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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 OSTI2017

Resilience and recovery of Dehalococcoides mccartyi following low pH exposure

Bioremediation treatment (e.g. biostimulation) can decrease groundwater pH with consequences for Dehalococcoides mccartyi (Dhc) reductive dechlorination activity. To explore the pH resilience of Dhc, the Dhc-containing consortium BDI was exposed to pH 5.5 for up to 40 days. Following 8- and 16-day exposure periods to pH 5.5, dechlorination activity and growth recovered when returned to pH 7.2; however, the ability of the culture to dechlorinate vinyl chloride (VC) to ethene was impaired (i.e. decreased rate of VC transformation). Dhc cells exposed to pH 5.5 for 40 days did not recover the ethene-producing phenotype upon transfer to pH 7.2 even after 200 days of incubation. When returned to pH 7.2 conditions after an 8-, a 16- and a 40-day low pH exposure, tceA and vcrA genes showed distinct fold increases, suggesting Dhc strain-specific responses to low pH exposure. Furthermore, a survey of Dhc biomarker genes in groundwater samples revealed the average abundances of Dhc 16S rRNA, tceA and vcrA genes in pH 4.5–6 groundwater were significantly lower (P-value < 0.05) than in pH 6–8.3 groundwater. Overall, the results of the laboratory study and the assessment of field data demonstrate that sustained Dhc activity should not be expected in low pH groundwater, and the duration of low pH exposure affects the ability of Dhc to recover activity at circumneutral pH.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Pressure Effects on the 4 f Electronic Structure of Light Lanthanides

Adopting the satellite structure of the $\mathcal{Lγ_1}$ line in nonresonant x-ray emission spectra, we probe the high-pressure evolution of the bare 4f signature of the early light lanthanides at ambient temperature. For Ce and Pr the satellite peak experiences a sudden reduction concurrent with their respective volume collapse (VC) transitions. These new experimental results are supported by calculations using state-of-the-art extended atomic structure codes for Ce and Pr, and also for Nd, which does not exhibit a VC. Here, our work suggests that changes to the 4f occupation are more consistently associated with evolution of the satellite than is the reduction of the 4f moment. Indeed, we show that in the case of Ce, mixing of a higher atomic angular momentum state, driven by the increased hybridization, acts to obscure the expected satellite reduction. These measurements emphasize the importance of a unified study of a full set of microscopic observables to obtain the most discerning test of the underlying, fundamental f-electron phenomena at high pressures.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Terrestrial biosphere models underestimate photosynthetic capacity and CO 2 assimilation in the Arctic

Terrestrial biosphere models (TBMs) are highly sensitive to model representation of photosynthesis, in particular the parameters maximum carboxylation rate and maximum electron transport rate at 25°C (V c,max.25 and J max.25 , respectively). Many TBMs do not include representation of Arctic plants, and those that do rely on understanding and parameterization from temperate species. We then measured photosynthetic CO 2 response curves and leaf nitrogen (N) content in species representing the dominant vascular plant functional types found on the coastal tundra near Barrow, Alaska. The activation energies associated with the temperature response functions of Vc,max and Jmax were 17% lower than commonly used values. When scaled to 25°C, Vc,max.25 and J max.25 were two- to five-fold higher than the values used to parameterize current TBMs. This high photosynthetic capacity was attributable to a high leaf N content and the high fraction of N invested in Rubisco. Leaf-level modeling demonstrated that current parameterization of TBMs resulted in a two-fold underestimation of the capacity for leaf-level CO 2 assimilation in Arctic vegetation. Our study highlights the poor representation of Arctic photosynthesis in TBMs, and provides the critical data necessary to improve our ability to project the response of the Arctic to global environmental change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

The ‘one–point method’ for estimating maximum carboxylation capacity of photosynthesis: a cautionary tale

The maximum carboxylation capacity of Rubisco, V c,max , is an important photosynthetic parameter that is key to accurate estimation of carbon assimilation. The gold-standard technique for determining V c,max is to derive Vc,max from the initial slope of an A–Ci curve (the response of photosynthesis, A to intercellular CO 2 concentration, Ci). Accurate estimates of V c,max derived from an alternative and rapid ‘one-point’ measurement of photosynthesis could greatly accelerate data collection and model parameterization. We evaluated the practical application of the one-point method in six species measured under standard conditions (saturating irradiance and 400 μmol CO 2 mol -1 ) and under conditions that would increase the likelihood for successful estimation of Vc,max: (a) ensuring Rubisco-limited A by measuring at 300 μmol CO 2 mol -1 , and (b) allowing time for acclimation to saturating irradiance prior to measurement. The one-point method significantly underestimated V c,max in four of the six species, providing estimates 21-32% below fitted values. We identified ribulose-1,5-bisphosphate-limited A, light acclimation and the use of an assumed respiration rate as factors that limited the effective use of the one-point method to accurately estimate V c,max . We conclude that the one-point method requires a species-specific understanding of its application, is often unsuccessful, and must be used with caution.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Mechanisms contributing to dark current across metal/CdMnTe/metal structures

