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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

High‐Spin and Reactive Fe 13 Cluster with Exposed Metal Sites

Abstract Atomically defined large metal clusters have applications in new reaction development and preparation of materials with tailored properties. Expanding the synthetic toolbox for reactive high nuclearity metal complexes, we report a new class of Fe clusters, Tp* 4 W 4 Fe 13 S 12 , displaying a Fe 13 core with M−M bonds that has precedent only in main group and late metal chemistry. M 13 clusters with closed shell electron configurations can show significant stability and have been classified as superatoms. In contrast, Tp* 4 W 4 Fe 13 S 12 displays a large spin ground state of S =13. This compound performs small molecule activations involving the transfer of up to 12 electrons resulting in significant cluster rearrangements.

Scott, Anna G.↗
DOE OSTI2020

Sub‐5 nm Intermetallic Nanoparticles Confined in Mesoporous Silica Wells for Selective Hydrogenation of Acetylene to Ethylene

Abstract We report the synthesis and catalytic application of intermetallic PtSn nanoparticles confined in MSWs (Mesoporous Silica Wells) in the semi‐hydrogenation of acetylene. Platinum nanoparticles with a size of 2.9 nm supported on amine‐functionalized ∼180 nm silica spheres were enmeshed in a mesoporous silica shell. After the addition of tin via a polyol synthesis method, we obtained the final PtSn x @MSW (x=0.30, 0.50, 0.70, 1.0 and 2.0). Owing to the mesoporous encapsulation the sub‐5 nm bimetallic particles are shown to be monodisperse and well protected against aggregation on the silica sphere even under high‐temperature treatment conditions. In the gas phase semi‐hydrogenation of acetylene, the PtSn@MSW with Sn/Pt molar ratios equal to or greater than one displayed higher selectivity to ethylene. Meanwhile, increasing Sn content decreases acetylene conversion. The intermetallic PtSn@MSW catalysts also displayed long‐term stability and regenerability due to the confined environment provided by MSW.

Maligal‐Ganesh, Raghu V.↗
DOE OSTI2023

Efficacy of one-time rotenone application for Westslope Cutthroat Trout restoration in Boulder Creek, Montana

Abstract Objective Although piscicides are an important tool for native fish management, our understanding of native fish population dynamics posttreatment (i.e., in putatively vacant habitat) is limited. Methods Here, we describe long-term trends in size and abundance of Cutthroat Trout Oncorhynchus clarkii in Lower Boulder Lake and Boulder Creek (Montana). Result No significant differences were found before and after treatment with rotenone in mean length and population density in Boulder Creek. Posttreatment genetic samples from Boulder Lake and upper Boulder Creek consisted entirely of the Westslope Cutthroat Trout Oncorhynchus clarkii lewisi used to refound the population. Middle and lower Boulder Creek genetic samples contained 99.4% and 98.4% Westslope Cutthroat Trout, indicating that some nonnative (Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri hybrid) fish survived the treatment. Population demographics showed robust recovery posttreatment; however, genetic results revealed the limitations of a one-time treatment—that is, an incomplete fish kill. Conclusion We demonstrate that Cutthroat Trout populations achieve recovery after rotenone treatment in the long term, but one-time rotenone treatments on large drainages often fail to totally eradicate populations. Therefore, managers should plan on multiple treatments and utilize environmental DNA to help achieve total removal of target species.

Lampton, Jared↗
DOE OSTI2020

Structure, properties, and applications of polyacrylonitrile/carbon nanotube ( CNT ) fibers at low CNT loading

Abstract Bi‐component, polyacrylonitrile (PAN)/carbon nanotube (CNT) fibers were processed, at different core‐sheath area ratios, by gel spinning. A percolated CNT network at 10 wt% CNT in the sheath enhanced electrical conductivity as compared to the neat PAN fiber, while PAN polymer in the core contributed to the good mechanical properties. Fibers with relatively thin sheath allowed overall CNT loading as low as 3.7 wt% to be made with good electrical conductivity, and PAN stabilization by Joule heating was demonstrated. Such fibers with combined good mechanical properties and electrical conductivity can also potentially be used for electrical heating of fabrics, for making smart textiles, and for electromagnetic interference shielding.

