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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Multiple redox mechanisms for water-gas shift reaction on Fe 3 O 4 (1 1 1) surface: A density functional theory and mean-field microkinetic modeling study

In this work, we investigated redox mechanisms for the high temperature (HT) water–gas shift reaction (WGSR) on the Fe 3 O 4 (1 1 1) surface using density functional theory (DFT) calculations and mean-field microkinetic modeling (MKM). The redox pathways branched into three Langmuir-Hinshelwood processes (LH1, LH2 and LH3) and one Mars-van-Krevelen (MVK) process (in the presence of oxygen vacancy) from multidentate binding of CO and CO 2 over four available reactive sites (Fe oct2 , Fe tet1 , Fe bridge, and O1). We found that the LH1 and LH2 processes have CO adsorption at a single iron site (Fe oct2 or Fe tet1 ), while the LH3 and MVK processes have stronger chemisorption of CO or CO 2 by both the Fe oct2 site and the O 1 site. From the mechanistic study of these reaction path, we recognized that availability of O 1 sites was key to proceed to either CO oxidation by the single site (LH1, LH2) or by the dual site (LH3, MVK). We observed that the reaction energetics were significantly different in the CO oxidation steps, where the single or dual site results in markedly different apparent activation energy (73–281 kJ/mol) and reaction rates (10 -3 –10 -10 mol∙m -2 ∙s -1 ) among the four reaction mechanisms. The utilization of mean field MKM with DFT reaction energetics helps explain the experimental debates for the catalytic reaction details as well as providing a possible direction to engineer the catalyst with higher activity.

42 ENGINEERING↗
DOE OSTI2019

Structural considerations of folded protein import through the chloroplast TOC/ TIC translocons

Protein import into chloroplasts is carried out by the protein translocons at the outer and inner envelope membranes (TOC and TIC). Detailed structures for these translocons are lacking, with only a low-resolution TOC complex structure available. Recently, we showed that the TOC/TIC translocons can import folded proteins, a rather unique feat for a coupled double membrane system. In this work we also determined the maximum functional TOC/TIC pore size to be 30–35 Å. Here, we discuss how such large pores could form and compare the structural dynamics of the pore-forming Toc75 subunit to its bacterial/mitochondrial Omp85 family homologs. We put forward structural models that can be empirically tested and also briefly review the pore dynamics of other protein translocons with known structures.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Near Neutral pH Redox Flow Battery with Low Permeability and Long-Lifetime Phosphonated Viologen Active Species

A highly stable phosphonate-functionalized viologen is introduced in this work as the redox-active material in a negative potential electrolyte for aqueous redox flow batteries (ARFBs) operating at nearly neutral pH. The solubility is 1.23 m and the reduction potential is the lowest of any substituted viologen utilized in a flow battery, reaching –0.462 V versus SHE at pH = 9. The negative charges in both the oxidized and the reduced states of 1,1'-bis(3-phosphonopropyl)-[4,4'-bipyridine]-1,1'-diium dibromide ( BPP–Vi ) effect low permeability in cation exchange membranes and suppress a bimolecular mechanism of viologen decomposition. A flow battery pairing BPP–Vi with a ferrocyanide-based positive potential electrolyte across an inexpensive, non-fluorinated cation exchange membrane at pH = 9 exhibits an open-circuit voltage of 0.9 V and a capacity fade rate of 0.016% per day or 0.00069% per cycle. Overcharging leads to viologen decomposition, causing irreversible capacity fade. Our research introduces extremely stable, extremely low-permeating and low reduction potential redox active materials into near neutral ARFBs.

