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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Orientation features of {sup 24}Mg(2+) aligned nuclei in (p, p) and (d, d) reactions at E{sub x} ≈ 7.5 MeV per nucleon

Experimental angular dependences of cross sections for elastic and inelastic scattering and the result obtained by reconstructing the populations of magnetic sublevels, multipole-moment orientation tensors, and polarization tensors are presented for {sup 24}Mg (2{sup +}, 1.369 MeV) aligned nuclei produced in inelastic proton scattering at E{sub p} = 7.4 MeV. The experimental results in question are compared with the results of calculations based on the coupled-channel method and on the compound-nucleus model, the 3/2{sup +} resonance in the {sup 25}Al compound nucleus being taken into account. The orientation features of {sup 24}Mg (2{sup +}, 1.369 MeV) nuclei produced in inelastic proton and deuteron scattering on {sup 24}Mg at E{sub x} ≈ 7.5 MeV per nucleon are found to be generally similar despite a substantial difference in the respective differential cross sections.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

A compact source for bunches of singly charged atomic ions

We have built, operated, and characterized a compact ion source for low-energy bunches of singly charged atomic ions in a vacuum beam line. It is based on atomic evaporation from an electrically heated oven and ionization by electron impact from a heated filament inside a grid-based ionization volume. An adjacent electrode arrangement is used for ion extraction and focusing by applying positive high-voltage pulses to the grid. The method is particularly suited for experimental environments which require low electromagnetic noise. It has proven simple yet reliable and has been used to produce μs-bunches of up to 10{sup 6} Mg{sup +} ions at a repetition rate of 1 Hz. We present the concept, setup and characterizing measurements. The instrument has been operated in the framework of the SpecTrap experiment at the HITRAP facility at GSI/FAIR to provide Mg{sup +} ions for sympathetic cooling of highly charged ions by laser-cooled {sup 24}Mg{sup +}.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Toward accurate thermochemistry of the {sup 24}MgH, {sup 25}MgH, and {sup 26}MgH molecules at elevated temperatures: Corrections due to unbound states

The total partition functions Q(T) and their first two moments Q{sup ′}(T) and Q{sup ″}(T), together with the isobaric heat capacities C{sub p}(T), are computed a priori for three major MgH isotopologues on the temperature range of T = 100–3000 K using the recent highly accurate potential energy curve, spin-rotation, and non-adiabatic correction functions of Henderson et al. [J. Phys. Chem. A 117, 13373 (2013)]. Nuclear motion computations are carried out on the ground electronic state to determine the (ro)vibrational energy levels and the scattering phase shifts. The effect of resonance states is found to be significant above about 1000 K and it increases with temperature. Even very short-lived states, due to their relatively large number, have significant contributions to Q(T) at elevated temperatures. The contribution of scattering states is around one fourth of that of resonance states but opposite in sign. Uncertainty estimates are given for the possible error sources, suggesting that all computed thermochemical properties have an accuracy better than 0.005% up to 1200 K. Between 1200 and 2500 K, the uncertainties can rise to around 0.1%, while between 2500 K and 3000 K, a further increase to 0.5% might be observed for Q{sup ″}(T) and C{sub p}(T), principally due to the neglect of excited electronic states. The accurate thermochemical data determined are presented in the supplementary material for the three isotopologues of {sup 24}MgH, {sup 25}MgH, and {sup 26}MgH at 1 K increments. These data, which differ significantly from older standard data, should prove useful for astronomical models incorporating thermodynamic properties of these species.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Form factors for dark matter capture by the Sun in effective theories

