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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Large eddy simulation of wind farm performance in horizontally and vertically staggered layouts

This numerical investigation employs Large Eddy Simulation (LES) coupled with Actuator Disk Model (ADM) to evaluate wind farm layout optimization strategies. The study presents a systematic analysis of aligned, horizontal staggering, vertical staggering, and mixed (combination of horizontal and vertical) staggering configurations, aiming to establish optimal design parameters for enhanced power production. The investigation examines key performance metrics including mean velocity distributions, turbulence intensity characteristics, and power generation efficiency. Results demonstrate better performance of both horizontal and vertical staggering patterns compared to conventional aligned configurations, with horizontal staggering exhibiting notably higher power output than vertical arrangements. Our findings also suggest that mixed configurations, incorporating both horizontal and vertical staggering, can offer optimal performance characteristics. As a result, this research advances the understanding of wake interactions in complex wind farm layouts and provides design guidelines for maximizing wind farm power generation efficiency through strategic turbine positioning.

17 WIND ENERGY↗
DOE OSTI2026

Enhancers that direct gene expression to central nervous system vascular endothelial cells in vivo

CNS vascular endothelial cells (ECs) exhibit a distinctive gene expression program that is foundational for the blood-brain barrier (BBB). Previous research identified candidate cis-regulatory elements (CREs) that were hypothesized to control this program. In this work, transgenic mice and recombinant adeno-associated virus (rAAV) vectors have been used to interrogate these candidate CREs in vivo. These experiments show that an 850 bp genomic DNA segment ∼60 kb 5′ of Slc2a1 possesses enhancer activity that is (1) specific for BBB+ CNS ECs and (2) both necessary and sufficient for BBB+ EC gene expression. A screen of >8,000 genomic DNA segments from CNS EC-specific CRE candidates reveals several hundred with enhancer activity. Transcription factors ERG and LEF1 are shown to occupy sites in brain ECs that are highly enriched in candidate and experimentally validated CREs, lending strong support to a model in which canonical Wnt signaling activates the BBB program via LEF1.

CUT&RUN↗
DOE OSTI2025

Quantum Monte Carlo and Density Functional Theory Study of Strain and Magnetism in 2D 1T-VSe 2 with Charge Density Wave States

Two-dimensional (2D) 1T-VSe 2 has prompted significant interest due to the discrepancies regarding alleged ferromagnetism (FM) at room temperature, charge density wave (CDW) states, and the interplay between the two. We employed a combined Diffusion Monte Carlo (DMC) and density functional theory (DFT) approach to accurately investigate the magnetic properties, CDW states, and their responses to strain in monolayer 1T-VSe 2 . Our calculations show the delicate competition between various phases, revealing critical insights into the relationship between their energetic and structural properties. Here, we performed classical Monte Carlo simulations informed by our DMC and DFT results and found the magnetic transition temperature (T c ) of the undistorted (non-CDW) FM phase to be 228 K and the distorted (CDW) phase to be 68 K. Additionally, we studied the response of biaxial strain on the energetic stability and magnetic properties of various phases of 2D 1T-VSe 2 and found that small amounts of strain can increase the T c , suggesting a promising route for engineering and enhancing magnetic behavior. Finally, we synthesized 1T-VSe 2 and performed Raman spectroscopy measurements, which were in close agreement with our calculated results, validating our computational approach. Our work emphasizes the role of highly accurate DMC methods in advancing the understanding of monolayer 1T-VSe 2 and provides a robust framework for future studies of 2D magnetic materials.

2D magnets↗
DOE OSTI2025

Symmetry-mediated quantum coherence of W 5+ spins in an oxygen-deficient double perovskite

Elucidating the factors limiting quantum coherence in real materials is essential to the development of quantum technologies. Here we report a strategic approach to determine the effect of lattice dynamics on spin coherence lifetimes using oxygen deficient double perovskites as host materials. In addition to obtaining millisecond T 1 spin-lattice lifetimes at T ~ 10 K, measurable quantum superpositions were observed up to room temperature. We determine that T 2 enhancement in Sr 2 CaWO 6-δ over previously studied Ba 2 CaWO 6-δ is caused by a dynamically-driven increase in effective site symmetry around the dominant paramagnetic site, assigned as W 5+ via electron paramagnetic resonance spectroscopy. Further, a combination of experimental and computational techniques enabled quantification of the relative strength of spin-phonon coupling of each phonon mode. This analysis demonstrates the effect of thermodynamics and site symmetry on the spin lifetimes of W 5+ paramagnetic defects, an important step in the process of reducing decoherence to produce longer-lived qubits.

