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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Cryo-electron microscopy structure of a zinc uptake ABC transporter

Zn2+ is an essential micronutrient required for many biological processes. Microorganisms employ high-affinity Zn2+ ABC transporters to take up zinc from the environment when it is scarce, yet the mechanism of zinc uptake and its regulation remain poorly understood. Here, we report the cryo-electron microscopy structure of the Zn2+ ABC transporter complex ZnuB-ZnuC from Escherichia coli. It contains two ZnuB transport and two ZnuC regulatory subunits. The ZnuB homodimer is in an outward-facing, closed conformation with a large hydrophilic cavity at the dimer interface. Each ZnuC subunit contains an N-terminal nucleotide-binding domain and a C-terminal zinc-sensing domain (ZSD). Zn2+ binding to the ZSD locks the transporter in a closed state, whereas under low-Zn2+ conditions, the disorder of ZSD permits ATP-driven zinc uptake. Zn2+ ABC transporters are ubiquitously utilized by pathogenic bacteria to compete with hosts for Zn2+. These findings reveal potential therapeutic targets for disrupting Zn2+ homeostasis in antibiotic-resistant pathogens.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

AmeriFlux FLUXNET-1F US-ABc Archbold grazed improved pasture

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site US-ABc Archbold grazed improved pasture. This is the FLUXNET version of the carbon flux data for the site US-ABc Archbold grazed improved pasture produced by applying the standard ONEFlux (1F) software. Site Description - This site is an improved pasture, regularly fertilized (nitrogen, ~26 kg/ha every 2 years) and limed (~229 kg/ha every 5 years, and historically received phosphorus fertilizer until 1986; . The soil type is a fine sandy Spodosol

Bernacchi, Carl [Global Change and Photosynthesis ↗
DOE OSTI2026

AmeriFlux US-ABc Archbold grazed improved pasture

This is the AmeriFlux version of the carbon flux data for the site US-ABc Archbold grazed improved pasture. Site Description - This site is an improved pasture, regularly fertilized (nitrogen, ~26 kg/ha every 2 years) and limed (~229 kg/ha every 5 years, and historically received phosphorus fertilizer until 1986; . The soil type is a fine sandy Spodosol

Bernacchi, Carl [Global Change and Photosynthesis ↗
DOE OSTI2025

A Recipe for ABC Multifamily Retrofits: Technologies, Financing, and Project Delivery

This report documents the final technical accomplishments and outcomes of Rocky Mountain Institute’s project under the U.S. Department of Energy (DOE) Award DE-EE0009064. The project aimed to develop, validate, and scale whole building retrofit solutions for multifamily buildings, including two configurations of Integrated Mechanical System Pods (IMSP-C and IMSP-U), in alignment with DOE Advanced Building Construction (ABC) initiative's decarbonization and energy efficiency goals. While the project made significant progress in Budget Period 1 (Phase 1) and throughout Budget Period 2 (Phase 2), activities were discontinued as of March 26, 2025, following a Stop Work Order issued by DOE. As such, this report reflects all completed work through that date. The project did not enter Budget Periods 3 and 4 (Phase 2), and demonstration site implementation, field M&V, and final commercialization execution were not conducted.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2026

The ABCs of phase retrieval: Connecting the acronyms of scanning transmission electron microscopy