In the effective theory of isoscalar and isovector dark matter-nucleon interactions mediated by a heavy spin-1 or spin-0 particle, 8 isotope-dependent nuclear response functions can be generated in the dark matter scattering by nuclei. We compute the 8 nuclear response functions for the 16 most abundant elements in the Sun, i.e. H, {sup 3}He, {sup 4}He, {sup 12}C, {sup 14}N, {sup 16}O, {sup 20}Ne, {sup 23}Na, {sup 24}Mg, {sup 27}Al, {sup 28}Si, {sup 32}S, {sup 40}Ar, {sup 40}Ca, {sup 56}Fe, and {sup 59}Ni, through numerical shell model calculations. We use our response functions to compute the rate of dark matter capture by the Sun for all isoscalar and isovector dark matter-nucleon effective interactions, including several operators previously considered for dark matter direct detection only. We study in detail the dependence of the capture rate on specific dark matter-nucleon interaction operators, and on the different elements in the Sun. We find that a so far neglected momentum dependent dark matter coupling to the nuclear vector charge gives a larger contribution to the capture rate than the constant spin-dependent interaction commonly included in dark matter searches at neutrino telescopes. Our investigation lays the foundations for model independent analyses of dark matter induced neutrino signals from the Sun. The nuclear response functions obtained in this study are listed in analytic form in an appendix, ready to be used in other projects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Inferred initial {sup 26}Al/{sup 27}Al ratios in presolar stardust grains from supernovae are higher than previously estimated

We performed an in-depth exploration of the Al–Mg system for presolar graphite, SiC, and Si{sub 3}N{sub 4} grains found to contain large excesses of {sup 26}Mg, indicative of the initial presence of live {sup 26}Al. Ninety of the more than 450 presolar grains processed in this study contain well-correlated δ{sup 26}Mg/{sup 24}Mg and {sup 27}Al/{sup 24}Mg ratios, derived from Nano-scale Secondary Ion Mass Spectrometer depth profiles, whose isochron-like regression lines yield inferred initial {sup 26}Al/{sup 27}Al ratios that, on average, are ∼1.5–2 times larger than the ratios previously reported for the grains. The majority of presolar graphite and SiC grains are heavily affected by Al contamination, resulting in large negative δ{sup 26}Mg/{sup 24}Mg intercepts of the isochron lines. Al contamination is potentially due to etching of the grains’ surfaces and subsequent capture of dissolved Al during the acid dissolution of their meteorite host rocks. From the isochron fits, the magnitude of Al contamination was quantified for each grain. The amount of Al contamination on each grain was found to be random and independent of grain size, following a uniform distribution with an upper bound at 59% contamination. The Al contamination causes conventional whole-grain estimates to underpredict the initial {sup 26}Al/{sup 27}Al ratios. The presolar grains with the highest {sup 26}Al/{sup 27}Al ratios are from Type II supernovae whose isochron-derived initial {sup 26}Al/{sup 27}Al ratios greatly exceed those predicted in the He/C and He/N zones of SN models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Incidence of nephrolithiasis in relation to environmental exposure to lead and cadmium in a population study

Whether environmental exposure to nephrotoxic agents that potentially interfere with calcium homeostasis, such as lead and cadmium, contribute to the incidence of nephrolithiasis needs further clarification. We investigated the relation between nephrolithiasis incidence and environmental lead and cadmium exposure in a general population. In 1302 participants randomly recruited from a Flemish population (50.9% women; mean age, 47.9 years), we obtained baseline measurements (1985–2005) of blood lead (BPb), blood cadmium (BCd), 24-h urinary cadmium (UCd) and covariables. We monitored the incidence of kidney stones until October 6, 2014. We used Cox regression to calculate multivariable-adjusted hazard ratios for nephrolithiasis. At baseline, geometric mean BPb, BCd and UCd was 0.29 µmol/L, 9.0 nmol/L, and 8.5 nmol per 24 h, respectively. Over 11.5 years (median), nephrolithiasis occurred in 40 people. Contrasting the low and top tertiles of the distributions, the sex- and age-standardized rates of nephrolithiasis expressed as events per 1000 person-years were 0.68 vs. 3.36 (p=0.0016) for BPb, 1.80 vs. 3.28 (p=0.11) for BCd, and 1.65 vs. 2.95 (p=0.28) for UCd. In continuous analysis, with adjustments applied for sex, age, serum magnesium, and 24-h urinary volume and calcium, the hazard ratios expressing the risk associated with a doubling of the exposure biomarkers were 1.35 (p=0.015) for BPb, 1.13 (p=0.22) for BCd, and 1.23 (p=0.070) for UCd. In conclusion, our results suggest that environmental lead exposure is a risk factor for nephrolithiasis in the general population. - Highlights: • Prevalence and incidence rates of nephrolithiasis are increasing worldwide. • Lead and cadmium interfere with calcium homeostasis and might cause nephrolithiasis. • Environmental exposure to lead, not cadmium, predicts nephrolithiasis in the population. • Safety standards for environmental lead exposure need to account for nephrolithiasis. • Reducing environmental exposure to lead remains a priority.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Magneto-optical trap formed by elliptically polarised light waves for Mg atoms

