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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Measuring short-range correlations and quasi-elastic cross sections in A(e,e’) at x > 1 and modest Q 2

We present results from the Jefferson Lab E08-014 experiment, investigating short-range correlations (SRC) through measurements of inclusive quasi-elastic scattering from 2 H, 3 He, 4 He, 12 C, 40 Ca, and 48 Ca. The kinematics were selected to isolate scattering from SRCs, yielding a plateau in the A/ 2 H cross-section ratios due to the universal two-body structure of the 2N-SRCs in light and heavy nuclei. We observe approximate plateaus in the A/ 2 H ratios and provide the first extractions of the A/ 2 H ratio for 40 Ca and 48 Ca. We also examine the A/ 3 He ratio, aiming to identify three-nucleon SRCs (3N-SRCs). Following the approach for isolating 2N-SRCs, searching for 3N-SRC dominance involved measuring the A/ 3 He cross section ratio at modest-to-large Q 2 values and looking for a plateau ratios for x ≳ 2.5. This was not observed in the data, and in fact increasing Q 2 values moved the data further away from the predicted plateau. We show here that, when analyzed in terms of the struck nucleon’s light-cone momentum, the data exhibited the expected trend, progressively approaching the predicted 3N-SRC plateau. These observations suggest that future measurements at higher energies may facilitate a definitive isolation and identification of 3N-SRCs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Complexions at the iron-magnetite interface

Synthesizing distinct phases and controlling crystalline defects are key concepts in materials design. These approaches are often decoupled, with the former grounded in equilibrium thermodynamics and the latter in nonequilibrium kinetics. By unifying them through defect phase diagrams, we can apply phase equilibrium models to thermodynamically evaluate defects—including dislocations, grain boundaries, and phase boundaries—establishing a theoretical framework linking material imperfections to properties. Using scanning transmission electron microscopy (STEM) with differential phase contrast (DPC) imaging, we achieve the simultaneous imaging of heavy Fe and light O atoms, precisely mapping the atomic structure and chemical composition at the iron-magnetite (Fe/Fe 3 O 4 ) interface. We identify a well-ordered two-layer interface-stabilized phase state (referred to as complexion) at the Fe[001]/Fe 3 O 4 [001] interface. Using density-functional theory (DFT), we explain the observed complexion and map out various interface-stabilized phases as a function of the O chemical potential. The formation of complexions increases interface adhesion by 20% and alters charge transfer between adjacent materials, impacting transport properties. Our findings highlight the potential of tunable defect-stabilized phase states as a degree of freedom in materials design, enabling optimized corrosion protection, catalysis, and redox-driven phase transitions, with applications in materials sustainability, efficient energy conversion, and green steel production.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Decoupled few-femtosecond phase transitions in vanadium dioxide

Abstract The nature of the insulator-to-metal phase transition in vanadium dioxide (VO 2 ) is one of the longest-standing problems in condensed-matter physics. Ultrafast spectroscopy has long promised to determine whether the transition is primarily driven by the electronic or structural degree of freedom, but measurements to date have been stymied by their sensitivity to only one of these components and/or their limited temporal resolution. Here we use ultra-broadband few-femtosecond pump-probe spectroscopy to resolve the electronic and structural phase transitions in VO 2 at their fundamental time scales. Our experiments show that the system transforms into a bad-metallic phase within 10 fs after photoexcitation, but requires another 100 fs to complete the transition, during which we observe electronic oscillations and a partial re-opening of the bandgap, signalling a transient semi-metallic state. Comparisons with tensor-network simulations and density-functional theory calculations show these features result from an unexpectedly fast structural transition, in which the vanadium dimers separate and untwist with two different timescales. Our results resolve the structural and electronic nature of the light-induced phase transition in VO 2 and establish ultra-broadband few-femtosecond spectroscopy as a powerful tool for studying quantum materials out of equilibrium.

