly EUV-emitting stars like R Aqr, as well as subtracting local absorption effects from absorption effects in distant sources themselves such as quasars, BL Lacertae objects and AGNs in general. A compilation of known properties of the local ISM with appropriate references has been performed. R Aqr is a symbiotic stellar system comprised of a mass-losing approx.1 - 2 solar mass Mira- like long period variable with a 387 day period and a approx. solar mass,) hot companion/accretion disk that is believed to give rise to the symmetrical jet seen at UV, optical radio wavelengths. Recent observations of R Aqr have been conducted at continuum wavelengths with the Very Large Array (VLA) at 7 mm that have resolved the stellar components in RAqr and a geometrical distance of approx. 200pc has been obtained, confirming that R Aqr is the nearest symbiotic star system to the Sun. The status of the local ISM is, therefore, of great importance in attempting to understand the UV properties of the hot companion in R Aqr and its prominent jet. Here a multifrequency approach is required from both ground observations (e.g. with the VLA) as well as from space-borne observations (with the International Ultraviolet Explorer-IUE; and the Hubble Space Telescope-HST). The R Aqr jet has been observed with the VLA B-configuration at two epochs separated by approx. 13.2 yr. Comparison of the resulting 6 cm continuum images show that the radio jet has undergone a lateral counterclockwise rotation of approx. 6 deg - 12 deg on the plane of the sky. Comparison of the most recent radio image with a nearly contemporaneous HSTIFOC ultraviolet image at approx 2330 A suggests that the UV emission lies along the leading edge of the rotating radio jet.

Kafatos, Menas↗
NASA NTRS1972

Effects of interplanetary magnetic field azimuth on auroral zone and polar cap magnetic activity

During relatively quiet times in the period 1964-1968, AE is found to be greater when the interplanetary magnetic field (b sub IMF) is directed toward the sun in Jan., Feb., and Apr., and when B sub IMF is directed away from the sun in Oct. to Dec. Using Murmansk hourly H values and the AE components, AU and AL, it is shown that this sector dependence is present only in the negative H deviations. This observation supports the idea that negative bay magnitudes are determined chiefly by particle-produced ionization, while positive bay magnitudes are rather insensitive to increases in particle precipitation. The ratio of DP2-type magnetic activity in the southern polar cap to that in the northern polar cap is found to be greater by a factor of about 1.75 for B sub IMF toward the sun.

Burch, J. L.↗
DOE OSTI2026

Low-Temperature Non-Oxidative Coupling of Methane on Atomically Dispersed Titanium–Aluminum–Boron Nanopowder

Nonoxidative coupling of methane represents a long-standing challenge in heterogeneous catalysis, as it requires activation of the carbon–hydrogen (C–H) bond, controlled carbon–carbon (C–C) bond formation, and effective hydrogen management without relying on oxidants. Here, we report a low-temperature C–H activation and nonoxidative C–C coupling of methane over atomically dispersed titanium–aluminum–boron nanopowder (Ti–Al–B NP) utilizing a catalytic microreactor coupled to synchrotron single-photon photoionization reflectron time-of-flight mass spectrometry. The soft-ionization, in situ probing method detects the nascent reaction products and radical intermediates under operando conditions, including methyl radical, C2 hydrocarbons, and molecular hydrogen. Methane activation is initiated at 800 K, approximately 700 K below the gas-phase decomposition threshold, leading predominantly to ethylene formation with selectivity reaching up to 78% among the C–C coupled products. Electronic structure calculations on model Ti–Al–B clusters elucidate a cooperative catalytic mechanism in which titanium enables methane adsorption and C–H activation, boron acts as a reversible hydrogen reservoir, and aluminum stabilizes methylene intermediates, thereby facilitating selective C–C coupling and dehydrogenation. These findings establish a distinct catalyst architecture for nonoxidative methane coupling based on earth abundant elements alternative to expensive platinum and other noble metal-containing conventional catalysts and provide molecular-level design principles for controlling dehydrogenation and subsequent C–C bond formation in challenging light alkane conversions.

