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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Design and implementation of a J -coupled spectrometer for multidimensional structure and relaxation detection at low magnetic fields

In recent years, it has been realized that low and ultra-low field (mT-nT magnetic field range) nuclear magnetic resonance (NMR) spectroscopy can be used for molecular structural analysis. However, spectra are often hindered by lengthy acquisition times or require large sample volumes and high concentrations. Here, we report a low field (50 µT) instrument that employs a linear actuator to shuttle samples between a 1 T prepolarization field and a solenoid detector in a laboratory setting. The current experimental setup is benchmarked using water and 13 C-methanol with a single scan detection limit of 2x10 20 spins (3 μL, 55 M H 2 O) and detection of 2.9x10 19 (200 μL, 617 mM 13 C-methanol) spins with signal averaging. The system has a dynamic range of >3 orders of magnitude. Investigations of room-temperature relaxation dynamics of 13Cmethanol show that sample dilution can be used in lieu of sample heating to acquire spectra with linewidths comparable to high-temperature spectra. These results indicate that the T 1 and T 2 mechanisms are governed by both the proton exchange rate and the dissolved oxygen in the sample. Finally, a 2D correlation spectroscopy (COSY) experiment is reported, performed in the strong coupling regime that resolves the multiple resonances associated with the heteronuclear Jcoupling. The spectrum was collected using 10 times less sample and in less than half the time from previous reports in the strong coupling limit.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Studying the Collective Functional Response of a Receptor in Alchemical Ligand Binding Free Energy Simulations with Accelerated Solvation Layer Dynamics

Ligand binding free energy simulations (LB-FES) that involve sampling of protein functional conformations have been longstanding challenges in research on molecular recognition. Particularly, modeling of the conformational transition pathway and design of the heuristic biasing mechanism are severe bottlenecks for the existing enhanced configurational sampling (ECS) methods. Inspired by the key role of hydration in regulating conformational dynamics of macromolecules, this report proposes a novel ECS approach that facilitates binding-associated structural dynamics by accelerated hydration transitions in combination with the lambda-exchange of free energy perturbation (FEP). Further, two challenging protein-ligand binding processes involving large configurational transitions of the receptor are studied, with hydration transitions at binding sites accelerated by Hamiltonian-simulated annealing of the hydration layer. Without the need for pathway analysis or ad hoc barrier flattening potential, LB-FES were performed with FEP/lambda-exchange molecular dynamics simulation at a minor overhead for annealing of the hydration layer. The LB-FES studies showed that the accelerated rehydration significantly enhances the collective conformational transitions of the receptor, and convergence of binding affinity calculations is obtained at a sweet-spot simulation time scale. Alchemical LB-FES with the proposed ECS strategy is free from the effort of trial and error for the setup and realizes efficient on-the-fly sampling for the collective functional response of the receptor and bound water and therefore presents a practical approach to high-throughput screening in drug discovery.

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

Quantum mechanical closure of partial differential equations with symmetries

We develop a statistical framework for the dynamical closure of spatiotemporal dynamics governed by partial differential equations. Employing the mathematical framework of quantum mechanics to embed the original classical dynamics into a quantum mechanical representation, we use the space of quantum density operators to model the unresolved degrees of freedom of the original dynamics in a statistical sense, and the framework of quantum measurement to predict their contributions to the resolved dynamics. The embedded dynamics is discretized by a positivity preserving process, leading to a compressed representation that is invariant under the dynamical symmetries of the resolved dynamics. We present a data based formulation of the closure scheme and apply it to a closure problem for the shallow water equations. The numerical results demonstrate that our closure model can accurately predict the main features of the true dynamics, including for out of sample initial conditions.

Delay embedding↗
NASA NTRS1988

Mars orbital tethered sample return: The feasibility and uses of obtaining entrained particulates from the atmosphere

By employing technology developed for the Tethered Satellite Program, it appears feasible to obtain Martian dust samples from the atmosphere using an orbiting spacecraft. If collected during an annual dust storm, such a sample would contain a global selection of windborne materials. Atmospheric dust sampling is of importance to the study of Martian surface geochemistry, soil mechanics, atmospheric dynamics, and atmospheric and radiative transfer. Tethered sample return offers two key advantages over a lander sample return: relative simplicity and low spacecraft weight. In another vein, the collection of atmospheric dust by a lander sample return mission is itself of scientific merit. By employing a mast and collection plate aboard a lander mission, it is possible to obtain dust from distant locations transported as entrained material in the local aeolian environment.