Science & Technology - Other Topics↗
DOE OSTI2024

High repetition-rate 0.5 Hz broadband neutron source driven by the Advanced Laser Light Source

Neutron beams are an essential tool to investigate material structure and perform nondestructive analysis, as they give unique access to element composition, thus ideally complementing density analysis allowed by standard x-rays investigation. Laser-driven neutron sources, though compact and cost-effective, currently have lower average flux than conventional neutron sources, due to the limited repetition rate of the lasers used so far. However, advancements in laser technology allow nowadays to address this challenge. Here, we report results obtained at the Advanced Laser Light Source characterizing stable production of broadband (0.1–2 MeV) neutrons produced at a high repetition rate (0.5 Hz). The interaction of laser pulses of 22 fs duration and 3.2 J on-target energy with 2-μm-thick tantalum targets produced protons in the Target Normal Sheath Acceleration (TNSA) regime up to 7.3 MeV. These protons were subsequently converted into neutrons by (p,n) reactions in lithium fluoride (LiF). Activation measurements and bubble detectors were used to characterize neutron emissions, with a neutron fluence of up to ∼1.4×105 neutrons/shot/sr and energies mainly between a few hundred of kilo-electron volt and 2 MeV. The total neutron yield was ∼5×105 neutrons/shot. This paves the way for numerous applications, e.g., in homeland security, materials science, or cultural heritage.

Physics↗
DOE OSTI2024

Structural, biophysical, and biochemical insights into C–S bond cleavage by dimethylsulfone monooxygenase

Sulfur is an essential element for life. Bacteria can obtain sulfur from inorganic sulfate; but in the sulfur starvation–induced response,Pseudomonadsemploy two-component flavin-dependent monooxygenases (TC-FMOs) from themsuandsfnoperons to assimilate sulfur from environmental compounds including alkanesulfonates and dialkylsulfones. Here, we report binding studies of oxidized FMN to enzymes involved within theP. fluorescensenzymatic pathway responsible for converting dimethylsulfone (DMSO 2 ) to sulfite. In this catabolic pathway, SfnG serves as the initial TC-FMO for sulfur assimilation, which is investigated in detail by solving the 2.6-Å resolution crystal structure of unliganded SfnG and the 1.75-Å resolution crystal structure of the SfnG ternary complex containing FMN and DMSO 2 . We find that SfnG adopts a (β/α) 8 barrel fold with a distinct quaternary configuration from other tetrameric class C TC-FMOs. To probe the unexpected tetramer arrangement, structural heterogeneity is assessed by chromatography and light scattering to confirm ligand binding correlates with a tetramer. Binding of FMN and DMSO 2 accompanies ordering of the active site, with DMSO 2 bound on thesi-face of the flavin. A previously unobserved protein backbone conformation is found within the oxygen-binding site on there-face of the flavin. Functional assays and the positioning of ligands with respect to the oxygen-binding site are consistent with use of an N5-(hydro)peroxyflavin pathway. Biochemical endpoint assays and docking studies reveal SfnG breaks the C–S bond of a range of dialkylsulfones.

Science & Technology - Other Topics↗
DOE OSTI2025

Structural and magnetic properties of CoTeMo⁢O 6

Here, we have conducted a comprehensive investigation into the magnetic properties of the chiral multiferroic material CoTeMo⁢O 6 . In contrast with the previous claim of canted antiferromagnetic order with ferromagnetic components [Y. Doi et al., J. Solid State Chem. 182, 3232 (2009)], our investigation reveals an antiferromagnetic ground state with compensated moments, providing an interesting platform for exploring exotic material properties. Through careful measurements of magnetization under a series of applied fields, we demonstrate that there exist two sequential field-induced magnetic transitions in CoTeMo⁢O 6 , with one occurring at 𝐻 𝑐⁢1 =460 Oe along the 𝑎 axis, and the other at 𝐻 𝑐⁢2 =1.16 T with the field along the 𝑏 axis. The values of 𝐻 𝑐⁢1 and 𝐻 𝑐⁢2 exhibit strong angular dependence and diverge with different rates as the applied field is rotated 90 ° within the 𝑎⁢𝑏 plane. This reflects the distinct nature of these transitions, which is further supported by the different critical behavior of 𝐻 𝑐⁢1 and 𝐻 𝑐⁢2 , characterized by the values of 𝛾, in the function of 𝐻 𝑐 =𝐻 0 ⁡(1−𝑇/𝑇 𝑐 ) 𝛾 . Furthermore, we have demonstrated that there exist structural and magnetic twin domains in CoTeMo⁢O 6 that strongly affect the experimental measurement of their macroscopic properties. Intriguingly, these twin domains can be related to the orthorhombicity/chirality of the crystal structure with the space group 𝑃⁢2 1 ⁢2 1⁢ 2. We further explored the magnetic and structural domains with uniaxial pressure and polarized light microscopy. Our results suggest that CoTeMo⁢O 6 could be used as a unique platform for investigating the intriguing physics involving intertwined degrees of freedom. The tunability of the underlying domain distribution and its strong anisotropy could also be useful for developing functional devices and applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Fermi Surface Nesting Driving the RKKY Interaction in the Centrosymmetric Skyrmion Magnet Gd 2 PdSi 3