25 ENERGY STORAGE↗
DOE OSTI2020

Instability and treatments of the coupled discrete element and lattice Boltzmann method by the immersed moving boundary scheme

The immersed moving boundary (IMB) scheme has been extensively used to couple the discrete element method (DEM) with the lattice Boltzmann method (LBM). In the literature, only the formulation of IMB for lattice nodal cells covered by a single-solid particle was given. The treatment of situations where a nodal cell is covered by two or more solid particles is seldom discussed. It is found that some numerical instability can occur for such situations due to an inappropriate computation of the weighting function in the IMB formulation. This work presents an enhanced treatment that can resolve the issue and validates it using some benchmark tests. Furthermore, to avoid the extra costs associated with the treatment and simplify the complicated procedure introduced, a simplified IMB scheme is proposed. The accuracy of both enhanced and simplified IMB schemes are validated by test cases including single-particle sedimentation, two-particle drafting-kissing-tumbling phenomenon, and multiple-particle sedimentation. Then, the robustness of both schemes is examined and discussed using a specially designed flow past cylinders test. Overall, the simplified IMB scheme is proved to be robust and sufficiently accurate and simpler and more effective than the enhanced scheme.

42 ENGINEERING↗
DOE OSTI2017

Comparing capacity coefficient and dual task assessment of visual multitasking workload

Capacity coefficient analysis could offer a theoretically grounded alternative approach to subjective measures and dual task assessment of cognitive workload. Workload capacity or workload efficiency is a human information processing modeling construct defined as the amount of information that can be processed by the visual cognitive system given a specified of amount of time. In this paper, I explore the relationship between capacity coefficient analysis of workload efficiency and dual task response time measures. To capture multitasking performance, I examine how the relatively simple assumptions underlying the capacity construct generalize beyond the single visual decision making tasks. The fundamental tools for measuring workload efficiency are the integrated hazard and reverse hazard functions of response times, which are defined by log transforms of the response time distribution. These functions are used in the capacity coefficient analysis to provide a functional assessment of the amount of work completed by the cognitive system over the entire range of response times. For the study of visual multitasking, capacity coefficient analysis enables a comparison of visual information throughput as the number of tasks increases from one to two to any number of simultaneous tasks. I illustrate the use of capacity coefficients for visual multitasking on sample data from dynamic multitasking in the modified Multi-attribute Task Battery.

capacity coefficient↗
DOE OSTI2013

Data Diodes in Support of Trustworthy Cyber Infrastructure and Net-Centric Cyber Decision Support

Data diodes provide protection of critical cyber assets by the means of physically enforcing traffic direction on the network. In order to deploy data diodes effectively, it is imperative to understand the protection they provide, the protection they do not provide, their limitations, and their place in the larger security infrastructure. In this work, we study data diodes, their functionalities and limitations. We then propose two critical infrastructure systems that can benefit from the additional protection offered by data diodes: process control networks and net-centric cyber decision support systems. We review the security requirements of these systems, describe the architectures, and study the trade-offs. Finally, the architectures are evaluated against different attack patterns.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Functional determinants of radial operators in AdS 2

We study the zeta-function regularization of functional determinants of Laplace and Dirac-type operators in two-dimensional Euclidean AdS 2 space. More specifically, we consider the ratio of determinants between an operator in the presence of background fields with circular symmetry and the free operator in which the background fields are absent. By Fourier-transforming the angular dependence, one obtains an infinite number of one-dimensional radial operators, the determinants of which are easy to compute. The summation over modes is then treated with care so as to guarantee that the result coincides with the two-dimensional zeta-function formalism. The method relies on some well-known techniques to compute functional determinants using contour integrals and the construction of the Jost function from scattering theory. Here, our work generalizes some known results in flat space. The extension to conformal AdS 2 geometries is also considered. We provide two examples, one bosonic and one fermionic, borrowed from the spectrum of fluctuations of the holographic 1/4-BPS latitude Wilson loop.