Stern, S. A.↗
DOE OSTI2018

Characterization and flux assessment of airborne phthalates released from polyvinyl chloride consumer goods

Highlights: • Enhanced levels of semi-volatile organic compounds (SVOCs) can affect human health. • The major SVOCs like phthalates are released into indoor by many sources like plasticizers. • This study investigated the emission characteristics of diverse phthalates from plastic/rubber products. • Emission behavior of phthalates is described in relation to several key variables, e.g., types of PVC. The concentrations and fluxes of airborne phthalates were measured from five types of polyvinyl chloride (PVC) consumer products (vinyl flooring, wallcovering, child's toy, yoga mat, and edge protector) using a small chamber (impinger) system. Airborne phthalates released from each of those PVC samples were collected using sorbent (Tenax TA) tubes at three temperature control intervals (0, 3, and 6 h) under varying temperature conditions (25, 40, and 90 °C). A total of 11 phthalate compounds were quantified in the five PVC products examined in this study. To facilitate the comparison of phthalate emissions among PVC samples, their flux values were defined for total phthalates by summing the average fluxes of all 11 phthalates generated during the control period of 6 h. The highest flux values were seen in the edge protector sample at all temperatures (0.40 (25 °C), 9.65 (40 °C), and 75.7 μg m{sup −2} h{sup −1} (90 °C)) of which emission was dominated by dibutyl isophthalate. In contrast, the lowest fluxes were found in wallcovering (0.01 (25 °C) and 0.05 μg m{sup −2} h{sup −1} (40 °C)) and child's toy (0.23 μg m{sup −2} h{sup −1} (90 °C)) at each temperature level. The information regarding phthalate composition and emission patterns varied dynamically with type of PVC sample, controlled temperature, and duration of control.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Benchmarking Quantum Simulators Using Ergodic Quantum Dynamics

Here we propose and analyze a sample-efficient protocol to estimate the fidelity between an experimentally prepared state and an ideal target state, applicable to a wide class of analog quantum simulators without advanced spatiotemporal control. Our protocol relies on universal fluctuations emerging from generic Hamiltonian dynamics, which we discover in the present work. It does not require fine-tuned control over state preparation, quantum evolution, or readout capability, while achieving near optimal sample complexity: a percent-level precision is obtained with ~103 measurements, independent of system size. Furthermore, the accuracy of our fidelity estimation improves exponentially with increasing system size. We numerically demonstrate our protocol in a variety of quantum simulator platforms, including quantum gas microscopes, trapped ions, and Rydberg atom arrays. We discuss applications of our method for tasks such as multiparameter estimation of quantum states and processes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Probing ultrafast C–Br bond fission in the UV photochemistry of bromoform with core-to-valence transient absorption spectroscopy

UV pump–extreme UV (XUV) probe femtosecond transient absorption spectroscopy is used to study the 268 nm induced photodissociation dynamics of bromoform (CHBr3). Core-to-valence transitions at the Br(3d) absorption edge (∼70 eV) provide an atomic scale perspective of the reaction, sensitive to changes in the local valence electronic structure, with ultrafast time resolution. The XUV spectra track how the singly occupied molecular orbitals of transient electronic states develop throughout the C–Br bond fission, eventually forming radical Br and CHBr2 products. Complementary ab initio calculations of XUV spectral fingerprints are performed for transient atomic arrangements obtained from sampling excited-state molecular dynamics simulations. C–Br fission along an approximately CS symmetrical reaction pathway leads to a continuous change of electronic orbital characters and atomic arrangements. Two timescales dominate changes in the transient absorption spectra, reflecting the different characteristic motions of the light C and H atoms and the heavy Br atoms. Within the first 40 fs, distortion from C3v symmetry to form a quasiplanar CHBr2 by the displacement of the (light) CH moiety causes significant changes to the valence electronic structure. Displacement of the (heavy) Br atoms is delayed and requires up to ∼300 fs to form separate Br + CHBr2 products. We demonstrate that transitions between the valence-excited (initial) and valence + core-excited (final) state electronic configurations produced by XUV absorption are sensitive to the localization of valence orbitals during bond fission. The change in valence electron-core hole interaction provides a physical explanation for spectral shifts during the process of bond cleavage.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Carbon Nanoparticles and Graphene Nanosheets as MALDI Matrices in Glycomics: a New Approach to Improve Glycan Profiling in Biological Samples

