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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Online Bayesian State Estimation for Real-Time Monitoring of Growth Kinetics in Thin Film Synthesis

Rapid validation of newly predicted materials through autonomous synthesis requires real-time adaptive control methods that exploit physics knowledge, a capability that is lacking in most systems. Here, in this study, we demonstrate an approach to enable real-time control of thin film synthesis by combining in situ optical diagnostics with a Bayesian state estimation method. We developed a physical model for film growth and applied the direct filter (DF) method for real-time estimation of nucleation and growth rates during pulsed laser deposition (PLD). We validated the approach using simulated and experimental reflectivity data for WSe 2 growth and ultimately deployed the algorithm on an autonomous PLD system during the growth of 1T'-MoTe 2 . The DF robustly estimates growth parameters in real time at early stages of growth, down to 15% monolayer area coverage. This fusion of in situ diagnostics, data assimilation, and physical modeling opens new opportunities in adaptive control of synthesis trajectories toward desired material states.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Structural optimization for joined-wing synthesis

The differences between fully stressed and minimum-weight joined-wing structures are identified, and these differences are quantified in terms of weight, stress, and direct operating cost. A numerical optimization method and a fully stressed design method are used to design joined-wing structures. Both methods determine the sizes of 204 structural members, satisfying 1020 stress constraints and five buckling constraints. Monotonic splines are shown to be a very effective way of linking spanwise distributions of material to a few design variables. Both linear and nonlinear analyses are employed to formulate the buckling constraints. With a constraint on buckling, the fully stressed design is shown to be very similar to the minimum-weight structure. It is suggested that a fully stressed design method based on nonlinear analysis is adequate for an aircraft optimization study.

Gallman, John W.↗
DOE OSTI2021

S ‐Adenosyl‐ l ‐ethionine is a Catalytically Competent Analog of S ‐Adenosyl‐ l ‐methionine (SAM) in the Radical SAM Enzyme HydG

Abstract Radical S ‐adenosyl‐ l ‐methionine (SAM) enzymes initiate biological radical reactions with the 5′‐deoxyadenosyl radical (5′‐dAdo . ). A [4Fe‐4S] + cluster reductively cleaves SAM to form the Ω organometallic intermediate in which the 5′‐deoxyadenosyl moiety is directly bound to the unique iron of the [4Fe‐4S] cluster, with subsequent liberation of 5′‐dAdo . . We present synthesis of the SAM analog S ‐adenosyl‐ l ‐ethionine (SAE) and show SAE is a mechanistically equivalent SAM‐alternative for HydG, both supporting enzymatic turnover of substrate tyrosine and forming the organometallic intermediate Ω. Photolysis of SAE‐bound HydG forms an ethyl radical trapped in the active site. The ethyl radical withstands prolonged storage at 77 K and its EPR signal is only partially lost upon annealing at 100 K, making it significantly less reactive than the methyl radical formed by SAM photolysis. Upon annealing above 77 K, the ethyl radical adds to the [4Fe‐4S] 2+ cluster, generating an ethyl‐[4Fe‐4S] 3+ organometallic species termed Ω E .

Impano, Stella↗
DOE OSTI2023

The effect of pore structure in ethane-selective metal-organic frameworks for ethylene purification

Separation of ethylene from ethane is of great importance in petrochemical industry. Adsorptive separation making use of porous materials such as metal-organic frameworks (MOFs) is an energy efficient technology compared to the conventional cryogenic distillation. However, preferential adsorption of ethylene over ethane represents the major current challenge. Here we demonstrate how pore structure can significantly alter the adsorption selectivity in two isoreticular Zr-MOFs. A simple ligand functionalization in UiO-66 yields smaller/better matching pore for ethane, and weaker interaction with ethylene, greatly enhancing ethane/ethylene selectivity in MOF-801. Ab initio calculations combined with in situ infrared spectroscopic analysis unveil the nature of host-guest interactions and differences in the overall binding energies. Polymer-grade ethylene (99.9%) can be produced directly from ethane/ethylene mixture in a single step. Having well-balanced adsorption capacity and selectivity, low-cost synthesis and easy scalability MOF-801 stands out as a promising ethane-selective adsorbent for one-step ethylene purification under ambient conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Machine learning-guided design, synthesis, and characterization of atomically dispersed electrocatalysts