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

The co-evolution of strong AGN and central galaxies in different environments

We exploit a sample of 80 000 Sloan Digital Sky Survey central galaxies to investigate the effect of active galactic nucleus (AGN) feedback on their evolution. We trace the demographics of optically selected AGN (Seyferts) as a function of their internal properties and environment. We find that the preeminence of AGN as the dominant ionizing mechanism increases with stellar mass, overtaking star formation for galaxies with M stellar ≥ 10 10 M ⊙ . The AGN fraction changes systematically with the galaxies’ star formation activity. Within the blue cloud, this fraction increases as star formation activity declines, reaching a maximum near the green valley (⁠~17 ± 4 per cent), followed by a decrease as the galaxies transition into the red sequence. This systematic trend provides evidence that AGN feedback plays a key role in regulating and suppressing star formation. In general, Seyfert central galaxies achieve an early-type morphology while they still host residual star formation. This suggests that, in all environments, the morphology of Seyfert galaxies evolves from late- to early-type before their star formation is fully quenched. Stellar mass plays an important role in this morphological transformation: while low-mass systems tend to emerge from the green valley with an elliptical morphology (T-Type ∼ −2.5 ± 0.7), their high-mass counterparts maintain a spiral morphology deeper into the red sequence. In high-stellar mass centrals, the fraction of Seyferts increases from early- to late-type galaxies, indicating that AGN feedback may be linked with the morphology and its transformation. As a result, our analysis further suggests that AGN are fuelled by their own host halo gas reservoir, but when in group centrals can also increase their gas reservoir via interactions with satellite galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1971

Circadian periodicity of resistance to ionizing radiation in the pocket mouse.

Investigation of the response of pocket mice to Co 60 irradiation delivered at two times of day - namely, the predicted high and low points of the metabolic rate. The validity of torpor as an assay of the circadian period of body temperature in pocket mice and as a basis for selecting irradiation times is examined. A study is made of the mitotic activity in the pocket mouse intestinal epithelium as an example of a physiological rhythm which might influence radiation sensitivity. The results of tests in which pocket mice were exposed to ionizing radiation at two different times of day are cited. It is found that under the investigated conditions pocket mice irradiated during their metabolically active period (2330 hr) live significantly longer than those irradiated while their metabolic rate is low (0900 hr).

Lindberg, R. G.↗
NASA NTRS1995

Wind Variability of B Supergiants: The Rapid Rotator HD 64760 (B0.5 Ib) - No. 1

We present the results of a 6 day time series of observations of the rapidly rotating B0.5 Ib star HD 64760. We point out several reasons why such intermediate luminosity B supergiants are ideal targets for wind variability studies and then present our results that show the following: continuous wind activity throughout the 6 day run with the wind never in steady state for more than a few hr; wind variability very near nu = 0 km sec(exp -1) in the resonance lines from the lower ionization stages (Al III and C II); a distinct correlation between variability in the Si III ; lambda(lambda)1300 triplets, the strong C III (lambda)1247 singlet, and the onset of extremely strong wind activity, suggesting a connection between photospheric and wind activity; long temporal coherence in the behavior of the strong absorption events; evidence for large-scale spatial coherence, implied by a whole scale, simultaneous weakening in the wind absorption over a wide range in velocities; and ionization variability in the wind accompanying the largest changes in the absorption strengths of the wind lines. In addition, modeling of the wind lines provides the following information about the state the wind in HD 64760. The number of structures on the portion of a constant velocity surface occulting the stellar disk at a particular time must be quite small, while the number on the entire constant velocity surface throughout the wind must be large. The escape probability at low velocity is overestimated by a normal beta approx. 1 velocity law, perhaps due to the presence of low-velocity shocks deep in the wind or a shallow velocity gradient at low velocity. Estimates of the ionization structure in the wind indicate that the ionization ratios are not those expected from thermal equilibrium wind models or from an extrapolation of previous O star results. The large observed q(N V)/q(Si IV) ratio is almost certainly due to distributed X-rays, but the level of ionization predicted by distributed X-ray wind models is inconsistent with the predicted mass-loss rate. Thus, it is impossible to reconcile the observed ionization ratios and the predicted mass-loss rate within the framework of the available models.

