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At least 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Diagenetic Crystal Growth in the Murray Formation, Gale Crater, Mars

The Pahrump region (Gale Crater, Mars) marks a critical transition between sedimentary environments dominated by alluvial-to-fluvial materials associated with the Gale crater rim, and depositional environments fundamentally linked to the crater's central mound, Mount Sharp. At Pahrump, the Murray formation consists of an approximately 14-meter thick succession dominated by massive to finely laminated mudstone with occasional interbeds of cross-bedded sandstone, and is best interpreted as a dominantly lacustrine environment containing tongues of prograding fluvial material. Murray formation mudstones contain abundant evidence for early diagenetic mineral precipitation and its subsequent removal by later diagenetic processes. Lenticular mineral growth is particularly common within lacustrine mudstone deposits at the Pahrump locality. High-resolution MAHLI images taken by the Curiosity rover permit detailed morphological and spatial analysis of these features. Millimeter-scale lenticular features occur in massive to well-laminated mudstone lithologies and are interpreted as pseudomorphs after calcium sulfate. The distribution and orientation of lenticular features suggests deposition at or near the sediment-water (or sediment-air) interface. Retention of chemical signals similar to host rock suggests that original precipitation was likely poikilotopic, incorporating substantial amounts of the primary matrix. Although poikilotopic crystal growth is common in burial environments, it also occurs during early diagenetic crystal growth within unlithified sediment where high rates of crystal growth are common. Loss of original calcium sulfate mineralogy suggests dissolution by mildly acidic, later-diagenetic fluids. As with lenticular voids observed at Meridiani by the Opportunity Rover, these features indicate that calcium sulfate deposition may have been widespread on early Mars; dissolution of depositional and early diagenetic minerals is a likely source for both calcium and sulfate ion-enrichment in burial fluids that precipitated in ubiquitous late-stage hydrofracture veins

Kah, L. C.↗
NASA NTRS2017

Evidence Report: Risk of Renal Stone Formation

The formation of renal stones poses an in-flight health risk of high severity, not only because of the impact of renal colic on human performance but also because of complications that could potentially lead to crew evacuation, such as hematuria, infection, hydronephrosis, and sepsis. Evidence for risk factors comes from urine analyses of crewmembers, documenting changes to the urinary environment that are conducive to increased saturation of stone-forming salts, which are the driving force for nucleation and growth of a stone nidus. Further, renal stones have been documented in astronauts after return to Earth and in one cosmonaut during flight. Biochemical analysis of urine specimens has provided indication of hypercalciuria and hyperuricemia, reduced urine volumes, and increased urine saturation of calcium oxalate and calcium phosphate. A major contributor to the risk for renal stone formation is bone atrophy with increased turnover of the bone minerals. Dietary and fluid intakes also play major roles in the risk because of the influence on urine pH (more acidic) and on volume (decreased). Historically, specific assessments on urine samples from some Skylab crewmembers indicated that calcium excretion increased early in flight, notable by day 10 of flight, and almost exceeded the upper threshold for normal excretion (300mg/day in males). Other crewmember data documented reduced intake of fluid and reduced intake of potassium, phosphorus, magnesium, and citrate (an inhibitor of calcium stone formation) in the diet. Hence, data from both short-duration and long-duration missions indicate that space travel induces risk factors for renal stone formation that continue to persist after flight; this risk has been documented by reported kidney stones in crewmembers.

Sibonga, Jean D.↗
DOE OSTI2021

Reaction kinetics during early hydration of calcined phyllosilicates in clinker-free model systems

Investigations of nearly pure, calcined phyllosilicates (“meta-phyllosilicates”) in clinker-free model systems were performed in presence and absence of sulfate. Calorimetric investigations show a pronounced reaction during the early reaction period only for metakaolin. Quantitative in situ X-ray diffraction reveals calcium silicate hydrate formation in the systems with metakaolin and metaillite, but not in those with metamuscovite. Ettringite crystallizes in all systems containing sulfate, where only the metakaolin system reaches the maximum ettringite content possible. The amount of aluminum ions released from 2:1 meta-phyllosilicates seems to be insufficient to reach the maximum content. Differences in portlandite dissolution and bound water indicate adsorption effects of calcium or calcium – sulfate ion pair complexes on surfaces of the calcined clay particles. Thus, the chemical as well as the physical influence of the meta-phyllosilicates must be considered to predict the reaction kinetics of calcined clays during early hydration.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A parametric study of accelerated carbonation in alkali-activated slag

