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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Revealing a Hidden Intermediate of Rotatory Catalysis with X-ray Crystallography and Molecular Simulations

The mechanism of rotatory catalysis in ATPhydrolyzing molecular motors remains an unresolved puzzle in biological energy transfer. Notwithstanding the wealth of available biochemical and structural information inferred from years of experiments, knowledge on how the coupling between the chemical and mechanical steps within motors enforces directional rotatory movements remains fragmentary. Even more contentious is to pinpoint the rate-limiting step of a multistep rotation process. Here, using vacuolar or V 1 -type hexameric ATPase as an exemplary rotational motor, we present a model of the complete 4-step conformational cycle involved in rotatory catalysis. First, using Xray crystallography, a new intermediate or “dwell” is identified, which enables the release of an inorganic phosphate (or P i ) after ATP hydrolysis. Using molecular dynamics simulations, this new dwell is placed in a sequence with three other crystal structures to derive a putative cyclic rotation path. Free-energy simulations are employed to estimate the rate of the hexameric protein transformations and delineate allosteric effects that allow new reactant ATP entry only after hydrolysis product exit. An analysis of transfer entropy brings to light how the side-chain-level interactions transcend into larger-scale reorganizations, highlighting the role of the ubiquitous arginine-finger residues in coupling chemical and mechanical information. An inspection of all known rates encompassing the 4-step rotation mechanism implicates the overcoming of the ADP interactions with V 1 -ATPase to be the rate-limiting step of motor action.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Entropic control of the free-energy landscape of an archetypal biomolecular machine

Biomolecular machines are complex macromolecular assemblies that utilize thermal and chemical energy to perform essential, multistep, cellular processes. Despite possessing different architectures and functions, an essential feature of the mechanisms of action of all such machines is that they require dynamic rearrangements of structural components. Surprisingly, biomolecular machines generally possess only a limited set of such motions, suggesting that these dynamics must be repurposed to drive different mechanistic steps. Although ligands that interact with these machines are known to drive such repurposing, the physical and structural mechanisms through which ligands achieve this remain unknown. Using temperature-dependent, single-molecule measurements analyzed with a time-resolution-enhancing algorithm, here, we dissect the free-energy landscape of an archetypal biomolecular machine, the bacterial ribosome, to reveal how its dynamics are repurposed to drive distinct steps during ribosome-catalyzed protein synthesis. Specifically, we show that the free-energy landscape of the ribosome encompasses a network of allosterically coupled structural elements that coordinates the motions of these elements. Moreover, we reveal that ribosomal ligands which participate in disparate steps of the protein synthesis pathway repurpose this network by differentially modulating the structural flexibility of the ribosomal complex (i.e., the entropic component of the free-energy landscape). Here, we propose that such ligand-dependent entropic control of free-energy landscapes has evolved as a general strategy through which ligands may regulate the functions of all biomolecular machines. Such entropic control is therefore an important driver in the evolution of naturally occurring biomolecular machines and a critical consideration for the design of synthetic molecular machines.

Science & Technology - Other Topics↗
DOE OSTI2026

Scalable multiplexed machine learning gas sensor chips for food classification

Multiplexed gas sensor arrays combined with machine learning have unlocked previously inaccessible applications for scent-based sensing. Current platforms are limited by overlapping sensing materials with similar compositions, leading to highly correlated responses, or multistep deposition processes that hinder scalability. In this work, we developed a 16-element monolithic chip with fully distinct sensing layers, enabling a truly heterogeneous array. The system consists of highly sensitive carbon nanotube field effect transistors that are functionalized through a single-step microdispensing method compatible with automated pipetting systems. The resulting chip produces characteristic signal patterns in response to object-specific scent profiles and, when combined with machine learning algorithms, can perform automated object identification. We demonstrate the classification of 16 different objects, including food spoilage and nut allergens, with a 92.6% overall prediction accuracy.