We consider a magneto-optical trap (MOT) formed by elliptically polarised waves for {sup 24}Mg atoms on a closed optical {sup 3}P{sub 2} → {sup 3}D{sub 3} (λ = 383.8 nm) transition in the ε – θ – ε̄ configuration of the field. Compared with a known MOT formed by circularly polarised waves (σ{sub +} – σ{sub -} configuration), the suggested configuration of the trap formed by fields of ε – θ – ε̄ configuration allows deeper sub-Doppler cooling of trapped {sup 24}Mg atoms, which cannot be implemented in a conventional trap formed by fields of σ{sub +} – σ{sub -} configuration. (optical traps)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Nuclear Data Sheets for A = 54

The 2005 evaluation for A=54 (2006Hu08) has been updated. Detailed experimental nuclear structure data and decay data for all nuclei with mass chain A=54 are presented in this current evaluation. The new data and information are given in following datasets: {sup 54}Ca: {sup 9}Be({sup 76}Ge, X) and Be({sup 55}Sc, p), ({sup 56}Ti, 2p) {sup 54}Sc: {sup 54}Ca β{sup −} decay and {sup 54}Sc IT decay {sup 54}Ti: {sup 54}Sc β{sup −} decay {sup 54}Cr: {sup 54}Mn ε decay, {sup 56}Fe(μ, nupng), and {sup 238}U({sup 64}Ni, Xγ) {sup 54}Mn: {sup 51}V({sup 20}Ne, Xγ), {sup 55}Mn(p, pn), and {sup 56}Fe(μ, nu2ng) {sup 54}Fe: {sup 58}Ni α decay, {sup 9}Be({sup 55}Co, Xγ), {sup 54}Fe(e, e'), {sup 54}Fe(p, p'), and Coulomb Excitation {sup 54}Co: {sup 54}Ni ε decay, {sup 55}Cu εp decay, {sup 28}Si({sup 32}S, αpnγ), {sup 54}Fe(p,n), and {sup 54}Fe({sup 3}He, t) {sup 54}Ni: {sup 54}Ni IT decay, {sup 55}Zn εp decay, {sup 9}Be({sup 55}Ni, Xγ), and {sup 24}Mg({sup 32}S, Xγ) {sup 54}Zn: Ni({sup 58}Ni, X)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Angular correlations in the inelastic-scattering process {sup 24}Mg(d, d{gamma}){sup 24}Mg at E{sub d} = 15.3 MeV

The double-differential cross sections for the reaction {sup 24}Mg(d, d{gamma}{sub 1.369}){sup 24}Mg at the projectiledeuteron energy of E{sub d} = 15.3 MeV weremeasured for deuteron emission angles in the forward hemisphere. All even spin-tensor components of the density matrix for the 2{sup +} state of the {sup 24}Mg nucleus at 1.369 MeV were reconstructed, and its orientation properties were determined. These experimental results were compared with the results of calculations based on various versions of the coupled-channel method.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2014