Resistance to carbonation is one important attribute that low-CO{sub 2} cement alternatives must possess, and is particularly crucial for cement alternatives subjected to aggressive CO{sub 2} concentrations such as those used in construction of oil wells and wells for below ground carbon sequestration. Here, a parametric study of alkali-activated slag (AAS) carbonation in aggressive environments has been conducted to examine (i) calcium carbonate polymorphism using X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy, and (ii) the extent of calcium carbonate formation and CO{sub 2} adsorption using thermogravimetric analysis (TGA). A range of AASs have been studied by varying the magnesium content of the slag, the activator type (sodium hydroxide and sodium silicate), the activator concentration, and the curing time prior to carbonation. It was uncovered that both (i) magnesium from the slag and (ii) silica from the activating solution are needed to reduce the propensity for the sodium-containing calcium-alumino-silicate-hydrate gel to undergo decalcification.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Portlandite solubility and Ca2+ activity in presence of gluconate and hexitols

The current paper investigates the impact of gluconate, D-sorbitol, d-mannitol and D-galactitol on calcium speciation at high pH values by i) solubility measurements of portlandite (Ca(OH){sub 2}) and ii) potentiometric titration measurements of calcium salt solutions. Thermodynamic modelling was used to fit the chemical activities of Ca{sup 2+} and OH{sup −} ions and thus to determine the strength and kind of the different Ca-organic-hydroxide complexes. The strength of complex formation with Ca{sup 2+} decreases in the order gluconate ≫ sorbitol > mannitol > galactitol, which follows the same order as sorption on portlandite. Heteropolynuclear gluconate complexes with calcium and hydroxide dominate the Ca-speciation in the presence of portlandite, while for sorbitol ternary CaSorbOH{sup +} complexes were dominant under alkaline conditions. We expect that these results will help in better understanding the influence of gluconate and hexitols on the hydration of alite and Portland cement.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Investigation of Ca Insertion into α-MoO 3 Nanoparticles for High Capacity Ca-Ion Cathodes

Calcium-ion batteries (CIBs) are a promising alternative to lithium-ion batteries (LIBs) due to the low redox potential of calcium metal and high abundance of calcium compounds. Due to its layered structure, α-MoO 3 is regarded as a promising cathode host lattice. While studies have reported that α-MoO 3 can reversibly intercalate Ca ions, limited electrochemical activity has been noted, and its reaction mechanism remains unclear. Here, we re-examine Ca insertion into α-MoO 3 nanoparticles with a goal to improve reaction kinetics and clarify the storage mechanism. The α-MoO 3 electrodes demonstrated a specific capacity of 165 mA h g –1 centered near 2.7 V vs Ca 2+ /Ca, stable long-term cycling, and good rate performance at room temperature. Furthermore, this work demonstrates that, under the correct conditions, layered oxides can be a promising host material for CIBs and renews prospects for CIBs.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Modeling beta-adrenergic control of cardiac myocyte contractility in silico

The beta-adrenergic signaling pathway regulates cardiac myocyte contractility through a combination of feedforward and feedback mechanisms. We used systems analysis to investigate how the components and topology of this signaling network permit neurohormonal control of excitation-contraction coupling in the rat ventricular myocyte. A kinetic model integrating beta-adrenergic signaling with excitation-contraction coupling was formulated, and each subsystem was validated with independent biochemical and physiological measurements. Model analysis was used to investigate quantitatively the effects of specific molecular perturbations. 3-Fold overexpression of adenylyl cyclase in the model allowed an 85% higher rate of cyclic AMP synthesis than an equivalent overexpression of beta 1-adrenergic receptor, and manipulating the affinity of Gs alpha for adenylyl cyclase was a more potent regulator of cyclic AMP production. The model predicted that less than 40% of adenylyl cyclase molecules may be stimulated under maximal receptor activation, and an experimental protocol is suggested for validating this prediction. The model also predicted that the endogenous heat-stable protein kinase inhibitor may enhance basal cyclic AMP buffering by 68% and increasing the apparent Hill coefficient of protein kinase A activation from 1.0 to 2.0. Finally, phosphorylation of the L-type calcium channel and phospholamban were found sufficient to predict the dominant changes in myocyte contractility, including a 2.6x increase in systolic calcium (inotropy) and a 28% decrease in calcium half-relaxation time (lusitropy). By performing systems analysis, the consequences of molecular perturbations in the beta-adrenergic signaling network may be understood within the context of integrative cellular physiology.