Wilson↗
DOE OSTI2021

Electropolymerized-molecularly imprinted polymers (E-MIPS) as sensing elements for the detection of dengue infection

Here, a straightforward in situ detection method for dengue infection was demonstrated through the molecular imprinting of a dengue nonstructural protein 1 (NS1) epitope into an electropolymerized molecularly imprinted polyterthiophene (E-MIP) film sensor. The key enabling step in the sensor fabrication is based on an epitope imprinting strategy, in which short peptide sequences derived from the original target molecules were employed as the main template for detection and analysis. The formation of the E-MIP sensor films was facilitated using cyclic voltammetry (CV) and monitored in situ by electrochemical quartz crystal microbalance (EC-QCM). Surface properties were analyzed using different techniques including atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and polarization modulation-infrared reflection-adsorption (PM-IRRAS). The standard calibration curve (R = 0.9830) was generated for the detection of the epitope, Ac-VHTWTEQYKFQ-NH 2 , with a linear range of 0.2 to 30 μg/mL and detection limit of 0.073 μg/mL. A separate calibration curve (R = 0.9786) was obtained using spiked buffered solutions of dengue NS1 protein, which resulted in a linear range of 0.2 to 10 μg/mL and a detection limit of 0.056 μg/mL. The fabricated E-MIP sensor exhibited long-term stability, high sensitivity, and good selectivity towards the targeted molecules. These results indicated that the formation of the exact and stable cavity imprints in terms of size, shape, and functionalities was successful. In our future work, we aim to use our E-MIP sensors for NS1 detection in real-life samples such as serum and blood.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Pretreatment of lignocellulosic feedstocks for cellulose nanofibril production

Cellulose nanofibrils (CNFs) have attracted a great deal of research interest in recent years attributable to the low cost and abundance of lignocellulosic biomass from which they can be extracted. These materials have potential applications in a wide array of areas because of their unique properties such as ultra-high aspect ratios and specific strengths. However, the high energy required to extract CNFs from biomass through fibrillation often makes them prohibitively expensive or negates their inherent sustainability. As such, a variety of biomass treatments prior to fibrillation have been investigated by researchers to reduce the energy requirements of CNF extraction, improve the efficacy of biomass fibrillation and subsequent processes, and/or impart functionality in resulting nanofibrils. In this work, both widely used and emerging mechanical, chemical, and enzymatic pretreatments used prior to fibrillation of lignocellulosic biomass for CNF extraction are reviewed. Attention is given to the effect of these various pretreatments on the properties of the resulting CNFs. Finally, the energy consumption in fibrillation processes with and without the use of pretreatments is compared, and future perspectives on challenges and opportunities in lignocellulosic feedstock pretreatments are discussed.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Evolution of the lithium morphology from cycling of thin film solid state batteries

Thin film batteries with a Lipon electrolyte and Li metal anode can be cycled thousands of times. During this time there is a gradual redistribution of the lithium at the top surface; the morphology that develops depends on a number of factors but is largely driven by dewetting. In this work, this redistribution is characterized as functions of the cycle number, duty cycle, cathode composition, and protective coating over the lithium. Observations of wrinkled and pitted surfaces are discussed considering the effects of defects and diffusion in the lithium and influences of film stresses and surface energy. In conclusion, similar processes may impact solid state lithium batteries with higher energy per active area.

25 ENERGY STORAGE↗
DOE OSTI2020

SuperCam Calibration Targets: Design and Development

Abstract SuperCam is a highly integrated remote-sensing instrumental suite for NASA’s Mars 2020 mission. It consists of a co-aligned combination of Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), Visible and Infrared Spectroscopy (VISIR), together with sound recording (MIC) and high-magnification imaging techniques (RMI). They provide information on the mineralogy, geochemistry and mineral context around the Perseverance Rover. The calibration of this complex suite is a major challenge. Not only does each technique require its own standards or references, their combination also introduces new requirements to obtain optimal scientific output. Elemental composition, molecular vibrational features, fluorescence, morphology and texture provide a full picture of the sample with spectral information that needs to be co-aligned, correlated, and individually calibrated. The resulting hardware includes different kinds of targets, each one covering different needs of the instrument. Standards for imaging calibration, geological samples for mineral identification and chemometric calculations or spectral references to calibrate and evaluate the health of the instrument, are all included in the SuperCam Calibration Target (SCCT). The system also includes a specifically designed assembly in which the samples are mounted. This hardware allows the targets to survive the harsh environmental conditions of the launch, cruise, landing and operation on Mars during the whole mission. Here we summarize the design, development, integration, verification and functional testing of the SCCT. This work includes some key results obtained to verify the scientific outcome of the SuperCam system.

