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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Submicron mass spectrometry imaging of single cells by combined use of mega electron volt time-of-flight secondary ion mass spectrometry and scanning transmission ion microscopy

In order to better understand biochemical processes inside an individual cell, it is important to measure the molecular composition at the submicron level. One of the promising mass spectrometry imaging techniques that may be used to accomplish this is Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS), using MeV energy heavy ions for excitation. MeV ions have the ability to desorb large intact molecules with a yield that is several orders of magnitude higher than conventional SIMS using keV ions. In order to increase the spatial resolution of the MeV TOF-SIMS system, we propose an independent TOF trigger using a STIM (scanning transmission ion microscopy) detector that is placed just behind the thin transmission target. This arrangement is suitable for biological samples in which the STIM detector simultaneously measures the mass distribution in scanned samples. The capability of the MeV TOF-SIMS setup was demonstrated by imaging the chemical composition of CaCo-2 cells.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Mass selective separation applied to radioisotopes of cesium: Mass selective applied to radioisotopes

A developed technique that uses the intrinsic mass-based separation capability of a quadrupole mass spectrometer has been used to resolve spectral radiometric interference of two isotopes of the same element. In this work the starting sample was a combination of 137Cs and 134Cs and was (activity) dominated by 137Cs and this methodology separated and “implanted” 134Cs that was later quantified for spectral features and ac- tivity with traditional radiometric techniques. This work demonstrated a 134Cs/137Cs activity ratio enhancement of >4 orders of magnitude and complete removal of 137Cs spectral features from the implanted target mass (i.e., 134).

Cesium↗
DOE OSTI2014

The 2012 Atomic Mass Evaluation and the Mass Tables

The new evaluation of the Atomic Masses, Ame2012, has just been released. It represents a major step in the history of the 60 year old Atomic Mass Evaluation based on the method developed by Wapstra. This new publication includes all material available to date. Some of the policies and procedures used in our evaluation are reported, together with an illustration of one specially difficult case, the energy available for the {sup 102}Pd double-electron capture. The observation of the mass surface reveals many important new features. We illustrate this statement by the double magicity of {sup 270}Hs at N = 162 and Z = 108.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Understanding Mass Transport in Copper Electrolyte-Based Dye-Sensitized Solar Cells

Copper redox shuttles, particularly [Cu(tmby) 2 ] 2+/1+ (tmby = bis(4,4',6,6'-tetramethyl-2,2'-bipyridine)), proved to be among the best electrolytes for dye-sensitized solar cells (DSCs), realizing higher power conversion efficiencies both under full sun and indoor illumination than conventional iodide/triiodide and cobalt electrolytes. Even though [Cu(tmby) 2 ] 2+/1+ renders a relatively higher performance, this metal complex is bulky and is limited by mass transport. Since the regeneration of the dye ground state by Cu I and the reaction of Cu II at the counter electrode are comparatively faster processes, the efficiency of DSC involving Cu I /Cu II electrolytes under relatively high light intensities is largely governed by the diffusion of Cu I /Cu II species. Understanding mass transport in these solar cells will enable further improvements in the performance of such copper-based DSCs. Here in the present study, the role of illumination intensity on the photogenerated current and its relationship to mass transport is evaluated using the best cosensitized dye (D35:XY1) and copper electrolyte ([Cu(tmby) 2 ] 2+/1+ ) combination.

14 SOLAR ENERGY↗
DOE OSTI2021

Correlating Nanoscale Secondary Ion Mass Spectrometry and Atom Probe Tomography Analysis of Uranium Enrichment in Metallic Nuclear Fuel

Distribution and enrichment of 235U within nuclear fuels are essential to material performance and reactor safety. With the development of metallic U fuels, understanding 235U homogeneity has become increasingly important, however, it is difficult to map with high spatial, and mass resolution to analyze both matrix and secondary phase precipitates. Here, we analyze 235U enrichment in matrix and carbide phases in LEU-Mo via two chemical imaging modalities: nanoscale secondary ion mass spectrometry (nanoSIMS) and atom probe tomography (APT). NanoSIMS and APT provided consistent results, with no statistically significant difference between measured and nominal enrichment (19.75 % 235U).