Lu, Mingxuan↗
DOE OSTI2021

Algorithm advances and applications of time‐dependent first‐principles simulations for ultrafast dynamics

Abstract Far from equilibrium phenomenon is a central theme of contemporary material research. Such phenomenon can exhibit itself in atomic structure and dynamics, but very often it also happens as non‐equilibrium phenomenon in the electronic structure. In ab initio material simulation, density functional theory (DFT) has played an essential role in studying electronic ground state problems. For excited states, besides many‐body perturbation theory, another powerful tool is the time dependent DFT (TDDFT) method. In particular, the real‐time TDDFT (rt‐TDDFT) method can be used to simulate many non‐equilibrium phenomena directly. Here we introduce our works on some algorithm advances based on our recently rt‐TDDFT method. This method uses the plane‐wave basis set, and significantly accelerates its efficiency by increasing the time step from 0.1–1 as in traditional methods to 0.2–0.5 fs. The noncollinear magnetic moments and spin–orbit coupling have also been included in our rt‐TDDFT method. Furthermore, a Boltzmann‐TDDFT algorithm has been developed to solve the hot carrier overheating problem in Ehrenfest dynamics, and a natural orbital branching algorithm has been developed to overcome the mean‐field approximation in Ehrenfest dynamics nuclear trajectory, thus allows stochastic multiple paths in chemical reactions. Utilizing these methods, we have studied the photoinduced ultrafast demagnetization, ultrafast phase transition, energy transfer between plasmon and hot carriers, as well as the high‐energy ion implantation and low‐energy atomic diffusion in semiconductors. We believe the tools as the ones introduced here can enable us to study a wide range of phenomena which are of great interest in modern day material research. This article is categorized under: Structure and Mechanism > Computational Materials Science Electronic Structure Theory > Ab Initio Electronic Structure Methods Electronic Structure Theory > Density Functional Theory

Liu, Wen‐Hao↗
DOE OSTI2021

Analysis-Specific Fast Simulation at the LHC with Deep Learning

Abstract We present a fast-simulation application based on a deep neural network, designed to create large analysis-specific datasets. Taking as an example the generation of W + jet events produced in $$\sqrt{s}=$$ s = 13 TeV proton–proton collisions, we train a neural network to model detector resolution effects as a transfer function acting on an analysis-specific set of relevant features, computed at generation level, i.e., in absence of detector effects. Based on this model, we propose a novel fast-simulation workflow that starts from a large amount of generator-level events to deliver large analysis-specific samples. The adoption of this approach would result in about an order-of-magnitude reduction in computing and storage requirements for the collision simulation workflow. This strategy could help the high energy physics community to face the computing challenges of the future High-Luminosity LHC.

Chen, C.↗
DOE OSTI2023

Using a physics-informed neural network and fault zone acoustic monitoring to predict lab earthquakes

Abstract Predicting failure in solids has broad applications including earthquake prediction which remains an unattainable goal. However, recent machine learning work shows that laboratory earthquakes can be predicted using micro-failure events and temporal evolution of fault zone elastic properties. Remarkably, these results come from purely data-driven models trained with large datasets. Such data are equivalent to centuries of fault motion rendering application to tectonic faulting unclear. In addition, the underlying physics of such predictions is poorly understood. Here, we address scalability using a novel Physics-Informed Neural Network (PINN). Our model encodes fault physics in the deep learning loss function using time-lapse ultrasonic data. PINN models outperform data-driven models and significantly improve transfer learning for small training datasets and conditions outside those used in training. Our work suggests that PINN offers a promising path for machine learning-based failure prediction and, ultimately for improving our understanding of earthquake physics and prediction.

42 ENGINEERING↗
DOE OSTI2021

An artificial spiking quantum neuron

Abstract Artificial spiking neural networks have found applications in areas where the temporal nature of activation offers an advantage, such as time series prediction and signal processing. To improve their efficiency, spiking architectures often run on custom-designed neuromorphic hardware, but, despite their attractive properties, these implementations have been limited to digital systems. We describe an artificial quantum spiking neuron that relies on the dynamical evolution of two easy to implement Hamiltonians and subsequent local measurements. The architecture allows exploiting complex amplitudes and back-action from measurements to influence the input. This approach to learning protocols is advantageous in the case where the input and output of the system are both quantum states. We demonstrate this through the classification of Bell pairs which can be seen as a certification protocol. Stacking the introduced elementary building blocks into larger networks combines the spatiotemporal features of a spiking neural network with the non-local quantum correlations across the graph.