Manrique, J. A. (ORCID:0000000220532819)↗
DOE OSTI2016

On the Structure Sensitivity of Formic Acid Decomposition on Cu Catalysts

Catalytic decomposition of formic acid (HCOOH) has attracted substantial attention since HCOOH is a major by-product in biomass reforming, a promising hydrogen carrier, and also a potential low temperature fuel cell feed. Despite the abundance of experimental studies for vapor-phase HCOOH decomposition on Cu catalysts, the reaction mechanism and its structure sensitivity is still under debate. In this work, self-consistent, periodic density functional theory calculations were performed on three model surfaces of copper—Cu(111), Cu(100) and Cu(211), and both the HCOO (formate)-mediated and COOH (carboxyl)-mediated pathways were investigated for HCOOH decomposition. The energetics of both pathways suggest that the HCOO-mediated route is more favorable than the COOH-mediated route on all three surfaces, and that HCOOH decomposition proceeds through two consecutive dehydrogenation steps via the HCOO intermediate followed by the recombinative desorption of H 2 . On all three surfaces, HCOO dehydrogenation is the likely rate determining step since it has the highest transition state energy and also the highest activation energy among the three catalytic steps in the HCOO pathway. The reaction is structure sensitive on Cu catalysts since the examined three Cu facets have dramatically different binding strengths for the key intermediate HCOO and varied barriers for the likely rate determining step—HCOO dehydrogenation. Cu(100) and Cu(211) bind HCOO much more strongly than Cu(111), and they are also characterized by potential energy surfaces that are lower in energy than that for the Cu(111) facet. Coadsorbed HCOO and H represents the most stable state along the reaction coordinate, indicating that, under reaction conditions, there might be a substantial surface coverage of the HCOO intermediate, especially at under-coordinated step, corner or defect sites. Therefore, under reaction conditions, HCOOH decomposition is predicted to occur most readily on the terrace sites of Cu nanoparticles. Finally, as a result, we hereby present an example of a fundamentally structure-sensitive reaction, which may present itself as structure-insensitive in typical varied particle-size experiments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Theoretical investigations of electrical transport properties in CoSb3 skutterudites under hydrostatic loadings

We report that CoSb 3 -based skutterudites have been a benchmark mid-temperature thermoelectric material under intensive experimental and theoretical studies for decades. Doping and filling, to the first order, alter the crystal lattice constant of CoSb 3 in the context of “chemical pressure.” In this work, we employed ab initio density functional theory in conjunction with semiclassical Boltzmann transport theory to investigate the mechanical properties and especially how hydrostatic loadings, i.e., “physical pressure,” impact the electronic band structure, Seebeck coefficient, and power factor of pristine CoSb 3 . It is found that hydrostatic pressure enlarges the band gap, suppresses the density of states (DOS) near the valence band edge, and fosters the band convergence between the valley bands and the conduction band minimum (CBM). By contrast, hydrostatic tensile reduces the band gap, increases the DOS near the valence band edge, and diminishes the valley bands near the CBM. Therefore, applying hydrostatic pressure provides an alternative avenue for achieving band convergence to improve thermoelectric properties of N-type CoSb 3 , which is further supported by our carrier concentration studies. Lastly, these results provide valuable insight into the further improvement of thermoelectric performance of CoSb 3 -based skutterudites via a synergy of physical and chemical pressures.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Overexpression of an Arabidopsis heterogeneous nuclear ribonucleoprotein gene, AtRNP1, affects plant growth and reduces plant tolerance to drought and salt stresses