The study of the electro-physical properties of n-type semi-insulating crystals of indium-doped Cd(Mn)Te solid solution with a resistivity ~ (4÷5)×10 10 Ohm×cm at T = 300 K was carried out. The structures both with an ohmic (In/Cd(Mn)Te/In) contacts and with the rectifying (Ni/Cd(Mn)Te/In) contact were fabricated. It was found that for the Ni/Cd(Mn)Te/In structure, the main mechanisms of charge transport were: the generation currents in the space-charge region, space-charge limited currents (SCLC) at high voltages, and the Ohm’s law was valid only on initial section the of the volt-ampere characteristics (I-VC). Calculation of the generation current dependence on the voltage according to the theory of Sah-Noyce-Shockley was carried out. For the In/Cd(Mn)Te/In structure it was observed the I-VC initial section, where the Ohm’s law was implemented, and the SCLCs with the participation of deep centers (traps) in semiinsulating crystal - at greater voltages. The concentration of deep centers (Nt ~ 7.4×10 10 cm -3 ) responsible for the trap mechanism in SCLC In/Cd(Mn)Te/In structures was calculated. The energy position Et of the deep levels was determined (provided that the energy was calculated from the valence band edge, Et = 0.89÷0.9 eV). It was discussed and grounded the assumption that SCLC was the main mechanism limiting the operating voltages and, consequently, the use of Cd(Mn)Te-based ionizing-radiation detectors with ohmic contacts.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Structure of Diamond-Like Silicon–Carbon Films Alloyed by Vanadium

The structure of diamond-like silicon–carbon films formed on silicon substrates by magnetron and plasmatron codeposition using a closed-field magnetron and a plasmatron activated by tungsten cathode has been studied by transmission electron microscopy. The main feature of the films alloyed by vanadium to concentrations of 12–31 at % was found to be a layered structure of the film cross section. It was established that vanadium alloying leads to the formation of vanadium carbide (VC) nanocrystals; the nanocrystal size increases from 1–2 to 10 nm. At the maximum vanadium content, VC nanocrystals have an anisotropic shape: they are extended in the direction perpendicular to the film–substrate interface.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The Low-Energy State of an Electron Beam in a Coaxial Diode with a Homogeneous Anode and Inhomogeneous Magnetic Field Profile

The possible formation of an extended low-energy state of electron beam in a coaxial diode with homogeneous cylindrical anode and moderate magnetic field with inhomogeneous profile is demonstrated for the first time. It is established that, depending on the magnetic field configuration, virtual cathodes (VCs) of two types can be formed: (i) a stationary VC with a localized reflection plane and (ii) a moving VC with a two-stream low-energy state of the electron beam.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

Quantifying SEI Reaction Rate in the Presence and Absence of Mn 2+

In this work, a methodology utilizing potentiostatic holds is developed for measuring side-reaction rates at graphite (Gr) electrodes. The influence of Mn 2+ on parasitic reactions is evaluated in the presence of various preformed solid-electrolyte interphases (SEI). Gr SEI preformation was carried out using vinylene carbonate (VC) or lithium difluoro(oxalato)borate (LiDFOB) as an additive. In addition, a highly fluorinated electrolyte, free of traditional non-fluorinated organic carbonates, was used. Parasitic current increases were observed for all preformed Gr SEIs when Mn 2+ was present. Of the preforming electrolytes, the VC-derived SEI showed the lowest parasitic currents both with and without Mn 2+ .