High-resolution scanning transmission electron microscopy (S/TEM) is an indispensable tool for characterizing the structure and properties of materials down to the atomic scale. Conventional S/TEM imaging, however, is limited by the phase problem, whereby the phase of the electron exit wave is lost upon detection. Recent advances in diffractive imaging and 4D-STEM have enabled a range of phase-retrieval techniques that computationally reconstruct the missing information encoded in the phase of the transmission function. These approaches offer improved dose efficiency and enhanced sensitivity to weakly scattering signals, extending quantitative imaging to beam-sensitive materials composed of light elements. In this work, we introduce the phase problem in electron microscopy and survey the diverse landscape of phase-retrieval techniques used in the field. Despite their many acronyms and algorithmic variations, these techniques share a common physical and mathematical foundation. We present a unified framework that connects these seemingly distinct methods, from parallax imaging and tilt-corrected bright-field (tcBF-STEM), to aberration-corrected bright-field (acBF-STEM), optimum bright-field (OBF-STEM) and single-sideband (SSB) ptychography, as well as first-moment integrated center of mass techniques (iCOM) and iterative ptychographic algorithms. Based on these insights, we discuss the opportunities and practical limitations of applying these methods across different materials systems, detector designs, and microscope configurations.Graphical abstractRepresentative electron microscopy configurations used for phase retrieval and diffractive imaging in S/TEM: (a) Zernike phase-contrast transmission electron microscopy (TEM), (b) small-convergence-angle four-dimensional scanning transmission electron microscopy (4D-STEM) for nanobeam-based phase reconstruction methods, and (c) large-convergence-angle 4D-STEM for ptychographic and related diffractive imaging techniques reviewed in this work.

36 MATERIALS SCIENCE↗
DOE OSTI2026

The ABCs of On-Demand Transit (ODT)

On-demand mobility - also referred to as on-demand transit (ODT) - is a form of public mobility that is flexible with respect to where and when service is provided, and ODT deployments have increased significantly in recent years. Transit agencies are becoming increasingly interested in ODT, and due to differing definitions and various service design and business model options, it can be difficult to learn about the emerging industry. This work provides an overview of the definitions of ODT, recent trends internationally and in the U.S., ODT's benefits and challenges (particularly compared to fixed-route transit), three primary service design options, system costs and funding considerations, and a metrics framework for evaluating ODT systems to ensure continued successful performance. Identified benefits include increased service areas, short ride and wait times, increased user flexibility, potential to reduce energy consumption and emissions through shared trips and smaller, right-sized vehicles, increased safety and comfort through door-to-door service, and rich data streams including granular spatio-temporal data that can be analyzed to continuously improve the service. Challenges include scaling ODT service up as small increases in ridership require additional supply to keep service quality high, serving peak times including keeping low wait times, the lack of fixed schedule being challenging for commuters, integrating ODT services with nearby transit systems, and equity for riders without smartphones who cannot track the vehicle in a mobile app. Finally, an overview of seven ODT case studies (in Texas, Missouri, New York, and Ontario, Canada) performed by NREL and related analysis of travel time, energy and emissions, costs, and equity are presented. Initial key findings include: ODT can be cost- and energy-effective compared to fixed-route transit, ODT serves more people than other transit options, and ODT system deployments can be followed by rapid growth.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2026

Durability of ABC Team Wall Assemblies

This study evaluates the long-term hygrothermal durability of four advanced retrofit wall systems using a field test facility located in Hollywood, South Carolina, representative of a mixed-humid coastal climate (Zone 3). The research focuses on assessing the thermal and moisture performance of a baseline wall assembly retrofitted with (1) Tremco/Dryvit prefabricated panel systems (Revitalite and Fedderlite), (2) Reinforced Fiberglass Plastic (RFP) panels developed by Oak Ridge National Laboratory (ORNL), and (3) Vacuum Insulated Panels (VIP) integrated with EPS by Home Innovation Research Labs (HIRL) and ORNL. A baseline wall representing a typical uninsulated wood-frame construction was used for comparison.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2025