36 MATERIALS SCIENCE↗
DOE OSTI2026

The superconducting diode effect in Josephson junctions fabricated from a structurally chiral superconductor

The superconducting diode effect occurs in superconducting materials in which both time-reversal and inversion symmetry are broken. The recently observed chirality-induced spin selectivity effect demonstrates that chiral materials break both symmetries. Thus, a Josephson junction interface with the left-handed structure on one side of the junction and the right-handed structure on the other should exhibit a diode effect. Here, we report the electrical transport properties of right-handed/left-handed and right-handed/right-handed devices fabricated from single crystals of the structurally chiral superconductor Mo 3 Al 2 C. Fraunhofer-like magnetic diffraction patterns confirm the presence of the Josephson effect in all but one of our devices. A magnetic-field-induced superconducting diode effect is demonstrated in the right-handed/left-handed devices by a statistically significant difference in I c + and ∣ I c −∣, with a maximum asymmetry of 5%. The intrinsic superconducting diode effect is not observed in the right-handed/right-handed devices. We provide an explanation for the presence of the superconducting diode effect in the right-handed/left-handed devices.

superconducting devices↗
DOE OSTI2025

Stereogenic-at-silicon hybrid conjugated polymers

Stereoregularity in carbon-based polymers impacts critical physical properties such as crystallinity, but achieving comparable precision in polysilanes remains challenging. Herein, we report the synthesis of hybrid σ,π-conjugated polysilanes with defined stereoregularity, derived from cis- and trans-cyclosilane building blocks. Using Kumada polycondensation, we accessed a series of atactic, trans-enriched, and cis-enriched polysilanes, enabling a systematic investigation of how tacticity influences thermal and optical properties. Differential scanning calorimetry revealed distinct glass transition behaviors for stereoregular polymers compared to their atactic counterpart, and UV-vis spectroscopy demonstrated enhanced spectral resolution upon annealing of stereoregular films. A linear silane-based analog further underscored the structural impact of cyclic stereogenic units. These findings highlight how stereochemical precision in silicon-containing backbones can modulate macromolecular properties, opening avenues for the rational design of stereoregular polysilanes.

36 MATERIALS SCIENCE↗
DOE OSTI2025

JWST’s PEARLS: A z ≃ 6 quasar in a train-wreck galaxy merger system

We present JWST NIRSpec integral field spectroscopy observations of the z = 5.89 quasar NDWFS J1425+3254 from 0.6–5.3 μm, covering the rest-frame ultraviolet and optical at a spectral resolution of R ∼ 100. The quasar has a black hole mass of M BH = (1.4 +3.1 −1.0 ) × 10 9 M ⊙ and an Eddington ratio of L Bol /L Edd = 0.3 +0.6 −0.2 , as implied from the broad Balmer Hα and Hβ lines. The quasar host has significant ongoing obscured star formation, as well as a quasar-driven outflow with velocity 6050 +460 −630 km s −1 and ionised outflow rate of 1650 +130 −1230 M ⊙ yr −1 . This is possibly one of the most extreme outflows in the early Universe. The data also reveal that two companion galaxies are merging with the quasar host. The north-eastern companion galaxy is relatively old and very massive, with a luminosity-weighted stellar age of 65 +9 −4 Myr, stellar mass of (3.6 +0.6 −0.3 #x00D7; 10 11 M ⊙ , and star-formation rate (SFR) of ∼15–30 M ⊙ yr −1 . A bridge of gas connects this companion galaxy and the host, confirming their ongoing interaction. A second merger is occurring between the quasar host and a much younger companion galaxy to the south, with a stellar age of 6.7 ± 1.8 Myr, stellar mass of (1.9 ± 0.4)×10 10 M ⊙ , and SFR of ∼40–65 M ⊙ yr −1 . There is also another galaxy in the field, likely in the foreground at z = 1.135, which could be gravitationally lensing the quasar with a magnification of 1 < μ < 2 and, thus, < 0.75 mag. Overall, the system is a ‘train-wreck’ merger of three galaxies, with star formation and extreme quasar activity that were likely triggered by these ongoing interactions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Time evolution of a pumped molecular magnet—A time-resolved inelastic neutron scattering study