Heterogeneous nuclear ribonucleoproteins (hnRNPs) participate in diverse regulations of plant growth and environmental stress responses. In this work, an Arabidopsis hnRNP of unknown function, AtRNP1, was investigated. We found that AtRNP1 gene is highly expressed in rosette and cauline leaves, and slightly induced under drought, salt, osmotic and ABA stresses. AtRNP1 protein is localized to both the nucleus and cytoplasm. We performed homologous overexpression of AtRNP1 and found that the transgenic plants showed shortened root length and plant height, and accelerated flowering. In addition, the transgenic plants also showed reduced tolerance to drought, salt, osmotic and ABA stresses. Further studies revealed that under both normal and stress conditions, the proline contents in the transgenic plants are markedly decreased, associated with reduced expression levels of a proline synthase gene and several stress-responsive genes. These results suggested that the overexpression of AtRNP1 negatively affects plant growth and abiotic stress tolerance. - Highlights: • AtRNP1 is a widely expressed gene and its expression is slightly induced under abiotic stresses. • AtRNP1 protein is localized to both the nucleus and cytoplasm. • Overexpression of AtRNP1 affects plant growth. • Overexpression of AtRNP1 reduces plant tolerance to drought and salt stresses. • AtRNP1 overexpression plants show decreased proline accumulation and stress-responsive gene expressions.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Cloning and functional characterization of a p-coumaroyl quinate/shikimate 3′-hydroxylase from potato (Solanum tuberosum)

Highlights: • StC3′H catalyzed the formation of coumaroyl quinate and coumaroyl shikimate in vitro. • Antisense downregulation of StC3′H in potato tubers caused moderate increases in ferulic acid conjugates and chlorogenic acid. • A reduction in tuber yield was observed in antisense StC3′H lines, though their response to a bacterial pathogen was not significantly affected. Chlorogenic acid (CGA) plays an important role in protecting plants against pathogens and promoting human health. Although CGA accumulates to high levels in potato tubers, the key enzyme p-coumaroyl quinate/shikimate 3′-hydroxylase (C3′H) for CGA biosynthesis has not been isolated and functionally characterized in potato. In this work, we cloned StC3′H from potato and showed that it catalyzed the formation of caffeoylshikimate and CGA (caffeoylquinate) from p-coumaroyl shikimate and p-coumaroyl quinate, respectively, but was inactive towards p-coumaric acid in in vitro enzyme assays. When the expression of StC3′H proteins was blocked through antisense (AS) inhibition under the control of a tuber-specific patatin promoter, moderate changes in tuber yield as well as phenolic metabolites in the core tuber tissue were observed for several AS lines. On the other hand, the AS and control potato lines exhibited similar responses to a bacterial pathogen Pectobacterium carotovorum. These results suggest that StC3′H is implicated in phenolic metabolism in potato. They also suggest that CGA accumulation in the core tissue of potato tubers is an intricately controlled process and that additional C3′H activity may also be involved in CGA biosynthesis in potato.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

CAR-mediated repression of Cdkn1a(p21) is accompanied by the Akt activation

Highlights: • CAR-mediated liver growth is accompanied by the decrease in PTEN. • CAR-mediated liver growth is accompanied by the Akt activation. • CAR-mediated Akt activation is accompanied by the decrease in Foxo1. • CAR activation decreased the level of p21. It was shown that CAR participates in the regulation of many cell processes. Thus, the activation of CAR causes a proliferating effect in the liver, which provides grounds to consider CAR as a therapeutic target when having a partial resection of this organ. Even though a lot of work has been done on the function of CAR in regulating hepatocyte proliferation, very little has been done on its complex mediating mechanism. This study, therefore, showed that the liver growth resulting from CAR activation leads to the decline in the level of PTEN protein and subsequent Akt activation in mouse liver. The increase of Akt activation produced by CAR agonist was accompanied by a decrease in the level of Foxo1, which was correlated with decreased expression of Foxo1 target genes, including Cdkn1a(p21). Moreover, the study also demonstrated that there exists a negative regulatory impact of CAR on the relationship between Foxo1 and targeted Cdkn1a(p21) promoter. Therefore, the study results revealed an essential function of CAR-Akt-Foxo1 signalling pathway in controlling hepatocyte proliferation by repressing the cell cycle regulator Cdkn1a (p21).