Bassil, Carla [University of California, Berkeley,↗
NASA NTRS1979

Open-circuit voltage improvements in low-resistivity solar cells

Mechanisms limiting the open-circuit voltage in 0.1 ohm-cm solar cells were investigated. It was found that a rather complicated multistep diffusion process could produce cells with significantly improved voltages. The voltage capabilities of various laboratory cells were compared independent of their absorption and collection efficiencies. This was accomplished by comparing the cells on the basis of their saturation currents or, equivalently, comparing their voltage outputs at a constant current-density level. The results show that for both the Lewis diffused emitter cell and the Spire ion-implanted emitter cell the base component of the saturation current is voltage controlling. The evidence for the University of Florida cells, although not very conclusive, suggests emitter control of the voltage in this device. The data suggest further that the critical voltage-limiting parameter for the Lewis cell is the electron mobility in the cell base.

Godlewski, M. P.↗
NASA NTRS1980

The effect of minority carrier mobility variations on the performance of high voltage silicon solar cells

A multistep diffusion processing schedule is described which allows the attainment of high open circuit voltages in 0.1 ohm/cm silicon cells. The schedule consists of a deep primary diffusion, followed by an acid etch of emmitter surface which is then followed by a shallow secondary diffusion. A correlation is made between the observed voltage increases and the time of primary diffusion. Results indicate that as the primary diffusion time increases, the voltage rises monotonically.

Weizer, V. G.↗
NASA NTRS1990

Cell separation and electrofusion in space

In microgravity, free-fluid electrophoretic methods for separating living cells and proteins are improved significantly by the absence of gravity-driven phenomena. Cell fusion, culture, and other bioprocessing steps are being investigated to understand the limits of earth-based processing. A multistep space bioprocess is described that includes electrophoretic separation of human target cells, single-cell manipulations using receptor-specific antibodies, electrofusion to produce immortal hybridomas, gentle suspension culture, and monoclonal antibody recovery using continuous-flow electrophoresis or recirculating isoelectric focusing. Improvements in several key steps already have been demonstrated by space experiments, and others will be studied on Space Station Freedom.

Morrison, D. R.↗
NASA NTRS2000

Analysis of Siderite Thermal Decomposition by Differential Scanning Calorimetry

Characterization of carbonate devolitilization has important implications for atmospheric interactions and climatic effects related to large meteorite impacts in platform sediments. On a smaller scale, meteorites contain carbonates which have witnessed shock metamorphic events and may record pressure/temperature histories of impact(s). ALH84001 meteorite contains zoned Ca-Mg-Fe-carbonates which formed on Mars. Magnetite crystals are found in the rims and cores of these carbonates and some are associated with void spaces leading to the suggestion by Brearley et al. that the crystals were produced by thermal decomposition of the carbonate at high temperature, possibly by incipient shock melting or devolitilization. Golden et al. recently synthesized spherical Mg-Fe-Ca-carbonates from solution under mild hydrothermal conditions that have similar carbonate compositional zoning to those of ALH84001. They have shown experimental evidence that the carbonate-sulfide-magnetite assemblage in ALH84001 can result from a multistep inorganic process involving heating possibly due to shock events. Experimental shock studies on calcium carbonate prove its stability to approx. 60 GPa, well in excess of the approx. 45 GPa peak pressures indicated by other shock features in ALH84001. In addition, Raman spectroscopy of carbonate globules in ALH84001 indicates no presence of CaO and MgO. Such oxide phases should be found associated with the magnetites in voids if these magnetites are high temperature shock products, the voids resulting from devolitilization of CO2 from calcium or magnesium carbonate. However, if the starting material was siderite (FeCO3), thermal breakdown of the ALH84001 carbonate at 470 C would produce iron oxide + CO2. As no documentation of shock effects in siderite exists, we have begun shock experiments to determine whether or not magnetite is produced by the decomposition of siderite within the < 45GPa pressure window and by the resultant thermal pulse to approx. 600 C experienced by ALH84001. Here, we report thermal and compositional characterization of unshocked siderite and its transition to magnetite. Additional information is contained in the original extended abstract.