Introducing an experimental technique of time-resolved inelastic neutron scattering (TRINS), we explore the time-dependent effects of resonant pulsed microwaves on the molecular magnet Cr 8 F 8 Piv 16 . The octagonal rings of magnetic Cr 3+ atoms with antiferromagnetic interactions form a singlet ground state with a weakly split triplet of excitations at 0.8 meV. A 4.6 tesla field was applied to tune the splitting between two members of the triplet excited level |1$\rangle$ ↔ |2$\rangle$ to resonance with 105 GHz (0.434 meV) microwaves. The time-dependent occupations of the ground state |0$\rangle$, lower lying levels |1$\rangle$ and |2$\rangle$, and higher energy states |λ ≥ 3$\rangle$ were extracted during and after 20 s long microwave pulses incident along the (101) direction of a Cr 8 F 8 Piv 16 crystal held at 1.9 K. At significantly elevated spin temperatures, we found underpopulation relative to thermal equilibrium of |2$\rangle$ and spin-lattice thermalization time scales ranging from 1.6(2) s to 5.7(2) s depending on the power level. This contrasts with the relaxation time τ 1 (T → 0) = 27(5) 𝛍 s inferred for |2$\rangle$ from in situ Electron Spin Resonance measurements. By probing a broad range of excited states during intense microwave pumping, TRINS thus provides a first view of long lived excited states in a molecular antiferromagnet.

Science & Technology - Other Topics↗
DOE OSTI2025

In-orbit performance of the soft X-ray imaging telescope Xtend aboard XRISM

Here, we present a summary of the in-orbit performance of the soft X-ray imaging telescope Xtend onboard the X-Ray Imaging and Spectroscopy Mission (XRISM), based on in-flight observation data, including first-light celestial objects, calibration sources, and results from the cross-calibration campaign with other currently operating X-ray observatories. XRISM/Xtend has a large field of view of ${38{^{\prime }_{.}}5}$ $\times$ ${38{^{\prime }_{.}}5}$, covering an energy range of 0.4–13 keV, as demonstrated by the first-light observation of the galaxy cluster Abell 2319. It also features an energy resolution of 170–180 eV at 6 keV, which meets the mission requirement and enables us to resolve He-like and H-like Fe K$\alpha$ lines. Throughout the observation during the performance verification phase, we confirm that two issues identified in the Soft X-ray Imager (SXI) onboard the previous Hitomi mission—light leakage and crosstalk events—are addressed and suppressed in the case of Xtend. A joint cross-calibration observation of the bright quasar 3C 273 results in an effective area measured to be $\sim$420 cm$^{2}$ at1.5 keV and $\sim$310 cm$^{2}$ at 6.0 keV, which matches values obtained in ground tests. We also continuously monitor the health of Xtend by analyzing overclocking data, calibration source spectra, and day-Earth observations; the readout noise is stable and low, and contamination is negligible even one year after launch. A low background level compared with other major X-ray instruments onboard satellites, combined with the largest grasp ($\Omega _{\rm eff}\sim 60$ cm$^2$ deg$^2$) of Xtend, will not only support Resolve analysis, but also enable significant scientific results on its own. This includes near-future follow-up observations and transient searches in the context of time-domain and multi-messenger astrophysics.

instrumentation: detectors: Xtend↗
DOE OSTI2024

Quasi-Two-Dimensional Antiferromagnetic Spin Fluctuations in the Spin-Triplet Superconductor Candidate CeRh 2 As 2