The magnetic skyrmions generated in a centrosymmetric crystal were recently first discovered in Gd 2 PdSi 3 . In light of this, we observe the electronic structure by angle-resolved photoemission spectroscopy (ARPES) and unveil its direct relationship with the magnetism in this compound. The Fermi surface and band dispersions are demonstrated to have a good agreement with the density functional theory (DFT) calculations carried out with careful consideration of the crystal superstructure. Most importantly, we find that the three-dimensional Fermi surface has extended nesting which matches well the q vector of the magnetic order detected by recent scattering measurements. Finally, the consistency we find among ARPES, DFT, and the scattering measurements suggests the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction involving itinerant electrons to be the formation mechanism of skyrmions in Gd 2 PdSi 3 .

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Enhancing Diagnosis through AI-driven Analysis of Reflectance Confocal Microscopy

Reflectance Confocal Microscopy (RCM) is a non-invasive imaging technique used in biomedical research and clinical dermatology. It provides virtual high-resolution images of the skin and superficial tissues, reducing the need for physical biopsies. RCM employs a laser light source to illuminate the tissue, capturing the reflected light to generate detailed images of microscopic structures at various depths. Recent studies explored AI and machine learning, particularly CNNs, for analyzing RCM images. Our study proposes a segmentation strategy based on textural features to identify clinically significant regions, empowering dermatologists in effective image interpretation and boosting diagnostic confidence. This approach promises to advance dermatological diagnosis and treatment.

Yoon, Hong-Jun↗
NASA NTRS1969

Fine-line sensitivity for holographic interferograms

Improvement in sensitivity of holography, the technique of lensless interferometry, is obtained by enhancing the higher-order structure in the interferogram. By using the light diffracted into higher orders than the first, phase sensitivity is increased over the first order sensitivity by a factor equal to the order number used.

Heflinger, L. O.↗
NASA NTRS1977

Structure-property relationships in oxide-dispersed iron-beryllia alloys

Two BeO dispersed iron alloys containing about 2.5 and 5.5 v/o dispersoid were produced by attritting, internally oxidizing, and extruding dilute, prealloyed Fe-Be powders. As-extruded alloys were given various thermomechanical treatments involving room temperature swaging and annealing above and below the allotropic transformation temperature. The elevated temperature rupture strengths were measured and correlated with changes in structure; strengthening trends were examined in the light of proposed models for such strengthening. The results obtained showed that the elevated temperature strength was determined by the oxide interparticle spacing (IPS) in recrystallized material and IPS as well as prior deformation in swaged specimens. In fact, a parametric correlation was found between rupture strength values in the longitudinal direction with prestrain during swaging. The overall pattern in strength and microstructural observations were more consistent with a strength-stored energy (substructure) dependence than a strength-grain shape (grain aspect ratio) relation.

Wolf, S.↗
NASA NTRS1977

The distribution of ammonia and its photochemical products on Jupiter

Altitude profiles of ammonia and its photochemical products are generated in the light of measurements of the Jovian temperature structure, eddy transport coefficient, improved chemical scheme, and rate constants. Realistic limits are placed on the concentration of hydrazine which may participate in the recycling of ammonia on Jupiter. The maximum hydrazine-ice production rate is calculated to be about 1.3 mg/sq m per Jovian day. The distribution of nitrogen gas is presented with and without supersaturation of hydrazine. The nitrogen mixing ratio near the ammonia cloud top is estimated to be in the range between 10 to the -9th and 10 to the -11th power. An appreciable latitudinal variation in the ammonia concentration is expected.