Massa, Derck↗
DOE OSTI2022

Characterization of Sequentially Extracted Soil Organic Matter by Electrospray Ionization and Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Soil organic matter (SOM) is a complex mixture of small molecules and biopolymers that are active in various biogeochemical processes. However, the chemical diversity of biopolymer-derived SOM remains poorly explored. Identifying this diversity is important because global environmental changes may well alter SOM chemistry, as field experiments are beginning to show. Here, organic solvent-extractable (DcMe-SOM), base-hydrolyzable (KOH Hy -SOM), and CuO-oxidizable (CuO Ox -SOM) SOM fractions from a forest with a long-term nitrogen addition experiment were sequentially extracted and characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with negative-ion electrospray ionization (ESI) or atmospheric pressure photoionization (APPI). From DcMe-SOM to CuO Ox -SOM, the total number of assigned formulas, average O/C ratio, aromaticity, and unsaturation degree of SOM continuously increased, while the average m/z and H/C ratio decreased. Moreover, the dominant chemical category shifted from lipid-like components to phytochemical- and protein-like components. Complementary to ESI, APPI effectively facilitated detection of additional compounds with low polarity. With long-term nitrogen addition, the average m/z, unsaturation degree, aromaticity, and oxidation state of SOM increased, and more aromatic nitrogen-containing formulas were detected in CuOOx-SOM. Our study demonstrates that chronic nitrogen deposition in forests alters both the small molecules and biopolymers of SOM fundamentally.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2010

Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) Model - An Unified Concept for Earthquake Precursors Validation

The paper presents a conception of complex multidisciplinary approach to the problem of clarification the nature of short-term earthquake precursors observed in atmosphere, atmospheric electricity and in ionosphere and magnetosphere. Our approach is based on the most fundamental principles of tectonics giving understanding that earthquake is an ultimate result of relative movement of tectonic plates and blocks of different sizes. Different kind of gases: methane, helium, hydrogen, and carbon dioxide leaking from the crust can serve as carrier gases for radon including underwater seismically active faults. Radon action on atmospheric gases is similar to the cosmic rays effects in upper layers of atmosphere: it is the air ionization and formation by ions the nucleus of water condensation. Condensation of water vapor is accompanied by the latent heat exhalation is the main cause for observing atmospheric thermal anomalies. Formation of large ion clusters changes the conductivity of boundary layer of atmosphere and parameters of the global electric circuit over the active tectonic faults. Variations of atmospheric electricity are the main source of ionospheric anomalies over seismically active areas. Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model can explain most of these events as a synergy between different ground surface, atmosphere and ionosphere processes and anomalous variations which are usually named as short-term earthquake precursors. A newly developed approach of Interdisciplinary Space-Terrestrial Framework (ISTF) can provide also a verification of these precursory processes in seismically active regions. The main outcome of this paper is the unified concept for systematic validation of different types of earthquake precursors united by physical basis in one common theory.

Pulinets, S.↗
DOE OSTI2022

Oxygen–Chlorine Chemisorption Scaling for Seawater Electrolysis on Transition Metals: The Role of Redox

To clarify what controls species oxidation selectivity in seawater electrolysis, density functional theory (DFT) is used to identify chemisorption enthalpy trends and scaling relations for the simplest relevant adsorbates (O, Cl, and H) on relevant surfaces of 3d transition metals, as well as Pd and Pt, in face-centered-cubic and, if different, their ground-state crystal structures. Approximations are tested for electron exchange-correlation (XC) and van der Waals interactions to assess their ability to reproduce experimental adsorption enthalpies of H and O on Pt(111). The vdW-uncorrected generalized gradient approximation to XC of Perdew, Burke, and Ernzerhof (PBE) agrees most closely with experiments. Using DFT-PBE thereafter, it is determined that the O chemisorption enthalpy on this wide range of transition-metal surfaces is proportional to the sum of first and second atomic ionization energies, akin to a Born–Haber cycle for a redox reaction, indicating that metal redox activity controls O chemisorption strength. Then it is shown that the O and Cl chemisorption enthalpies are strongly correlated, suggesting that the transition metals considered will oxidize unselectively water and Cl – . This strong correlation appears also for crystal reduction potentials of binary oxides and chlorides, indicating a fundamental challenge for future seawater electrode materials design.

