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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Heliomagnetic Latitude Dependence of Heliospheric Magnetic Field

ICE and IMP-8 magnetic field data from 1984 1988 were analyzed in a magnetic coordinate system defined by the orientation of the solar magnetic dipole. The heliomagnetic latitude dependence of the radial component of the magnetic field (Br) was then investigated in the range of magnetic latitudes from 60 above and below the heliospheric current sheet. Investigators found that Br reverses sign abruptly across the current sheet, consistent with solar magnetic field models, but inconsistent with the source surface models.

ICE↗
NASA NTRS1995

Heliomagnetic Latitude Dependence of the Heliospheric Magnetic Field

ICE and IMP-8 data were analyzed in a heliomagnetic coordinate system defined by the orientation of the solar magnetic dipole. Observations were compared with several solar magnetic field models. The radial component of the magnetic field was found to reverse sign abruptly at the sector boundary; this is consistent with the sheet model, but inconsistent with source surface models .

ICE↗
DOE OSTI2023

Mesoporous CuFe 2 O 4 Photoanodes for Solar Water Oxidation: Impact of Surface Morphology on the Photoelectrochemical Properties**

Abstract Metal oxide‐based photoelectrodes for solar water splitting often utilize nanostructures to increase the solid‐liquid interface area. This reduces charge transport distances and increases the photocurrent for materials with short minority charge carrier diffusion lengths. While the merits of nanostructuring are well established, the effect of surface order on the photocurrent and carrier recombination has not yet received much attention in the literature. To evaluate the impact of pore ordering on the photoelectrochemical properties, mesoporous CuFe 2 O 4 (CFO) thin film photoanodes were prepared by dip‐coating and soft‐templating. Here, the pore order and geometry can be controlled by addition of copolymer surfactants poly(ethylene oxide)‐ block ‐poly(propylene oxide)‐ block ‐poly(ethylene oxide) (Pluronic® F‐127), polyisobutylene‐ block ‐poly(ethylene oxide) (PIB‐PEO) and poly(ethylene‐ co ‐butylene)‐ block ‐poly(ethylene oxide) (Kraton liquid™‐PEO, KLE). The non‐ordered CFO showed the highest photocurrent density of 0.2 mA/cm 2 at 1.3 V vs. RHE for sulfite oxidation, but the least photocurrent density for water oxidation. Conversely, the ordered CFO presented the best photoelectrochemical water oxidation performance. These differences can be understood on the basis of the high surface area, which promotes hole transfer to sulfite (a fast hole acceptor), but retards oxidation of water (a slow hole acceptor) due to electron‐hole recombination at the defective surface. This interpretation is confirmed by intensity‐modulated photocurrent (IMPS) and vibrating Kelvin probe surface photovoltage spectroscopy (VKP‐SPS). The lowest surface recombination rate was observed for the ordered KLE‐based mesoporous CFO, which retains spherical pore shapes at the surface resulting in fewer surface defects. Overall, this work shows that the photoelectrochemical energy conversion efficiency of copper ferrite thin films is not just controlled by the surface area, but also by surface order.

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

Shallow Embedded Strain Measurements and Analysis for a NbTi Superconducting Sextupole Coil During Cooling, Excitation, and Quench

The present study deals with strain measurements and their numerical analysis for a niobium titanium wire wounded superconducting sextupole coil in a multi-field operation environment, including cooling down, excitation, and quench. Four low-temperature resistance strain gauges with designed compensation circuits were affixed directly on the surface of the superconducting wires but within glass fiber cloth. Before the sextuple coil’s test was carried out, for the purpose of reliability, based on the designed compensation circuit, some basic experiments were carried out during cooling down, excitation, and quench. The experimental results showed that the shallow embedded low-temperature resistance strain gauges were still highly reproducible with an error of 1% for a variable magnetic field and an error of 5% for a variable thermal field by executing various modes. It shows multi-stage strain monitoring is feasible for the superconducting sextupole. In addition, a numerical multiphysics model for the sextuple coil is also built from Maxwell’s equations and the equilibrium equations for mechanical and thermal deformation. A self-tested elastic modulus of NbTi/Cu stack with epoxy, which is cut from a NbTi/Cu sextupole prototype, at low temperature is used in this simulation. The numerical results have reasonable agreement with the experimental observations and show the multiphysics model with self-tested elastic modulus can be applied to analysis strain behaviors under complicated fields before superconducting magnet assembly. The present results will also provide some strain-measuring technology and multiphysics numerical analysis on an LTS/HTS superconducting magnet developed at the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Highly deformable Mg–Al–Ca alloy with Al 2 Ca precipitates