Glycomics continues to be a highly dynamic and interesting research area due to the need to comprehensively understand the biological attributes of glycosylation in many important biological functions such as the immune response, cell development, cell differentiation/adhesion, and host-pathogen interactions. Although matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) has proven to be suitable for glycomic profiling studies, there is a need for improved sensitivity in the detection of native glycans, which ionize inefficiently. In this study, we investigated the efficiencies of graphene nanosheets (GNs) and carbon nanoparticles (CNPs) as MALDI matrices and co-matrices in glycan profiling. Our results indicated an enhancement of signal intensity by several orders of magnitude upon using GNs and CNPs in MALDI analysis of N-glycans derived from a variety of biological samples. Interestingly, increasing the amounts of CNPs and GNs improved not only the signal intensities but also prompted in-source decay (ISD) fragmentations, which produced extensive glycosidic and cross-ring cleavages. Our results indicated that the extent of ISD fragmentation could be modulated by CNP and GN concentrations, to obtain MS{sup 2} and pseudo-MS{sup 3} spectra. The results for glycan profiling in high salt solutions confirmed high salt-tolerance capacities for both CNPs and GNs. Finally, the results showed that by using CNPs and GNs as co-matrices, DHB crystal formation was more homogeneous which improved shot-to-shot reproducibility and sensitivity. .

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

A Novel Approach for Plate Impact Experiments to Determine the Dynamic Behavior of Materials Under Extreme Conditions

Here we present a unique approach to plate impact experiments for characterization of dynamic material behavior under extreme conditions, i.e., ultra-high strain-rates (~10 6 /s) and test temperatures up to 1000 °C. Strategic modifications are made to the existing singlestage gas-gun facility at CWRU to enable this approach. These include an extension of the gun barrel at the breech end of the gas-gun, which now incorporates a precision machined steel housing that carries a vertical heater well to accommodate an 800 W resistance coil heater with axial and rotational degrees of freedom. This custom designed heater assembly enables specimens placed on the flyer plate carried by the sabot to be heated uniformly across the diameter in a 100 mTorr vacuum prior to impact at the breech end of the gun barrel. A new sabot design is utilized to minimize heat transfer from the heated flyer plate to the sabot body. Using this modified gas-gun facility, the dynamic strength of pre-heated commercial purity polycrystalline aluminum samples is investigated at the onset of plastic flow in response to weak normal shock compression at test temperatures ranging from room to near melt point of aluminum. Lastly, the dynamic strength of aluminum samples, as inferred from the measured normal particle velocity history at the free (rear) surface of the target plate, show progressive weakening with increasing specimen temperatures in the temperature range 23–643 °C; at higher test temperatures, however, the rate of softening in dynamic strength is observed to weaken and even reverse as the sample temperatures approach the melt point of aluminum (test temperature ~643 °C).

36 MATERIALS SCIENCE↗
DOE OSTI2023

Insights from a workplace SARS-CoV-2 specimen collection program, with genomes placed into global sequence phylogeny

In 2020, the Department of Energy established the National Virtual Biotechnology Laboratory (NVBL) to address key challenges associated with COVID-19. As part of that effort, Pacific Northwest National Laboratory (PNNL) established a capability to collect and analyze specimens from employees who self-reported symptoms consistent with the disease. During the spring and fall of 2021, 688 specimens were screened for SARS-CoV-2, with 64 (9.3%) testing positive using reverse-transcriptase quantitative PCR (RT-qPCR). Of these, 36 samples were released for research. All 36 positive samples released for research were sequenced and genotyped. Here, the relationship between patient age and viral load as measured by Ct values was measured and determined to be only weakly significant. Consensus sequences for each sample were placed into a global phylogeny and transmission dynamics were investigated, revealing that the closest relative for many samples was from outside of Washington state, indicating mixing of viral pools within geographic regions.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1998