08 HYDROGEN↗
DOE OSTI2024

A neutron fluence map of the Los Alamos National Laboratory Godiva IV critical assembly

A neutron fluence map and a total ionizing dose map of the Los Alamos National Laboratory Godiva IV fast burst critical assembly was generated using passive reactor dosimetry, comprised of sulfur pellets and thermoluminescent dosimeters. Godiva IV is an unmoderated, fast burst, critical assembly constructed of approximately 65 kg of highly enriched uranium fuel alloyed with 1.5 % molybdenum for strength. The mapping was performed during a single 75.6 ºC temperature rise burst operation, with the top and sides of the cylindrical Godiva-IV Top Hat covered in passive dosimetry. Dosimetry was placed in a symmetric pattern around the Top Hat, with higher concentrations near the control rods and burst rod. A specific portion of the lower quadrant of the burst rod was mapped to confirm a testing region where the neutron fluence varied by no more than ± 5%. The results will be used to assess the neutron, gamma, and total ionizing dose environment in three-dimensional space around the assembly for higher fidelity experiment placement, active dosimetry positioning, and radiation field characterization.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Carbon-loud SDSS BOSS type II quasars at z > 2: high-density gas or secondary production of carbon?

ABSTRACT We study the ultraviolet (UV) emission-line ratios of a sample of 145 type II quasars (QSO2s) from Sloan Digital Sky Survey iii Baryon Oscillation Spectroscopic Survey, and compare against a grid of active galactic nucleus (AGN) photoionization models with a range in gas density, gas chemical abundances, and ionization parameter. Most of the quasars are ‘carbon-loud’, with C iv/He ii ratios that are unusually high for the narrow-line region, implying higher than expected gas density (>106 cm−3) and/or significantly supersolar-relative carbon abundance. We also find that solar or supersolar nitrogen abundance and metallicity are required in the majority of our sample, with potentially significant variation between objects. Compared to radio galaxies at similar redshifts (HzRGs; z > 2), the QSO2s are offset to higher N v/He ii, C iv/He ii, and C iii]/He ii, suggesting systematically higher gas density and/or systematically higher C and N abundances. We find no evidence for a systematic difference in the N/C abundance ratio between the two types of objects. Scatter in the N iv]/C iv ratio implies a significant scatter in the N/C abundance ratio among the QSO2s and HzRGs, consistent with differences in the chemical enrichment histories between objects. Interestingly, we find that adopting secondary behaviour for both N and C alleviates the long-standing ‘N iv] problem’. A subset of the QSO2s and HzRGs also appear to be ‘silicon-loud’, with Si iii] relative fluxes suggesting Si/C and Si/O are an order of magnitude above their solar values. Finally, we propose new UV-line criteria to select genuine QSO2s with low-density narrow-line regions.

Silva, M.↗
NASA NTRS1979

Semiconductor technology program. Progress briefs

The current status of NBS work on measurement technology for semiconductor materials, process control, and devices is reported. Results of both in-house and contract research are covered. Highlighted activities include modeling of diffusion processes, analysis of model spreading resistance data, and studies of resonance ionization spectroscopy, resistivity-dopant density relationships in p-type silicon, deep level measurements, photoresist sensitometry, random fault measurements, power MOSFET thermal characteristics, power transistor switching characteristics, and gross leak testing. New and selected on-going projects are described. Compilations of recent publications and publications in press are included.

Bullis, W. M.↗
NASA NTRS1981

Modulation of Venus ion densities associated with solar variations

The dayside ion concentrations in the Venus ionosphere obtained by the Pioneer Venus orbiter ion mass spectrometer exhibit a modulation corresponding to the 27-day solar variation. Comparisons were made of the amplitudes of modulation of CO(2(+), C(+), and O2(+), with the amplitudes of the 27-day variation in the 10.7-cm solar radio flux and the simultaneously measured EUV fluxes at He II (304 A) and Lyman-beta(1026 A), together with a theoretical analysis of the effects of solar variability on the ionosphere and neutral atmosphere of Venus. This analysis leads to the conclusion that the observed modulation of dayside ion densities is primarily due to the variability in the ionizing EUV radiations and, to a much lesser extent, the result of the variability with solar activity of the neutral atmosphere via the variability in exospheric temperature. In this connection, it is also shown theoretically why the percentage variation of exospheric temperature on Venus (as observed in the ONMS data) for a given variation in the 10.7-cm radio flux is only half of the exospheric temperature variation for earth.