Efficiency droop contributors in InGaN green light emitting diodes

Here, efficiency droop contributors (i.e., inherent Auger–Meitner recombination, polarization-induced effects, thermal effects, and light extraction) in InGaN green light emitting diodes (LEDs) are decoupled and quantified. First, a modified ABC model is developed, and external quantum efficiency measurements are taken under constant and pulsed currents (⁠ EQE Constant and EQE Pulsed ⁠, respectively). The LED internal quantum efficiency with and without thermal effects (⁠ IQE$^{ABC}_{Constant}$ and IQE$^{ABC}_{Pulsed}$⁠, respectively) is extracted using the modified model. Then, using Raman spectroscopy, the LED junction temperature is extracted. Finally, using the optical-electrical model (OEM), the polarization- and temperature-independent LED internal quantum efficiency (⁠ IQE OEM ) is calculated from the modified ABC model and the extracted junction temperature. By comparing external (⁠ EQE Constant ⁠) and the three internal quantum efficiencies (⁠ IQE$^{ABC}_{Constant}$, IQE$^{ABC}_{Pulsed}$⁠, and IQE OEM ), the impacts of inherent Auger–Meitner recombination, polarization-induced effects, thermal effects, and light extraction on the efficiency droop are decoupled and quantified. It is found that inherent Auger–Meitner recombination-induced droop is approximately 49% of the total efficiency droop in commercial green LEDs, while polarization-induced effects contribute about 35%, and thermal droop accounts for nearly 16%. Lastly, these findings suggest, to quash the green gap, it is critical to search for materials and device designs with low inherent Auger–Meitner coefficients and polarization fields, respectively.

42 ENGINEERING↗
DOE OSTI2025

Insights into regulatory T-cell and type-I interferon roles in determining abacavir-induced hypersensitivity or immune tolerance

Introduction Clinical use of several small molecule drugs may lead to severe T-cell-mediated idiosyncratic drug hypersensitivity reactions (iDHR) linked to HLA alleles, including abacavir (ABC) with HLA-B*57:01. Due to study limitations in humans, pathogenic networks in iDHR remain elusive. HLA transgenic murine models have been proposed to bridge knowledge gaps in tolerance and susceptibility to drugs. Methods Mice expressing HLA-B*57:01 and Foxp3-DTR/EGFP were generated to selectively deplete regulatory T-cells (Treg) with diphtheria toxin. ABC was administered for 8 days alone or together with cell- and cytokine-depleting antibodies. Cellular and transcriptomic responses were analyzed by RNA, flow cytometry and fluorescence methods. Results While CD8 + T-cell responses to ABC require HLA presentation, ABC also triggered mitochondrial stress in macrophagesin vitro, independently of HLA.In vivo, Treg were the primary mechanism of drug tolerance controlling HLA presentation and costimulation by antigen presenting cells. Treg ablation uncovered immune adverse events linked to activation and proliferation of both drug-specific and bystander CD8 + T-cells through CD28-mediated pathways with support from CD4 + non-Treg. Type-I interferon (IFN-I) and cellular-stress pathways influenced the fate of lymph node cells responding to ABC, implicating innate immune cells such as macrophages and plasmacytoid dendritic cells in the development of T-cell responses against the drug. IFN-I and IL-2 were necessary for CD8 + T-cell differentiation and ABC-induced adverse reactions. Conclusions This study unveils novel immune mechanisms driven by drug and host-related factors required forin vivoreactions and sheds light on potential biomarker and therapeutic targets for managing and preventing severe and life-threatening iDHR.

Immunology↗
DOE OSTI2025

RANGE: A robust adaptive nature-inspired global explorer of potential energy surfaces

With the growing demand for realistic representations of chemical structures and the advent of exascale computing, the intelligent sampling of potential energy surfaces and efficient identification of global minima have become more essential but also more feasible. Building on prior studies demonstrating the efficiency of the Artificial Bee Colony (ABC) swarm intelligence algorithm, we report a hybrid metaheuristic framework that integrates the adaptive exploration capabilities of ABC coupled with the exploitation strengths of genetic algorithms (GA) in a scalable, Python-based implementation. The resulting tool, RANGE (Robust Adaptive Nature-inspired Global Explorer), provides seamless interfaces to multiple potential energy evaluators, either directly or via widely used Python libraries, and is designed for high-performance computing environments. We describe the implementation details of RANGE and evaluate its performance, relative to ABC- or GA-alone based algorithms, on a variety of chemical systems, including molecular clusters and heterogeneous surfaces. In conclusion, our results demonstrate RANGE’s efficiency, robustness, and broad applicability in addressing challenging global optimization problems in computational chemistry and materials science.

