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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Evaluation of The NSUF Reactor Activation and Damage (RAD) Calculator: Assessing the Accuracy of the Activation Calculator

Nuclear Science User Facilities developed an activation calculator as part of the Combined Material Experiment Toolbox project. The activation calculator estimates the radionuclide concentration in an irradiated sample to indicate when and where the samples may best be examined to only help with scoping the experiment. To verify the accuracy of the calculator, the results from the specific gamma dose rate [mrem/hr/g] at various cooldown times were compared to equivalent results generated in ORIGEN. Most elements were tested as a sample composed solely of that element. These samples were exposed to thirteen different lengths of irradiation in all reactor positions included in the calculator. For elements of interest (i.e., ones currently included in the Nuclear Fuels and Materials Library), 83% of the test cases fell within the allowed tolerance for this scoping tool of ±50%. The overall error is logarithmic with irradiation length and is almost completely independent of reactor position. The primary source of error is missing nuclear data and reactions. NSUF believes that the RAD Calculator can be deployed to the user community because it is designed to provide estimates to aid researchers in planning experiments, and users are cautioned about the limitations of the calculator.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2016

The NuSTAR extragalactic surveys: the number counts of active galactic nuclei and the resolved fraction of the cosmic X-ray background

We present the 3–8 keV and 8–24 keV number counts of active galactic nuclei (AGNs) identified in the Nuclear Spectroscopic Telescope Array (NuSTAR) extragalactic surveys. NuSTAR has now resolved 33%–39% of the X-ray background in the 8–24 keV band, directly identifying AGNs with obscuring columns up to ∼10{sup 25} cm{sup −2}. In the softer 3–8 keV band the number counts are in general agreement with those measured by XMM-Newton and Chandra over the flux range 5×10{sup −15} ≲ S(3–8 keV)/erg s{sup −1} cm{sup −2} ≲ 10{sup −12} probed by NuSTAR. In the hard 8–24 keV band NuSTAR probes fluxes over the range 2×10{sup −14} ≲ S(8–24 keV)/erg s{sup −1} cm{sup −2} ≲ 10{sup −12}, a factor ∼100 fainter than previous measurements. The 8–24 keV number counts match predictions from AGN population synthesis models, directly confirming the existence of a population of obscured and/or hard X-ray sources inferred from the shape of the integrated cosmic X-ray background. The measured NuSTAR counts lie significantly above simple extrapolation with a Euclidian slope to low flux of the Swift/BAT 15–55 keV number counts measured at higher fluxes (S(15–55 keV) ≳ 10{sup −11} erg s{sup −1} cm{sup −2}), reflecting the evolution of the AGN population between the Swift/BAT local (z<0.1) sample and NuSTAR’s z∼1 sample. CXB synthesis models, which account for AGN evolution, lie above the Swift/BAT measurements, suggesting that they do not fully capture the evolution of obscured AGNs at low redshifts.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Reverberation Mapping of Optical Emission Lines in Five Active Galaxies

We present the first results from an optical reverberation mapping campaign executed in 2014 targeting the active galactic nuclei (AGNs) MCG+08-11-011, NGC 2617, NGC 4051, 3C 382, and Mrk 374. Our targets have diverse and interesting observational properties, including a “changing look” AGN and a broad-line radio galaxy. Based on continuum-H β lags, we measure black hole masses for all five targets. We also obtain H γ and He ii λ 4686 lags for all objects except 3C 382. The He ii λ 4686 lags indicate radial stratification of the BLR, and the masses derived from different emission lines are in general agreement. The relative responsivities of these lines are also in qualitative agreement with photoionization models. These spectra have extremely high signal-to-noise ratios (100–300 per pixel) and there are excellent prospects for obtaining velocity-resolved reverberation signatures.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2003

An Arabidopsis Ran-binding protein, AtRanBP1c, is a co-activator of Ran GTPase-activating protein and requires the C-terminus for its cytoplasmic localization

Ran-binding proteins (RanBPs) are a group of proteins that bind to Ran (Ras-related nuclear small GTP-binding protein), and thus either control the GTP/GDP-bound states of Ran or help couple the Ran GTPase cycle to a cellular process. AtRanBP1c is a Ran-binding protein from Arabidopsis thaliana (L.) Heynh. that was recently shown to be critically involved in the regulation of auxin-induced mitotic progression [S.-H. Kim et al. (2001) Plant Cell 13:2619-2630]. Here we report that AtRanBP1c inhibits the EDTA-induced release of GTP from Ran and serves as a co-activator of Ran-GTPase-activating protein (RanGAP) in vitro. Transient expression of AtRanBP1c fused to a beta-glucuronidase (GUS) reporter reveals that the protein localizes primarily to the cytosol. Neither the N- nor C-terminus of AtRanBP1c, which flank the Ran-binding domain (RanBD), is necessary for the binding of PsRan1-GTP to the protein, but both are needed for the cytosolic localization of GUS-fused AtRanBP1c. These findings, together with a previous report that AtRanBP1c is critically involved in root growth and development, imply that the promotion of GTP hydrolysis by the Ran/RanGAP/AtRanBP1c complex in the cytoplasm, and the resulting concentration gradient of Ran-GDP to Ran-GTP across the nuclear membrane could be important in the regulation of auxin-induced mitotic progression in root tips of A. thaliana.