Magnesium (Mg) is the lightest structural metal. However, the poor formability of Mg alloys to great extent limits their applications in making structural parts. Formability is strongly correlated to both high tensile elongation and large work hardening capacity. In this work, we report a new Mg-Al-Ca alloy in which a majority of deformable Al 2 Ca precipitates form while the formation of Laves phases of Mg 17 Al 12 and Mg 2 Ca seems suppressed. Al 2 Ca precipitates imped dislocation motion, leading to large work hardening. Then, Al 2 Ca precipitates deform with dislocations and stacking faults under the enhanced flow stress, which relieve local stress concentration and improve tensile elongation. In addition, solutes Al and Ca suppress twin nucleation while promoting non-basal dislocations in Mg. Our Mg-Al-Ca alloy demonstrates one of the highest combinations of tensile elongation and work hardening capacity among existing Mg alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Crystal structure of cbbF from Zymomonas mobilis and its functional implication

Highlights: • The crystal structure of one cbbF from Zymomonas mobilis was revealed. • Scores of residues form two secondary structures with a non-polar protruded residue. • It exists as a dimeric form in solution. - Abstract: A phosphate group at the C1-atom of inositol-monophosphate (IMP) and fructose-1,6-bisphosphate (FBP) is hydrolyzed by a phosphatase IMPase and FBPase in a metal-dependent way, respectively. The two enzymes are almost indiscernible from each other because of their highly similar sequences and structures. Metal ions are bound to residues on the β1- and β2-strands and one mobile loop. However, FBP has another phosphate and FBPases exist as a higher oligomeric state, which may discriminate FBPases from IMPases. There are three genes annotated as FBPases in Zymomonas mobilis, termed also cbbF (ZmcbbF). The revealed crystal structure of one ZmcbbF shows a globular structure formed by five stacked layers. Twenty-five residues in the middle of the sequence form an α-helix and a β-strand, which occupy one side of the catalytic site. A non-polar Leu residue among them is protruded to the active site, pointing out unfavorable access of a bulky charged group to this side. In vitro assays have shown its dimeric form in solution. Interestingly, two β-strands of β1 and β2 are disordered in the ZmcbbF structure. These data indicate that ZmcbbF might structurally belong to IMPase, and imply that its active site would be reorganized in a yet unreported way.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Intracellular calcium levels can regulate Importin-dependent nuclear import

Highlights: • High intracellular calcium inhibits Impα/β1- or Impβ1-dependent nuclear protein import. • The effect of Ca{sup 2+} on nuclear import does not relate to changes in the nuclear pore. • High intracellular calcium can result in mislocalisation of Impβ1, Ran and RCC1. - Abstract: We previously showed that increased intracellular calcium can modulate Importin (Imp)β1-dependent nuclear import of SRY-related chromatin remodeling proteins. Here we extend this work to show for the first time that high intracellular calcium inhibits Impα/β1- or Impβ1-dependent nuclear protein import generally. The basis of this relates to the mislocalisation of the transport factors Impβ1 and Ran, which show significantly higher nuclear localization in contrast to various other factors, and RCC1, which shows altered subnuclear localisation. The results here establish for the first time that intracellular calcium modulates conventional nuclear import through direct effects on the nuclear transport machinery.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Guanine and inosine nucleotides/nucleosides suppress murine T cell activation

