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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

High performance Calcium Copper Titanate/Polyimide dielectrics composites enabled through colloidal stabilization

Transition to electrified transportation demands advanced power electronic components with the capability to improve range, reliability, and cost of ownership to accelerate mass market adoption. Thus, improvement in the current designs, manufacturing processes, materials, and components capable of providing reliable and efficient operation at higher temperatures play important roles in meeting future needs. To address these challenges, this article focuses on novel dielectric materials designed to reduce the volume of the most important and bulky component of a power electronic system, a capacitor. A new composite dielectric material was developed by integrating the positive attributes of both polymer and ceramic capacitors to overcome the challenges of state-of-the-art dielectric materials. Further, the developed composite properties have been evaluated and showed promising results, achieving a dielectric constant of 250 at 100 Hz, 25°C, unseen in current literature. Additionally, these materials can function at high temperatures (>150°C) with good breakdown strength, providing promising working conditions for capacitors, especially in electric vehicle applications.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Prehydration of calcium sulfoaluminate (CSA) clinker at different relative humidities

The use of CSA cement in practice has been hindered by its unstable performance and short shelf-life caused by the prehydration of CSA clinker. In this study, the effect of ambient humidity on the prehydration rate and process of CSA clinker was investigated. The prehydration degree, ageing progress, and the dynamic change of mineral composition of CSA clinker exposed to five different relative humidities (ranging from 23% to 98%) for up to 180 days were studied. Experiments revealed that the ambient humidity of 60% RH can be considered a threshold value for storage of CSA clinker. Exposure of CSA clinker to RH higher than 60% will not only result in a significant decrease of hydraulic reactivity, but also in agglomeration of the clinker. Although the exposure of CSA clinker to RH lower than 60% has little effect on the hydraulic reactivity, the main hydration peak was found to be slightly delayed with the increase of RH.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Near-field infrared microscopy: A novel analytic mapping technique to nanocharacterize calcium silicate-based cement materials

Infrared imaging via scattering-type scanning near-field optical microscopy (s-SNOM) allows chemical mapping of organic and inorganic materials with nanoscale spatial resolution. However, its potential adaptation to the complex multiphase structure of Portland cement is yet to be explored. Here we demonstrate the successful implementation of s-SNOM to spatially resolve coexisting chemical phases in tricalcium silicate, Portland cement's main compound, with 20-nm resolution. We found that s-SNOM is sensitive to different anhydrous polymorphic phases, revealing nanoscale domains that are ‘invisible’ to other microscopic techniques. Furthermore, s-SNOM's ability to distinguish the unhydrated and hydrated phases signifies its great promise as an analytical tool to study the complex hydration process of cement. The key to s-SNOM's application was nano-modifying the surface roughness of the cement samples, allowing nanoscale infrared imaging without topographical artifacts. Our study opens a window for infrared spectral microscopy in cement and other porous inorganic materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Ultra-high gamma irradiation of calcium silicate hydrates: Impact on mechanical properties, nanostructure, and atomic environments

The concrete biological shield in a nuclear power plant receives ~100–200 MGy gamma dosage during an 80-year design life. However, precise changes in the mechanical properties and atomic environments of C-S-H at ultrahigh irradiation dosages have not been systematically documented. Here, we report that irradiation decreases C-S-H basal spacing (~ 0.6 ± 0.1 Å for 189 MGy) and increases its Young's modulus, which is attributed to the lower basal spacing as the nano porosity potentially increased and microporosity remained unchanged. Irradiation also decreased the molecular water content and increased hydroxyl groups in C-S-H, showing that interlayer water removal reduces the basal spacing. Finally, 1 H and 29 Si NMR results indicate some disorder in the local proton CaO-H species and slight depolymerization of the silicate structure. Together, these results indicate that the C-S-H gel stiffens upon ultrahigh gamma irradiation dosage, a finding which concerns long-term nuclear power plants operations worldwide.

1H NMR↗
DOE OSTI2020

Effects of sodium and calcium chloride ionic stresses on model yeast membranes revealed by molecular dynamics simulation

As efforts to move a renewable economy grow, it will be necessary to make use of microbial conversion strategies for the production of novel materials or the upgrading of waste to high-value products. One critical technical challenge currently limiting waste upgrading remains the difficulty in obtaining single-pot conversion techniques where physical, chemical, and biological conversion are performed in a single step. To overcome this challenge, a detailed understanding of how different stresses impact microbial membrane stability will be necessary. In this work, using all-atom molecular dynamics simulations, we examine the impacts of moderate concentrations of NaCl and CaCl 2 on a model yeast plasma membrane. Weak, though statistically significant, changes in membrane morphology and dynamics functions are observed that are consistent with swelling and stiffening. Additionally, an examination of the ion-lipid contacts and the behavior of water at the water-membrane interface suggests that the impacts of these common salts may, in part, be mediated through changes to water-membrane hydrogen-bonding and hydration water dynamics.

