Search NASA⌕ Search

SEARCH · Search NASA

Results for “CALCIUM 40”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Calculation of nucleon densities in calcium, nickel, and molybdenum isotopes on the basis of the dispersive optical model

The radial distributions of proton and neutron densities in the even–even isotopes {sup 40−70}Cа and {sup 48−78}Ni and the analogous distributions of neutron densities in the even–even isotopes {sup 92−138}Mo were calculated on the basis of the mean-fieldmodel involving a dispersive optical potential. The respective root-mean-square radii and neutron-skin thicknesses were determined for the nuclei under study. In N > 40 calcium isotopes, the calculated neutron root-mean-square radius exhibits a fast growth with increasing N, and this is consistent with the prediction of the neutron-halo structure in calcium isotopes near the neutron drip line.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Ca-isotopes as a robust tracer of magmatic differentiation

The large mass difference (~10%) between the two most abundant isotopes of calcium, 40 Ca and 44 Ca, gives Ca great potential in tracking mass-dependent fractionation during magmatic processes. Resolvable Ca-isotope fractionation during fractional crystallization of magma, particularly by feldspar in evolved melts, has been theoretically inferred but not robustly tested in nature. To further explore the effects of magmatic differentiation on Ca-isotope systematics, we studied the late-Permian alkaline igneous suite of the Øyangen Caldera, Oslo Rift, Norway, consisting of volcanic and intrusive units ranging from basanitic to rhyolitic compositions. Major and trace element variations and modeling demonstrate that the main series of samples (N = 21), including basanites, ring-dyke syenites, and central-dome syenites, likely documents a co-genetic and closed-system fractional crystallization sequence. Our data show minimal δ 44/40 Ca variation (< 0.05 ‰) in the intermediate magma and a marked increase in δ 44/40 Ca in the felsic magma of the Øyangen Caldera (from 0.62 ± 0.02 ‰ to 1.15 ± 0.03 ‰ relative to Ca standard, SRM915a). The systematic increase is best explained by equilibrium isotopic fractionation dominated by alkali feldspar in the fractionating mineral assemblage. This is further supported by strong correlations between δ 44/40 Ca, CaO, and Eu/Eu* in the main-series samples. Implementing a Monte Carlo approach, isotopic modeling of the liquid line of descent using Rayleigh fractionation is highly consistent with the observed Ca-isotope evolution. For the first time, we confirm prominent Ca stable isotope fractionation in felsic-stage differentiation of alkaline magma and constrain the isotope fractionation factors of plagioclase and K-feldspar. Integrated with extant estimations on mineral fractionation factors from the literature, our results suggest increasing fractionation effects of rock-forming minerals with decreasing Ca content. Finally, the affirmation of significant Ca-isotope fractionation in alkaline magma by feldspar empowers the application of Ca as a versatile tracer of crustal evolution, allowing further tests in other magmatic conditions across various planetary objects.

58 GEOSCIENCES↗
DOE OSTI2017

Nuclear Data Sheets for A=40

The experimental nuclear structure data and decay data are evaluated for the known nuclides of mass 40 (Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti). Detailed evaluated nuclear structure information is presented with the best values recommended for level energies, half-lives, γ-ray energies and intensities, decay properties (energies, intensities and placement of radiations), and other spectroscopic data. The {sup 40}Ca and {sup 40}K nuclides remain as the most extensively studied from many different reactions and decays; no excited states are known in {sup 40}Mg, {sup 40}Al, {sup 40}P and {sup 40}Ti. This work supersedes the earlier full evaluation of A=40 by J. Cameron and B. Singh (2004Ca38).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Calcium Treatment for FeSi-killed Fe-13 Pct Cr Stainless Steel with Various Top Slag Compositions