Bell, M. S.↗
DOE OSTI2021

Molecular Iodine Interactions with Fe, Ni, Cr, and Stainless Steel Alloys

The adsorption behavior of molecular iodine is important for understanding the spread of radioiodine in a nuclear accident. Prior experiments indicate that, in addition to the interaction with Fe, molecular iodine [i.e., I 2(g) ] also interacts with the next most abundant components of austenitic stainless steel (i.e., Ni, and Cr) at room temperature. Here, we investigate iodine adsorption on Fe, Ni, and Cr while focusing on understanding the variables affecting adsorption as well as the iodine compounds that are formed during adsorption. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to characterize the surfaces of exposed metal particles and aid in the understanding of the morphology and chemistry of iodine interactions with the substrates. Inductively coupled plasma optical emission spectroscopy was used to detect low levels of metal iodides and X-ray photoelectron spectroscopy was used to confirm the formation of the metal iodides. The role of environmental factors (e.g., humidity and oxygen content) for iodine adsorption on metal substrates is addressed. The individual metals demonstrated formation of metal iodides for Fe and Ni particles from interaction with I 2(g) . The formation of metal iodides may indicate the affinity of iodine for the respective metal. In this study, the iodine affinities ranked Fe > Ni > Cr as determined by the quantity of chemisorbed iodine. This trend is also supported by the distributions and proportions of metals in the corrosion product of the stainless steels. The exposures without oxygen and humidity indicate the potential of a multistep iodine adsorption process where iodine first attacks the oxide layer and then chemisorbs to the exposed metal.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Experimental and Computational Mechanisms that Govern Long-Term Stability of CO 2 -Adsorbed ZIF-8-Based Porous Liquids

Porous liquids (PLs) based on the zeolitic imidazole framework ZIF-8 are attractive systems for carbon capture since the hydrophobic ZIF framework can be solvated in aqueous solvent systems without porous host degradation. However, solid ZIF-8 is known to degrade when exposed to CO 2 in wet environments, and therefore the long-term stability of ZIF-8-based PLs is unknown. Here, through aging experiments, the long-term stability of a ZIF-8 PL formed using the water, ethylene glycol, and 2-methylimidazole solvent system was systematically examined, and the mechanisms of degradation were elucidated. The PL was found to be stable for several weeks, with no ZIF framework degradation observed after aging in N 2 or air. However, for PLs aged in a CO 2 atmosphere, formation of a secondary phase occurred within 1 day from the degradation of the ZIF-8 framework. From the computational and structural evaluation of the effects of CO 2 on the PL solvent mixture, it was identified that the basic environment of the PL caused ethylene glycol to react with CO 2 forming carbonate species. These carbonate species further react within the PL to degrade ZIF-8. The mechanisms governing this process involves a multistep pathway for PL degradation and lays out a long-term evaluation strategy of PLs for carbon capture. Additionally, it clearly demonstrates the need to examine the reactivity and aging properties of all components in these complex PL systems in order to fully assess their stabilities and lifetimes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Real-Time High-Accuracy Digital Wireless Time, Frequency, and Phase Calibration for Coherent Distributed Antenna Arrays

his work presents a fully-digital high-accuracy real-time calibration procedure for frequency and time alignment of open-loop wirelessly coordinated coherent distributed antenna array (CDA) modems, enabling radio frequency (RF) phase coherence of spatially separated commercial off-the-shelf (COTS) software-defined radios (SDRs) without cables or external references such as the global navigation satellite system (GNSS). Building on previous work using high-accuracy spectrally-sparse time of arrival (ToA) waveforms and a multistep ToA refinement process, a high-accuracy two-way time transfer (TWTT)-based time–frequency coordination approach is demonstrated. Due to the two-way nature of the high-accuracy TWTT approach, the time and frequency estimates are Doppler and multipath tolerant, so long as the channel is reciprocal over the synchronization epoch. This technique is experimentally verified using COTS SDRs in a lab environment in static and dynamic scenarios and with significant multipath scatterers. Time, frequency, and phase stability were evaluated by beamforming over coaxial cables to an oscilloscope which achieved time and phase precisions of ~60– 70 ps , with median coherent gains above 99% using optimized coordination parameters, and a beamforming frequency root-mean-square error (RMSE) of 3.73 ppb in a dynamic scenario. Finally, experiments were conducted to compare the performance of this technique with previous works using an analog continuous-wave two-tone (CWTT) frequency reference technique in both static and dynamic settings.

