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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Structure and Synthesizability of Iron–Sulfur Metal–Organic Frameworks

Sulfur-based metal–organic frameworks (MOFs) and coordination polymers (CPs) are an emerging class of hybrid materials that have received growing attention due to their magnetic, conductive, and catalytic properties with potential applications in electrocatalysis and energy storage. In this work, we report a high-throughput virtual screening protocol to predict the synthesizability of candidate metal–sulfur MOFs/CPs by computing the thermodynamically stable structures resulting from a particular combination of metal cluster, linker, cation, and synthetic conditions. Free energies are computed by using all-atom classical mechanical thermodynamic integration. Low-free-energy structures are refined using ab initio density functional theory, and pair distribution functions and powder X-ray diffraction patterns are calculated to complement and guide experimental structure determination. We validate the computational approach by retrospective predictions of the stable structure produced by experimental syntheses, and a subsequent screen predicts Fe 4 S 4 -BDT–TPP as a new thermodynamically stable one-dimensional (1D) CP comprising a redox-active Fe 4 S 4 cluster, a 1,4-benzenedithiolate (BDT) linker, and a tetraphenylphosphonium (TPP) countercation. Furthermore, this material is experimentally synthesized, and the 1D chain structure of the crystal is confirmed using microcrystal electron diffraction. The computational screening pipeline is generically transferable to neutral and ionic MOFs/CPs comprising arbitrary metal clusters, linkers, cations, and synthetic conditions, and we make it freely available as an open source tool to guide and accelerate the discovery and engineering of novel porous materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

A functional map of HIV-host interactions in primary human T cells

Human Immunodeficiency Virus (HIV) relies on host molecular machinery for replication. Systematic attempts to genetically or biochemically define these host factors have yielded hundreds of candidates, but few have been functionally validated in primary cells. Here, we target 426 genes previously implicated in the HIV lifecycle through protein interaction studies for CRISPR-Cas9-mediated knock-out in primary human CD4+ T cells in order to systematically assess their functional roles in HIV replication. We achieve efficient knockout (>50% of alleles) in 364 of the targeted genes and identify 86 candidate host factors that alter HIV infection. 47 of these factors validate by multiplex gene editing in independent donors, including 23 factors with restrictive activity. Both gene editing efficiencies and HIV-1 phenotypes are highly concordant among independent donors. Importantly, over half of these factors have not been previously described to play a functional role in HIV replication, providing numerous novel avenues for understanding HIV biology. These data further suggest that host-pathogen protein-protein interaction datasets offer an enriched source of candidates for functional host factor discovery and provide an improved understanding of the mechanics of HIV replication in primary T cells.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Sub-threshold ultrafast one-photon photoemission from a Cu(111) photocathode

Single-photon photoemission of electrons for incident photon energies below the surface work function is reported for a single-crystal Cu(111) photocathode. Spectral characterization of the quantum efficiency and mean transverse energy of the emitted electrons is shown to be consistent with emission from a thermalized hot electron distribution photoexcited on sub-picosecond time scales into an upper conduction band at the L-point of the Brillouin zone of copper. To our knowledge, this is the first time that such excited-state thermionic emission has been observed from a planar metal photocathode, and then from a commonly used photocathode material. The results, therefore, indicate the potential importance of such band structure dependent sub-threshold photoemission mechanisms on the performance of photocathodes employed for the generation of short electron pulses using sub-picosecond laser pulses. Consequently, the combined experimental and theoretical work presented in this paper contributes to solid-state photocathode-based research aimed at our understanding and selection (or discovery) of high brightness photo-electron sources required for many electron-based diffraction, imaging, and accelerator applications.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