U-10Mo, atom probe tomography, nanoscale secondary↗
DOE OSTI2014

Molecular outflows driven by low-mass protostars. I. Correcting for underestimates when measuring outflow masses and dynamical properties

We present a survey of 28 molecular outflows driven by low-mass protostars, all of which are sufficiently isolated spatially and/or kinematically to fully separate into individual outflows. Using a combination of new and archival data from several single-dish telescopes, 17 outflows are mapped in {sup 12}CO (2-1) and 17 are mapped in {sup 12}CO (3-2), with 6 mapped in both transitions. For each outflow, we calculate and tabulate the mass (M {sub flow}), momentum (P {sub flow}), kinetic energy (E {sub flow}), mechanical luminosity (L {sub flow}), and force (F {sub flow}) assuming optically thin emission in LTE at an excitation temperature, T {sub ex}, of 50 K. We show that all of the calculated properties are underestimated when calculated under these assumptions. Taken together, the effects of opacity, outflow emission at low velocities confused with ambient cloud emission, and emission below the sensitivities of the observations increase outflow masses and dynamical properties by an order of magnitude, on average, and factors of 50-90 in the most extreme cases. Different (and non-uniform) excitation temperatures, inclination effects, and dissociation of molecular gas will all work to further increase outflow properties. Molecular outflows are thus almost certainly more massive and energetic than commonly reported. Additionally, outflow properties are lower, on average, by almost an order of magnitude when calculated from the {sup 12}CO (3-2) maps compared to the {sup 12}CO (2-1) maps, even after accounting for different opacities, map sensitivities, and possible excitation temperature variations. It has recently been argued in the literature that the {sup 12}CO (3-2) line is subthermally excited in outflows, and our results support this finding.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

The masses of local group dwarf spheroidal galaxies: The death of the universal mass profile

We investigate the claim that all dwarf spheroidal galaxies (dSphs) reside within halos that share a common, universal mass profile as has been derived for dSphs of the galaxy. By folding in kinematic information for 25 Andromeda dSphs, more than doubling the previous sample size, we find that a singular mass profile cannot be found to fit all of the observations well. Further, the best-fit dark matter density profile measured solely for the Milky Way dSphs is marginally discrepant with that of the Andromeda dSphs (at just beyond the 1σ level), where a profile with lower maximum circular velocity, and hence mass, is preferred. The agreement is significantly better when three extreme Andromeda outliers, And XIX, XXI, and XXV, all of which have large half-light radii (≳ 600 pc) and low-velocity dispersions (σ {sub v} < 5 km s{sup –1}), are omitted from the sample. We argue that the unusual properties of these outliers are likely caused by tidal interactions with the host galaxy.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Dark Energy Survey Year 1 results: weak lensing mass calibration of redMaPPer galaxy clusters

We constrain the mass-richness scaling relation of redMaPPer galaxy clusters identified in the Dark Energy Survey Year 1 data using weak gravitational lensing. We split clusters into 4 x 3 bins of richness lambda and redshift z for lambda >= 20 and 0.2 <= z <= 0.65 and measure the mean masses of these bins using their stacked weak lensing signal. By modelling the scaling relation as M-200m|lambda, M-0(lambda/40)(F)((1 + /1.35)(G), we constrain the normalization of the scaling relation at the 5.0 per cent level, finding M-0 = [3.081 +/- 0.075(stat) +/- 0.133(sys)] center dot 10(14) M-aS (TM) at lambda = 40 and = 0.35. The recovered richness scaling index is F = 1.356 +/- 0.051 (stat) +/- 0.008 (sys) and the redshift scaling index G = -0.30 +/- 0.30 (stat) +/- 0.06 (sys). These are the tightest measurements of the normalization and richness scaling index made to date from a weak lensing experiment. We use a semi-analytic covariance matrix to characterize the statistical errors in the recovered weak lensing profiles. Our analysis accounts for the following sources of systematic error: shear and photometric redshift errors, cluster miscentring, cluster member dilution of the source sample, systematic uncertainties in the modelling of the halo-mass correlation function, halo triaxiality, and projection effects. We discuss prospects for reducing our systematic error budget, which dominates the uncertainty on M-0. Our result is in excellent agreement with, but has significantly smaller uncertainties than, previous measurements in the literature, and augurs well for the power of the DES cluster survey as a tool for precision cosmology and upcoming galaxy surveys such as LSST, Euclid, and WFIRST

clusters↗
DOE OSTI2020

Exploring the mass surface near the rare-earth abundance peak via precision mass measurements at JYFLTRAP