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Atomic structure and grain shape evolution of nanodiamond during annealing in oxidizing atmosphere from neutron diffraction and MD simulations

In this work, real space pair-distribution function (PDF) analysis in conjunction with molecular dynamics (MD) simulations was applied to characterize crystal structure, shape and surface structure of diamond nanoparticles annealed in air up to 880 °C. MD simulated models of individual nanodiamond particles of various shapes and sizes were used to calculate theoretical radial distribution functions G(r) for powders with different grain size distributions. The calculated curves, showing distinct differences for the explored parameter space, were compared to the experimental G(r) functions obtained from neutron scattering for annealed detonated nanodiamond samples in a search for a model best describing the actual powders. It was found that as-synthesized nanodiamond grains are terminated by equally abundant (100), (110) and (111) crystallographic faces and their structure does not change upon annealing in air up to 280 °C. The shape and size of grains annealed above 480 °C changes due to surface etching. The etching rate differs between crystals faces and depends on temperature, resulting in the observed differences in grain shape. Below 680 °C the share of the (110) facets gradually increases and at 680 °C the grains become rhombic dodecahedra terminated solely by (110) surfaces. Further increase of the annealing temperature promotes formation of (111) surfaces and at 880 °C the preferred grain shape becomes an octahedron terminated by a variant of (111) surfaces possessing three dangling sp3 bonds per atom. At lower temperatures all grains become smaller and the size distribution moves towards the lower values. Furthermore, as the annealing temperature increases, the smallest grains disappear entirely and the average grain size grows back.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Sintering and collapse of synthetic coal ash and slag cones as observed through constant heating rate optical dilatometry

Ash agglomeration and slagging are responsible for costly maintenance problems in coal-fired boilers. Boiler design and operation rely on critical ash fusion temperatures defined by geometric criteria that explicitly ignore shrinkage or warping. Reproducibility of ash fusion test (AFT) results is known to be a major problem, given the subjective nature of some criteria used in critical temperature reporting. Decades of faulty predictions based on AFT data underscore the need for an objective measure of the likelihood for agglomeration and slagging as a function of coal ash composition and temperature. Heating microscopes and ash fusibility determinators are AFT instruments that are widely available and readily adapted for optical dilatometry of ash cones through digital image analysis. Optical dilatometry enables the continuous measurement of cone height and face area, and the calculation of changes in cone volume and density as a function of temperature during constant heating. A strong correlation was found between the sintering onset temperatures of two synthetic ash compositions measured through optical dilatometry and their corresponding solidus temperatures predicted through thermophysical modeling. The sintering onset temperatures of synthetic slag cones appears consistent with glass transition temperatures estimated using the Kauzmann-Beaman rule. Cone collapse is highly correlated with softening, hemispherical, and fluid temperatures for ash cones. Rapid changes in solid, liquid, and gas volume fractions near the collapse temperature suggest that a transition from capillary to slurry state may play an important role in triggering collapse. Slag cone collapse is better explained by a decrease in viscosity as a function of temperature in the glass working range. Furthermore, the sintering onset temperature and cone collapse temperature are readily understood through thermophysical modeling based on ash composition and provide two additional critical temperatures in the modeling of coal ash agglomeration and slagging.

01 COAL, LIGNITE, AND PEAT↗

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