Search NASA⌕ Search

SEARCH · Search NASA

Results for “ORIGINS”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Search for meteoritic GEMS II: Comparison of inclusions in amorphous silicates from the Paris chondrite and from anhydrous chondritic interplanetary dust particles

Amorphous silicates containing abundant nano-inclusions have been reported in the Paris CM chondrite (Leroux et al., 2015). They have chemical and morphological similarities to glass with embedded metal and sulfides (GEMS) found in interplanetary dust particles (IDPs) and micrometeorites believed to originate from comets. We used scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS) and nanodiffraction to study the chemistry and mineralogy of these inclusions in order to understand the origin of the GEMS-like material in Paris and its possible relationships to other materials found in primitive chondritic materials including IDP GEMS. EDS and diffraction analyses indicate compositional and mineralogical differences between the nanophase inclusions in cometary GEMS and Paris GEMS-like material. Metal inclusions are notably absent within Paris amorphous silicate. Ni-rich sulfides, including pentlandite, are common in even the least altered matrix material of Paris, while they are absent in GEMS-bearing IDPs and Ultracarbonaceous Antarctic Micrometeorites (UCAMMs). From examination of the inclusions, we cannot yet confirm or refute the possibility that GEMS-like material in Paris is related to cometary GEMS. The distinct compositions and mineralogy of the Paris material may be due to aqueous alteration of cometary GEMS precursors, but they may also denote an independent origin for meteoritic GEMS-like assemblages.

58 GEOSCIENCES↗
DOE OSTI2021

Experimental study of plate materials for evaporative air coolers

Following paper presents an experimental study on eight potential plate materials for evaporative air coolers. There are three groups of materials: currently used plate materials (kraft papers), new natural origin plate materials (cotton fibers), and new synthetic plate materials (synthetic fibers). Proposed materials were examined in terms of different properties such as upward and downward distribution height, water capacity, durability and diffusivity. The results were compared with data presented by other authors. It was established that, synthetic materials are characterized by superior water distribution qualities in comparison to the materials of natural origin. Basalt paper-like synthetic fiber allowed to rise water vertically to 40 cm during 120 min tests. The highest water rise obtained in other studies was 18 cm, hence basalt paper-like fiber is visibly superior in comparison with the currently known materials. In terms of downward water distribution, two new synthetic surfactant non-wovens show better performance than the existing materials by quickly and evenly distributing water over the entire length of the sample. The durability of synthetic fibers and non-wovens is higher comparing with the materials of natural origin. The results show that synthetic materials are better suited to the role of plate materials in evaporative air coolers.

Experiment↗
DOE OSTI2023

NMR investigation of proton transport in polybenzimidazole/polyphosphoric acid membranes prepared via novel synthesis route

Here, in this work, we present a molecular-level view of the structural changes in polybenzimidazole (PBI) membranes doped with phosphoric acid (PA) generated by a novel membrane fabrication technique. The modified PA doped membranes displayed unprecedented ionic conductivity at elevated temperatures, comparable to the starting PBI gel membranes prepared by the commonly used PPA process, while also exhibiting enhanced mechanical properties. To elucidate the cause of these effects, we used multi-nuclear ( 1 H, 13 C, 31 P) 1D PFG, MAS and CPMAS, and 2D HETCOR magnetic resonance (NMR) techniques to characterize the structure and dynamics of the modified film and the original gel PBI membranes. 1 H diffusivity measurements show significantly enhanced proton diffusivity, both in magnitude and in lower activation energy, which were consistent with its high ionic conductivity despite the lower PA content compared to the original gel membrane. CPMAS experiments further substantiated that the location of these distinct phosphate environments as being close to the polymer network. Finally, the phosphate groups in the modified membrane were revealed to be strongly bounded to each other and to the PBI polymer backbone in contrast to the combination of weakly and strongly bounded groups of the original gel membrane.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2022

Two-step annealing induced structural rejuvenation: A cause for memory effect in metallic glasses