Calcium treatment of Fe-13 pct Cr stainless steel, with inclusion modification as its main purpose, was evaluated on a laboratory scale. The stability diagram of Ca-Al was obtained using the FactSage software and could be divided into three parts based on the [Al] content: the ultra-low-Al region, the low-Al region, and the medium-high-Al region. Each of these regions required different amounts of calcium for inclusion modification. The ferrosilicon deoxidation product could be modified into low melting temperature inclusions by a CaO-SiO{sub 2} top slag in the ultra-low-Al region ([Al] content less than 40 ppm). Calcium treatment was necessary to modify the ferrosilicon deoxidation product into low melting temperature inclusions in the low-Al region ([Al] content from 40 to 100 ppm) for the CaO-SiO{sub 2}-Al{sub 2}O{sub 3} top slag. Calcium addition has a “liquid window” where adding calcium can accelerate inclusion modification. Adding calcium for 15 and 30 minutes resulted in complete modification times of 45 and 60 minutes, respectively, which indicates that early calcium treatment can produce plastic inclusions sooner. The relationship between the steel and inclusion content was determined by fitting the experimental data in the low-Al region. An appropriate range of T.Ca/T.O (total calcium content/total oxygen content) for inclusion modification is 0.99 to 1.44.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Sensitivity to Thermonuclear Reaction Rates in Modeling the Abundance Anomalies of NGC 2419

Abundance anomalies in globular clusters provide strong evidence for multiple stellar populations within each cluster. These populations are usually interpreted as distinct generations, with the currently observed second-generation stars having formed in part from the ejecta of massive, first-generation “polluter” stars, giving rise to the anomalous abundance patterns. The precise nature of the polluters and their enrichment mechanism are still unclear. Even so, the chemical abundances measured in second-generation stars within the globular cluster NGC 2419 provide insight into this puzzling process. Previous work used Monte Carlo nuclear reaction network calculations to constrain the temperature–density conditions that could reproduce the observed abundances, thereby placing robust limits on the origins of the polluter material. The effect of individual reaction rates on these conditions has not been studied, however. Thus, we perform an exhaustive sensitivity study on the nuclear physics input to determine which reactions have the greatest impact on these predictions. We find that the {sup 30}Si(p,γ){sup 31}P, {sup 37}Ar(p,γ){sup 38}K, {sup 38}Ar(p,γ){sup 39}K, and {sup 39}K(p,γ){sup 40}Ca reactions are all critical in determining the temperature–density conditions, and ultimately, the origins of the polluter material. We conclude with recommendations for future experiments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Study of Inelastic A(p, p′)X Reaction with Nuclei at 1 GeV

The secondary-proton polarization and differential cross sections for the (p, p') inelastic reaction on {sup 28}Si and {sup 56}Fe nuclei at the initial proton energy of 1 GeV were measured over a wide range of the scattered-proton momenta at a laboratory angle of Θ = 21◦. Scattered protons were detected by means of a magnetic spectrometer equipped with a polarimeter based on multiwire proportional chambers and a carbon analyzer. A structure in the polarization and cross section data, which is probably related to quasielastic scattering off nucleon correlations in the {sup 28}Si and {sup 56}Fe nuclei, was observed as earlier in the analogous data for {sup 12}C and {sup 40}Ca nuclei. Momentum intervals within which cross-section ratios for nuclei did not depend on the scattered-proton momentum were found.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Time-Dependent Description of Incomplete Fusion of Nuclei and Cluster and Nucleon-Transfer Reactions

A numerical solution of the time-dependent Schrödinger equation is applied in studying the dynamics of incomplete fusion of nuclei and cluster- and nucleon-transfer reactions at energies near the Coulomb barrier. The evolution of wave functions for all nucleons is used to describe multineutron- and multiproton-transfer reactions in {sup 40}Ca+{sup 124}Sn collisions. The results of the calculations are in satisfactory agreement with experimental data. The evolution of the alpha-cluster wave function in the {sup 12}C nucleus is used to calculate the incomplete-fusion cross section for the {sup 12}C+{sup 51}V reaction. Agreement with experimental data for the ({sup 12}C, α) and ({sup 12}C, 2α) channels is attained.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Structure effects in polarization and cross sections for A(p, p’)X inelastic reactions on {sup 40}Ca and {sup 12}C nuclei at 1 GeV

The polarization of secondary protons in the (p, p’) inelastic reactions on {sup 40}Ca and {sup 12}C nuclei at the initial proton energy of 1 GeV was measured over a wide range of scattered-proton momenta at a laboratory angle of Θ = 21°. The reaction cross sections were also measured. Scattered protons were detected by means of magnetic spectrometer equipped with a polarimeter based on multiwire-proportional chambers. A structure in the polarization and cross-section data, which is probably related to scattering off nucleon correlations in the nuclei involved, was observed.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Direct measurement of astrophysically important resonances in K 38 ( p , γ ) Ca 39