The tetragonal heavy-fermion superconductor CeRh 2 ⁢As 2 (T c = 0.3 K) exhibits an exceptionally high critical field of 14 T for B ∥ c. It undergoes a field-driven first-order phase transition between superconducting states, potentially transitioning from spin-singlet to spin-triplet superconductivity. To further understand these superconducting states and the role of magnetism, we probe spin fluctuations in CeRh 2 ⁢As 2 using neutron scattering. Here, we find dynamic (π, π) antiferromagnetic (AFM) spin correlations with an anisotropic quasi-two-dimensional correlation volume. Our data place an upper limit of 0.31 μ B on the staggered magnetization of corresponding Néel orders at T = 0.08 K. Density functional theory calculations, treating Ce 4⁢ƒ electrons as core states, show that the AFM wave vector connects significant areas of the Fermi surface. Our findings indicate that the dominant excitations in CeRh 2 ⁢As 2 for ℏω⁢ < 1.2 meV are magnetic and suggest that superconductivity in CeRh 2⁢ As 2 is mediated by AFM spin fluctuations associated with a proximate quantum critical point.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Pre- and post-launch operation of the Resolve soft X-ray spectrometer onboard the XRISM satellite

Resolve is a high-resolution X-ray spectrometer onboard the X-Ray Imaging and Spectroscopy Mission (XRISM), launched on September 6 (UT), 2023. The Resolve has performed better than its required spectral resolution (7 eV at full width at half maximum at 6 keV), both on the ground and in orbit, and has been confirmed to have comparable performance to the soft X-ray spectrometer onboard the ASTRO-H (Hitomi) satellite. The focal plane is composed of an array of microcalorimeter detectors operated at 50 mK to achieve the required energy resolution, and the cooling system is designed to satisfy the lifetime requirement of over 3 years. The focal plane and cooling system are contained in a vacuum-insulated dewar. The cooling system is equipped with a two-stage adiabatic demagnetization refrigerator (ADR) that uses superfluid liquid helium (LHe) as its heat sink. The system includes a third ADR stage that can be used to provide the heat sink when the helium is exhausted. A Joule–Thomson cooler and several two-stage Stirling coolers are used to reduce the heat load on the LHe. During pre-launch operations, we carried out a superfluid LHe top-off operation. The resultant amount of LHe onboard Resolve was over 35 L before launch, which is sufficient to meet the lifetime requirement. During post-launch operation, the LHe vent valve was opened 5 min after launch during rocket acceleration, and the cryocoolers were turned on after several orbits, as planned, which established stable cooling within the dewar. Pre- and post-launch operations for the Resolve instrument were planned around multiple constraints from launch vehicle operations; all were successfully completed, and the launch requirements were fully met.

X-Ray Imaging and Spectroscopy Mission↗
DOE OSTI2025

Resolve instrument onboard XRISM: design, integration, and instrument test results

The Resolve instrument onboard the X-Ray Imaging and Spectroscopy Mission (XRISM) consists of an array of 6 × 6 silicon-thermistor microcalorimeters cooled down to 50 mK and a high-throughput X-ray mirror assembly (XMA) with a focal length of 5.6 m. XRISM is a recovery mission of ASTRO-H/Hitomi, and the Resolve instrument is a rebuild of the ASTRO-H Soft X-ray spectrometer (SXS) and the Soft X-ray Telescope (SXT) that achieved energy resolution of ∼ 5 eV FWHM on orbit, with several important changes based on lessons learned from ASTRO-H. The flight models of the Dewar and the electronics boxes were fabricated, and the instrument test and calibration were conducted in 2021. By tuning the cryocooler frequencies, energy resolution better than 4.9 eV FWHM at 6 keV was demonstrated for all 36 pixels and high-resolution grade events, as well as energy-scale accuracy better than 2 eV up to 30 keV. The immunity of the detectors to microvibration, electrical conduction, and radiation was evaluated. The instrument was delivered to the spacecraft system in April 2022. The XMA was tested and calibrated separately. Its angular resolution is 1.27′, and the effective area of the mirror itself is 570 cm 2 at 1 keV and 424 cm 2 at 6 keV. We report the design and the major changes from the ASTRO-H SXS, the integration, and the results of the instrument test.