Bauer, S. J.↗
NASA NTRS1987

Ultraviolet Al III emission lines and the physics of the solar transition region

Two lines of the solar UV spectrum were identified as due to 3p-3d Al III transitions near 1612 A; the ratios of these lines to the 3s-3p Al III doublet near 1855 A were found to be very sensitive to temperature. Thus, the temperatures of formation of the Al III lines could be determined by using one of the line ratios in two quiet sun regions, a coronal hole, and an active region. The results were found to be consistent with expectations based on the assumption of ionization equilibrium for Al III. It is suggested that S III lines near 1350 A and 1200 A may also serve as a temperature diagnostic.

Doschek, G. A.↗
NASA NTRS1990

Effects of neutral gas releases on electron beam injection from electrically tethered spacecraft

The presence of high neutral densities at low altitudes and/or during thruster firings is known to modify the spacecraft potential during active electron beam injection. Two-dimensional (three velocity) particle simulations are used to investigate the ionization processes including the neutral density required, the modification of the spacecraft potential, beam profile and spatial distribution of the return current into the spacecraft. Three processes are identified: (1) beam-induced ionization, (2) vehicle-induced ionization, and (3) beam plasma discharge. Only in the first two cases does the beam propagate away with little distortion.

Winglee, R. M.↗
NASA NTRS1991

Solar control of the earth's emission of energetic O(+)

Energetic (0.1-16 keV/e) O(+) data obtained in the earth's plasma sheet (between 10 and 23 RE) by an ion mass spectrometer on the ISEE-1 spacecraft are compared statistically with published data on the concurrent solar wind and IMF. The most strongly variable parameter of the plasma sheet O(+) is its density, which is found to be well correlated with certain solar wind parameters, especially with the solar wind flow speed and the IMF component perpendicular to the flow vector. When those two solar wind parameters are combined to form an electric field (-v x B), both the number density and the energy density of the O(+) are found to vary in proportion to the square of that electric field, on average, suggesting that the emission of energetic O(+) ions from the earth may be powered by that same field. Based on this and on the previously published correlation with solar activity, it is argued that the emission of O(+) is controlled by a combination of HF (ionizing) and quasi-static (accelerating) solar electromagnetic fields.

Lennartsson, W.↗
NASA NTRS1995

Near-infrared (Fe II) and Pa Beta imaging and spectroscopy of Arp 220

We have imaged the ultraluminous infrared galaxy Arp 220 in light of the near-infrared (Fe II) 1.257 micron and Pa-beta lines, and have obtained spectra in the J- and H-band atmospheric windows. Arp 220 is a strong source of (Fe II) and Pa-beta emission, with luminosities of 1.3 x 10(exp 41) and 9.2 x 10(exp 40) ergs/s, respectively. The (Fe II) and Pa-beta emission are both extended over the central 2 sec-3 sec, but with different morphologies. We suggest that the extended (Fe II) emission is produced through the interaction of fast shocks with ambient gas in the interstellar medium (ISM) at the base of the outflowing, supernovae-driven superwind mapped by Heckman et al. (1987). The bolometric luminosity of the starburst required to power this wind is estimated to be at least 2 x 10(exp 11) solar luminosity. If the spatially unresolved (Fe II) emission is produced via a large number of supernova remnants, the implied rate is approximately 0.6/yr. The overall luminosity of such a starburst could account for a large fraction (1/2-1/3) of the Arp 220 energy budget, but the large deficit of ionizing photons (as counted by the Pa-beta luminosity) requires that the starburst be rapidly declining and/or have a low upper mass cutoff. Alternatively, dust may effectively compete with the gas for ionizing photons, or much of the ionizing radiation may escape through 'holes' in the ISM. It is also possible that a buried active galactic nuclei (AGN) produces a large fraction of the unresolved (Fe II) and Pa-beta emission. We briefly discuss these possibilities in light of these new imaging and spectroscopic data.

Armus, L.↗
NASA NTRS1998

Flow Tube Studies of Gas Phase Chemical Processes of Atmospheric Importance

The objective of this project is to conduct measurements of elementary reaction rate constants and photochemical parameters for processes of importance in the atmosphere. These measurements are being carried out under temperature and pressure conditions covering those applicable to the stratosphere and upper troposphere, using the chemical ionization mass spectrometry turbulent flow technique developed in our laboratory. The next section summarizes our research activities during the first year of the project, and the section that follows consists of the statement of work for the third year. Additional details concerning the projects listed in the statement of work were described in our original proposal.

Molina, Mario J.↗