Classical novae are cataclysmic nuclear explosions occurring when a white dwarf in a binary system accretes hydrogen-rich material from its companion star. Novae are partially responsible for the galactic synthesis of a variety of nuclides up to the calcium (A ~ 40) region of the nuclear chart. Although the structure and dynamics of novae are thought to be relatively well understood, the predicted abundances of elements near the nucleosynthesis endpoint, in particular Ar and Ca, appear to sometimes be in disagreement with astronomical observations of the spectra of nova ejecta.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Calcium-mediated nitrogen reduction for electrochemical ammonia synthesis

Ammonia (NH 3 ) is a key commodity chemical for the agricultural, textile and pharmaceutical industries, but its production via the Haber–Bosch process is carbon-intensive and centralized. Alternatively, an electrochemical method could enable decentralized, ambient NH 3 production that can be paired with renewable energy. The first verified electrochemical method for NH 3 synthesis was a process mediated by lithium (Li) in organic electrolytes. So far, however, elements other than Li remain unexplored in this process for potential benefits in efficiency, reaction rates, device design, abundance and stability. In our demonstration of a Li-free system, we found that calcium can mediate the reduction of nitrogen for NH 3 synthesis. Here we verified the calcium-mediated process using a rigorous protocol and achieved an NH 3 Faradaic efficiency of 40 ± 2% using calcium tetrakis(hexafluoroisopropyloxy)borate (Ca[B(hfip) 4 ] 2 ) as the electrolyte. Our results offer the possibility of using abundant materials for the electrochemical production of NH 3 , a critical chemical precursor and promising energy vector

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

Sequential removal of cation/H + exchangers reveals their additive role in elemental distribution, calcium depletion and anoxia tolerance

Multiple Arabidopsis H + /Cation exchangers (CAXs) participate in high-capacity transport into the vacuole. Previous studies have analysed single and double mutants that marginally reduced transport; however, assessing phenotypes caused by transport loss has proven enigmatic. Here, in this study, we generated quadruple mutants (cax1-4: qKO) that exhibited growth inhibition, an 85% reduction in tonoplast-localised H + /Ca transport, and enhanced tolerance to anoxic conditions compared to CAX1 mutants. Leveraging inductively coupled plasma mass spectrometry (ICP-MS) and synchrotron X-ray fluorescence (SXRF), we demonstrate CAX transporters work together to regulate leaf elemental content: ICP-MS analysis showed that the elemental concentrations in leaves strongly correlated with the number of CAX mutations; SXRF imaging showed changes in element partitioning not present in single CAX mutants and qKO had a 40% reduction in calcium (Ca) abundance. Reduced endogenous Ca may promote anoxia tolerance; wild-type plants grown in Ca-limited conditions were anoxia tolerant. Sequential reduction of CAXs increased mRNA expression and protein abundance changes associated with reactive oxygen species and stress signalling pathways. Multiple CAXs participate in postanoxia recovery as their concerted removal heightened changes in postanoxia Ca signalling. This work showcases the integrated and diverse function of H + /Cation transporters and demonstrates the ability to improve anoxia tolerance through diminishing endogenous Ca levels.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Stabilization/Solidification of Tritiated Water - 20135

Tritiated water was stabilized/solidified by using calcium oxide and a polymer. First, tritiated water was changed into the powder form of calcium hydroxide by addition of tritiated water into calcium oxide. Then the produced calcium hydroxide was solidified in waste form by using a polymer binder. The specimens of waste form prepared by surrogate calcium hydroxide were subjected to compressive strength testing and water immersion testing. In addition, the specimens of waste form prepared by tritiated calcium hydroxide were subjected to leach testing. The mean compressive strength of the specimens containing 40 wt % of the surrogate calcium hydroxide was about 98.5 MPa (14,300 psi). After water immersion testing, there was no distinct change in the appearance of the specimens. The mean compressive strength of the specimens after water immersion was 79.1 MPa (11,470 psi). The mean diffusion coefficient of tritium for the specimens containing 40 wt% of tritiated calcium hydroxide was 5.4 x 10-10 cm{sup 2}/s. These findings indicate that the waste form has enough mechanical integrity and durability for final disposal and releases tritium very slowly. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2026

A mild calcium carbonate treatment improves moisture resistance and mechanical/interfacial properties of jute and hemp fibers