Atreya, S. K.↗
NASA NTRS1977

Interaction of the surfaces of the moon and Mercury with their exospheric atmospheres

A model of atmosphere-surface interactions on the moon and on Mercury is presented. This model rejects the traditional assumption that the atmospheric particle source is a 'saturated' absorbed surface layer of gas and instead assumes that interaction is with solid atoms bound in a lattice structure so that most collisions with the light atmospheric particles are free-free rather than free-bound. The energy accommodation per collision for He and H is dominated by first-order interaction terms and is generally less than 0.1 per collision. It follows that estimated thermal escape is drastically reduced for the light atoms on both bodies. Thus the model requires much reduced solar wind collection efficiencies for protons and alpha particles. Some peculiarities of the Mercury He and H atmospheres might possibly be explained by the nature of the gas-surface coupling.

Shemansky, D. E.↗
NASA NTRS1978

Composite bolometers for submillimeter wavelengths

The fabrication and optimization of composite submillimeter wave bolometers with metal film absorbing elements and doped Ge thermometers are described. Performance characteristics are given for 4 x 4-mm bolometers designed for operation at both He-4 and He-3 temperatures. The performance expected from such bolometers when they are optimized for various values of background loading is calculated. Current dependent noise, which can arise from any of several sources, is included in the analysis. This can make it impossible to reach the background fluctuation noise limit. Feed structures for these bolometers which employ Winston light concentrators are described.

Nishioka, N. S.↗
NASA NTRS1976

The status of cometary science

The problem of determining the chemical composition and physical structure of comet nuclei are discussed in light of recent analytical improvements. The development of radio and infrared techniques, improved sensing equipment, and the ability to conduct observations in space using satellites or skylabs are highlighted. The studies of two major comets, Kohoutek and West 1975n, are presented as examples of the utilization of these improved analytic tools.

Whipple, F. L.↗
NASA NTRS1985

Ripple Ring Basins on Ganymede and Callisto

The unusual morphology of the Valhalla multiple or ripple-ring basin in Callisto was totally unexpected in light of the morphologies of large impact structures on the terrestrial planets. Two other ripple-ring basins (RRB's), Asgard and a smaller structure near the crater Adlinda are also described. Several additional RRB's were found on Callisto, an example of which is shown. A previously unrecognized RRB on Ganymede was also found. An image and geologic sketch map of this RRB are shown. Morphometric and positional data for all known RRB's are given.

Croft, S. K.↗
NASA NTRS1986

Very extended infrared emission at the center of M51 - The role of star formation

Low surface brightness 10 micron emission has been detected in M51 extending more than 1 arcmin, or 3 kpc, in RA. The emission has roughly uniform brightness and originates from dust in a region that is prominent visually and centered on the nucleus. Complementary near-infrared scans, which are dominated by the light from red stars, also show notable structure from hot dust. The dust is heated predominately by young stars, although a nonthermal source and, to a lesser extent, red stars may power the emission at the nucleus. Simple starburst models imply that the star formation rate per square parsec in the extended infrared-disk is at least two to three orders of magnitude higher than in the solar neighborhood.

Telesco, C. M.↗
NASA NTRS1987

Coronagraph for astronomical imaging and spectrophotometry

A coronagraph designed to minimize scattered light in astronomical observations caused by the structure of the primary mirror, secondary mirror, and secondary support structure of a Cassegrainian telescope is described. Direct (1:1) and reducing (2.7:1) imaging of astronomical fields are possible. High-quality images are produced. The coronagraph can be used with either a two-dimensional charge-coupled device or photographic film camera. The addition of transmission dispersing optics converts the coronagraph into a low-resolution spectrograph. The instrument is modular and portable for transport to different observatories.

Vilas, Faith↗