Algorithms and data structure↗
DOE OSTI2025

Electronic Excitation‐Driven β‐Ga 2 O 3 Metastability Transformation and Self‐Organization Mechanism: β→κ/γ/δ Phases

Here, irradiation-driven multiphase self-organization presents emergent opportunities for the customization of nanoscale engineering properties, dynamically tuning strain-field distributions and interfacial electronic structures. Responding to intense electronic excitation-induced energy deposition, the dominant phase transformations, with varying Gibbs free energy $Δ,G^o_f$ are confirmed as β → κ → γ → δ that are located in specific microregions for Gallium (III) oxide (Ga 2 O 3 ), as follows: (i) Surface-localized interstitial accumulation under compressive stress triggers β → δ via semi-coherent interface formation. (ii) Tensile stress within latent tracks drives vacancy-mediated oxygen layer truncation (4/12 periodicity along ⟨0001⟩), stabilizing coherent 4H (ABCB) κ and 3C (ABC) β (ABC) interfaces through strain-compensated octahedral distortion. (iii) Screw dislocation-mediated lattice relaxation induces β → γ via cation disordering (Ga 3+ occupancy at β-interstitial sites), forming metastable spinel γ with mixed occupancy across 16d/8a Wyckoff sites. Irradiation-driven β-Ga 2 O 3 →κ/γ/δ transitions, as mechanistically revealed via inelastic thermal spike (i-TS) calculations and molecular dynamics simulations, induce defect-mediated nonlinear photoresponse, critical for optoelectronic engineering.

Han, Xinqing [Shandong Univ., Jinan (China)]↗
DOE OSTI2025

Self-Trapped-Exciton Radiative Recombination in β–Ga 2 O 3 : Impact of Two Concurrent Nonradiative Auger Processes

The peculiarities of radiative and nonradiative processes associated with self-trapped intrinsic eXcitons in the excited β-Ga 2 O 3 crystals are studied via time-resolved techniques of induced absorption, transient grating, and photoluminescence (PL) at room temperature. The excitation above the bandgap is produced by laser pulses with linear light polarization parallel and orthogonal in the (–201) and (001) planes. We elucidate that the nonradiative recombination rate occurring in the eXciton prevails over its radiative emission rate in a wide range of free carrier concentration composed of excited and equilibrium electrons. Hence, the nonradiative recombination has no effect on the strong anisotropy and the shape of the eXciton emission band. However, we find out that the conventional ABC model of electron effective lifetime is insufficient for explanation of the excitation dependences. Inclusion of two nonradiative Auger mechanisms in a modified ABC formula provides excellent agreement of these dependences. We conclude that the trap-assisted Auger process is in proportion to the free electron density with coefficient B = 1.1 × 10 –11 cm 3 /s and appears at low/intermediate excitation, while the triple-particle Auger process is in proportion to Δn 2 with coefficient C = 8 × 10 –30 cm 6 /s and appears at high excitation conditions. The transition between two Auger mechanisms is accompanied by a rise of the eXciton diffusivity in preferred crystallographic directions where the radiative PL intensity is maximal. The diffusion length LD in these directions can reach values ~300 nm, but, at high excitations, LD becomes limited by Auger lifetimes. These findings pave the way for the implementation of self-trapped eXcitons into specific optoelectronic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Coupled Roles of Surface Chemistry and Hydrogen-Assisted Cycling in Ruthenium Atomic Layer Deposition on Silicon Oxides