Highlights: • We investigated T-cell activation by guanine and inosine nucleotides/nucleosides. • They dose-dependently suppressed IL-2 production via T-cell receptor stimulation. • GTP, ITP, guanosine and inosine suppressed ConA-induced IL-2/IL-6 production. • They did not affect CD25 expression or ERK1/2 activation during T cell activation. • These nucleotides/nucleosides are candidate agents to treat inflammatory diseases. Damaged tissues and cells release intracellular purine nucleotides, which serve as intercellular signaling factors. We previously showed that exogenously added adenine nucleotide (250 μM ATP) suppressed the activation of murine splenic T lymphocytes. Here, we examined the effects of other purine nucleotides/nucleosides on mouse T cell activation. First, we found that pretreatment of mouse spleen T cells with 250 μM GTP, GDP, GMP, guanosine, ITP, IDP, IMP or inosine significantly reduced the release of stimulus-inducible cytokine IL-2. This suppression of IL-2 release was not caused by induction of cell death. Further studies with GTP, ITP, guanosine and inosine showed that pretreatment with these nucleotides/nucleosides also suppressed release of IL-6. However, these nucleotides/nucleosides did not suppress stimulus-induced phosphorylation of ERK1/2, suggesting that the suppression of the release of inflammatory cytokines does not involve inhibition of ERK1/2 signaling. In contrast to ATP pretreatment at the same concentration, guanine or inosine nucleotides/nucleosides did not attenuate the expression of CD25. Our findings indicate that exogenous guanine or inosine nucleotides/nucleosides can suppress inflammatory cytokine release from T cells, and may be promising candidates for use as supplementary agents in the treatment of T cell-mediated immune diseases.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

First benchmarked electron cooling simulations from first principles

We present the first microscopic electron cooling simulations from first principles with accurate prediction of cooling time. These simulations were performed using our previously developed numerical method, PHAD, which is the first efficient large-scale collisional numerical method in beam physics. The simulation results are benchmarked with the experimental data of the low energy bunched electron cooling of ion beams at the storage ring CSRm at the IMP facility in China. Here, we have accurately considered the nonlinear dynamics in the whole accelerator system in addition to the electron cooling section. As a result, our simulations correctly reproduced cooling times of the experiments from first principles and without any tuning or fitting parameters in the code.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Interaction between amiodarone and hepatitis-C virus nucleotide inhibitors in human induced pluripotent stem cell-derived cardiomyocytes and HEK-293 Cav{sub 1.2} over-expressing cells

Several clinical cases of severe bradyarrhythmias have been reported upon co-administration of the Hepatitis-C NS5B Nucleotide Polymerase Inhibitor (HCV-NI) direct-acting antiviral agent, sofosbuvir (SOF), and the Class-III anti-arrhythmic amiodarone (AMIO). We model the cardiac drug-drug interaction (DDI) between AMIO and SOF, and between AMIO and a closely-related SOF analog, MNI-1 (Merck Nucleotide Inhibitor #1), in functional assays of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), to provide mechanistic insights into recently reported clinical cases. AMIO co-applied with SOF or MNI-1 increased beating rate or field potential (FP) rate and decreased impedance (IMP) and Ca{sup 2+} transient amplitudes in hiPSC-CM syncytia. This action resembled that of Ca{sup 2+} channel blockers (CCBs) in the model, but CCBs did not substitute for AMIO in the DDI. AMIO analog dronedarone (DRON) did not substitute for, but competed with AMIO in the DDI. Ryanodine and thapsigargin, decreasing intracellular Ca{sup 2+} stores, and SEA-0400, a Na{sup +}/Ca{sup 2+} exchanger-1 (NCX1) inhibitor, partially antagonized or suppressed DDI effects. Other agents affecting FP rate only exerted additive or subtractive effects, commensurate with their individual effects. We also describe an interaction between AMIO and MNI-1 on Cav{sub 1.2} ion channels in an over-expressing HEK-293 cell line. MNI-1 enhanced Cav{sub 1.2} channel inhibition by AMIO, but did not affect inhibition of Cav{sub 1.2} by DRON, verapamil, nifedipine, or diltiazem. Our data in hiPSC-CMs indicate that HCV-NI agents such as SOF and MNI-1 interact with key intracellular Ca{sup 2+}-handling mechanisms. Additional study in a Cav{sub 1.2} HEK-293 cell-line suggests that HCV-NIs potentiate the inhibitory action of AMIO on L-type Ca{sup 2+} channels. - Highlights: • Adverse clinical interaction between amiodarone and HCV-NI drugs is captured by in vitro models. • Human iPSC-derived cardiomyocyte beating syncytial model points to Ca{sup 2+} handling effects. • Overexpressing human Ca{sup 2+} channel line model points to shifts in Ca{sup 2+} influx. • Shifts in Ca{sup 2+} current voltage-dependent inactivation play a role in the AER interaction.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Facet-Dependent Kinetics and Energetics of Hematite for Solar Water Oxidation Reactions