An off-nucleus nonstellar black hole in the Seyfert galaxy NGC 5252

We report the discovery of an ultraluminous X-ray source (ULX; CXO J133815.6+043255) in NGC 5252. This ULX is an off-nuclear point source, which is 22″ away from the center of NGC 5252, and has an X-ray luminosity of 1.5 × 10{sup 40} erg s{sup −1}. It is one of the rare examples of a ULX, which exhibits clear counterparts in radio, optical, and UV bands. A follow-up optical spectrum of the ULX shows strong emission lines. The redshift of the [O iii] emission line coincides with the systematic velocity of NGC 5252, suggesting that the ULX is gravitationally bound to NGC 5252. The flux of [O iii] appears to be correlated with both X-ray and radio luminosity in the same manner as ordinary active galactic nuclei (AGNs), indicating that the [O iii] emission is intrinsically associated with the ULX. Based on the multiwavelength data, we argue that the ULX is unlikely to be a background AGN. A more likely option is an accreting black hole with a mass of ⩾10{sup 4} M{sub ⊙}, which might be a stripped remnant of a merging dwarf galaxy.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

SU-F-T-398: Improving Radiotherapy Treatment Planning Using Dual Energy Computed Tomography Based Tissue Characterization

Purpose: Both kVp settings and geometric distribution of various materials lead to significant change of the HU values, showing the largest discrepancy for high-Z materials and for the lowest CT scanning kVp setting. On the other hand, the dose distributions around low-energy brachytherapy sources are highly dependent on the architecture and composition of tissue heterogeneities in and around the implant. Both measurements and Monte Carlo calculations show that improper tissue characterization may lead to calculated dose errors of 90% for low energy and around 10% for higher energy photons. We investigated the ability of dual-energy CT (DECT) to characterize more accurately tissue equivalent materials. Methods: We used the RMI-467 heterogeneity phantom scanned in DECT mode with 3 different set-ups: first, we placed high electron density (ED) plugs within the outer ring of the phantom; then we arranged high ED plugs within the inner ring; and finally ED plugs were randomly distributed. All three setups were scanned with the same DECT technique using a single-source DECT scanner with fast kVp switching (Discovery CT750HD; GE Healthcare). Images were transferred to a GE Advantage workstation for DECT analysis. Spectral Hounsfield unit curves (SHUACs) were then generated from 50 to 140-keV, in 10-keV increments, for each plug. Results: The dynamic range of Hounsfield units shrinks with increased photon energy as the attenuation coefficients decrease. Our results show that the spread of HUs for the three different geometrical setups is the smallest at 80 keV. Furthermore, among all the energies and all materials presented, the largest difference appears at high Z tissue equivalent plugs. Conclusion: Our results suggest that dose calculations at both megavoltage and low photon energies could benefit in the vicinity of bony structures if the 80 keV reconstructed monochromatic CT image is used with the DECT protocol utilized in this work.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Noble-Lab/crema

Confidence Estimation for Mass Spectrometry Proteomics. Crema is an open-source Python tool that estimates the false discovery rate (FDR) of a set of peptide-spectrum matches that result from proteomics data analysis. Crema implements standard FDR estimation methods that are widely used within the field. This package is meant to be simple, easy to use, stand-along, and easy to maintain.

See, Donavan↗
DOE OSTI2019

A data ecosystem to support machine learning in materials science

Facilitating the application of machine learning to materials science problems requires enhancing the data ecosystem to enable discovery and collection of data from many sources, automated dissemination of new data across the ecosystem, and the connecting of data with materialsspecific machine learning models. Here, we present two projects, the Materials Data Facility (MDF) and the Data and Learning Hub for Science (DLHub), that address these needs. We use examples to show how MDF and DLHub capabilities can be leveraged to link data with machine learning models and how users can access those capabilities through web and programmatic interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2016