X-ray↗
DOE OSTI2025

Background Measurements and Simulations of the ComPair Balloon Flight

ComPair, a prototype of the All-sky Medium Energy Gamma-ray Observatory (AMEGO), completed a short-duration high-altitude balloon campaign on 27 August 2023 from Fort Sumner, New Mexico, USA. The goal of the balloon flight was to demonstrate ComPair as both a Compton and Pair telescope in flight, reject the charged particle background, and measure the background γ-ray spectrum. This analysis compares measurements from the balloon flight with Monte Carlo simulations to benchmark the instrument. The comparison finds good agreement between the measurements and simulations and supports the conclusion that ComPair accomplished its goals for the balloon campaign. Additionally, two charged particle background rejection schemes are discussed: a soft ACD veto that records a higher charged particle event rate but with less risk of event loss, and a hard ACD veto that limits the charged particle event rate on board. There was little difference in the measured spectra from the soft and hard ACD veto schemes, indicating that the hard ACD veto could be used for future flights. The successes of ComPair’s engineering flight will inform the development of the next generation of ComPair with upgraded detector technology and larger active area.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Generative learning for slow manifolds and bifurcation diagrams

In dynamical systems characterized by separation of time scales, the approximation of so called “slow manifolds”, on which the long term dynamics lie, is a useful step for model reduction. Initializing on such slow manifolds is a useful step in modeling, since it circumvents fast transients, and is crucial in multiscale algorithms (like the equation-free approach) alternating between fine scale (fast) and coarser scale (slow) simulations. In a similar spirit, when one studies the infinite time dynamics of systems depending on parameters, the system attractors (e.g., its steady states) lie on bifurcation diagrams (curves for one-parameter continuation, and more generally, on manifolds in state parameter space. Sampling these manifolds gives us representative attractors (here, steady states of ODEs or PDEs) at different parameter values. Algorithms for the systematic construction of these manifolds (slow manifolds, bifurcation diagrams) are required parts of the “traditional” numerical nonlinear dynamics toolkit. In more recent years, as the field of Machine Learning develops, conditional score-based generative models (cSGMs) have been demonstrated to exhibit remarkable capabilities in generating plausible data from target distributions that are conditioned on some given label. It is tempting to exploit such generative models to produce samples of data distributions (points on a slow manifold, steady states on a bifurcation surface) conditioned on (consistent with) some quantity of interest (QoI, observable). In this work, we present a framework for using cSGMs to quickly (a) initialize on a low-dimensional (reduced-order) slow manifold of a multi-time-scale system consistent with desired value(s) of a QoI (a “label”) on the manifold, and (b) approximate steady states in a bifurcation diagram consistent with a (new, out-of-sample) parameter value. This conditional sampling can help uncover the geometry of the reduced slow-manifold and/or approximately “fill in” missing segments of steady states in a bifurcation diagram. Finally, the quantity of interest, which determines how the sampling is conditioned, is either known a priori or identified using manifold learning-based dimensionality reduction techniques applied to the training data.

Dynamical systems↗
DOE OSTI2024

Flow field design for zero-gap microbial electrolysis cells using synthetic and real wastewater

Increasing performance in microbial electrolysis cells (MECs) requires the development of optimized reactor configurations with minimal internal resistance and capable to operate with real wastewater. Here, the impact of two different flow fields (serpentine and circular) was examined in zero-gap MECs with synthetic and real wastewaters. The serpentine flow field enabled a uniform distribution of the electrolyte in the anode chamber, resulting in larger current densities at lower flow rates compared to the circular flow field. Electrochemical tests using synthetic media with high buffer capacity revealed more stable and higher performance with the serpentine flow field compared to the circular flow path, producing larger current density (23.7 ± 0.8 A/m 2 vs 21.9 ± 5.6 A/m 2 ), hydrogen production rate (75.8 ± 4.1 L/L-d vs 54.3 ± 2.4 L/L-d), cathodic coulombic efficiency (>91 % vs >50 %), and an overall lower internal resistance (12.5 ± 0.5 mΩm 2 vs 14.8 ± 3.7 mΩm 2 ). Continuous operation for over 30 days with real wastewater indicated higher tolerance of the MECs with serpentine flow field toward media with large concentration of suspended solids, producing a current density of 5.4 ± 1.1 A/m 2 and a hydrogen production rate of 22.2 ± 6.2 L/L-d. Furthermore, the results presented here underscore the importance of reactor design and architecture in optimizing MEC performance for hydrogen production from liquid wastes.