Non-NASA Center↗
NASA NTRS1985

Polar transport of 45Ca2+ across the elongation zone of gravistimulated roots

The movement of calcium across the elongation zone of gravistimulated primary roots of maize (Zea mays L.) was measured using 45Ca2+. Radioactive calcium was applied to one side of the elongation zone about 4 mm back from the root tip and the distribution of radioactivity across the root in the region of application was determined using scintillation spectrometry. The movement of 45Ca2+ across the elongation zone was non-polar in vertically oriented roots. In gravistimulated roots the movement of label was polarized with about twice as much label moving from top to bottom as from bottom to top. A variety of treatments which interfere with gravitropism was found to eliminate the polar movement of 45Ca2+ across the elongation zone. In maize cultivars which require light for gravitropic competency, dark grown roots exhibited neither gravitropism nor polar movement of 45Ca2+ across the elongation zone. Upon illumination the roots developed but gravitropic competency and gravity-induced polar movement of 45Ca2+ across the elongation zone. Similarly, roots of light-grown seedlings lost both gravitropic competency and 45Ca2+ transport polarity upon transfer to the dark. The results indicate a close correlation between calcium movement and gravitropism in primary roots in maize.

NASA Discipline Number 40-10↗
DOE OSTI2021

Concentrating rare earth elements to phosphate in molten coal ash by a temperature gradient approach

Synthetic coal ash bearing 560 ppm europium oxide, blended with aluminum phosphate, was heat treated above its melting temperature and crystal evolutions with respect to europium concentration under controlled cooling were studied. The sample in a boat crucible was subjected to a temperature gradient of 100 °C across it to cause zone refining effects on crystallization behaviors in the melt (slag). Post analysis found six mineral phases formed from the melt while europium was only present in calcium phosphate, implying the majority of europium was segregated to the calcium phosphate. Europium concentrations in the calcium phosphate phase tended to be higher at zones with higher temperatures: as high as 7200 ppm, a 13-fold increase from the initial concentration.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2022

A broad specificity β-propeller enzyme from Rhodopseudomonas palustris that hydrolyzes many lactones including γ-valerolactone

Lactones are prevalent in biological and industrial settings, yet there is a lack of information regarding enzymes used to metabolize these compounds. One compound, γ-valerolactone (GVL), is used as a solvent to dissolve plant cell walls into sugars and aromatic molecules for subsequent microbial conversion to fuels and chemicals. Despite the promise of GVL as a renewable solvent for biomass deconstruction, residual GVL can be toxic to microbial fermentation. Here, we identified a Ca 2+ -dependent enzyme from Rhodopseudomonas palustris (Rpa3624) and showed that it can hydrolyze aliphatic and aromatic lactones and esters, including GVL. Maximum-likelihood phylogenetic analysis of other related lactonases with experimentally determined substrate preferences shows that Rpa3624 separates by sequence motifs into a subclade with preference for hydrophobic substrates. Additionally, we solved crystal structures of this β-propeller enzyme separately with either phosphate, an inhibitor, or a mixture of GVL and products to define an active site where calcium-bound water and calcium-bound aspartic and glutamic acid residues make close contact with substrate and product. Our kinetic characterization of WT and mutant enzymes combined with structural insights inform a reaction mechanism that centers around activation of a calcium-bound water molecule promoted by general base catalysis and close contacts with substrate and a potential intermediate. Similarity of Rpa3624 with other β-propeller lactonases suggests this mechanism may be relevant for other members of this emerging class of versatile catalysts.

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

Linking water quality, fouling layer composition, and performance of reverse osmosis membranes

Fouling of polyamide membranes during reverse osmosis (RO) is a major challenge for adopting membrane technologies to treat highly contaminated waters, especially those containing organic foulants (e.g., natural organic matter (NOM), polysaccharides) and dominant cations (e.g., sodium, magnesium, calcium). Here, this work combines bench-scale membrane fouling experiments with detailed characterization of feedwater chemistry and fouling layer composition/morphology to reveal fundamental mechanisms of (in)organic fouling during RO. Divalent cations are shown to promote fouling by hydrophobic NOM containing aromatic and carboxyl groups, while NOM fouling in the presence of a monovalent cation, sodium, occurs by smaller fulvic acids containing larger fractions of carboxyl groups and other oxygen-rich moieties. Calcium-carboxyl bridging occurs in solution and near the membrane surface to induce NOM aggregation on nanometer length scales. In complex waters containing foulant mixtures, co-fouling by calcium-carboxyl bridging and CaCO 3 precipitation influence membrane performance at longer timeframes. However, the flux decline observed for the co-fouling mechanism was less significant than the sum of its parts, suggesting both synergistic and antagonistic fouling mechanisms should be considered in membrane design/operation. These results encourage the design of pretreatment processes to reduce concentrations of multivalent ions and hydrophobic NOM in RO feedwaters, and of membrane materials to limit attachment/deposition of aggregates to/on polyamide surfaces.