High-Energy Neutron Backgrounds for Underground Dark Matter Experiments

Direct dark matter detection experiments usually have excellent capability to distinguish nuclear recoils, expected interactions with Weakly Interacting Massive Particle (WIMP) dark matter, and electronic recoils, so that they can efficiently reject background events such as gamma-rays and charged particles. However, both WIMPs and neutrons can induce nuclear recoils. Neutrons are then the most crucial background for direct dark matter detection. It is important to understand and account for all sources of neutron backgrounds when claiming a discovery of dark matter detection or reporting limits on the WIMP-nucleon cross section. One type of neutron background that is not well understood is the cosmogenic neutrons from muons interacting with the underground cavern rock and materials surrounding a dark matter detector. The Neutron Multiplicity Meter (NMM) is a water Cherenkov detector capable of measuring the cosmogenic neutron flux at the Soudan Underground Laboratory, which has an overburden of 2090 meters water equivalent. The NMM consists of two 2.2-tonne gadolinium-doped water tanks situated atop a 20-tonne lead target. It detects a high-energy (>~ 50 MeV) neutron via moderation and capture of the multiple secondary neutrons released when the former interacts in the lead target. The multiplicity of secondary neutrons for the high-energy neutron provides a benchmark for comparison to the current Monte Carlo predictions. Combining with the Monte Carlo simulation, the muon-induced high-energy neutron flux above 50 MeV is measured to be (1.3 ± 0.2) ~ 10-9 cm-2s-1, in reasonable agreement with the model prediction. The measured multiplicity spectrum agrees well with that of Monte Carlo simulation for multiplicity below 10, but shows an excess of approximately a factor of three over Monte Carlo prediction for multiplicities ~ 10 - 20. In an effort to reduce neutron backgrounds for the dark matter experiment SuperCDMS SNO- LAB, an active neutron veto was developed. It is estimated that the current design of the neutron veto with a 40 cm thick layer of boron-doped liquid scintillator can achieve a > 90% efficiency for tagging the single-scatter neutrons. In addition, a one-quarter scale prototype detector for neutron veto has been built and tested.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Discovery of the TeV Emission from the Jet Interaction Regions of SS 433 with HAWC

The High Altitude Water Cherenkov (HAWC) observatory recently published the discovery of SS 433 as a TeV source, reporting the observation of multi-TeV gamma-ray emission from the jet interaction regions e1 and w1, suggesting in-situ particle acceleration. This showed the first direct evidence of acceleration in jets at energies greater than a few TeV. SS 433 was the first microquasar to be discovered and is still considered special in that the accretion is supercritical and the luminosity of the system is very high (~10 40 erg s -2 ). The lobes of the supernova remnant W 50 in which the jets terminate, about 40 parsecs from the central binary, are expected to accelerate charged particles, and indeed radio and X-ray emission consistent with electron synchrotron emission in a magnetic field have been observed. SS 433 has also been a strong candidate for hadronic acceleration due to spectroscopic evidence of ionized nuclei in the inner jets. However, multiwavelength fits including the HAWC measurements favor the leptonic production of the observed gamma rays. Here, we present new follow-up measurements of the jet interaction regions of SS 433 using the most recent data from HAWC.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Integrated Bioinformatic Analyses and Immune Characterization of New Neisseria gonorrhoeae Vaccine Antigens Expressed during Natural Mucosal Infection

There is an increasingly severe trend of antibiotic-resistant Neisseria gonorrhoeae strains worldwide and new therapeutic strategies are needed against this sexually-transmitted pathogen. Despite the urgency, progress towards a gonococcal vaccine has been slowed by a scarcity of suitable antigens, lack of correlates of protection in humans and limited animal models of infection. N. gonorrhoeae gene expression levels in the natural human host does not reflect expression in vitro, further complicating in vitro-basedvaccine analysis platforms. We designed a novel candidate antigen selection strategy (CASS), based on a reverse vaccinology-like approach coupled with bioinformatics. We utilized the CASS to mine gonococcal proteins expressed during human mucosal infection, reported in our previous studies, and focused on a large pool of hypothetical proteins as an untapped source of potential new antigens. Via two discovery and analysis phases (DAP), we identified 36 targets predicted to be immunogenic, membrane-associated proteins conserved in N. gonorrhoeae and suitable for recombinant expression. Six initial candidates were produced and used to immunize mice. Characterization of the immune responses indicated cross-reactive antibodies and serum bactericidal activity against different N. gonorrhoeae strains. These results support the CASS as a tool for the discovery of new vaccine candidates.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