The structural origin of the memory effect is still elusive in glassy materials. Here, in this letter, the memory effect in a series of metallic glasses (MGs) is observed by two step annealing using differential scanning calorimetry (DSC) and molecular dynamics simulations. It demonstrates that the Kovacs peak can be reflected from not only the system potential energy but also the atomic dynamics, showing the memory effect could originate from the formation of more loose packing configurations around mobile atoms by structural rejuvenation in the second step of high temperature annealing. In contrast, the high-low temperature annealing protocol can only induce the monotonic relaxation. Therefore, our results pave a pathway to better understand the origin of memory effect in MGs and other glassy materials from their dynamics and local atomic structure.

Memory effect↗
DOE OSTI2020

Reduction of waveguide vacuum trips in CEBAF accelerating cavities with a combination ion pump and non-evaporable getter pump

Pressure spikes in the fundamental power coupler waveguide are a significant source of trips during the operation of both original and refurbished superconducting radio-frequency cavities installed in the CEBAF accelerator. In its original configuration, two waveguides from a cavity-pair are connected to a single 32 l/s ion pump. In 2017 a new cavity-pair was installed in a refurbished cryomodule in which a NEXTorr® D200-5 combination ion pump and non-evaporable getter pump was installed for each waveguide. It is shown that hydrogen is the dominant residual gas in the waveguide and simulations with Molflow+ indicated that the new pumping scheme allows reducing the pressure at the end of the waveguide by a factor of ~5 , compared to the original configuration. In conclusion, the new cavity-pair has been operating in CEBAF for a total of 431 days and it only had a total of 3 trips due to vacuum spikes in the waveguide.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Development and evaluation of a list mode neutron coincidence collar for spatial response measurements of fresh fuel assemblies

A traditional safeguards neutron coincidence counting system, the Neutron Coincidence Collar, has been modified to incorporate individual preamplifiers on each of its 18 3He tubes in active interrogation mode. When used with list mode data acquisition (LMDA) and analysis, a signal from each 3He tube can be recorded and analyzed to allow a spatial response measurement to be performed on an item based on count rate and 3He tube location within the system. The ultimate goal of this project is to demonstrate the capabilities of a list mode response matrix for the nondestructive assay of fresh nuclear fuel assemblies. To enable partial defect detection of fuel pin locations and absences within an assembly, the project aims to extend well-established correlated neutron analysis techniques on a preexisting Neutron Coincidence Collar by extracting a greater number of useful signatures from the system than are currently generated. LMDA, combined with the addition of multiple preamplifiers, facilitates this capability by increasing the number of simultaneous signals that can be measured; this allows an in-depth analysis of neutron coincidence events to determine a fissioning item’s location based on the measured doubles count rate in various channel logic coincidence combinations. All of this can be done from a single measurement pulse train in offline analysis, which is the major benefit provided by LMDA. Through various stages of development and testing, a Mirion Technologies model JCC-71 Neutron Coincidence Collar has been successfully retrofit with modern electronics designed in-house at Oak Ridge National Laboratory, matching preexisting JAB-01 electronics performance, while maintaining the original system footprint. This paper presents these various stages of development and experimental evaluation of the proof of concept system.

Moore, Angela S.↗
DOE OSTI2026

Clash of the titans: ultra-high energy KM3NeT event versus IceCube data

KM3NeT has reported the detection of a remarkably high-energy through-going muon. Lighting up about a third of the detector, this muon likely originated from a neutrino exceeding 10 PeV in energy. The crucial question we need to answer is where this event comes from and what its source is. Intriguingly, IceCube has been operating with a much larger effective area for a considerably longer time, yet it has not reported neutrinos above 10 PeV. We quantify the tension between the KM3NeT event and the absence of similar high-energy events in IceCube under various assumptions of the origin for the neutrino including the isotropic diffuse flux, cosmogenic flux, and a steady or transient point source. Through a detailed analysis, we determine the most likely neutrino energy to be in the range of 23 – 2400 PeV, and find a tension between the experiments ranging from 3.6 to 3.1 σ for diffuse origins and 2.9 to 2.0 σ for point sources. The lack of observation of high-energy events in IceCube seriously challenges the explanation of this event coming from any known diffuse fluxes. Our results indicate the KM3NeT event is likely the first observation of a new astrophysical source.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Natural organic matter composition and nanomaterial surface coating determine the nature of platinum nanomaterial-natural organic matter corona