The recent integration of machine learning into materials design has revolutionized the understanding of structure–property relationships and optimization of material properties beyond the trial-and-error paradigm. On one hand, machine learning has significantly accelerated the development of atomically dispersed metal-nitrogen-carbon (M-N-C) electrocatalysts, which traditionally heavily relied on heuristic approaches. On the other hand, the primary challenge of leveraging machine learning to expedite M-N-C materials discovery lies in the cost associated with data collection. Here, we review recent machine learning integration strategies for M-N-C catalyst development, including discussions on the typical algorithms such as symbolic regression and convolutional neural networks employed for the theoretical design, synthesis optimization via active learning, and advanced microscopy characterization. Subsequently, we provide our perspective on potential near-future directions for furthering machine learning-assisted development of new M-N-C catalysts and elucidating the complex physicochemical mechanisms governing the selectivity, activity, and durability in this class of materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Private, public, and bottled drinking water: Shared contaminant-mixture exposures and effects challenge

Background: Humans are primary drivers of environmental–contaminant exposures worldwide, including in drinking-water (DW). In the United States, point-of-use DW (POU–DW) is supplied via private tapwater (TW), public-supply TW, and bottled water (BW). Differences in management, monitoring, and messaging and lack of directly–intercomparable exposure data influence the actual and perceived quality and safety of different DW supplies and directly impact consumer decision–making. Objectives: The purpose of this paper is to provide a meta-analysis (quantitative synthesis) of POU–DW contaminant–mixture exposures and corresponding potential human–health effects of private-TW, public-TW, and BW by aggregating exposure results and harmonizing apical–health–benchmark–weighted and bioactivity–weighted effects predictions across previous studies by this research group. Discussion: Simultaneous exposures to multiple inorganic and organic contaminants of known or suspected human-health concern are common across all three DW supplies, with substantial variability observed in each and no systematic difference in predicted cumulative risk between supplies. Differences in contaminant or contaminant–class exposures, with important implications for DW–quality improvements, were observed and attributed to corresponding differences in regulation and compliance monitoring. Conclusion: The results indicate that human-health risks from contaminant exposures are common to and comparable in all three DW–supplies, including BW. Importantly, this study’s target analytical coverage, which exceeds that currently feasible for water purveyors or homeowners, nevertheless is a substantial underestimation of the breadth of contaminant mixtures in the environment and potentially present in DW. Thus, the results emphasize the need for improved understanding of the adverse human-health implications of long-term exposures to low–level inorganic–/organic–contaminant mixtures across all three distribution pipelines and do not support commercial messaging of BW as a systematically safer alternative to public-TW. Regardless of the supply, increased public engagement in source-water protection and drinking–water treatment is necessary to reduce risks associated with long-term DW–contaminant exposures, especially in vulnerable populations, and to reduce environmental waste and plastics contamination.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Integrated CO 2 capture and hydrogenation in presence of Ru–Na 2 ZrO 3 : An in-situ study

Integrated CO 2 capture and conversion (ICCC) by hydrogenation is a promising strategy to utilize carbon dioxide and this work add to the effort to elucidate the catalytic hydrogenation mechanism using Ru based dual functional materials (DFM). Ru-Na 2 ZrO 3 DFMs, obtained through different wet methods, were evaluated for the first time and the relationship between Ru and support systematically investigated. The thermally stable and cyclable Ru-Na 2 ZrO 3 -a (obtained without filtration step) exhibited CO 2 conversion of 80% and a higher yield of CO at 400°C compared to previously tested DFM, while the Na depleted/Zr rich Ru-Na 2 ZrO 3 -b resulted in 90% selectivity to CH 4 with yield of 1.11 mmol/g at the same temperature. The in-situ experiments have provided conclusive evidence showing that CO 2 hydrogenation on the two Ru DFMs is fundamentally different. In Ru-Na 2 ZrO 3 -a, the monoclinic Na 2 ZrO 3 support acted as the active centre (not as promoter) for CO 2 bridging binding and hydrogenation to CH 4 at the metal-support interface through associative formate pathway with limited further reduction to methane due to lack of H 2 spillover from the small and well dispersed Ru NPs, which results in CO desorption. Conversely, abundant clusters of larger Ru NPs in Ru-Na 2 ZrO 3 -b, led to CH 4 production due to co-existent Ru on-top direct dissociation of CO 2 (preferential) and monodentate formate adsorption and further methanation. Alkali zirconates doped metals, and their synthesis method could thus play a crucial role in designing tuneable heterogeneous catalysis in C 1 chemistry, which could significantly benefit the environment by lowering CO 2 levels, encouraging cleaner industrial practices, supporting a circular economy, and converting waste CO 2 into valuable products.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Facet-Dependent Photodegradation of Methylene Blue by Hematite Nanoplates in Visible Light

The expression of specific crystal facets in different nanostructures is known to play a vital role in determining the sensitivity toward photodegradation of organics, which can generally be ascribed to differences in surface structure and energy. Herein, we report the synthesis of hematite nanoplates with controlled relative exposure of basal (001) and edge (012) facets, enabling us to establish direct correlation between surface structure and the photocatalytic degradation efficiency of methylene blue (MB) in the presence of hydrogen peroxide. MB adsorption experiments showed that the capacity on (001) is about three times larger than on (012), and this is supported by density functional theory calculations suggesting adsorption energies about 1.5 times higher. However, this alone cannot explain the observed MB photodegradation rate, which is around 14.5 times faster on (001) than (012). The enhancement we attribute to a higher availability of photoelectron accepting surface Fe3+ sites on the (001) facet. This facilitates more efficient iron valence cycling and the heterogeneous photo-Fenton reaction yielding MB-oxidizing hydroxyl radicals at the surface. Our findings help establish a rational basis for design and optimization of hematite nanostructures as photocatalysts for environmental remediation.