Study of {sup 24}Mg resonances relevant for carbon burning nucleosynthesis

We have studied decays of resonances in {sup 24}Mg at excitation energies above the {sup 12}C+{sup 12}C decay threshold, using {sup 12}C({sup 16}O,α){sup 24}Mg* reaction. This experiment has been performed at INFNLNS, using Tandem accelerator beam of 16O at E = 94 MeV. Some preliminary results are presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Clustering effects in fusion evaporation reactions with light even-even N = Z nuclei. The {sup 24}Mg and {sup 28}Si cases

In the recent years, cluster structures have been evidenced in many ground and excited states of light nuclei [1, 2]. Within the currently ongoing experimental campaign by the NUCL-EX collaboration we have measured the {sup 12}C+{sup 12}C and {sup 14}N+{sup 10}B reactions at 95 MeV and 80 MeV respectively, and compared experimental data corresponding to complete fusion of target and projectile into an excited {sup 24}Mg nucleus to the results of a pure statistical model[3, 4]. We found clear deviations from the statstical model in the decay pattern: emission channels involving multiple α particles are more probable than expected from a purely statistical behavior. To continue the investigation on light systems, we have recentely measured the {sup 16}O+{sup 12}C reaction at three different beam energies, namely E{sub beam} = 90, 110 and 130 MeV.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

In-Beam γ -Ray Spectroscopy of Mg 34 , 36 , 38 : Merging the N = 20 and N = 28 Shell Quenching

Neutron-rich N = 22, 24, 26 magnesium isotopes were studied in this paper via in-beam γ-ray spectroscopy at the RIKEN Radioactive Isotope Beam Factory following secondary fragmentation reactions on a carbon target at ≈ 200 MeV /nucleon. In the one- and two-proton removal channels from 39 Al and 40 Si beams, two distinct γ-ray transitions were observed in 38 Mg, while in the one-proton removal reaction from 37 Al a new transition was observed in addition to the known 2 + 1 → 0 + g.s. decay. From the experimental systematics and comparison to theoretical predictions it is concluded that the transitions belong to the 2 + 1 → 0 + g.s. and 4 + 1 → 2 + 1 decays in 36 Mg and 38 Mg, respectively. For 34 Mg, previously reported 2 + 1 and 4 + 1 level energies were remeasured. Finally, the deduced E(4 + 1 )/E(2 + 1 ) ratios for 34,36,38 Mg of 3.14(5), 3.07(5), and 3.07(5) are almost identical and suggest the emergence of a large area of deformation extending from the N = 20 to the N = 28 shell quenching.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Thermal and chemical evolution in the early Solar System as recorded by FUN CAIs: Part II - Laboratory evaporation of potential CMS-1 precursor material

We present the results of laboratory experiments in which a forsterite-rich melt estimated to be a potential precursor of Allende CMS-1 FUN CAI was evaporated into vacuum for different lengths of time at 1900 °C. The evaporation of this melt resulted in residues that define trajectories in chemical as well as magnesium, silicon and oxygen isotopic composition space and come very close to the measured properties of CMS-1. The isotopic composition of the evaporation residues was also used to determine the kinetic isotopic fractionation factors [α 2,1 (vapor-melt) defined as the ratio of isotopes 2 and 1 of a given element in the evaporating gas divided by their ratio in the evaporating source] for evaporation of magnesium (α 25,24 for 25Mg/24Mg), silicon (α 29,28 for 29 Si/ 28 Si) and oxygen (α 18,16 for 18 O/ 16 O) from the forsterite-rich melt at 1900 °C. The values of α 25,24 = 0.98383 ± 0.00033 and α 29,28 = 0.99010 ± 0.00038 are essentially independent of change in the melt composition as evaporation proceeds. In contrast, α18,16 changes from 0.9815 ± 0.0016 to ~0.9911 when the residual melt composition changes from forsteritic to melilitic. Using the determined values of α 25,24 and α 29,28 and present-day bulk chemical composition of the CMS-1, the composition of the precursor of the inclusion was estimated to be close to the clinopyroxene + spinel + forsterite assemblage condensed from a solar composition gas. The correspondence between the chemical composition and isotopic fractionation of experimental evaporation residues and the present-day bulk chemical and isotopic compositions of CMS-1 is evidence that evaporation played a major role in the chemical evolution of CMS-1.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