The JYFLTRAP double Penning trap at the Ion Guide Isotope Separator On-Line facility has been used to measure the atomic masses of 13 neutron-rich rare-earth isotopes. Eight of the nuclides, 161 Pm, 163 Sm, 164,165 Eu, 167 Gd, and 165,167,168 Tb, were measured for the first time. The systematics of the mass surface has been studied via one- and two-neutron separation energies as well as neutron pairing-gap and shell-gap energies. The proton-neutron pairing strength has also been investigated. Furthermore, the impact of the new mass values on the astrophysical rapid neutron capture process has been studied. The calculated abundance distribution results in a better agreement with the solar abundance pattern near the top of the rare-earth abundance peak at around A≈165.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2025

Assessment of Low-Level Pu Isotope Ratio Measurements Using Multicollector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS/MS) Equipped with a Pre-Mass Filter

We present an initial investigation into the performance of a multicollector inductively coupled plasmamass spectrometer equipped with a pre-mass filter (Neoma MC-ICP-MS/MS) for making plutonium (Pu) isotope ratio measurements on solutions containing low level (i.e., pg mL –1 ) Pu concentrations. This assessment was achieved by comparison of the 240 Pu/ 239 Pu, 241 Pu/ 239 Pu, and 242 Pu/ 239 Pu ratios attained over a one month period on the MC-ICP-MS/MS with the long-term (∼1 year) performance observed on the predecessor MC-ICP-MS (Neptune Plus) instrument each equipped with an equipped with an APEXΩ desolvating nebulizer for repeated measurements of certified reference materials from New Brunswick Program Office (NBL PO) CRM 136a and CRM 137. The MC-ICP-MS/MS performance of repeated measurement of CRM 136a (n = 20) resulted in mean values of 240 Pu/ 239 Pu = 0.1448 ± 0.0006, 241 Pu/ 239 Pu = 0.00371 ± 0.00006, and 242 Pu/ 239 Pu = 0.00682 ± 0.00006 (k = 2). The CRM 137 (n = 20), analyzed during the same analytical sessions, produced mean values for 240 Pu/ 239 Pu = 0.2414 ± 0.0006, 241 Pu/ 239 Pu = 0.00464 ± 0.00007, and 242 Pu/ 239 Pu = 0.0157 ± 0.0001 (k = 2). These results closely align with the certificate values for CRM 136a and CRM 137 and are within the k = 2 envelopes defined by the long-term performance of the traditional MC-ICP-MS approach (Neptune Plus). Examination of the performance of the various Pu isotope ratios as a function of total Pu content revealed accurate results (<3% relative difference, or RD) above ∼50 fg total Pu. The results presented here demonstrate the capability of the MC-ICP-MS/MS making accurate and precise low level Pu isotopic measurements. While the intent of this work was not to investigate the functionality of the collision cell, the pre-mass filter was employed. Future studies are warranted to investigate the entire capability of the MC-ICP-MS/MS collision cell and pre-cell mass filter optimization for performing low level Pu isotope measurements, even in mixed matrix samples.

CRM↗
DOE OSTI2016

EVOLUTION OF THERMALLY PULSING ASYMPTOTIC GIANT BRANCH STARS. V. CONSTRAINING THE MASS LOSS AND LIFETIMES OF INTERMEDIATE-MASS, LOW-METALLICITY AGB STARS