Tornheim, Adam [Argonne National Laboratory (ANL),↗
DOE OSTI2026

matsim-agents v1.0

matsim-agents is a multi-agent AI framework for atomistic materials simulation and discovery. It orchestrates large language models (LLMs), machine-learned interatomic potentials (MLIPs), and DFT codes into a single agentic loop running on laptops and DOE leadership-class supercomputers. MULTI-AGENT ORCHESTRATION A LangGraph state machine with three nodes: a Planner that converts a natural-language research objective into structured tasks; an Executor that dispatches atomistic tools and loops until the queue is empty; and an Analyst that summarizes results into a human-readable report. State is checkpointed after every step and human-in-the-loop gates can be inserted at any edge. HYPOTHESIS-DRIVEN DISCOVERY CHAT An interactive REPL (matsim-agents chat) that couples LLM dialogue with atomistic simulation. Chemical formulas are automatically detected in conversation turns and trigger a full crystal-phase exploration: structure generation → relaxation → stability scoring → result injection back into the conversation, creating a closed hypothesis-refinement loop. CRYSTAL PHASE ENUMERATION Given a composition, the phase explorer enumerates prototypes by stoichiometry: elemental (fcc/bcc/hcp/sc/diamond), binary 1:1 (rocksalt/CsCl/zincblende/ wurtzite/fluorite/rutile), ternary 1:1:3 (cubic perovskite), ternary 1:2:4 (perovskite + spinel), quaternary 1:1:2:6 (Fm-3m double perovskite). 2-D prototypes (graphene, h-BN, MoS2 2H/1T) and multilayer stacking are also supported via --include-2d and --num-layers. SUPERCELL GENERATION AND SITE DECORATION Auto-tiling to a minimum atom count (--min-atoms), explicit NxNxN tiling (--supercell), symmetry-distinct site decorations (--n-orderings), and isotropic lattice-scale sweeps (--lattice-scales) for volume bracketing. MLFF RELAXATION AND STABILITY SCORING HydraGNN (multi-headed GNN) drives structure relaxation via ASE with FIRE, BFGS, or BFGSLineSearch. Stability output: delta-E/atom ranking across phases and a max-residual-force dynamical-stability proxy. Other MLIPs (MACE, NequIP, Orb) can be plugged in through the same interface. DFT BACKENDS Quantum ESPRESSO pw.x and VASP 6.6 are first-class labellers. Both have validated GPU builds and SLURM/PBS launchers for three DOE platforms: Frontier (AMD MI250X, ROCm), Aurora (Intel PVC, oneAPI), Perlmutter (NVIDIA A100, CUDA). QE produces ~100 binaries (pw.x, ph.x, epw.x, ...). VASP supports scf, relax, vc-relax, and vc-relax-shape run types. ACTIVE-LEARNING LOOP matsim-agents al run CONFIG.yaml drives an iterative HydraGNN-DFT loop: MD generates candidates → ensemble/MC-dropout uncertainty selects the most informative → DFT labels them in parallel inside one allocation → dataset grows → HydraGNN retrains → repeat. DFT backend is a single YAML toggle (dft.backend: vasp | qe). LLM-generated seed structures are supported (no curated POSCAR library needed). Config uses ${VAR}, ${VAR:-default}, ${VAR:?msg} shell-style substitution for cross-user/cross-site portability. LLM BACKENDS Ollama (local, default), vLLM (HPC multi-GPU serving), OpenAI, Anthropic, HuggingFace Transformers+Accelerate. Selected at runtime via flag or env var with no code changes. HPC PORTABILITY Same Python entry points run on Frontier (ROCm 7.2), Aurora (oneAPI), and Perlmutter (CUDA 12). DFT and ML stacks are never co-loaded in the same shell; they couple through the scheduler and filesystem. Advanced multi-node launchers (serve, discovery-chat, single-relaxation, active-learning, QE warm-start) are provided for all three platforms. CODABENCH COMPETITION BUNDLE A self-contained benchmark: 159 atomistic test structures across 11 material classes, 5 tasks (formation energy, forces, ML relaxation, AI-DFT relaxation, phase stability ranking), public/private leaderboard split (30/70), and four ready-to-run baselines: MACE-MP-0, HydraGNN, UMA, AllScAIP.

Lupo Pasini, Massimiliano [Oak Ridge National Labo↗
DOE OSTI2025

Distributed Online Voltage Control in Distribution Network: A Two-Stage Real-Time Implementation

The increasing integration of renewable-based distributed generation (DG) brings growing challenges to distribution network (DN) voltage control. To address this issue, a two-stage distributed online voltage control framework (TDO-VC) is proposed in this paper. In the proposed method, legacy voltage control devices are controlled in the upper stage on an hourly timescale, while DGs operate autonomously online in the lower stage to remove instantaneous voltage violations. The idea of receding horizon control is applied in the upper stage to comprehensively consider the current and future renewable generation, and the generalized fast dual ascent (Gf-DA) is employed in the lower stage to effectively manage DGs through near real-time optimization. The effectiveness of the proposed TDO-VC is demonstrated by rigorous theoretical analysis and case studies on IEEE-123 bus system.