NASA Discipline Plant Biology↗
NASA NTRS1993

Staphylococcus-mediated T-cell activation and spontaneous natural killer cell activity in the absence of major histocompatibility complex class II molecules

We used major histocompatibility complex class II antigen-deficient transgenic mice to show that in vitro natural killer cell cytotoxicity and T-cell activation by staphylococcal exotoxins (superantigens) are not dependent upon the presence of major histocompatibility complex class II molecules. T cells can be activated by exotoxins in the presence of exogenously added interleukin 1 or 2 or in the presence of specific antibody without exogenously added cytokines.

Non-NASA Center↗
NASA NTRS2022

Low-Speed Performance Enhancement using Localized Active Flow Control: Integration Study of Localized Active Flow Control on a Performance Reference Aircraft (3/4)

A study of conceptual integration and performance aspects of localized active flow control (AFC) technology onto wings of short-to-medium-range project passenger airplanes is summarized. Using predicted aerodynamic performance improvement opportunities on the CFD Reference Aircraft, estimated benefit opportunities for conceptual implementation of studied wing localized active flow control (AFC) technology for low-speed (take-off and landing) application on a Performance Reference Aircraft configuration are presented. Using conceptual AFC systems and structural integration weight penalties for studied concepts, potential relevant net performance benefits can be obtained with reliable AFC in takeoff and landing. The conceptual integration study identifies potential promising localized wing AFC application opportunities for high-lift conditions using energy sources for modern aircraft. Material benefits are estimated for take-off and landing configurations for selected localized AFC applications. Next steps to refine and expand results of investigated topics, as well as possible other local AFC wing applications, are suggested.

AFC↗
DOE OSTI2018

Determining the Activation Network of Stainless Steel in Different Neutron Energy Regimes and Decay Scenarios Using Foil Activation Experiments and FISPACT-II Calculations

Here, the activation network of stainless steel grade 304 was investigated using foil activation experiments from two neutron sources, along with FISPACT-II calculations. A critical assembly and d+Be converter were used as neutron sources to cover different neutron energy ranges. Experimental production rates were compared against calculated values from FISPACT-II in order to validate neutron energy distributions and assess available cross-section data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Ice nucleation activity of diesel soot particles at Cirrus relevant conditions: Effects of hydration, secondary organics coating, hydration, soot morphology, and coagulation

The role of atmospheric relevant soot particles that are processed in the atmosphere toward ice nucleation at cirrus cloud condition is poorly understood. In this study, the ice nucleating properties of diesel soot particles subjected to various physical and chemical aging treatments were investigated at temperatures ranging from -40 to -50 °C. We show that bare soot particles nucleate ice in deposition mode, but coating with secondary organics suppresses the heterogeneous ice nucleation potential of soot particles requiring homogeneous freezing threshold conditions. However, the ice nucleation efficiency of soot particles coated with an aqueous organic layer was similar to bare soot particles. Hydration of bare soot particles slightly enhanced the ice nucleation efficiency, and the IN abilities of compact soot particles (roundness = ~ 0.6) were similar to bare lacey soot particles (roundness = ~ 0.4). These results indicate that ice nucleation properties are sensitive to the various aging treatments.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2021

Enhancing Oxygen Reduction Activity and Cr Tolerance of Solid Oxide Fuel Cell Cathodes by a Multiphase Catalyst Coating