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

Comparison of Single-Ion Conducting Polymer Gel Electrolytes for Sodium, Potassium, and Calcium Batteries: Influence of Polymer Chemistry, Cation Identity, Charge Density, and Solvent on Conductivity

From the standpoint of material diversification and sustainability, the development of so-called “beyond lithium-ion” battery chemistries is important for the future of energy storage. Na, K, and Ca are promising as the basis for battery chemistries in that these elements are highly abundant. Here, a series of single-ion conducting polymer electrolytes (SIPEs) for Na, K, and Ca batteries are synthesized and investigated. The two classes of metal cation neutralized SIPEs compared are crosslinked poly(ethylene glycol) dimethacrylate-x-styrene sulfonate (PEGDMA-SS) and poly(tetrahydrofuran) diacrylate-x-4-styrenesulfonyl (trifluoromethylsulfonyl)imide (PTHFDA-STFSI); three cation types, three charge densities, and four swelling states are examined. The impact on conductivity of all of these parameters is studied, and in conjunction with small angle X-ray scattering (SAXS), it is found that promoting ion dissociation and preventing the formation of dense ionic aggregates facilitates ion transport. These results indicate many of the lessons learned from the Li SIPE literature can be translated to beyond Li chemistries. At 25 °C, the best performing Na/K and Ca exchanged polymers yield active cation conductivity on the order of 10 –4 S/cm and 10 –6 S/cm, respectively, for ethylene carbonate:propylene carbonate gelled SIPEs, and 10 –5 S/cm and 10 –7 S/cm, respectively, for glyme gelled SIPEs.

X-ray scattering↗
NASA NTRS1987

Calcium messenger system in plants

The purpose of this review is to delineate the ubiquitous and pivotal role of Ca2+ in diverse physiological processes. Emphasis will be given to the role of Ca2+ in stimulus-response coupling. In addition to reviewing the present status of research, our intention is to critically evaluate the existing data and describe the newly developing areas of Ca2+ research in plants.

NASA Discipline Number 40-30↗
NASA NTRS1993

Calcium and signal transduction in plants

Environmental and hormonal signals control diverse physiological processes in plants. The mechanisms by which plant cells perceive and transduce these signals are poorly understood. Understanding biochemical and molecular events involved in signal transduction pathways has become one of the most active areas of plant research. Research during the last 15 years has established that Ca2+ acts as a messenger in transducing external signals. The evidence in support of Ca2+ as a messenger is unequivocal and fulfills all the requirements of a messenger. The role of Ca2+ becomes even more important because it is the only messenger known so far in plants. Since our last review on the Ca2+ messenger system in 1987, there has been tremendous progress in elucidating various aspects of Ca(2+) -signaling pathways in plants. These include demonstration of signal-induced changes in cytosolic Ca2+, calmodulin and calmodulin-like proteins, identification of different Ca2+ channels, characterization of Ca(2+) -dependent protein kinases (CDPKs) both at the biochemical and molecular levels, evidence for the presence of calmodulin-dependent protein kinases, and increased evidence in support of the role of inositol phospholipids in the Ca(2+) -signaling system. Despite the progress in Ca2+ research in plants, it is still in its infancy and much more needs to be done to understand the precise mechanisms by which Ca2+ regulates a wide variety of physiological processes. The purpose of this review is to summarize some of these recent developments in Ca2+ research as it relates to signal transduction in plants.

NASA Program Space Biology↗
NASA NTRS1987

The role of calcium ions in gravity signal perception and transduction

Ca2+ is implicated as a messenger in coupling various environmental stimuli, such as gravity and light, to response. In recent years, it has become evident that Ca2+ plays a central role in all three phases of gravitropism--perception, transduction and response. The root cap, which is known to contain high amounts of Ca2+ and calmodulin, is the primary site of gravity perception. The possible role of phosphoinositide turnover and Ca(2+) - and Ca(2+) -calmodulin-dependent enzymes such as Ca(2+) -ATPase and protein kinases in gravitropism is discussed. A model is proposed to describe the role of Ca2+ in both normal and light-dependent gravity response in roots.

NASA Program Space Biology↗
NASA NTRS1985

Polar transport of auxin across gravistimulated roots of maize and its enhancement by calcium

The effect of Ca on the polar movement of [3H]indoleacetic acid ([3H]IAA) in gravistimulated roots was examined using 3-day-old seedlings of maize (Zea mays L.). Transport of label was measured by placing an agar donor block containing [3H]IAA on one side of the elongation zone and measuring movement of label across the root into an agar receiver block on the opposite side. In vertically oriented roots, movement of label across the elongation zone into the receiver was slight and was not enhanced by incorporating 10 millimolar CaCl2 into the receiver block. In horizontally oriented roots, movement of label across the root was readily detectable and movement to a receiver on the bottom was about 3-fold greater than movement in the opposite direction. This polarity was abolished in roots from which the caps were removed prior to gravistimulation. When CaCl2 was incorporated into the receivers, movement of label across horizontally oriented intact roots was increased about 3-fold in both the downward and upward direction. The ability of Ca to enhance the movement of label from [3H]IAA increased with increasing Ca concentration in the receiver up to 5 to 10 millimolar CaCl2. With the inclusion of CaCl2 in the receiver blocks, gravity-induced polar movement of label into receiver blocks from applied [3H]IAA was detectable within 30 minutes, and asymmetric distribution of label within the tissue was detectable within 20 minutes. The results indicate that gravistimulation induces a physiological asymmetry in the auxin transport system of maize roots and that Ca increases the total transport of auxin across the root.