Radio Occultation Studies of Venus' Atmosphere with Magellan

We have been conducting a systematic study of the middle and lower atmosphere of Venus through analysis of 20 radio occultation experiments conducted with the Magellan spacecraft between October, 1991, and August, 1994. These studies have revealed a rich but sparsely sampled trove of information regarding the structure, composition and dynamics of the Venus atmosphere. The five sets of experiments sampled a variety of latitudes. Basic results include vertical profiles of: (1) electron density in the ionosphere, (2) pressure, temperature, density, and static stability in the neutral atmosphere (from 33 km to 98 km), and (3) sulfuric acid vapor (H2SO4) abundance below the main cloud deck. Further analysis of the temperature profiles led to the discovery of small vertical-scale gravity waves in the neutral atmosphere. The retrieved profiles show intriguing zonal variations that might be due to planetary- scale waves. During the performance period of this grant, we have concentrated on reanalyzing the 15 experiments conducted in 1994 using improved trajectory files for Magellan provided by JPL, obtaining more reliable results, and on conducting an error analysis of the derived profiles. In addition, we have begun an analysis of microwave emission maps of Venus obtained at the Very Large Array (VLA) in April, 1996. This report is organized as follows: A summary of results is presented, giving representative examples of the various physical profiles retrieved from all the Magellan radio occultation studies, emphasizing latitudinal variations evident in the data. Next, a preliminary analysis of the VLA maps is given. A summary of activities follows the scientific results, detailing papers published and presented at various conferences. This report concludes with a "Conclusions and Suggestions for Future Work" section.

Jenkins, Jon M.↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Stardust Mission

The Stardust Mission session included the following reports:The Stardust:A Successful Encounter with the Remarkable Comet Wild 2; Stardust Imaging of Comet Wild 2: First Look; Preliminary Results from the Dust Flux Monitoring Instrument During the Encounter of Stardust Spacecraft with Wild-2 Comet; Streaming Clumps Ejection Model and the Heterogeneous Inner Coma of Comet Wild 2; Stardust: First Results from the Cometary and Interstellar Dust Analyzer; STARDUST Sample Collection at Wild 2 and Its Preliminary Examination; Stardust Dynamic Science at Wild 2: First Look; and Preliminary Sample Analysis Plan for the Cometary and Interstellar Samples Being Returned by the Stardust Spacecraft.

Source record↗
NASA NTRS2019

Recent Advances in High Altitude Pseudosatellites (HAPS) and Potential Roles in Future Earth Observing Systems

In August 2001 the NASA Environmental Research Aircraft and Sensor Technology (ERAST) Program flew the Helios aircraft to an altitude of nearly 100,000ft, demonstrating a new type of remote sensing platform. Nearly 20 years later the earth science community has unmet observational requirements to loiter over regions of interest for days or weeks as well as to follow airmasses to study chemistry and dynamics in concert with spaceborne observations. Recent advances in materials science and engineering have enabled improved battery power density, solar panel efficiency, and light yet strong structural materials required to effectively operate high-altitude (50-70k ft altitude) Pseudo-Satellites (HAPS) for 30+ days. The rapid commercialization of small unmanned aircraft has also contributed to the maturation of HAPS by making avionics, GPS, and other sub-systems smaller and less expensive. HAPS payloads provide high-resolution data that complement geostationary and polar orbiting satellites, while also enabling in-situ sampling of atmospheric chemistry and dynamics. Recent commercial interest in HAPS for 4G/5G and WIFI has funded development of a new generation of aircraft available to the science community. Here I report on a project under the NASA Airborne Science Program to test and demonstrate earth observations from a prototype aircraft being developed under a NASA Small Business Innovative Research Phase II. This aircraft will demonstrate the ability for a solar electric aircraft to deliver a 2u cubesat-based passive optical imaging satellite to 70,000ft for 30 or more days. Discussion will include the anticipated maturation timeline for HAPS, development and operational challenges, and examples of mission concepts that might contribute to future earth observing systems.

Helios aircraft↗
DOE OSTI2016

High precision Hugoniot measurements on statically pre-compressed fluid helium

Here we describe how the capability for statically pre-compressing fluid targets for Hugoniot measurements utilizing gas gun driven flyer plates has been developed. Pre-compression expands the capability for initial condition control, allowing access to thermodynamic states off the principal Hugoniot. Absolute Hugoniot measurements with an uncertainty less than 3% on density and pressure were obtained on statically pre-compressed fluid helium utilizing a two stage light gas gun. Helium is highly compressible; the locus of shock states resulting from dynamic loading of an initially compressed sample at room temperature is significantly denser than the cryogenic fluid Hugoniot even for relatively modest (0.27–0.38 GPa) initial pressures. Lastly, the dynamic response of pre-compressed helium in the initial density range of 0.21–0.25 g/cm3 at ambient temperature may be described by a linear shock velocity (us) and particle velocity (u p ) relationship: u s = C 0 + su p , with C 0 = 1.44 ± 0.14 km/s and s = 1.344 ± 0.025.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1993