42 ENGINEERING↗
DOE OSTI2022

Amyloid-like amelogenin nanoribbons template mineralization via a low-energy interface of ion binding sites

Protein scaffolds direct the organization of amorphous precursors that transform into mineralized tissues, but the templating mechanism remains elusive. Motivated by models for the biomineralization of tooth enamel, wherein amyloid-like amelogenin nanoribbons guide the mineralization of apatite filaments, we investigated the impact of nanoribbon structure, sequence, and chemistry on amorphous calcium phosphate (ACP) nucleation. Using full-length human amelogenin and peptide analogs with an amyloid-like domain, films of β-sheet nanoribbons were self-assembled on graphite and characterized by in situ atomic force microscopy and molecular dynamics simulations. All sequences substantially reduce nucleation barriers for ACP by creating low-energy interfaces, while phosphoserines along the length of the nanoribbons dramatically enhance kinetic factors associated with ion binding. Furthermore, the distribution of negatively charged residues along the nanoribbons presents a potential match to the Ca–Ca distances of the multi-ion complexes that constitute ACP. These findings show that amyloid-like amelogenin nanoribbons provide potent scaffolds for ACP mineralization by presenting energetically and stereochemically favorable templates of calcium phosphate ion binding and suggest enhanced surface wetting toward calcium phosphates in general.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Arabidopsis fad4 mutant analysis provides insights into thermo sensing within plant plasma membrane

Increasing evidence suggests that the plasma membrane is the initial site for temperature sensing. In searching for the contributions of membrane lipids to stress-induced cytosolic calcium, we found that FATTY ACID DESATURASE 4 (FAD4) knockout mutant exhibited an elevated acute cytosolic calcium spike in response to heat shock or oxidative stress, but not cold shock. fad4 mutant plants are more tolerant to heat stress but less tolerant to cold or high light stress. Lipidomic profiling demonstrated that overall phosphatidylglycerol (PG) levels, specifically, PG (36:7) levels, were reduced in the plasma membrane of fad4 mutants. Based on liposome binding assays, calcium channel proteins annexin2 and annexin4 showed higher association with fad4 plasma membranes compared to wild type (WT) control. Fat Western analyses indicated that anionic lipids, including phosphatidylserine (PS), phosphatidic acid (PA), and PG, bind to annexin1, 2, 3, and 4 with variable affinity, with PS binding the most tightly and PG the least. These results support the hypothesis that the plasma membrane is the initial site of thermo sensing in Arabidopsis.

annexins↗
NASA NTRS1994

Contemplating the plasmalemmal control center model

An abundant epidermal mechanosensory calcium-selective ion channel appears able not only to detect mechanical stimuli such as those that initiate gravitropism but also to detect thermal, electrical, and various chemical stimuli. Because it responds to multimodal input with a second messenger output, this channel system seems likely to be an integrator that can engage in feedbacks with many other systems of the cell--and feedback is the hallmark of regulation. In general, the mechanical tension required for channel activation is likely transmitted from the relatively rigid cell wall to the plasma membrane system via linkage or adhesion sites that display antigenicities recognized by antibodies to animal beta-1 integrin, vitronectin, and fibronectin and which have mechanical connections to the cytoskeleton. Thus, functionally, leverage exerted against any given adhesion site will tend to control channels within a surrounding domain. Reactions initiated by passage of calcium ions through the channels could presumably be more effectively regulated if channels within the domains were somewhat clustered and if appropriate receptors, kinases, porters, pumps, and some key cytoskeletal anchoring sites were in turn clustered about them. Accumulating evidence suggests not only that activity of clusters of channels may contribute to control of cytoskeletal architecture and of regulatory protein function within their domain, but also that both a variety of regulatory proteins and components of the cortical cytoskeleton may contribute to control of channel activity. The emerging capabilities of electronic optical microscopy are well suited for resolving the spatial distributions of many of these cytoskeletal and regulatory molecules in living cells, and for following some of their behaviors as channels are stimulated to open and cytosolic calcium builds in their vicinity. Such microscopy, coupled with biochemical and physiological probing, should help to establish the nature of the feedback loops putatively controlled by the linkage sites and their channel domains.