Natural organic matter corona (NOM corona) is an interfacial area between nanomaterials (NMs) and the sur- rounding environment, which gives rise to NMs' unique surface identity. While the importance of the formation of natural organic matter (NOM) corona on engineered nanomaterials (NMs) to NM behavior, fate, and toxicity has been well-established, the understanding of how NOM molecular properties affect NOM corona composition remains elusive due to the complexity and heterogeneity of NOM. This is further complicated by the variation of NOMs from different origins. Here we use eight NOM isolates of different molecular composition and ultrahigh resolution Fourier-transform ion cyclotron resonance-mass spectrometry (ESI-FT-ICR-MS) to determine the mol- ecular composition of platinum NM-NOM corona as a function of NOM composition and NM surface coating. We observed that the composition of PtNM-NOM corona varied with the composition of the original NOM. The per- centage of NOM formulas that formed PVP-PtNM-NOM corona was higher than those formed citrate-PtNM-NOM corona, due to increased sorption of NOM formulas, in particular condensed hydrocarbons, to the PVP coating. The relative abundance of heteroatom formulas (CHON, CHOS, and CHOP) was higher in the PVP-PtNM-NOM corona than in citrate-PtNM-corona which was in turn higher than those in the original NOM isolate, indicating preferential partitioning of heteroatom-rich molecules to NM surfaces. The relative abundance of CHO, CHON, CHOS, CHOP and condensed hydrocarbons in PtNM-NOM corona increased with their increase in NOM isolates. Furthermore, PtNM-NOM corona is rich with compounds with high molecular weight. This study demonstrates that the composition and properties of PtNM-NOM corona depend on NOM molecular properties and PtNM sur- face coating. The results here provide evidence of molecular interactions between NOM and NMs, which are crit- ical to understanding NM colloidal properties (e.g., surface charge and stability), interaction forces (e.g., van der Waals and hydrphobic), environmental behaviors (e.g., aggregation, disso.

Baalousha, Mohammed↗
DOE OSTI2020

Nitrate loading projection is sensitive to freeze-thaw cycle representation

Climate change can have substantial impacts on nitrogen runoff, which is a major cause of eutrophication, harmful algal blooms, and hypoxia in freshwaters and coastal regions. We examined responses of nitrate loading to climate change in the Upper Mississippi River Basin (UMRB) with an enhanced Soil and Water Assessment Tool with physically based Freeze-Thaw cycle representation (SWAT-FT), as compared with the original SWAT model that employs an empirical equation. Driven by future climate projections from five General Circulation Models (GCMs) from 1960 to 2099 under the Representative Concentrations Pathways (RCP) 8.5 scenario, we analyzed changes in riverine nitrate loadings, as well as terrestrial surface and subsurface contributions of the UMRB in the 21st century relative to the baseline period of 1960–1999. By the end of the 21st century, the original SWAT model predicted about a 50% increase in riverine nitrate loadings which is nearly twice as much as that estimated by SWAT-FT (ca. 25%). Such a large difference in projected nitrate changes can potentially mislead mitigation strategies that aim to reduce nitrogen runoff from the UMRB. Further analysis shows that the difference between the original SWAT model and SWAT-FT led to substantial discrepancies in the spatial distribution of surface and subsurface nitrate loadings in the UMRB. In general, SWAT-FT predicted more nitrate leaching for northwestern parts of the UMRB which are more sensitive to freeze-thaw cycle, mainly because SWAT-FT simulated less frequent frozen soils. This study highlights the importance of using physically based freeze-thaw cycle representation in water quality modeling. Design of future nitrogen runoff reduction strategies should include careful assessment of effects that land management has on the freeze-thaw cycles to provide reliable projection of water quality under climate change.