NASA Program Space Biology↗
NASA NTRS1993

Mechanosensory calcium-selective cation channels in epidermal cells

This paper explores the properties and likely functions of an epidermal Ca(2+)-selective cation channel complex activated by tension. As many as eight or nine linked or linkable equivalent conductance units or co-channels can open together. Open time for co-channel quadruplets and quintuplets tends to be relatively long with millimolar Mg2+ (but not millimolar Ca2+) at the cytosolic face of excised plasma membrane. Sensitivity to tension is regulated by transmembrane voltage and temperature. Under some circumstances channel activity is sychronized in rhythmic pulses. Certain lanthanides and a cytoskeleton-disturbing herbicide that inhibit gravitropic reception act on the channel system at low concentrations. Specifically, ethyl-N-phenylcarbamate promotes tension-dependent activity at micromolar levels. With moderate suction, Gd3+ provided at about 0.5 micromole at the extracellular face of the membrane promotes for several seconds but may then become inhibitory. Provision at 1-2 micromoles promotes and subsequently inhibits more vigorously (often abruptly and totally), and at high levels inhibits immediately. La3+, a poor gravitropic inhibitor, acts similarly but much more gradually and only at much higher concentrations. These properties, particularly these susceptibilities to modulation, indicate that in vivo the mechanosensitive channel must be mechanosensory and mechanoregulatory. It could serve to transduce the shear forces generated in the integrated wall-membrane-cytoskeleton system during turgor changes and cell expansion as well as transducing the stresses induced by gravity, touch and flexure. In so far as such transduction is modulated by voltage and temperature, the channels would also be sensors for these modalities as long as the wall-membrane-cytoskeleton system experiences mechanical stress.

NASA Discipline Number 40-50↗
NASA NTRS2000

A calcium-dependent protein kinase can inhibit a calmodulin-stimulated Ca2+ pump (ACA2) located in the endoplasmic reticulum of Arabidopsis

The magnitude and duration of a cytosolic Ca(2+) release can potentially be altered by changing the rate of Ca(2+) efflux. In plant cells, Ca(2+) efflux from the cytoplasm is mediated by H(+)/Ca(2+)-antiporters and two types of Ca(2+)-ATPases. ACA2 was recently identified as a calmodulin-regulated Ca(2+)-pump located in the endoplasmic reticulum. Here, we show that phosphorylation of its N-terminal regulatory domain by a Ca(2+)-dependent protein kinase (CDPK isoform CPK1), inhibits both basal activity ( approximately 10%) and calmodulin stimulation ( approximately 75%), as shown by Ca(2+)-transport assays with recombinant enzyme expressed in yeast. A CDPK phosphorylation site was mapped to Ser(45) near a calmodulin binding site, using a fusion protein containing the N-terminal domain as an in vitro substrate for a recombinant CPK1. In a full-length enzyme, an Ala substitution for Ser(45) (S45/A) completely blocked the observed CDPK inhibition of both basal and calmodulin-stimulated activities. An Asp substitution (S45/D) mimicked phosphoinhibition, indicating that a negative charge at this position is sufficient to account for phosphoinhibition. Interestingly, prior binding of calmodulin blocked phosphorylation. This suggests that, once ACA2 binds calmodulin, its activation state becomes resistant to phosphoinhibition. These results support the hypothesis that ACA2 activity is regulated as the balance between the initial kinetics of calmodulin stimulation and CDPK inhibition, providing an example in plants for a potential point of crosstalk between two different Ca(2+)-signaling pathways.

NASA Discipline Plant Biology↗
NASA NTRS1998

Calcium-independent activation of extracellular signal-regulated kinases 1 and 2 by cyclic strain

We have previously demonstrated that cyclic strain induces extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation in endothelial cells (EC). The aim of this study was to investigate the effect of Ca2+ on the activation of ERK1/2. Bovine aortic EC were pretreated with a chelator of extracellular Ca2+, ethylaneglycol-bis(aminoethylether)-tetra-acetate (EGTA), a depleter of Ca2+ pools, 2,5-Di-(tert-butyl)-1,4-benzohydroquinone (BHQ), or a Ca2+ channel blocker, GdCl3, and subjected to an average 10 % strain at a rate of 60 cycles/min for 10 min. BHQ and GdCl3 did not inhibit the strain-induced ERK1/2 activation. Chelation of normal extracellular Ca2+ (1.8 mM) medium with EGTA (3 mM) acutely stimulated baseline phosphorylation and activation of ERK1/2, thereby obscuring any strain-induced activation of ERK1/2. However, in EC preincubated for 24 hours in Ca2+-free medium, elevated baseline phosphorylation was minimally activated by EGTA (200 microM) such that cyclic strain stimulated ERK1/2 in the presence or absence of BHQ. These results suggest a Ca2+ independence of the ERK1/2 signaling pathway by cyclic strain. Copyright 1998 Academic Press.

NASA Discipline Cell Biology↗