Intermediate temperature solid oxide fuel cells (IT-SOFCs) are cost-effective and efficient energy conversion systems. Here, the sluggish oxygen reduction reaction (ORR) and the degradation of cathodes are critical challenges to the commercialization of IT-SOFCs. Here, a highly efficient multiphase (MP) catalyst coating, consisting of Ba 1–x Co 0.7 Fe 0.2 Nb 0.1 O 3–δ (BCFN) and BaCO 3 , to enhance the ORR activity and durability of the state-of-the-art lanthanum strontium cobalt ferrite (La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3–δ , LSCF) cathode is reported. The conformal MP catalyst-coated LSCF cathode shows a polarization resistance (R p ) of 0.048 Ω cm 2 at 650 °C, about one order of magnitude smaller than that of the bare LSCF. In an accelerated Cr-poisoning test, the degradation rate of the catalyst-coated LSCF electrode is 10 –3 Ω cm 2 h –1 (0.59% h –1 ) over 200 h, only one fifth of the degradation rate of the bare LSCF electrode at 750 °C. In addition, anode-supported single cells with the MP catalyst-coated LSCF cathode show a dramatically enhanced peak power density (1.4 W cm –2 vs 0.67 W cm –2 at 750 °C) and increased durability against Cr and H 2 O. Both experimental results and density functional theory-based calculations indicate that the BCFN phase improves the ORR activity while the BaCO 3 phase enhances the stability of the LSCF cathode.

solid oxide fuel cells↗
DOE OSTI2020

An Active‐Site Sulfonate Group Creates a Fast Water Oxidation Electrocatalyst That Exhibits High Activity in Acid

Abstract The storage of solar energy in chemical bonds will depend on pH‐universal catalysts that are not only impervious to acid, but actually thrive in it. Whereas other homogeneous water oxidation catalysts are less active in acid, we report a catalyst that maintained high electrocatalytic turnover frequency at pH values as low as 1.1 and 0.43 ( k cat =1501±608 s −1 and 831±254 s −1 , respectively). Moreover, current densities, related to catalytic reaction rates, ranged from 15 to 50 mA cm −2 mM −1 comparable to those reported for state‐of‐the‐art heterogeneous catalysts and 30 to 100 times greater than those measured for two prominent literature homogeneous catalysts at pH 1.1 and 0.43. The catalyst also exhibited excellent durability when a chemical oxidant was used (Ce IV , 7400 turnovers, TOF 0.88 s −1 ). Preliminary computational studies suggest that the unusual active‐site sulfonate group acts a proton relay even in strong acid, as intended.

Nash, Aaron G.↗
DOE OSTI2020

An Active–Site Sulfonate Group Creates a Fast Water Oxidation Electrocatalyst That Exhibits High Activity in Acid

The storage of solar energy in chemical bonds will depend on pH–universal catalysts that are not only impervious to acid, but actually thrive in it. Whereas other homogeneous water oxidation catalysts are less active in acid, we report a catalyst that maintained high electrocatalytic turnover frequency at pH values as low as 1.1 and 0.43 (k cat = 1501±608 s –1 and 831±254 s –1 , respectively). Moreover, current densities, related to catalytic reaction rates, ranged from 15 to 50 mA cm –2 mM –1 comparable to those reported for state–of–the–art heterogeneous catalysts and 30 to 100 times greater than those measured for two prominent literature homogeneous catalysts at pH 1.1 and 0.43. The catalyst also exhibited excellent durability when a chemical oxidant was used (Ce IV , 7400 turnovers, TOF 0.88 s –1 ). Here, preliminary computational studies suggest that the unusual active–site sulfonate group acts a proton relay even in strong acid, as intended.

14 SOLAR ENERGY↗
DOE OSTI2019

Optical and photoluminensce properties of Eu{sup 2+}-activated strontium magnesium silicate phosphors using different rare earth co-activators

Nanostructured powders of Sr{sub 1.96}MgSi{sub 2}O{sub 7}:Eu{sub 0.01}{sup 2+}, R{sub 0.01}{sup 3+} (R{sup 3+ }= Er{sup 3+}, Tm{sup 3+} and Tb{sup 3+}) have been fabricated via urea combustion technique. XRD results implied that tetragonal Sr{sub 2}MgSi{sub 2}O{sub 7} was the major phase whereas monoclinic Sr{sub 2}SiO{sub 4} and SrSiO{sub 3} were the minor phases. Meanwhile, field emission SEM textures showed the hollow spherical network-like shape structures filled with fused interconnections for the Sr{sub 1.96}MgSi{sub 2}O{sub 7}:Eu{sub 0.01}{sup 2+} sample. It has been recognized that the replacement of Sr{sup 2+} with co-dopant R{sup 3+} ions e.g. Er{sup 3+}, Tm{sup 3+} and Tb{sup 3+} considerably help obtaining homogeneous structure as well. The values of band gap energy and calculated refractive index were ultimately dependant on the ionic radius of R{sup 3+} co-doping ion. It has been suggested that the divalent activator ion (Eu{sup 2+}) was responsible for the number of PL emission spectra, while the trivalent co-activator ions (R{sup 3+}) were the key reasons for variations in the broadening and intensity of PL emission spectra.

77 NANOSCIENCE AND NANOTECHNOLOGY↗