Natural fibers are attractive, sustainable reinforcements, but often exhibit high moisture uptake and weak bonding with polymer matrices. In this study, jute and hemp were treated by immersion in aqueous calcium carbonate (CaCO3) suspensions (10–40?wt.%, 1.5?h, room temperature) and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), moisture sorption testing, single-fiber tensile testing, and bundle pull-out testing. SEM showed granular CaCO3 deposition on fiber surfaces, with particulates bridging surface voids and microcracks. At 40 wt.% CaCO3, equilibrium moisture uptake decreased to ~5% (hemp) and ~3% (jute), while tensile strength increased to ~904 MPa (hemp) and ~960 MPa (jute). Apparent interfacial shear strength from pull-out testing increased up to ~1.35 MPa (hemp) and ~0.56 MPa (jute). These results indicate that CaCO3 deposition is a mild, scalable surface treatment that improves moisture resistance, fiber tensile strength, and interfacial load transfer relevant to semi-structural composite applications, including interior and secondary automotive components.

Calcium carbonate treatment↗
DOE OSTI2020

High-performance concrete mix for precast wythes

A lightweight concrete composition includes the concrete components, per yd3 of concrete: Type III Portland cement (lb/yd3) 200-900; metakaolin (lb/yd3) 100-520; calcium sulfoaluminate cement (CSA) (lb/yd3) 40-840; 3/8″ lightweight expanded slate aggregate (lb/yd3) 70-550; lightweight fine expanded slate aggregate (lb/yd3) 300-550; expanded glass fine aggregate (0.5-1 mm) 35-90 (lb/yd3); expanded glass fine aggregate (1-2 mm) 35-90 (lb/yd3); water (lb/yd3) 300-350; CSA cement set retarder 0.015 to 0.06 oz per lb of CSA cement; high-range water-reducing admixture 120-1000 (fl. oz/yd3); hydration controlling admixture 0-80 (fl. oz/yd3); reinforcing non-metallic lightweight fibers <1.5″ in length 0-8 (lb/yd3); wherein the concrete has a flexural strength of at least 600 psi at 12 hours, a density of 95 to 110 lb/ft3, and a compressive strength at 28 days of at least 7,000 psi. A lightweight concrete wythe and method of making a lightweight concrete wythe are also disclosed.

Hun, Diana E.↗
DOE OSTI2017

The influence of seawater carbonate chemistry, mineralogy, and diagenesis on calcium isotope variations in Lower-Middle Triassic carbonate rocks

The geological calcium cycle is linked to the geological carbon cycle through the weathering and burial of carbonate rocks. As a result, calcium (Ca) isotope ratios ( 44 Ca/ 40 Ca, expressed as δ 44/40 Ca) can help to constrain ancient carbon cycle dynamics if Ca cycle behavior can be reconstructed. But, the δ 44/40 Ca of carbonate rocks is influenced not only by the δ 44/40 Ca of seawater but also by diagenetic processes and fractionation associated with carbonate precipitation. In this study, we investigate the dominant controls on carbonate δ 44/40 Ca in Upper Permian to Middle Triassic limestones (ca. 253 to 244 Ma) from south China and Turkey. This time interval is ideal for assessing controls on Ca isotope ratios in carbonate rocks because fluctuations in seawater δ 44/40 Ca may be expected based on several large carbon isotope (δ 13 C) excursions ranging from -2 to + 8‰. Parallel negative δ 13 C and δ 44/40 Ca excursions were previously identified across the end-Permian extinction horizon. Here, we find a second negative excursion in δ 44/40 Ca of ~ 0.2‰ within Lower Triassic strata in both south China and Turkey; however, this excursion is not synchronous between regions and thus cannot be interpreted to reflect secular change in the δ 44/40 Ca of global seawater. Additionally, δ 44/40 Ca values from Turkey are consistently 0.3‰ lower than contemporaneous samples from south China, providing further support for local or regional influences. By measuring δ 44/40 Ca and Sr concentrations ([Sr]) in two stratigraphic sections located at opposite margins of the Paleo-Tethys Ocean, we can determine whether the data represent global conditions (e.g., secular variations in the δ 44/40 Ca of seawater) versus local controls (e.g., original mineralogy or diagenetic alteration). The [Sr] and δ 44/40 Ca data from this study are best described statistically by a log-linear correlation that also exists in many previously published datasets of various geological ages. By using a model of early marine diagenetic water-rock interaction, we illustrate that this general correlation can be explained by the chemical evolution of bulk carbonate sediment samples with different initial mineralogical compositions that subsequently underwent recrystallization. Although early diagenetic resetting and carbonate mineralogy strongly influence the carbonate δ 44/40 Ca values, the relationship between [Sr] and δ 44/40 Ca holds potential for reconstructing first-order secular changes in seawater δ 44/40 Ca composition.