Wang, Qianfeng↗
DOE OSTI2020

Capturing Deuteration Effects in a Molecular Mechanics Force Field: Deuterated THF and the THF–Water Miscibility Gap

Deuteration is a common chemical modification used in conjunction with experiments such as neutron scattering, NMR, and Fourier-transform infrared for the study of molecular systems. Under the Born–Oppenheimer (BO) approximation, while the underlying potential energy surface remains unchanged by isotopic substitutions, isotopic substitution still alters intramolecular vibrations, which in turn may alter intermolecular interactions. Molecular mechanics (MM) force fields used in classical molecular dynamics simulations are assumed to represent local approximations of the BO potential energy surfaces, and hence, MD simulations using simple isotopic mass substitutions should capture BO-compatible isotope effects. However, standard MM force-field parameterizations do not directly fit to the local harmonic quantum mechanical (QM) Hessian that describes the BO surface, but rather to QM normal-modes and/or mass-dependent internal-coordinate derived distortion energies. In this study, using tetrahydrofuran (THF)–water mixtures as our model system, we show that not only does a simple mass-substitution approach fail to capture an experimentally characterized deuteration effect (the loss of the closed-loop miscibility gap associated with the complete deuteration of THF) but also it is necessary to generate new MM force-field parameters that correctly describe isotopic dependent vibrations to capture the experimental deuteration effect. We show that the origin of this failure is a result of using mass-dependent features to fit the THF MM force field, which unintentionally biases the bonded terms of the force field to represent only the isotopologue used during the original force-field parameterization. In addition, we make use of our isotopologue-corrected force field for D 8 THF to examine the molecular origins of the isotope-dependent loss of the THF–water miscibility gap.

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

Examination of Replicate Syntheses of Metal Organic Frameworks as a Window into Reproducibility in Materials Chemistry

Replicate experiments are a useful tool in understanding the repeatability of scientific measurements. In 2019, a systematic search for replicate syntheses of a collection of 130 metal–organic frameworks (MOFs) found that 89% of these materials had no reported replicate syntheses apart from the original publications identifying the material (Agrawal, M. Proc. Natl. Acad. Sci. U.S.A. 2020, 117, 877−88210.1073/pnas.1918484117). A potential weakness of that search was that only 5–11 years had elapsed since the original publication of each material. Here, this analysis is extended to all publications 11–17 years after the original publication. Although this extended time period identifies more repeat syntheses, 83% of the materials still have no reported replicate syntheses. We also consider how appropriately selected Density Functional Theory (DFT) calculations can provide corroboration for the experimentally reported crystal structures. By using data from previous high-throughput DFT studies, corroborating evidence from DFT was available for 17% of the 130 structures for which no replicate syntheses are available. In total, approximately 1/3 of the 130 MOFs have data associated with replicate synthesis experiments and/or directly corroborating DFT calculations.

Sholl, David S. [Oak Ridge National Laboratory (OR↗
DOE OSTI2021

Atmospheric River Lifecycle Responses to the Madden‐Julian Oscillation

Abstract We investigate how the Madden‐Julian Oscillation (MJO), the dominant mode of tropical subseasonal variability, modulates the lifecycle of cool‐season North Pacific atmospheric rivers (ARs). When the enhanced (suppressed) convection center is located over the Indian Ocean (western Pacific), more AR events originate over eastern Asia and with fewer over the subtropical northern Pacific. When the enhanced (suppressed) convection is over the western Pacific (Indian Ocean), the opposite changes occur, with more AR events originate over the subtropical northern Pacific and fewer over eastern Asia. Dynamical processes involving anomalous MJO wind and seasonal mean moisture are found to be the dominant factors impacting these variations in AR origins. The MJO‐related anomalous geopotential height patterns are also shown to modulate the propagation of the AR events. These MJO–AR lifecycle relationships are further supported by model simulations.