flow path↗
DOE OSTI2025

Grain boundary metastability controls irradiation resistance in nanocrystalline metals

Grain boundaries (GBs) in polycrystalline materials are powerful sinks for irradiation defects. While standard theories assume that a GB’s efficiency as a sink is defined solely by its character before irradiation, recent evidence conclusively shows that the irradiation sink efficiency is a highly dynamic property controlled by the intrinsic metastability of GBs under far-from-equilibrium irradiation conditions. In this paper, we reveal that the denuded (i.e., defect-free) zone, typically the signature of a strong sink, can collapse as irradiation damage accumulates. We propose a radiation damage evolution model that captures this behavior based on the emergence of a series of irradiation defect-enabled metastable GB microstate changes that dynamically alter the ability of the GB to absorb further damage. We show that these microstate changes control further defect absorption and give rise to the formation of a defect network that manifests itself as a net Nye-tensor signal detectable via lattice curvature experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Enabling microbial electrolysis cell scale-up via electrochemistry-, hydrodynamic-, and microbial ecology-informed framework

Microbial electrolysis cells (MECs) can produce green hydrogen while removing organic contaminants from liquid waste streams by leveraging the metabolic activity of electroactive microorganisms. Despite their potential in a sustainable, circular economy, large-scale MECs that can treat relevant volumes of wastewater have failed to deliver performance proportional to their lab-scale counterparts. The reason behind this lower performance at scale remains unclear. Here, in this study, we developed a combined electrochemistry-, hydrodynamic-, and microbial ecology-informed framework to analyze and optimize MEC performance during scale-up, enabling accurate quantification of major limitations and the identification of strategies to overcome them, ultimately facilitating equivalent performance at scale. Applying this framework to the scale-up of a zero-gap MEC from 9 cm 2 electrode area to 100 cm 2 electrode area, resulted in similar maximum current densities in a 100 cm 2 MEC (21.7 ± 1.1 A/m 2 ) compared to a 9 cm 2 system (25.1 ± 2.7 A/m 2 ), as well as equivalent hydrogen production rates of 69.3 L/L-d (100 cm 2 ) and 67.7 ± 2.4 L/L-d (9 cm 2 ). COMSOL flow dynamics simulations were used to scale up the reactor configuration without negatively affecting electrolyte velocity and distribution in the cell, minimizing the increase in internal resistances during scale-up (11.7 ± 0.5 mΩm 2 at 9 cm 2 ; 19.7 ± 1.3 mΩm 2 at 100 cm 2 ). Microbial community structures were assessed at both scales using high-throughput sequencing, highlighting the differences of populations across electrode dimensions and operational parameters. The framework presented here accelerates the development of effective strategies toward the scale-up of MECs by furthering the understanding of how electrochemical, hydrodynamic, and microbial ecology parameters change as the reactor dimension is increased. Ultimately, this approach contributes to advancing electrochemical biotechnology toward practical deployment in energy-efficient wastewater treatment systems.

Flow path↗
DOE OSTI2024

Activation of H 2 O by ThO 2 – Experimental and Computational Studies

Here, a synergetic study that utilized anion photoelectron spectroscopy and high-level abinitio calculations has explored the activation of H 2 O molecules by ThO 2 – molecular anions. Both experiment and theory found conclusive evidence for said activation. In the experiments, this appeared as a tell-tale directional shift in the spectral profile of the anionic complex that ruled out physisorption,i.e., ThO 2 – (H 2 O), and implied chemisorption. In the computations, good agreement was found between the calculated and measured vertical detachment energies, and the atomic connectivity (the structure) of the resulting anionic complex was found to be [OTh(OH) 2 ] – .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