DISCOVERY OF ULTRA-STEEP SPECTRUM GIANT RADIO GALAXY WITH RECURRENT RADIO JET ACTIVITY IN ABELL 449

We report a discovery of a 1.3 Mpc diffuse radio source with extremely steep spectrum fading radio structures in the vicinity of the Abell 449 cluster of galaxies. Its extended diffuse lobes are bright only at low radio frequencies and their synchrotron age is about 160 Myr. The parent galaxy of the extended relic structure, which is the dominant galaxy within the cluster, is starting a new jet activity. There are three weak X-rays sources in the vicinity of the cluster as found in the ROSAT survey, however it is not known if they are connected with this cluster of galaxies. Just a few radio galaxy relics are currently known in the literature, as finding them requires sensitive and high angular resolution low-frequency radio observations. Objects of this kind, which also are starting a new jet activity, are important for understanding the life cycle and evolution of active galactic nuclei. A new 613 MHz map as well as the archival radio data pertaining to this object are presented and analyzed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

UCB-GLOBES: An open-access mass spectral database of identified and unidentified atmospheric organic compounds

Chemical characterization of atmospheric organic aerosols using gas chromatography with 70 eV electron ionization mass spectrometry (GC/EI-MS) has been used for decades in advancing molecular marker detection and identification, though primarily through suspect screening and/or targeted analyses. To advance non-targeted analyses of environmental samples, we have catalogued approximately 27 000 mass spectra (MS) of the trimethylsilyl derivatives of semi-volatile organic aerosol (OA) analytes in the open-access University of California Berkeley Goldstein Library of Organic Biogenic Environmental Spectra (UCB-GLOBES). Analytes were observed in ambient samples from the U.S. and the Central Amazon and/or laboratory simulations of secondary OA (SOA) formation. These samples are representative of OA under urban and biomass burning influences as well as SOA derived from biogenic precursors (e.g., isoprene, monoterpenes, sesquiterpenes) and biomass burning intermediates. MS are documented in UCB-GLOBES without regard to known chemical identity, annotated with extensive metadata such as sample source/experimental conditions, any structural information gained from MS analyses, and predicted chemical properties such as average carbon oxidation state and carbon number. UCB-GLOBES MS are compatible for importing into the NIST MS Search program, and we have also provided a Jupyter Notebook for MS visualization and comparisons. We demonstrate the utility of UCB-GLOBES through MS reanalyses of prior analytes observed in ambient data, finding a 20 % reduction in the number of analytes assigned to OA source categories reliant solely on time series correlation and an overall 11 % increase in new MS-based OA source categorization for the Southeast U.S. For 1513 analytes observed previously in the Central Amazon, we found 375 MS matches using UCB-GLOBES vs. 136 MS matches during prior analyses, representing a 14 % gain in newly confirmed or newly categorized OA species. While OA from laboratory oxidation experiments in UCB-GLOBES are highly diverse chemically, on average only 29 % of UCB-GLOBES MS have a mass spectral match to another MS entry in UCB-GLOBES and/or in databases of known compounds (i.e. NIST MS Database, Adams Essential Oil, MANE Flavor and Fragrance Company). This indicates that roughly 70 % of UCB-GLOBES MS are unique thus far, not observed more than once among the laboratory oxidation samples and ambient data in UCB-GLOBES MS. Further, only 18 % can be positively identified using these databases or known authentic standards. This points to a large gap between these laboratory simulations and ambient OA. Overall, the UCB-GLOBES database can be utilized for improving confidence in OA source categorization and/or identification, novel chemical marker discovery, tracking chemical diversity, de novo structure and properties prediction, and improving MS search and matching algorithms. This can ultimately inform future research priorities for the chemical characterization of atmospheric organic samples.

Mass spectrometry↗
NASA NTRS1978

Discovery and optical identification of 2S0921-630

The discovery of a faint X-ray source at approximately 282 deg galactic longitude, -9 deg galactic latitude with the rotation modulation collimator X-ray detectors aboard SAS 3 is reported. The source is designated 2S 0921-630 and is tentatively identified, on the basis of an optical search, with a 17th magnitude star exhibiting the He II line at 4686 A and H-beta in emission. The optical spectrum of this star is shown to be similar to those of the optical counterparts of Sco X-1 and other such galactic X-ray sources. It is suggested that 2S 0921-630 may belong to the class of low-luminosity galactic X-ray binaries.