Ruthenium (Ru) is a promising interconnect material for advanced semiconductor technologies due to its favorable scaling characteristics, including a short electron mean free path and strong electromigration resistance. In semiconductor integration, silicon oxide-based dielectrics serve as dominant insulating materials and constitute ubiquitous interfaces for metallization; however, their formation-dependent surface chemistry and its impact on Ru growth remain insufficiently explored. Here, we investigate Ru ALD on native oxide SiO x (N-SiO x ) and thermally grown SiO 2 (T-SiO 2 ) as model substrates using bis(ethylcyclopentadienyl)ruthenium(II) [Ru(EtCp) 2 ] under two distinct reactant-sequence environments: AB-type (Ru(EtCp) 2 /O 2 ) and hydrogenassisted ABC-type (Ru(EtCp) 2 /O 2 /H 2 ). Under the AB-type process, both N-SiO x and T-SiO 2 exhibit pronounced nucleation delay. N-SiO x shows earlier nucleation and higher nucleation density than T-SiO 2 , plausibly attributed to differences in surface hydroxyl populations. Similar temperature-dependent phase evolution is observed on both substrates, with mixed Ru and RuO 2 phases at 250 °C and predominantly metallic Ru at 300 °C accompanied by increased morphological roughening. In contrast, incorporating an H 2 subpulse (ABC-type) mitigates nucleation delay, particularly on hydroxyl-deficient T-SiO 2 , thereby reducing the substratedependent disparity observed under AB cycling. Moreover, RuO 2 formation is suppressed even at 250 °C on both substrates, shifting growth toward more metallic Ru with reduced resistivity (∼20 μΩ·cm at ∼ 20 nm on N-SiO x ). These trends suggest that H 2 influences the surface reaction pathway, contributing to enhanced metallic stabilization and altered early stage growth kinetics. Overall, this work clarifies the coupled roles of substrate chemistry and reactant-sequence design in governing Ru nucleation and early stage film evolution, providing insight relevant to next-generation interconnect integration and future area-selective deposition strategies.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Spontaneous emergence of straintronics effects and striped stacking domains in untwisted three-layer epitaxial graphene

Emergent electronic phenomena, from superconductivity to ferroelectricity, magnetism, and correlated many-body band gaps, have been observed in domains created by stacking and twisting atomic layers of Van der Waals materials. In graphene, emergent properties have been observed in ABC stacking domains obtained by exfoliation followed by expert mechanical twisting and alignment with the desired orientation, a process very challenging and nonscalable. Here, conductive atomic force microscopy shows in untwisted epitaxial graphene grown on SiC the surprising presence of striped domains with dissimilar conductance, a contrast that demonstrates the presence of ABA and ABC domains since it matches exactly the conductivity difference observed in ABA/ABC domains in twisted exfoliated graphene and calculated by density functional theory. The size and geometry of the stacking domains depend on the interplay between strain, solitons crossing, and shape of the three-layer regions. Interestingly, we demonstrate the growth of three-layer regions in which the ABA/ABC stacking domains self-organize in stable stripes of a few tens of nanometers. The growth-controlled production of isolated and stripe-shaped ABA/ABC domains open the path to fabricate quantum devices on these domains. These findings on self-assembly formation of ABA/ABC epitaxial graphene stripes on SiC without the need of time-consuming and nonscalable graphene exfoliation, alignment, and twisting provide different potential applications of graphene in electronic devices.

Rejhon, Martin (ORCID:000000017775487X)↗
DOE OSTI2024

Calibration verification for stochastic agent-based disease spread models

Accurate disease spread modeling is crucial for identifying the severity of outbreaks and planning effective mitigation efforts. To be reliable when applied to new outbreaks, model calibration techniques must be robust. However, current methods frequently forgo calibration verification (a stand-alone process evaluating the calibration procedure) and instead use overall model validation (a process comparing calibrated model results to data) to check calibration processes, which may conceal errors in calibration. In this work, we develop a stochastic agent-based disease spread model to act as a testing environment as we test two calibration methods using simulation-based calibration, which is a synthetic data calibration verification method. The first calibration method is a Bayesian inference approach using an empirically-constructed likelihood and Markov chain Monte Carlo (MCMC) sampling, while the second method is a likelihood-free approach using approximate Bayesian computation (ABC). Simulation-based calibration suggests that there are challenges with the empirical likelihood calculation used in the first calibration method in this context. These issues are alleviated in the ABC approach. Despite these challenges, we note that the first calibration method performs well in a synthetic data model validation test similar to those common in disease spread modeling literature. We conclude that stand-alone calibration verification using synthetic data may benefit epidemiological researchers in identifying model calibration challenges that may be difficult to identify with other commonly used model validation techniques.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Advanced Building Construction Collaborative (Final Technical Report)