Kristensen, Lasse Bjørn (ORCID:0000000239398170)↗
DOE OSTI2024

Protocols for x-ray transient grating pump/optical probe experiments at x-ray free electron lasers

Abstract Transient grating spectroscopy is a specialized application of the four-wave-mixing methodology and constitutes a versatile technique for investigating the dynamics of vibrational, magnetic and electronic degrees of freedom of matter in a background-free fashion. Recent developments in free-electron laser sources have enabled the extension of this technique into the extreme ultraviolet range. Ongoing efforts to expand transient grating spectroscopy into the x-ray regime promise numerous advantages: (1) substantial penetration depths that allow for probing bulk material properties, (2) element specificity via specific core-excited states, and (3) short wavelengths that allow for excitation gratings with higher momentum transfer and improved spatial resolution. In this study, we comprehensively outline the procedures for conducting x-ray transient grating pump/optical probe experiment. The process encompasses the design and alignment of the experimental setup, as well as the subsequent steps involved in data acquisition and analysis. This paper is intended as a comprehensive guide for researchers interested in implementing x-ray transient grating spectroscopy, providing valuable insights into the intricacies of the experimental workflow required for this novel technique. Furthermore, we discuss the potential for extending this methodology to an x-ray pump/x-ray probe scheme, envisioning a future direction that holds promise for enhancing the capabilities and scope of x-ray transient grating spectroscopy, opening new opportunities for studying ultrafast processes with unprecedented temporal and spatial resolutions.

Optics↗
DOE OSTI2020

AC loss and contact resistance in REBCO CORC ® , Roebel, and stacked tape cables

Abstract Many high-temperature superconductor (HTS) applications require superconducting cables with high currents while operating in an alternating magnetic field. HTS cables should be composed of numerous superconducting tapes to achieve the required current capacity. Alternating current and magnetic fields cause AC losses in such cables and can provoke conductor instability. AC losses and contact resistances were measured of several cable designs based on commercially available REBCO tapes at the University of Twente. The AC loss was measured under identical conditions for eight REBCO conductors manufactured according to three types of cabling methods—CORC ® (Conductor on Round Core), Roebel, and stacked tape, including a full-size REBCO CICC (cable in conduit conductor). The measurements were done at T = 4.2 K without transport current in a sinusoidal AC magnetic field of 0.4 T amplitude and frequencies from 5 to 55 mHz. The AC loss was measured simultaneously by calibrated gas flow calorimeter utilizing the helium boil-off method and by the magnetization method using pick-up coils. Also, the AC loss of two CORC® conductors and a Roebel cable was measured at 77 K. Each conductor was measured with and without background field of 1 T. The measured AC coupling loss in the CORC ® and Roebel conductors is negligible at 4.2 K for the applied conditions while at 77 K coupling loss was observed for all conductors. The absence of coupling loss at 4.2 K can be explained by shielding of the conductor interior; this is confirmed with measurement and calculation of the penetration field of CORC ® and Roebel cables. The inter-tape contact resistance was measured for CORC ® and stacked tape samples at 4.2 and 77 K. It was demonstrated that a short heat treatment of CORC ® conductor with solder-coated tapes activates tape-to-tape soldering and decreases the contact resistance. The reduction of contact resistance by two orders in magnitude to tens of nΩm is comparable with the interstrand contact resistance in ITER Nb 3 Sn type conductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

The picasso map-making code: application to a simulation of the QUIJOTE northern sky survey

ABSTRACT Map-making is an important step for the data analysis of cosmic microwave background (CMB) experiments. It consists of converting the data, which are typically a long, complex, and noisy collection of measurements, into a map, which is an image of the observed sky. We present in this paper a new map-making code named picasso (Polarization and Intensity CArtographer for Scanned Sky Observations), which was implemented to construct intensity and polarization maps from the Multi Frequency Instrument (MFI) of the QUIJOTE (Q-U-I Joint TEnerife) CMB polarization experiment. picasso is based on the destriping algorithm, and is suited to address specific issues of ground-based microwave observations, with a technique that allows the fit of a template function in the time domain, during the map-making step. This paper describes the picasso code, validating it with simulations and assessing its performance. For this purpose, we produced realistic simulations of the QUIJOTE-MFI survey of the northern sky (approximately ∼20 000 deg2), and analysed the reconstructed maps with picasso, using real and harmonic space statistics. We show that, for this sky area, picasso is able to reconstruct, with high fidelity, the injected signal, recovering all the scales with ℓ > 10 in TT, EE, and BB. The signal error is better than 0.001 per cent at 20 < ℓ < 200. Finally, we validated some of the methods that will be applied to the real wide-survey data, like the detection of the CMB anisotropies via cross-correlation analyses. Despite that the implementation of picasso is specific for QUIJOTE-MFI data, it could be adapted to other experiments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Improved net carbon budgets in the US Midwest through direct measured impacts of enhanced weathering