Clock synchronization↗
NASA NTRS1974

The long-term prediction of artificial satellite orbits

Survey of averaging and multirevolution methods for long-term orbit prediction. A technical approach with the following features is recommended: (1) averaged variation-of-parameter equations, (2) analytical expressions for oblateness and third-body effects, (3) definite integrals for atmospheric drag and lunar effects (for long-period orbits), (4) nonsingular equinoctial element formulation, (5) multistep numerical integration processes, and (6) precise osculating-to-mean element transformation. Several orbital predictions illustrate the contribution of this technical approach to overall accuracy and efficiency. Future development of the analytical averaging method in nonsingular coordinates by automated manipulation of literal series is discussed.

Cefola, P. J.↗
DOE OSTI2023

Continuous recovery of phosphoric acid and Rare-Earths containing particles from phosphoric acid sludge using a decanter centrifuge

Recovery of rare earth elements (REEs) from various industrial and natural streams currently draws significant attention in efforts to meet the demands of the manufacturing industry. Among many industrial byproducts and waste streams, phosphoric acid sludge could be one of the most economically feasible resources for the recovery of REEs because solid particles in the sludge contain relatively concentrated REEs, up to 3,000 ppm, while the liquid component of the sludge is valuable phosphoric acid (P 2 O 5 ) that can be recovered and returned to the main product. Due to high viscosity and large solids content (e.g., 30–40 %), however, this byproduct stream requires multistep separation and purification processes. In this study, a single-step process involving a continuous-flow decanter centrifuge (CFDC) was employed to investigate its feasibility for continuous solid/liquid separation from real phosphoric acid sludge. High centrifugal forces generated from up to 1500 G gravity acceleration separate solid particles from the sludge, generating a liquid-rich stream and a solids-rich stream at the exit of the CFDC. A single pass of phosphoric-acid sludge through the CFDC yielded 95 % liquid recovery and 90 % recovery of REEs-containing solids from 20 to 34 wt% solids-containing sludge. Finally, a reduced order model developed for the CFDC operation showed good agreement with experimental data, and preliminary technoeconomic analysis revealed potential process feasibility.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Single vs double atom catalyst for N 2 activation in nitrogen reduction reaction: A DFT perspective

Abstract Ammonia synthesis through electrochemical reduction of nitrogen molecules is a promising strategy to significantly reduce the energy consumption in traditional industrial process. Detailed mechanism study of multistep complex nitrogen reduction reaction is prerequisite for the design of highly efficient catalyst. Stable atomically dispersed catalyst with unique geometric and electronic structure is suitable for the mechanism clarification of such a complex reaction. In this study, d ‐block transition‐metal (TM) anchored C 2 N single layer catalyst is investigated by the density functional theory (DFT) calculation. Both single TM‐anchored single atom catalyst (SAC) and double TM‐anchored double atom catalyst (DAC) exhibit good thermodynamic stability in atomically dispersed catalyst. In the case of SACs, IVB metals (Ti, Zr, Hf) exhibit the highest reactivity and lowest overpotential. While in the case of DACs, Cr─Cr system leads to the NH 3 formation, but V─V system leads to the N 2 H 4 formation. The SACs show much lower overpotential and stronger activation of N 2 molecule than the DACs due to the different activation mechanisms: traditional σ ‐donation/ π ‐backdonation N 2 activation mechanism is found in SACs, while a new π ‐donation/π‐backdonation N 2 activation mechanism is found in the DACs. The present work demonstrates that the different catalytic effect for NRR between SAC and DAC and their corresponding electronic structure origin, which gives more insight into the single atom catalyst. image