Comparison of dynamic height variations in the tropical Atlantic during 1987-1989 as viewed in sections hydrography and Geosat altimetry

During the 1980s the Soviet Union conducted a series of 25 hydrographic cruises in the tropical Atlantic under the Sections (acronym for Energetically Active Zones of the Ocean and Climate Variability) program. As one of its objectives, Sections has produced the most extensive hydrographic data set ever collected in the tropical Atlantic. Here we examine dynamic topography from seven cruises during the years 1987 through 1989 and compare them to corresponding maps of sea level from the Geosat satellite mission. The two independent estimates of sea level variation are well correlated, with the sea level fields explaining approximately half of the variance of dynamic height fields. There is a seasonal variation to the agreement, so that the correlation increases somewhat in summer and fall, as the variability of the height field increases. Wavenumber spectra of both dynamic height and sea level are quite red for wavelengths greater than 400-600 km. Smaller wavelengths cannot be resolved by the hydrographic sampling program. A comparison of the dynamic height and sea level spectra indicates that sea level has somewhat less variability than dynamic height at all wavenumbers.

Carton, James A.↗
DOE OSTI2023

Growth phase estimation for abundant bacterial populations sampled longitudinally from human stool metagenomes

Longitudinal sampling of the stool has yielded important insights into the ecological dynamics of the human gut microbiome. However, human stool samples are available approximately once per day, while commensal population doubling times are likely on the order of minutes-to-hours. Despite this mismatch in timescales, much of the prior work on human gut microbiome time series modeling has assumed that day-to-day fluctuations in taxon abundances are related to population growth or death rates, which is likely not the case. Here, we propose an alternative model of the human gut as a stationary system, where population dynamics occur internally and the bacterial population sizes measured in a bolus of stool represent a steady-state endpoint of these dynamics. We formalize this idea as stochastic logistic growth. We show how this model provides a path toward estimating the growth phases of gut bacterial populations in situ. We validate our model predictions using an in vitro Escherichia coli growth experiment. Finally, we show how this method can be applied to densely-sampled human stool metagenomic time series data. We discuss how these growth phase estimates may be used to better inform metabolic modeling in flow-through ecosystems, like animal guts or industrial bioreactors.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Chemical imaging of individual stratospheric particles sampled over North America

The increasing size, severity, and frequency of wildfires have led to dramatic increases in particulate matter concentrations in the troposphere. Severe wildfires can generate intense convective systems capable of transporting large quantities of biomass burning organic aerosols (BBOA) to the upper troposphere and lower stratosphere (UTLS). Chemically complex organic matter and light-absorbing carbonaceous material is introduced into stratospheric regions that were historically isolated from direct surface emissions. In this study, stratospheric particles were sampled over North America during the Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) campaign, an aircraft-based research project designed to characterize convective perturbation in the UTLS. Particle samples collected from six research flights during summer 2022 were analyzed using Computer-Controlled Scanning Electron Microscopy and Scanning Transmission X-ray Microscopy to investigate particle size distributions, morphology, chemical composition, and mixing state of stratospheric particles along transects across the continental United States and adjacent Pacific Ocean airspace. Analysis revealed that all sampled particles contained detectable levels of carbon, with most exhibiting organic volume fractions of 0.37 ± 0.20. Notably, about 5% of the particles also contained soot inclusions, which indicates the presence of refractory black carbon transported to stratospheric altitudes and provides direct evidence of wildfire-derived black carbon reaching the UTLS. Typical particle morphology exhibits organic shells over soot and inorganic cores and suggests secondary processing and aging of BBOA during transport to and within the UTLS. These findings provide compelling evidence that wildfire emissions play a critical role in affecting the long-term composition and radiative properties of stratospheric particles.

Sharpe, Steven [Purdue Univ., West Lafayette, IN (↗
DOE OSTI2020

Associating damage nucleation and distribution with grain boundary characteristics in Ta

Here, the effect of grain boundary (GB) characteristics (as represented by misorientation angle) on its dynamic response is investigated by sampling a large set of 185 GBs in Ta bi-crystals. These GBs encompass both ordered and disordered structures – typically referred to as metastable structures, in order to reflect the diversity in the local atomic structure observed in realistic GBs. The results reveal four distinct regimes in damage distribution and failure modes as a function of misorientation angle. The above trends also correlate with the variation in the corresponding void nucleation stress.

36 MATERIALS SCIENCE↗