Abstract Terrestrial enhanced weathering (EW) through the application of Mg‐ or Ca‐rich rock dust to soil is a negative emission technology with the potential to address impacts of climate change. The effectiveness of EW was tested over 4 years by spreading ground basalt (50 t ha −1 year −1 ) on maize/soybean and miscanthus cropping systems in the Midwest US. The major elements of the carbon budget were quantified through measurements of eddy covariance, soil carbon flux, and biomass. The movement of Mg and Ca to deep soil, released by weathering, balanced by a corresponding alkalinity flux, was used to measure the drawdown of CO 2 , where the release of cations from basalt was measured as the ratio of rare earth elements to base cations in the applied rock dust and in the surface soil. Basalt application stimulated peak biomass and net primary production in both cropping systems and caused a small but significant stimulation of soil respiration. Net ecosystem carbon balance (NECB) was strongly negative for maize/soybean (−199 to −453 g C m −2 year −1 ) indicating this system was losing carbon to the atmosphere. Average EW (102 g C m −2 year −1 ) offset carbon loss in the maize/soybean by 23%–42%. NECB of miscanthus was positive (63–129 g C m −2 year −1 ), indicating carbon gain in the system, and EW greatly increased inorganic carbon storage by an additional 234 g C m −2 year −1 . Our analysis indicates a co‐deployment of a perennial biofuel crop (miscanthus) with EW leads to major wins—increased harvested yields of 29%–42% with additional carbon dioxide removal (CDR) of 8.6 t CO 2 ha −1 year −1 . EW applied to maize/soybean drives a CDR of 3.7 t CO 2 ha −1 year −1 , which partially offsets well‐established carbon losses from soil from this crop rotation. EW applied in the US Midwest creates measurable improvements to the carbon budgets perennial bioenergy crops and conventional row crops.

enhanced weathering↗
DOE OSTI2025

Polyyne production is regulated by the transcriptional regulators PgnC and GacA in Pseudomonas protegens Pf-5

ABSTRACT Polyynes produced by bacteria have promising applications in agriculture and medicine due to their potent antimicrobial activities. Polyyne biosynthetic genes have been identified inPseudomonasandBurkholderia. However, the molecular mechanisms underlying the regulation of polyyne biosynthesis remain largely unknown. In this study, we used a soil bacteriumPseudomonas protegensPf-5, which was recently reported to produce polyyne called protegenin, as a model to investigate the regulation of bacterial polyyne production. Our results show that Pf-5 controls polyyne production at both the pathway-specific level and a higher global level. Mutation ofpgnC, a transcriptional regulatory gene located in the polyyne biosynthetic gene cluster, abolished polyyne production. Gene expression analysis revealed that PgnC directly activates the promoter of polyyne biosynthetic genes. The production of polyyne also requires a global regulator GacA. Mutation ofgacAdecreased the translation of PgnC, which is consistent with the result thatpgnCleader mRNA bound directly to RsmE, an RNA-binding protein negatively regulated by GacA. These results suggest that GacA induces the expression of the PgnC regulator, which in turn activates polyyne biosynthesis. Additionally, the polyyne-producing strain of Pf-5, but not the polyyne-nonproducing strain, could inhibit a broad spectrum of bacteria including both Gram-negative and Gram-positive bacteria. IMPORTANCE Antimicrobial metabolites produced by bacteria are widely used in agriculture and medicine to control plant, animal, and human pathogens. Although bacteria-derived polyynes have been identified as potent antimicrobials for decades, the molecular mechanisms by which bacteria regulate polyyne biosynthesis remain understudied. In this study, we found that polyyne biosynthesis is directly activated by a pathway-specific regulator PgnC, which is induced by a global regulator GacA through the RNA-binding protein RsmE inPseudomonas protegens. To our knowledge, this work is the first comprehensive study of the regulatory mechanisms of bacterial polyyne biosynthesis at both pathway-specific level and global level. The discovered molecular mechanisms can help us optimize polyyne production for agricultural or medical applications.

Biotechnology & Applied Microbiology↗