Qian, Yumin↗
DOE OSTI2024

Aerosol jet printing of surface acoustic wave microfluidic devices

Abstract The addition of surface acoustic wave (SAW) technologies to microfluidics has greatly advanced lab-on-a-chip applications due to their unique and powerful attributes, including high-precision manipulation, versatility, integrability, biocompatibility, contactless nature, and rapid actuation. However, the development of SAW microfluidic devices is limited by complex and time-consuming micro/nanofabrication techniques and access to cleanroom facilities for multistep photolithography and vacuum-based processing. To simplify the fabrication of SAW microfluidic devices with customizable dimensions and functions, we utilized the additive manufacturing technique of aerosol jet printing. We successfully fabricated customized SAW microfluidic devices of varying materials, including silver nanowires, graphene, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). To characterize and compare the acoustic actuation performance of these aerosol jet printed SAW microfluidic devices with their cleanroom-fabricated counterparts, the wave displacements and resonant frequencies of the different fabricated devices were directly measured through scanning laser Doppler vibrometry. Finally, to exhibit the capability of the aerosol jet printed devices for lab-on-a-chip applications, we successfully conducted acoustic streaming and particle concentration experiments. Overall, we demonstrated a novel solution-based, direct-write, single-step, cleanroom-free additive manufacturing technique to rapidly develop SAW microfluidic devices that shows viability for applications in the fields of biology, chemistry, engineering, and medicine.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Open-air plasma-assisted deposition of organosilicon coating for corrosion protection of AZ91D Mg alloy

As a corrosion barrier layer, open-air plasma-assisted organosilicon coating was applied on AZ91D Mg alloy. Organosilicon-coated AZ91D samples, prepared from two different plasma coating processes, were used for corrosion evaluation based on multistep electrochemical and H 2 collection measurements in 3.5 wt% sodium chloride (NaCl) solution. Some coated AZ91D samples were characterized with and without corrosion exposure in NaCl solution using electron microscopies and X-ray chemical analysis techniques. Further, the results indicate that the organosilicon coatings from open-air plasma processes are effective to delay the initiation of corrosion attack and also reduce the corrosion rate for AZ91D substrate. The corrosion attack was considered to develop after permeation of NaCl solution through the coating layer.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Capabilities and constraints of NASA's ground-based reduced gravity facilities

The ground-based reduced gravity facilities of NASA have been utilized to support numerous investigations addressing various processes and phenomina in several disciplines for the past 30 years. These facilities, which include drop towers, drop tubes, aircraft, and sounding rockets are able to provide a low gravity environment (gravitational levels that range from 10(exp -2)g to 10(exp -6)g) by creating a free fall or semi-free fall condition where the force of gravity on an experiment is offset by its linear acceleration during the 'fall' (drop or parabola). The low gravity condition obtained on the ground is the same as that of an orbiting spacecraft which is in a state of perpetual free fall. The gravitational levels and associated duration times associated with the full spectrum of reduced gravity facilities including spaced-based facilities are summarized. Even though ground-based facilities offer a relatively short experiment time, this available test time has been found to be sufficient to advance the scientific understanding of many phenomena and to provide meaningful hardware tests during the flight experiment development process. Also, since experiments can be quickly repeated in these facilities, multistep phenomena that have longer characteristic times associated with them can sometimes be examined in a step-by-step process. There is a large body of literature which has reported the study results achieved through using reduced-gravity data obtained from the facilities.

Lekan, Jack↗
NASA NTRS1993

Fabrication of micro-optical devices

We have fabricated a variety of micro-optic components including Fresnel and non-Frensel lenses, off-axis and dispersive lenses with binary stepped contours, and analog contours. Process details for all lens designs fabricated are given including multistep photolithography for binary fabrication and grayscale mask photolithography for analog fabrication. Reactive ion etching and ion beam milling are described for the binary fabrication process, while ion beam milling was used for the analog fabrication process. Examples of micro-optic components fabricated in both Si and CdTe substrates are given.

Anderson, W. W.↗