Thermally pulsing asymptotic giant branch (TP-AGB) stars are relatively short lived (less than a few Myr), yet their cool effective temperatures, high luminosities, efficient mass loss, and dust production can dramatically affect the chemical enrichment histories and the spectral energy distributions of their host galaxies. The ability to accurately model TP-AGB stars is critical to the interpretation of the integrated light of distant galaxies, especially in redder wavelengths. We continue previous efforts to constrain the evolution and lifetimes of TP-AGB stars by modeling their underlying stellar populations. Using Hubble Space Telescope (HST) optical and near-infrared photometry taken of 12 fields of 10 nearby galaxies imaged via the Advanced Camera for Surveys Nearby Galaxy Survey Treasury and the near-infrared HST/SNAP follow-up campaign, we compare the model and observed TP-AGB luminosity functions as well as the ratio of TP-AGB to red giant branch stars. We confirm the best-fitting mass-loss prescription, introduced by Rosenfield et al., in which two different wind regimes are active during the TP-AGB, significantly improves models of many galaxies that show evidence of recent star formation. This study extends previous efforts to constrain TP-AGB lifetimes to metallicities ranging −1.59 ≲ [Fe/H] ≲ −0.56 and initial TP-AGB masses up to ∼4 M {sub ⊙}, which include TP-AGB stars that undergo hot-bottom burning.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

2M17091769+3127589: A Mass-transfer Binary with an Extreme Mass Ratio

We present the orbital solution of a peculiar double-lined spectroscopic and eclipsing binary system, 2M17091769+3127589. This solution was obtained by a simultaneous fit of both APOGEE radial velocities and TESS and ASAS-SN light curves to determine masses and radii. This system consists of an M=0.256{sub -0.006}{sup +0.010} M {sub ⊙}, R=3.961{sub -0.032}{sup +0.049} R {sub ⊙} red giant and a hotter M=1.518{sub -0.031}{sup +0.057} M {sub ⊙}, R=2.608{sub -0.321}{sup +0.034} R {sub ⊙} subgiant. Modeling with the MESA evolutionary codes indicates that the system likely formed 5.26 Gyrs ago, with a M = 1.2 M {sub ⊙} primary that is now the system’s red giant and a M = 1.11 M {sub ⊙} secondary that is now a more massive subgiant. Due to Roche-lobe overflow as the primary ascends the red giant branch, the more evolved “primary” (i.e., originally the more massive star of the pair) is now only one sixth as massive as the “secondary.” Such a difference between the initial and the current mass ratio is one of the most extreme detected so far. Evolutionary modeling suggests the system is still engaged in mass transfer, at a rate of M-dot ~10{sup -9} M {sub ⊙}/yr, and it provides an example of a less evolved precursor to some of the systems that consist of white dwarfs and blue stragglers.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Mass–metallicity relation for local analogs of high-redshift galaxies: implications for the evolution of the mass–metallicity relations

We revisit the evolution of the mass–metallicity relation of low- and high-redshift galaxies by using a sample of local analogs of high-redshift galaxies. These analogs share the same location of the UV-selected star-forming galaxies at z∼2 on the [O iii]λ5007/Hβ versus [N ii]λ6584/Hα nebular emission-line diagnostic (or BPT) diagram. Their physical properties closely resemble those in z∼2 UV-selected star-forming galaxies being characterized, in particular, by high ionization parameters (logq≈7.9) and high electron densities (n{sub e}≈100 cm{sup −3}). With the full set of well-detected rest-frame optical diagnostic lines, we measure the gas-phase oxygen abundance in the SDSS galaxies and these local analogs using the empirical relations and the photoionization models. We find that the metallicity difference between the SDSS galaxies and our local analogs in the 8.5<log(M{sub ∗}/M{sub ⊙})<9.0 stellar mass bin varies from −0.09 to 0.39 dex, depending on strong-line metallicity measurement methods. Due to this discrepancy, the evolution of mass–metallicity should be used to compare with the cosmological simulations with caution. We use the [S ii]/Hα and [O i]/Hα BPT diagram to reduce the potential AGN and shock contamination in our local analogs. We find that the AGN/shock influences are negligible on the metallicity estimation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