Zong, Meirong↗
DOE OSTI2020

NMR-Guided High-Temperature Electrolyte Design Using a Novel PF 5 Marker

The thermal degradation of electrolytes containing lithium hexafluorophosphate (LiPF 6 ) is a well-studied subject. However, practical application of the knowledge is difficult since the effects of the degradation process on battery performance are not well known. In this work, we propose a novel NMR experimental setup allowing direct observation of the effects of various perturbations on the electrolyte thermal degradation process, which guides the design and synthesis of new additives that improve lithium-ion battery performance at elevated temperatures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Intense Reactivity in Sulfur–Hydrogen Mixtures at High Pressure under X-ray Irradiation

Superconductivity near room temperature in the sulfur–hydrogen system arises from a sequence of reactions at high pressures, with X-ray diffraction experiments playing a central role in understanding these chemical–structural transformations and the corresponding S:H stoichiometry. Here we document X-ray irradiation acting as both a probe and as a driver of chemical reaction in this dense hydride system. We observe a reaction between molecular hydrogen (H 2 ) and elemental sulfur (S 8 ) under high pressure, induced directly by X-ray illumination, at photon energies of 12 keV using a free electron laser. The rapid synthesis of hydrogen sulfide (H 2 S) at 0.3 GPa was confirmed by optical observations, spectroscopic measurements, and microstructural changes detected by X-ray diffraction. These results document X-ray induced chemical synthesis of superconductor-forming dense hydrides, revealing an alternative production strategy and confirming the disruptive nature of X-ray exposure in studies on high-pressure hydrogen chalcogenides, from water to high-temperature superconductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Evolutionary and functional relationships between plant and microbial C 1 metabolism in terrestrial ecosystems

One-carbon (C 1 ) metabolism, centered on the universal methyl donor S-adenosyl methionine (SAM), plays critical roles in biosynthesis, redox regulation, and stress responses across plants and microbes. A recently proposed photosynthetic C 1 pathway links SAM methyl groups directly to RuBisCO-mediated CO 2 assimilation and integrates with nitrogen and sulfur metabolism. Light-dependent SAM synthesis may regulate the methylation of biopolymers and specialized metabolites and help mitigate photorespiratory stress under elevated temperature and drought. Phylogenetic analysis of two core enzymes suggests evolutionary continuity from methylotrophic microbes to land plants, supporting microbial origins via endosymbiotic gene transfer. Beyond intracellular roles, C 1 metabolism drives biosphere–atmosphere exchange via gases such as methane, methanol, formic acid, and formaldehyde, and numerous specialized volatiles synthesized through SAM methylation. S-methylmethionine, a mobile C 1 metabolite, may mediate phloem transport of reduced sulfur, nitrogen, and methyl groups, linking above- and belowground C 1 cycling in plants. Advances in real-time gas sensing now allow the high-frequency quantification of C 1 fluxes from leaves, stems, and soils, highlighting C 1 metabolism as a critical and underrecognized component of terrestrial carbon and nutrient cycling. Given its microbial ancestry and the production of diverse volatile biosignatures, C 1 metabolism may also offer unique insights into life's origins and biosignature detection on exoplanets.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Ultrahigh-resolution scanning microwave impedance microscopy of moiré lattices and superstructures

Two-dimensional heterostructures composed of layers with slightly different lattice vectors exhibit new periodic structure known as moiré lattices, which, in turn, can support novel correlated and topological phenomena. Moreover, moiré superstructures can emerge from multiple misaligned moiré lattices or inhomogeneous strain distributions, offering additional degrees of freedom in tailoring electronic structure. High-resolution imaging of the moiré lattices and superstructures is critical for understanding the emerging physics. Here, we report the imaging of moiré lattices and superstructures in graphene-based samples under ambient conditions using an ultrahigh-resolution implementation of scanning microwave impedance microscopy. Although the probe tip has a gross radius of ~100 nm, spatial resolution better than 5 nm is achieved, which allows direct visualization of the structural details in moiré lattices and the composite super-moiré. We also demonstrate artificial synthesis of novel superstructures, including the Kagome moiré arising from the interplay between different layers.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Stable and selective catalysts for propane dehydrogenation operating at thermodynamic limit