Distributed generation↗
DOE OSTI2024

Evaluation of partial volume correction and analysis of longitudinal [ 18 F]GTP1 tau PET imaging in Alzheimer's disease using linear mixed-effects models

Purpose: We evaluated the impact of partial volume correction (PVC) methods on the quantification of longitudinal [ 18 F]GTP1 tau positron-emission tomography (PET) in Alzheimer's disease and the suitability of describing the tau pathology burden temporal trajectories using linear mixed-effects models (LMEM). Methods: We applied van Cittert iterative deconvolution (VC), 2-compartment, and 3-compartment, and the geometric transfer matrix plus region-based voxelwise methods to data acquired in an Alzheimer's disease natural history study over 18 months at a single imaging site. We determined the optimal PVC method by comparing the standardized uptake value ratio change (%ΔSUVR) between diagnostic and tau burden–level groups and the longitudinal repeatability derived from the LMEM. The performance of LMEM analysis for calculating %ΔSUVR was evaluated in a natural history study and in a multisite clinical trial of semorinemab in prodromal to mild Alzheimer's disease by comparing results to traditional per-visit estimates. Results: The VC, 2-compartment, and 3-compartment PVC methods had similar performance, whereas region-based voxelwise overcorrected regions with a higher tau burden. The lowest within-subject variability and acceptable group separation scores were observed without PVC. The LMEM-derived %ΔSUVR values were similar to the per-visit estimates with lower variability. Conclusion: The results indicate that the tested PVC methods do not offer a clear advantage or improvement over non-PVC images for the quantification of longitudinal [ 18 F]GTP1 PET data. LMEM offers a robust framework for the longitudinal tau PET quantification with low longitudinal test–retest variability. Clinical trial registration: NCT02640092 and NCT03289143.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Reduction of Chlorinated Ethenes by Ag- and Cu-Amended Green Rust

Chlorinated ethenes have been used extensively as solvents, degreasers, and dry-cleaning agents in a range of commercial and industrial applications. This has created a legacy of contaminated soils and groundwater, particularly with respect to perchloroethylene (PCE; a.k.a. tetrachloroethene—C 2 Cl 4 ), and trichloroethylene (TCE; a.k.a. trichloroethene—C 2 HCl 3 ), prompting the development of a wide array of treatment technologies for remediation of chlorinated ethene-contaminated environments. Green rusts are highly redox-active layered Fe(II)-Fe(III) hydroxides that have been shown to be facile reductants for a wide range of organic and inorganic pollutants. The reduction of chlorinated ethenes [vinyl chloride (VC); 1,1-dichloroethene(11DCE), cis-1,2-dichloroethene (c12DCE), trans-1,2-dichloroethene (t12DCE), TCE, and PCE] was examined in aqueous suspensions of green rust, alone as well as with the addition of Ag(I) (AgGR) or Cu(II) (CuGR). Green rust alone was ineffective as a reductant for the reductive dechlorination for all of the chlorinated ethenes. Near-complete removal of PCE was observed in the presence of AgGR, but all other chlorinated ethenes were essentially non-reactive. Partial removal of chlorinated ethenes was observed in the presence of CuGR, particularly 11DCE (34%), t12DCE (51%), and VC (66%). Significant differences were observed in the product distributions of chlorinated ethene reduction by AgGR and CuGR. The effectiveness of Ag(I)- and Cu(II)-amended green rusts for removal of chlorinated ethenes may be improved under different conditions (e.g., pH and interlayer anion) and warrants further investigation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Evaluation of the One-point Method for Estimating Carboxylation Capacity, Utqiagvik (Barrow), Alaska and Upton, New York, 2018

The maximum carboxylation efficiency of Rubisco (Vc,max) fitted from CO2 response curves and estimated from light-saturated photosynthesis using the one-point method. Data were collected in Utqiagvik (Barrow), AK and New York in 2018 on 6 species - Arctagrostis latifolia, Helianthus annuus, Populus canadensis, Phaseolus vulgaris, Quercus coccinea, Raphanus sativus. These data were used to compare fitted with estimated values of Vc,max to test the efficacy of the one-point method. Arctic data were used alongside temperate data for an evaluation of one-point gas exchange methodology, supported in part by NGEE Arctic. This dataset is comprised of fitted parameter values and raw gas exchange data files and metadata files in csv format. File formats have been updated from the original publication on the NGEE-Arctic archive, but the data has not been modified. The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic), was a research effort to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy's Office of Biological and Environmental Research. The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska. Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy's Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1983

Creation of high-energy electron tails by means of the modified two-stream instability

Particle simulations of the modified two-stream instability demonstrate strong electron acceleration rather than bulk heating when the relative drift speed is below a critical speed Vc. A very interesting nonlinear mode transition and autoresonance acceleration process is observed which accelerates the electrons much above the phase speed of the linearly unstable modes. Simple criteria are presented that predict the value of Vc and the number density of the accelerated electrons.