Zhou, Yang↗
DOE OSTI2021

Uncertainties in Atmospheric River Lifecycles by Detection Algorithms: Climatology and Variability

Atmospheric rivers (ARs) are long and narrow filaments of vapor transport that are responsible for most poleward moisture transport outside of the tropics. Many AR detection algorithms have been developed to automatically identify ARs in climate data. The diversity of these algorithms has introduced appreciable uncertainties in quantitative measures of AR properties and thereby impedes the construction of a unified and internally consistent climatology of ARs. This paper compares nine global AR detection algorithms from the perspective of AR lifecycles following the propagation of ARs from origin to termination in the MERRA2 reanalysis over the period 1980–2017. Uncertainties in AR lifecycle characteristics, including event number, lifetime, intensity, and frequency distribution are discussed. Notably, the number of AR events per year in the Northern Hemisphere can vary by a factor of 5 with different algorithms. Although all algorithms show that the maximum AR origin (termination) frequency is located over the western (eastern) portion of ocean basins, significant disagreements appear in regional distribution. Spreads are large in AR lifetime and intensity. Here, the number of landfalling AR events produced by the algorithms can vary from 16 to 80 events per year, although the agreement improves for stronger ARs. By examining the ARs' connections with the Madden-Julian Oscillation and El Niño Southern Oscillation, we find that the overall responses of ARs (such as changes in AR frequency, origin, and landfall activity) to climate variability are consistent among algorithms.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Full Implementation of Matrix Approach to Biogeochemistry Module of CLM5

Abstract Earth system models (ESMs) have been rapidly developed in recent decades to advance our understanding of climate change‐carbon cycle feedback. However, those models are massive in coding, require expensive computational resources, and have difficulty in diagnosing their performance. It is highly desirable to develop ESMs with modularity and effective diagnostics. Toward these goals, we implemented a matrix approach to the Community Land Model version 5 (CLM5) to represent carbon and nitrogen cycles. Specifically, we reorganized 18 balance equations each for carbon and nitrogen cycles among the 18 vegetation pools in the original CLM5 into two matrix equations. Similarly, 140 balance equations each for carbon and nitrogen cycles among the 140 soil pools were reorganized into two additional matrix equations. The vegetation carbon and nitrogen matrix equations are connected to soil matrix equations via litterfall. The matrix equations fully reproduce simulations of carbon and nitrogen dynamics by the original model. The computational cost for forwarding simulation of the CLM5 matrix model was 26% more expensive than the original model, largely due to calculation of additional diagnostic variables, but the spin‐up computational cost was significantly saved. We showed a case study on modeled soil carbon storage under two forcing data sets to illustrate the diagnostic capability that the matrix approach uniquely offers to understand simulation results of global carbon and nitrogen dynamics. The successful implementation of the matrix approach to CLM5, one of the most complex land models, demonstrates that most, if not all, the biogeochemical models can be reorganized into the matrix form to gain high modularity, effective diagnostics, and accelerated spin‐up.

58 GEOSCIENCES↗
DOE OSTI2022

Amazonian Moisture Recycling Revisited Using WRF With Water Vapor Tracers

Previous studies have estimated that 25%–35% of Amazonian precipitation comes from evapotranspiration (ET) within the basin. However, due to simplifying assumptions of traditional models, these studies primarily focus on large spatial and temporal scales. This study is the first to analyze the moisture of Amazonian origin at the annual to daily timescale in four different subregions of the Amazon. We analyze the sources, sinks and stores of moisture that originates as Amazonian ET. To do this, we use the Weather Research and Forecast (WRF) regional meteorological model with the added capability of water vapor tracers to track this moisture. Moisture of Amazonian origin shows strong annual and semi-annual signals, with contrasting behavior between the northern and southern parts of the basin. The tracers reveal a strong diurnal cycle of Amazonian water vapor which had not been previously reported. This signal is related to the diurnal cycle of ET, convective precipitation and advected moisture. ET's contribution to atmospheric moisture increases from early morning into the afternoon. Some of this moisture is rained out through convective storms in the early evening. Later in the night and following morning, strong winds associated with the South American Low Level Jet advect moisture downwind. Overall, the beating pattern becomes apparent when visualizing the Amazonian water vapor as an animation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