Currently, the performance of a photoelectrochemical (PEC) system is highly dependent on the charge separation, transport and transfer characteristics at the photoelectrode|electrolyte interface. Of the factors that influence the charge behaviors, the crystalline facets of the semiconductor in contact with the electrolyte play an important role but has been poorly studied previously. Here, we present a study aimed at understanding how the different facets of hematite affect the charge separation and transfer behaviors in a solar water oxidation reaction. Specifically, hematite crystallites with predominantly {012} and {001} facets exposed were synthesized. Density functional theory (DFT) calculations revealed that hematite {012} surfaces feature higher OH coverage, which was confirmed by X-ray photoelectron spectroscopy (XPS). These surface OH groups act as active sites to mediate water oxidation reactions, which plays a positive role for the PEC system. These surface OH groups also facilitate charge recombination, which compromises the charge separation capabilities of hematite. Moreover, intensity modulated photocurrent spectroscopy (IMPS) confirmed that hematite {012} surfaces exhibit higher rate constants for both charge transfer and recombination. Open circuit potential (OCP) measurements revealed that the hematite {012} surface reflects a greater degree of Fermi level pinning effect. Our results shed light on how different surface crystal structures may change surface kinetics and energetics. The information is anticipated to contribute to efforts on optimizing PEC performance for practical solar fuel synthesis.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Structural and Biochemical Characterization of Human Adenylosuccinate Lyase (ADSL) and the R303C ADSL Deficiency-Associated Mutation

Adenylosuccinate lyase (ADSL) deficiency is a rare autosomal recessive disorder, which causes a defect in purine metabolism resulting in neurological and physiological symptoms. ADSL executes two nonsequential steps in the de novo synthesis of AMP: the conversion of phosphoribosylsuccinyl-aminoimidazole carboxamide (SAICAR) to phosphoribosylaminoimidazole carboxamide, which occurs in the de novo synthesis of IMP, and the conversion of adenylosuccinate to AMP, which occurs in the de novo synthesis of AMP and also in the purine nucleotide cycle, using the same active site. Mutation of ADSL's arginine 303 to a cysteine is known to lead to ADSL deficiency. Interestingly, unlike other mutations leading to ADSL deficiency, the R303C mutation has been suggested to more significantly affect the enzyme's ability to catalyze the conversion of succinyladenosine monophosphate than that of SAICAR to their respective products. To better understand the causation of disease due to the R303C mutation, as well as to gain insights into why the R303C mutation potentially has a disproportional decrease in activity toward its substrates, the wild type (WT) and the R303C mutant of ADSL were investigated enzymatically and thermodynamically. Additionally, the X-ray structures of ADSL in its apo form as well as with the R303C mutation were elucidated, providing insight into ADSL's cooperativity. By utilizing this information, a model for the interaction between ADSL and SAICAR is proposed.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Drift Transport in Al 2 O 3 -Sheathed 3-D Transparent Conducting Oxide Photoanodes Observed in Liquid Electrolyte-Based Dye-Sensitized Solar Cells

It has long been taken for granted that electron transport in liquid-electrolyte-based dye-sensitized solar cells (DSSCs) undergoes an ambipolar diffusive transport due to the strong coupling between electrons in the photoanode and the nearby mobile cations in liquid electrolyte, which, therefore, screens off any electric field in the photoanodes and consequently eliminates the possibility for drift transport. In this work, we demonstrate the existence of drift transport in liquid electrolyte-based DSSCs using a thin Al 2 O 3 -sheathed 3-dimentional (3-D) fluorinated tin oxide (FTO), as photoanodes. The electron diffusion rate in such 3-D TCO based DSSC exhibits a striking enhancement to the value of ~10 –2 cm 2 /s, about 10 4 times faster than that of the TiO 2 nanoparticle-based DSSCs. The electron diffusion coefficient is independent of the photoelectron density, while intensity modulated photocurrent spectroscopy (IMPS) suggests that the time constants of electron transport exhibit a linear dependence on the bias voltage, a strong indication of drift transport behavior in this 3-D FTO hollow nanobeads-based DSSC, despite the use of liquid I – /I 3 – electrolyte.

14 SOLAR ENERGY↗