Tanaka, M.↗
NASA NTRS1987

A passive vibration-cancelling isolation mount

An analysis of an idealized passive vibration-cancelling two-terminal mount with one degree of freedom at each mechanical terminal isolating a nonrigid machine from a nonrigid foundation is presented. To evaluate a vibration-cancelling (VC) mount, its effectiveness as a function of frequency is compared with the effectiveness of both conventional and compound mounts isolating a rigid machine from a nonrigid foundation. The comparisons indicate that a carefully designed and manufactured VC mount should provide substantially greater vibration reduction at its cancellation frequency than either a conventional or compound mount having the same low frequency stiffness, i.e., stiffness at the natural frequency of the machine mount system.

Sykes, Alan O.↗
NASA NTRS1992

Spatiotemporal chaos near the onset of cellular growth during thin-film solidification of a binary alloy

Thin-film solidification experiments with a succinonitrile-acetone alloy are used to observe the long time-scale dynamics of cellular crystal growth at growth rates only slightly above the critical value VC = Vc(lambda sub c) for the onset of morphological instability. Under these conditions only very small amplitude cells are observed with wavelengths near the value predicted by linear stability theory lambda = lambda sub c. At long times, microstructures with wavelengths significantly finer than lambda suc c form by nucleation at defects across the interface. These interfaces do not have a unique microstructure, but seem to exhibit spatiotemporal chaos on a long time scale caused by the continual birth and death of cells by tip splitting and cell annihilation in grooves.

Lee, J. T. C.↗
NASA NTRS1996

High-Lift Systems on Commercial Subsonic Airliners

The early breed of slow commercial airliners did not require high-lift systems because their wing loadings were low and their speed ratios between cruise and low speed (takeoff and landing) were about 2:1. However, even in those days the benefit of high-lift devices was recognized. Simple trailing-edge flaps were in use, not so much to reduce landing speeds, but to provide better glide-slope control without sideslipping the airplane and to improve pilot vision over the nose by reducing attitude during low-speed flight. As commercial-airplane cruise speeds increased with the development of more powerful engines, wing loadings increased and a real need for high-lift devices emerged to keep takeoff and landing speeds within reasonable limits. The high-lift devices of that era were generally trailing-edge flaps. When jet engines matured sufficiently in military service and were introduced commercially, airplane speed capability had to be increased to best take advantage of jet engine characteristics. This speed increase was accomplished by introducing the wing sweep and by further increasing wing loading. Whereas increased wing loading called for higher lift coefficients at low speeds, wing sweep actually decreased wing lift at low speeds. Takeoff and landing speeds increased on early jet airplanes, and, as a consequence, runways worldwide had to be lengthened. There are economical limits to the length of runways; there are safety limits to takeoff and landing speeds; and there are speed limits for tires. So, in order to hold takeoff and landing speeds within reasonable limits, more powerful high-lift devices were required. Wing trailing-edge devices evolved from plain flaps to Fowler flaps with single, double, and even triple slots. Wing leading edges evolved from fixed leading edges to a simple Krueger flap, and from fixed, slotted leading edges to two- and three-position slats and variable-camber (VC) Krueger flaps. The complexity of high-lift systems probably peaked on the Boeing 747, which has a VC Krueger flap and triple-slotted, inboard and outboard trailing-edge flaps. Since then, the tendency in high-lift system development has been to achieve high levels of lift with simpler devices in order to reduce fleet acquisition and maintenance costs. The intent of this paper is to: (1) review available high-lift devices, their functions, and design criteria; (2) appraise high-lift systems presently in service on commercial air liners; (3) present personal study results on high-lift systems; (4) develop a weight and cost model for high-lift systems; and (5) discuss the development tendencies of future high-lift systems.

Rudolph, Peter K. C.↗
NASA NTRS1999

Overshooting in Massive Stars: Conceptual Problems and Suggested Solution

Overshooting in massive stars faces a basic difficulty: what theoretical models offer is not what stellar structure studies need. The former use Delta(sub mu) = 0 and define the OV where the negative convective flux J vanishes while the latter need to know where the concentration flux J(sub C) vanishes. We suggest that J may be dynamically irrelevant and derive the new dynamic equations for J(sub C). A new feature emerges: for large concentration gradients VC, J(sub C) is no longer proportional to VC, as always assumed.

Canuto, V. M.↗