Li, F. K.↗
NASA NTRS1981

The Ophiuchus cluster - A bright X-ray cluster of galaxies at low galactic latitude

The discovery of an extended X-ray source identified with a cluster of galaxies at low galactic latitude is reported. The source, designated the Ophiuchus cluster, was detected near 4U 1708-23 with the HEAO 1 Scanning Modulation Collimator, and identified with the cluster on the basis of extended X-ray size and positional coincidence on the ESO/SRC (J) plate of the region. An X-ray flux density in the region 2-10 keV of approximately 25 microJ was measured, along with an X-ray luminosity of 1.6 x 10 to the 45th ergs/sec and an X-ray core radius of approximately 4 arcmin (0.2 Mpc) for an assumed isothermal sphere surface brightness distribution. The X-ray spectrum in the range 2-10 keV obtained with the HEAO 1 A-2 instrument is well fit by a thermal bremsstrahlung model with kT = 8 keV and a 6.7-keV iron line of equivalent width 450 eV. The steep-spectrum radio source MSH 17-203 also appears to be associated with the cluster, which is the closest and brightest representative of the class of X-ray clusters with a dominant central galaxy.

Johnston, M. D.↗
NASA NTRS1985

The 4U 0115+63: Another energetic gamma ray binary pulsar

Following the discovery of Her X-1 as a source of pulsed 1000 Gev X-rays, a search for emission from an X-ray binary containing a pulsar with similar values of period, period derivative and luminosity was successful. The sporadic X-ray binary 4U 0115-63 has been observed, with probability 2.5 x 10 to the minus 6 power ergs/s to emit 1000 GeV gamma-rays with a time averaged energy flux of 6 to 10 to the 35th power.

Chadwick, P. M.↗
NASA NTRS2001

Oscillations During Thermonuclear X-ray Bursts

High amplitude, nearly coherent X-ray brightness oscillations during thermonuclear X-ray bursts were discovered with the Rossi X-ray Timing Explorer (RXTE) in early 1996. Spectral and timing evidence strongly supports the conclusion that these oscillations are caused by rotational modulation of the burst emission and that they reveal the spin frequency of neutron stars in low mass X-ray binaries, a long sought goal of X-ray astronomy. Studies carried out over the past year have led to the discovery of burst oscillations in four new sources, bringing to ten the number with confirmed burst oscillations. I review the status of our knowledge of these oscillations and indicate how they can be used to probe the physics of neutron stars. For a few burst oscillation sources it has been proposed that the strongest and most ubiquitous frequency is actually the first overtone of the spin frequency and hence that two nearly antipodal hot spots are present on the neutron star. This inference has important implications for both the physics of thermonuclear burning as well as the mass - radius relation for neutron stars, so its confirmation is crucial. I discuss recent attempts to confirm this hypothesis for 4U 1636-53, the source for which a signal at the putative fundamental (290Hz) has, been claimed.

Strohmayer, Tod E.↗
NASA NTRS2004

Mapping Weak Crustal Magnetic Fields on Mars with Electron Reflectometry

One of the great surprises of the Mars Global Surveyor (MGS) mission was the discovery of intensely magnetized crust. These magnetic sources are at least ten times stronger than their terrestrial counterparts, probably requiring large volumes of coherently magnetized material, very strong remanence, or both. Perhaps the most intriguing aspect of these fields is their large scale coherence and organization into east-west stripes thousands of kilometers long. The anomalies were almost certainly created by thermoremanent magnetization (TRM) in the presence of a strong Martian dynamo. With few exceptions, the crustal fields are associated with the oldest terrain on Mars. Much of the northern lowlands appears to be non-magnetic, except for the relatively weak north polar anomalies and a few sources adja-cent to the dichotomy boundary, which appear to be associated with strongly magnetized crust south of the boundary. There is clear evidence for impact demagnetization of the Hellas, Argyre, and Isidis basins. Thus, Mars' crustal magnetic fields are among the oldest preserved geologic features on the planet.

Mitchell, D. L.↗