Hitting the limits on propene synthesis The greater abundance of propane from shale gas has spurred efforts to use it as a propylene feedstock. Direct dehydrogenation catalysts consisting of platinum–tin alloy nanoparticles supported on alumina often must run with hydrogen dilution to avoid carbon buildup and excess tin to avoid alloy segregation. Motagamwala et al. report that platinum–tin nanoparticles interact more weakly with a silica support and the metals thus do not segregate. The use of undiluted reactants allowed the reaction to run near the thermodynamically limit of about 67% conversion with a selectivity to propylene of more than 99%. This catalyst also does not build up carbon and could run up to 30 hours without deactivation. Science , abg7894, this issue p. 217

Science & Technology - Other Topics↗
NASA NTRS1972

An approximate method for the synthesis of optimal control of distributed systems.

An approximate method is presented for the synthesis of an optimal control of distributed parameter systems, based on a combination of the ideas of Lyapunov's direct method and those of Bellman's successive approximation in policy space. The method is such that the approximate equation is improved after each iteration in the sense of the performance index being used.

Park, K. E.↗
NASA NTRS1980

A comparison of flight and simulation data for three automatic landing system control laws for the Augmentor wing jet STOL research airplane

Automatic flare and decrab control laws for conventional takeoff and landing aircraft were adapted to the unique requirements of the powered lift short takeoff and landing airplane. Three longitudinal autoland control laws were developed. Direct lift and direct drag control were used in the longitudinal axis. A fast time simulation was used for the control law synthesis, with emphasis on stochastic performance prediction and evaluation. Good correlation with flight test results was obtained.

Feinreich, B.↗
NASA NTRS1987

The case for an ancestral genetic system involving simple analogues of the nucleotides

The idea that the first living systems on earth were based on self-replicating RNA molecules has recently become popular as a result of the discovery of ribozymes. However, there are several major problems associated with the prebiotic synthesis of ribonucleotides. In addition, there is the newly recognized problem of enantiomeric cross-inhibition, whereby template-directed polymerization involving one enantiomer of RNA is inhibited strongly by the presence of the other enantiomer. Here, it is proposed that RNA was preceded in the evolution of life by a polymer constructed from flexible, acyclic, probably prochiral nucleotide analogues that were synthesized readily on the primitive earth. Several potentially prebiotic nucleotide analogues are considered in this context, and some of the consequences of this proposal are discussed.

Joyce, Gerald F.↗
NASA NTRS1998

Tutorial on the Psychophysics and Technology of Virtual Acoustic Displays

Virtual acoustics, also known as 3-D sound and auralization, is the simulation of the complex acoustic field experienced by a listener within an environment. Going beyond the simple intensity panning of normal stereo techniques, the goal is to process sounds so that they appear to come from particular locations in three-dimensional space. Although loudspeaker systems are being developed, most of the recent work focuses on using headphones for playback and is the outgrowth of earlier analog techniques. For example, in binaural recording, the sound of an orchestra playing classical music is recorded through small mics in the two "ear canals" of an anthropomorphic artificial or "dummy" head placed in the audience of a concert hall. When the recorded piece is played back over headphones, the listener passively experiences the illusion of hearing the violins on the left and the cellos on the right, along with all the associated echoes, resonances, and ambience of the original environment. Current techniques use digital signal processing to synthesize the acoustical properties that people use to localize a sound source in space. Thus, they provide the flexibility of a kind of digital dummy head, allowing a more active experience in which a listener can both design and move around or interact with a simulated acoustic environment in real time. Such simulations are being developed for a variety of application areas including architectural acoustics, advanced human-computer interfaces, telepresence and virtual reality, navigation aids for the visually-impaired, and as a test bed for psychoacoustical investigations of complex spatial cues. The tutorial will review the basic psychoacoustical cues that determine human sound localization and the techniques used to measure these cues as Head-Related Transfer Functions (HRTFs) for the purpose of synthesizing virtual acoustic environments. The only conclusive test of the adequacy of such simulations is an operational one in which the localization of real and synthesized stimuli are directly compared in psychophysical studies. To this end, the results of psychophysical experiments examining the perceptual validity of the synthesis technique will be reviewed and factors that can enhance perceptual accuracy and realism will be discussed. Of particular interest is the relationship between individual differences in HRTFs and in behavior, the role of reverberant cues in reducing the perceptual errors observed with virtual sound sources, and the importance of developing perceptually valid methods of simplifying the synthesis technique. Recent attempts to implement the synthesis technique in real time systems will also be discussed and an attempt made to interpret their quoted system specifications in terms of perceptual performance. Finally, some critical research and technology development issues for the future will be outlined.

Wenzel, Elizabeth M.↗