The Amazon and La Plata River Basins as Moisture Sources of South America: Climatology and Intraseasonal Variability

Abstract Land‐atmosphere interactions are critical for precipitation (PPT) over South America where terrestrial evapotranspiration (ET) constitutes a significant fraction of moisture for rainfall over the ecologically and socio‐economically vital Amazon (AMZ) and La Plata (LPB) river basins. We quantify the contribution of ET from AMZ and LPB to PPT over the continent with a focus on the intraseasonal time scale. Using numerical water tracers embedded in the Weather Research and Forecasting model we track the moisture originating from the two basins. Our findings indicate that approximately 40% of annual rainfall over the eastern foothills of the Andes originates as AMZ ET, and nearly 30% of rainfall over northern Argentina originates as LPB ET. Analysis of moisture transport during both phases of the dominant intraseasonal oscillation pattern over South America reveals an intraseasonal “sloshing” of LPB moisture between the South Atlantic convergence zone (SACZ) and southeastern South America (SESA) regions. AMZ and LPB each supply approximately 6% of moisture for SACZ PPT during periods of intraseasonal enhancement (positive anomalies), highlighting the importance of moisture from the Atlantic Ocean. For the SESA region, LPB supplies 26% of the moisture for PPT during periods of intraseasonal enhancement while AMZ supplies 5%.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Insights Into Lightning K‐Leader Initiation and Development From Three Dimensional Broadband Interferometric Observations

Abstract We report detailed observations of K‐leaders and the activity between them with the three‐dimensional Broadband Interferometric Mapping and Polarization system (BIMAP‐3D) at Los Alamos National Laboratory. It is found that K‐leaders have a general propagation trend of initial acceleration and then gradual deceleration, and the corresponding very high frequency (VHF) radiation power is exponentially correlated with the leader speed. Based on the 3D development and simultaneous electric field change measurement, some simple K‐leaders can be modeled with time‐evolving point charges at the propagating leader tip and at the stationary origin. We found that the charge magnitude increases during the initial acceleration stage and stays relatively constant for the rest of the development. K‐leaders are observed to interact with other branches; the branches affect the leader's propagation speed, and may affect the charge transfer. After the occurrence of a K‐leader, VHF emissions are quenched for several milliseconds. VHF sources then reappear in an impulsive and scattered manner as “twinkling,” and these sources are found not uniquely on the so‐called needles, but also on the main channel. These twinkling sources start near the apparent positive leader tip, and extend back toward the direction of the flash origin at about 10 5 m/s, while the apparent positive tip continues to extend forward at about 10 4 m/s. The twinkling extending toward the direction of flash origin appears to initiate the following K‐leader, although it may be interrupted by a K‐leader along a different branch, or simply die out without more K‐leader activity.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Drivers of Atlantic Tropical Cyclogenesis: African Easterly Waves and the Environment

Abstract Tropical cyclone (TC) genesis requires favorable environmental conditions and an initial disturbance, which, in the North Atlantic, is often an African easterly wave (AEW). Although studies have examined how AEWs and the environment affect TC genesis, their relative importance is less understood. Here, we examine whether AEW strength or sea surface temperatures (SSTs) are the primary drivers of TC genesis. Regional model simulations were performed to address how increased AEW strength and SSTs affect the frequency of AEWs that develop into TCs in a year with below‐average TCs with AEW origins and SSTs. We found that environmental favorability plays a larger role than AEW strength in driving the frequency of TCs with AEW origins. Strengthening the AEWs did not affect the frequency of AEWs that develop into TCs due to low environmental favorability. Warmer SSTs led to increased environmental favorability and a statistically significant increase in TCs with AEW origins.

Bercos‐Hickey, Emily [Climate and Ecosystem Scienc↗