THE DISTRIBUTION OF MASS SURFACE DENSITIES IN A HIGH-MASS PROTOCLUSTER

We study the probability distribution function (PDF) of mass surface densities, Σ, of infrared dark cloud (IRDC) G028.37+00.07 and its surrounding giant molecular cloud. This PDF constrains the physical processes, such as turbulence, magnetic fields, and self-gravity, that are expected to be controlling cloud structure and star formation activity. The chosen IRDC is of particular interest since it has almost 100,000 solar masses within a radius of 8 pc, making it one of the most massive, dense molecular structures known and is thus a potential site for the formation of a “super star cluster.” We study Σ in two ways. First, we use a combination of NIR and MIR extinction maps that are able to probe the bulk of the cloud structure up to Σ ∼ 1 g cm{sup −2}( A {sub V}≃ 200 mag). Second, we study the FIR and submillimeter dust continuum emission from the cloud utilizing Herschel -PACS and SPIRE images and paying careful attention to the effects of foreground and background contamination. We find that the PDFs from both methods, applied over a ∼20′(30 pc)-sized region that contains ≃1.5 × 10{sup 5} M {sub ⊙} and enclosing a minimum closed contour with Σ ≃ 0.013 g cm{sup −2} ( A {sub V} ≃ 3 mag), shows a lognormal shape with the peak measured at Σ ≃ 0.021 g cm{sup −2} ( A {sub V}≃ 4.7 mag). There is tentative evidence for the presence of a high-Σ power-law tail that contains from ∼3% to 8% of the mass of the cloud material. We discuss the implications of these results for the physical processes occurring in this cloud.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Production of highly-enriched 134Ba for a reference material for isotope dilution mass spectrometry measurements

Isotope dilution mass spectrometry (IDMS) is an analytical technique capable of providing accurate and precise quantitation of trace isotope abundance and assay providing measurement uncertainties below 1 %. To achieve these low uncertainties, the IDMS method ideally utilizes chemically pure “spike” solutions that consist of a single highly enriched isotope that is well-characterized relating to the abundance of companion isotopes and concentration in solution. To address a current demand for accurate 137Cs/137Ba ratio measurements for “age” determination of radioactive 137Cs sources, Idaho National Laboratory (INL) is producing enriched 134Ba isotopes that are tobe used for IDMS spikes to accurately determine 137Ba accumulation from the decay of 137Cs. The final objective of this work it to provide a homogenous set of reference materials that the National Institute of Standards and Technology can certify as standard reference materials used for IDMS. The process that was developed at INL for the separation and isolation of Ba isotopes, chemical purification of the isotopes in solution, and the encapsulation of the materials will be described.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2015

New Insights into Low-Temperature Oxidation of Propane from Synchrotron Photoionization Mass Spectrometry and Multiscale Informatics Modeling

We investigated the low-temperature oxidation of propane at 4 Torr and temperatures of 530, 600, and 670 K. The oxidation is initiated by pulsed laser photolysis of oxalyl chloride, (COCl)2, at 248 nm, which rapidly generates a ~1:1 mixture of 1-propyl (n-propyl) and 2-propyl (i-propyl) radicals via the fast Cl + propane reaction. Reactants, intermediates and products are probed with isomeric selectivity by time-resolved multiplexed photoionization mass spectrometry (MPIMS) with tunable synchrotron vacuum UV radiation as the ionization source. At all three temperatures, the major stable product species is propene, formed in the C3H7 + O2 reactions by direct HO2-elimination from both n- and i-propyl peroxy radicals. The experimentally derived propene yields relative to the initial concentration of Cl atoms are (20 ± 4)% at 530 K, (55 ± 11)% at 600 K, and (86 ± 17)% at 670 K at a reaction time of 20 ms. The lower yield of propene at low temperature reflects substantial formation of propyl peroxy radicals, which do not completely decompose on the experimental time scale. In addition, we detect the C3H6O isomers methyloxirane, oxetane, acetone and propanal as minor products. Our measured yields of oxetane and methyloxirane, which are co-products of OH radicals, suggest a revision of the OH formation pathways in models of low-temperature propane oxidation. The experimental results are modeled and interpreted using a multi-scale informatics approach that is presented in detail in a separate publication (Burke, M. P.; Goldsmith, C. F.; Klippenstein, S. J.; Welz, O.; Huang H.; Antonov I. O.; Savee J. D.; Osborn D. L.; Zádor, J.; Taatjes, C. A.; Sheps, L., Multi-Scale Informatics for Low-Temperature Propane Oxidation: Further Complexities in Studies of Complex Rections, submitted, 2015). The model predicts the time profiles and yields of the experimentally observed primary products well, and shows satisfactory agreement for products formed mostly via secondary radical-radical reactions.

Combustion↗