Review↗
NASA NTRS1995

Polar distribution of annexin-like proteins during phytochrome-mediated initiation and growth of rhizoids in the ferns Dryopteris and Anemia

Although the calcium requirement of phytochrome-mediated fern spore germination and early rhizoid growth is well established, the calcium-binding proteins that serve as transducers for these responses are not known. Here we report the presence of annexin-like proteins in germinating spores of Dryopteris filix-mas (L.) Schott and Anemia phyllitidis (L.) Sw. and evidence that they may be important participants in early photomorphogenic changes in gametophytes. Immunolocalization and immunoblot assays of these proteins were carried out using polyclonal antibodies raised either against a 35-kDa annexin-like protein from pea or against anchorin CII from chicken. Western-blot analysis showed that crude protein extracts obtained from both species after red-light treatment contained two cross-reactive protein bands with molecular weights around 70 kDa. These proteins were annexin-like in that they bound to a phosphatidylserine affinity column in a calcium-dependent fashion. Using this column, two protein bands around 70 kDa, i.e. 67 and 73 kDa, were partially purified together with proteins at 36 kDa and a doublet at 54 kDa. Proteins of these latter molecular weights are suggested to be members of the annexin family, but no cross-reactivity could be found between these and the two antibodies used in our investigations. Immunodetectable levels of these proteins were observed only after light-mediated induction of spore germination. Imaging of the immuno-localization patterns observed with both antibodies showed that the annexin-like proteins are concentrated at the extreme tips of the rhizoids in D. filix-mas and A. phyllitidis during rhizoid initiation and all stages of elongation. We suggest that these proteins may play a major role in the tip-oriented exocytosis events that are critical for the initiation and growth of fern rhizoids.

NASA Discipline Number 40-50↗
DOE OSTI2026

Hybrid Additive Manufacturing and Electric Field-Assisted Sintering of High-temperature Heat Exchangers via Sacrificial Channel Molds

A hybrid manufacturing approach, integrating additive manufacturing (AM) with powder methodology via electric field-assisted sintering (EFAS), was developed for the fabrication of high-temperature compact heat exchangers (CHX) from refractory metals. The methodology employed additively manufactured sacrificial channel molds (SCMs) as shapeholders for CHX channels, which were embedded in metal powders using EFAS. Following embedding, the SCMs were chemically dissolved to form the internal channel network. SCMs were fabricated using both digital light processing (DLP) and direct ink writing (DIW) from chemically reactive, calcium-based ceramic feedstocks with varying ratios of Al2O3 reinforcement. The microstructure, phase composition, and dissolution behavior of both as-printed and embedded SCMs were investigated. The shrinkage behavior of the SCMs embedded in refractory metals, as well as the interfacial characteristics between the SCMs and metal matrix, were studied. The results showed that the SCMs containing sufficient chemical reactive ceramics dissolved effectively before and after embedding. The as-printed SCMs retained the phase composition of their feedstocks, but the embedded SCMs containing calcium-based ceramics and Al2O3 exhibited the formation of calcium aluminates due to high temperature exposure during embedding. Most SCMs exhibited a cellular Al2O3 network filled with Ca-rich ceramics. Shrinkage after embedding was strongly dependent on SCM density, with lower density SCMs exhibiting greater shrinkage. A thin SCM-affected zone was observed at the metal matrix surface, characterized by increased porosity compared to the bulk matrix. This effect was attributed to infiltration of the SCM materials into powder particle boundaries under pressure, followed by their removal during dissolution. This study demonstrates the feasibility of manufacturing CHXs from hard-to-process refractory metals for use in harsh environments.

36 - MATERIALS SCIENCE↗
DOE OSTI2023

Early age hydration behavior of portland cement-based binders incorporating fly ash contaminated with flue gas desulfurization products

Fly ash co-mingled with flue gas desulfurization (FGD) products are currently discarded as off-specification materials based on their high SO3 content. However, previous studies have shown that performance of these fly ashes varies significantly based on FGD product type and as such they may be viable for use in low-CO2 concrete as supplementary cementitious materials (SCMs). In this study, fly ashes with three different types of FGD products including calcium sulfite hemihydrate, calcium sulfate (with some unreacted lime), and sodium sulfate (with some unreacted sodium carbonate) were evaluated. The early age hydration behavior in blended cementitious systems at 20% cement replacement level was studied using Vicat setting time tests, isothermal calorimetry, in-situ quantitative X-ray diffraction, and pore solution analysis. The cause of the setting time retardation and flash setting observed in fly ashes with calcium sulfite hemihydrate and sodium carbonate, respectively, were identified and suitable beneficiation options were suggested for the valorized use of these materials in low-CO 2 concrete.

36 MATERIALS SCIENCE↗