An Investigation of the Formation and Line Properties of MgH in 3D Hydrodynamical Model Stellar Atmospheres

Studies of the isotopic composition of magnesium in cool stars have so far relied upon the use of 1D model atmospheres. Since the isotopic ratios derived are based on asymmetries of optical MgH lines, it is important to test the impact from other effects affecting line asymmetries, like stellar convection. Here, we present a theoretical investigation of the effects of including self-consistent modeling of convection. Using spectral syntheses based on 3D hydrodynamical CO{sup 5}BOLD models of dwarfs (4000 K ≲ T {sub eff} ≲ 5160 K, 4.0 ≤ logg ≤ 4.5, −3.0⩽[Fe/H]⩽−1.0) and giants (T {sub eff} ∼ 4000 K, logg = 1.5, −3.0⩽[Fe/H]⩽−1.0), we perform a detailed analysis comparing 3D and 1D syntheses. We describe the impact on the formation and behavior of MgH lines from using 3D models, and perform a qualitative assessment of the systematics introduced by the use of 1D syntheses. Using 3D model atmospheres significantly affect the strength of the MgH lines, especially in dwarfs, with 1D syntheses requiring an abundance correction of up to +0.69 dex, with the largest for our 5000 K models. The corrections are correlated with T {sub eff} and are also affected by the metallicity. The shape of the strong {sup 24}MgH component in the 3D syntheses is poorly reproduced in 1D. This results in 1D syntheses underestimating {sup 25}Mg by up to ∼5 percentage points and overestimating {sup 24}Mg by a similar amount for dwarfs. This discrepancy increases with decreasing metallicity. {sup 26}Mg is recovered relatively well, with the largest difference being ∼2 percentage points. The use of 3D for giants has less impact, due to smaller differences in the atmospheric structure and a better reproduction of the line shape in 1D.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Electrochemical Behavior Assessment of As-Cast Mg-Y-RE-Zr Alloy in Phosphate Buffer Solutions (X Na{sub 3}PO{sub 4} + Y Na{sub 2}HPO{sub 4}) Using Electrochemical Impedance Spectroscopy and Mott–Schottky Techniques

In the present study, electrochemical behavior of as-cast Mg-Y-RE-Zr alloy (RE: rare-earth alloying elements) was investigated using electrochemical tests in phosphate buffer solutions (X Na{sub 3}PO{sub 4} + Y Na{sub 2}HPO{sub 4}). X-ray diffraction techniques and Scanning electron microscopy equipped with energy dispersive x-ray spectroscopy were used to investigate the microstructure and phases of the experimental alloy. Different electrochemical tests such as potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and Mott–Schottky (M–S) analysis were carried out in order to study the electrochemical behavior of the experimental alloy in phosphate buffer solutions. The PDP curves and EIS measurements indicated that the passive behavior of the as-cast Mg-Y-RE-Zr alloy in phosphate buffer solutions was weakened by an increase in the pH, which is related to formation of an imperfect and less protective passive layer on the alloy surface. The presence of the insoluble zirconium particles along with high number of intermetallic phases of RE elements mainly Mg{sub 24}Y{sub 5} in the magnesium matrix can deteriorate the corrosion performance of the alloy by disrupting the protective passive layer that is formed at pH values over 11. These insoluble zirconium particles embedded in the matrix can detrimentally influence the passivation. The M–S analysis revealed that the formed passive layers on Mg-Y-RE-Zr alloy behaved as an n-type semiconductor. An increase in donor concentration accompanying solutions of higher alkalinity is thought to result in the formation of a less resistive passive layer.