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

The Effect of Positioning on Ureteral Stone Retropulsion: “Gravity Works”

To evaluate the potential impact of alterations in “patient” position on laser-induced ureteral stone retropulsion in an in vitro model. In this paper, a ceramic (phantom) stone was placed in a water-filled clear polymer tube and subjected to continuous laser energy until the stone had retropulsed a distance of 10cm. The trial was stopped after 60 seconds if the stone had not reached 10cm. The time and total energy needed to cause 10cm of retropulsion were recorded at an incline angle of 0°, 10°, 20°, and 40°; ten trials at each angle were completed. The study was then repeated with pure calcium phosphate brushite stones. Retropulsion decreased with increasing incline angle of the saline-filled clear polymer tube. At 0° of incline the phantom stone reached a distance of 10cm after 7.4 seconds. At 10°, 20°, and 40° the phantom stone migrated a mean maximum distance of 3.1 cm, 1.2 cm, and 0.7 cm, respectively, and the trial was stopped after 60 seconds. For the calcium phosphate stone, at 0° and 10° of incline, the stone reached 10cm after 6.9 seconds and 42.8 seconds respectively (p<0.05). At 20° and 40°, the calcium phosphate stone moved a mean maximum distance of 2.4cm and 1cm, and the trial was stopped after 60 seconds. Alterations in the angle of inclination reduced stone retropulsion during ureteroscopic lithotripsy in an in vitro model to <1cm. Finally, increasing the incline angle of a patient may effectively preclude retropulsion when performing laser lithotripsy of ureteral stones.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1991

Cytoplasmic calcium levels in protoplasts from the cap and elongation zone of maize roots

Calcium has been implicated as a key component in the signal transduction process of root gravitropism. We measured cytoplasmic free calcium in protoplasts isolated from the elongation zone and cap of primary roots of light-grown, vertically oriented seedlings of Zea mays L. Protoplasts were loaded with the penta-potassium salts of fura-2 and indo-1 by incubation in acidic solutions of these calcium indicators. Loading increased with decreasing pH but the pH dependence was stronger for indo-1 than for fura-2. In the case of fura-2, loading was enhanced only at the lowest pH (4.5) tested. Dyes loaded in this manner were distributed predominantly in the cytoplasm as indicated by fluorescence patterns. As an alternative method of loading, protoplasts were incubated with the acetoxymethylesters of fura-2 and indo-1. Protoplasts loaded by this method exhibited fluorescence both in the cytoplasm and in association with various organelles. Cytoplasmic calcium levels measured using spectrofluorometry, were found to be 160 +/- 40 nM and 257 +/- 27 nM, respectively, in populations of protoplasts from the root cap and elongation zone. Cytoplasmic free calcium did not increase upon addition of calcium to the incubation medium, indicating that the passive permeability to calcium was low.

NASA Discipline Plant Biology↗
DOE OSTI2021

Calcium Carbonate Cement: A Carbon Capture, Utilization, and Storage (CCUS) Technique

A novel calcium carbonate cement system that mimics the naturally occurring mineralization process of carbon dioxide to biogenic or geologic calcium carbonate deposits was developed utilizing carbon dioxide-containing flue gas and high-calcium industrial solid waste as raw materials. The calcium carbonate cement reaction is based on the polymorphic transformation from metastable vaterite to aragonite and can achieve >40 MPa compressive strength. Due to its unique properties, the calcium carbonate cement is well suited for building materials applications with controlled factory manufacturing processes that can take advantage of its rapid curing at elevated temperatures and lower density for competitive advantages. Examples of suitable applications are lightweight fiber cement board and aerated concrete. The new cement system described is an environmentally sustainable alternative cement that can be carbon negative, meaning more carbon dioxide is captured during its manufacture than is emitted.

36 MATERIALS SCIENCE↗