This report summarizes the outcomes of RMI’s five-year U.S. Department of Energy–funded Advanced Building Construction Collaborative (ABC-C), which accelerated adoption of high-performance construction through industry collaboration, market research, technology commercialization, and demand aggregation. It highlights the Collaborative’s achievements—including engagement of more than 130 organizations, support for over $637 million in funding for ABC companies, and recommendations to scale advanced building construction through coordinated market, policy, and investment strategies.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2025

Editorial: Structure and mechanism of microbial membrane active transporters

Membrane active transporters play essential roles in microbial physiology. They couple energy transduction to conformational changes that drive translocation of nutrients, substrates and ions, as well as molecular communication. The structure and function of microbial membrane active transporters are highly diverse. Typical examples include the primary active transporters in the ATP-binding cassette (ABC) superfamily (Thomas and Tampé, 2020; Davidson et al., 2008; Locher et al., 2002), the secondary active transporters in the Major Facilitator Superfamily (MFS) (Drew et al., 2021; Kaback and Guan, 2019), and the ligand-gated porins in the TonB-dependent transporter (TBDT) family (Klebba et al., 2021). As structural, proteogenomic, and computational methods advance, active transporters are increasingly recognized as dynamic molecular machines whose mechanisms can now be visualized and modeled with remarkable precision, building on decades of biochemical and biophysical discovery that established the foundations of this field. The transporter studies recruited in this Research Topic provide us with new insights into the field including structure-function of sugar transporters in yeast, structural prediction and classification of ABC complexes in Bacillus subtilis, Type VI Secretion System (T6SS) in Bacteroides fragilis, amino acids uptake in Escherichia coli and bacterial spore germination.

mechanism↗
DOE OSTI2026

Small Molecule Inhibitor-Modulated Al 2 O 3 Atomic Layer Deposition on Monolayer MoS 2 for Controlled Nucleation

The integration of ultrathin dielectrics on two-dimensional (2D) semiconductors is essential for advancing beyond-Si electronics. However, the intrinsic inertness of van der Waals 2D basal planes remains a primary bottleneck to achieving uniform dielectric nucleation and growth. Here, in this study, we introduce a small molecule inhibitor (SMI)-modulated thermal atomic layer deposition (ALD) strategy, exemplified by aluminum oxide (Al 2 O 3 ) ALD on monolayer molybdenum disulfide (1L MoS 2 ) with acetic acid (HAc) SMI. The ABC-type sequence comprises HAc inhibitor (A), trimethylaluminum (TMA) precursor (B), and deionized H 2 O coreactant (C). In situ quartz crystal microbalance (QCM) studies reveal robust HAc adsorption on Al 2 O 3 and suppression of subsequent oxide growth on HAc-passivated surfaces. When applied to 1L MoS 2 , this inhibitory pathway enables HAc to selectively passivate nascent Al 2 O 3 nuclei formed on the MoS 2 surface, limiting their three-dimensional (3D) island coarsening and redirecting precursor adsorption toward the uncovered basal plane. Consequently, nearly continuous ultrathin (∼1.5 nm) Al 2 O 3 films are achieved on 1L MoS 2 with markedly improved uniformity compared to standard Al 2 O 3 ALD using TMA and H 2 O, as validated by atomic force microscopy (AFM), cross-sectional scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectroscopy (EDS). Density functional theory (DFT) calculations further provide atomistic insight into HAc-modulated Al 2 O 3 nucleation, corroborating the energetic preference of HAc for Al 2 O 3 over MoS 2 and attenuated TMA adsorption on HAc-passivated surfaces. Spatially resolved Raman spectroscopy also confirms that the HAc-modulated process preserves the structural integrity of 1L MoS 2 , with only minimal strain and doping perturbations observed after dielectric deposition. This SMI-modulated approach offers a broadly applicable framework for controlling ALD nucleation across various inhibitors, ALD chemistries, and 2D materials, opening opportunities for reliable dielectric integration in next-generation nanoelectronics.

36 MATERIALS SCIENCE↗