36 MATERIALS SCIENCE↗
DOE OSTI2013

MAGNESIUM ISOTOPE EVIDENCE FOR SINGLE STAGE FORMATION OF CB CHONDRULES BY COLLIDING PLANETESIMALS

Chondrules are igneous spherical objects preserved in chondritic meteorites and believed to have formed during transient heating events in the solar protoplanetary disk. Chondrules present in the metal-rich CB chondrites show unusual chemical and petrologic features not observed in other chondrite groups, implying a markedly distinct formation mechanism. Here, we report high-precision Mg-isotope data for 10 skeletal olivine chondrules from the Hammadah al Hamra 237 (HH237) chondrite to probe the formation history of CB chondrules. The {sup 27}Al/{sup 24}Mg ratios of individual chondrules are positively correlated to their stable Mg-isotope composition (μ{sup 25}Mg), indicating that the correlated variability was imparted by a volatility-controlled process (evaporation/condensation). The mass-independent {sup 26}Mg composition (μ{sup 26}Mg*) of chondrules is consistent with single stage formation from an initially homogeneous magnesium reservoir if the observed μ{sup 25}Mg variability was generated by non-ideal Rayleigh-type evaporative fractionation characterized by a β value of 0.5142, in agreement with experimental work. The magnitude of the mass-dependent fractionation (∼300 ppm) is significantly lower than that suggested by the increase in {sup 27}Al/{sup 24}Mg values, indicating substantial suppression of isotopic fractionation during evaporative loss of Mg, possibly due to evaporation at high Mg partial pressure. Thus, the Mg-isotope data of skeletal chondrules from HH237 are consistent with their origin as melts produced in the impact-generated plume of colliding planetesimals. The inferred μ{sup 26}Mg* value of –3.87 ± 0.93 ppm for the CB parent body is significantly lower than the bulk solar system value of 4.5 ± 1.1 ppm inferred from CI chondrites, suggesting that CB chondrites accreted material comprising an early formed {sup 26}Al-free component.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Which Plant Traits Increase Soil Carbon Sequestration? Empirical Evidence From a Long‐Term Poplar Genetic Diversity Trial

Plants play a key role in mediating soil response to global change, and breeding or engineering crops to increase soil organic carbon (SOC) storage is a potential route to land-based carbon dioxide removal in agricultural systems. However, due to limited observational datasets plus shifting paradigms of SOC stabilization, it is unclear which plant traits are most important for enhancing different types of soil organic matter. Existing long-term common gardens of genetically diverse plant populations may provide an opportunity to evaluate biological controls on SOC, separate from environmental or management variability. Here we report on soil and root chemical data collected for 24 genotypes within a 13-year-old common garden in northwestern Oregon planted with a large natural variant population of Populus trichocarpa. Fractionating surface soil (0–15 cm) revealed substantial variation in stocks of mineral-associated organic matter (MAOM; 18–67 t C/ha) and particulate organic matter (POM; 2–22 t C/ha). Tree genotype explained 24% and 26% of the MAOM and POM stock variability, respectively, after controlling for background variability. We found minimal association between SOC concentration and either aboveground tree productivity or root biomass recalcitrance (C/N ratios and lignin content). In contrast, root elemental content appeared influential for MAOM-C concentration, which showed a strong positive association with root aluminum (Al) and a strong negative association with root boron (B) and magnesium (Mg). Furthermore, root concentrations of these elements were highly heritable (57%–78%) and not simply a reflection of background variation in soil elemental concentrations. We estimate that surface SOC stocks under these 24 genotypes have diverged at rates of up to 1.2–4.3 t C/ha/year. These results suggest that long-term genetic diversity trials have value for elucidating biological controls on soil organic matter dynamics, and that traits associated with root elemental content may be a useful target for enhancing biosequestration.

biomass recalcitrance↗