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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 1,621 records · Page 90
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Mapping Metals Incorporation of a Whole Single Catalyst Particle Using Element Specific X-ray Nanotomography

Full-field transmission X-ray microscopy has been used to determine the 3D structure of a whole individual fluid catalytic cracking (FCC) particle at high spatial resolution and in a fast, noninvasive manner, maintaining the full integrity of the particle. Using X-ray absorption mosaic imaging to combine multiple fields of view, computed tomography was performed to visualize the macropore structure of the catalyst and its availability for mass transport. We mapped the relative spatial distributions of Ni and Fe using multiple-energy tomography at the respective X-ray absorption K-edges and correlated these distributions with porosity and permeability of an equilibrated catalyst (E-cat) particle. Both metals were found to accumulate in outer layers of the particle, effectively decreasing porosity by clogging of pores and eventually restricting access into the FCC particle.

02 PETROLEUM↗
DOE OSTI2021

Probing the subcellular nanostructure of engineered human cardiomyocytes in 3D tissue

Abstract The structural and functional maturation of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) is essential for pharmaceutical testing, disease modeling, and ultimately therapeutic use. Multicellular 3D-tissue platforms have improved the functional maturation of hiPSC-CMs, but probing cardiac contractile properties in a 3D environment remains challenging, especially at depth and in live tissues. Using small-angle X-ray scattering (SAXS) imaging, we show that hiPSC-CMs matured and examined in a 3D environment exhibit a periodic spatial arrangement of the myofilament lattice, which has not been previously detected in hiPSC-CMs. The contractile force is found to correlate with both the scattering intensity ( R 2 = 0.44) and lattice spacing ( R 2 = 0.46). The scattering intensity also correlates with lattice spacing ( R 2 = 0.81), suggestive of lower noise in our structural measurement than in the functional measurement. Notably, we observed decreased myofilament ordering in tissues with a myofilament mutation known to lead to hypertrophic cardiomyopathy (HCM). Our results highlight the progress of human cardiac tissue engineering and enable unprecedented study of structural maturation in hiPSC-CMs.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Structure and osmotic pressure of ionic microgel dispersions

We investigate structural and thermodynamic properties of aqueous dispersions of ionic microgels—soft colloidal gel particles that exhibit unusual phase behavior. Starting from a coarse-grained model of microgel macroions as charged spheres that are permeable to microions, we perform simulations and theoretical calculations using two complementary implementations of Poisson-Boltzmann (PB) theory. Within a one-component model, based on a linear-screening approximation for effective electrostatic pair interactions, we perform molecular dynamics simulations to compute macroion-macroion radial distribution functions, static structure factors, and macroion contributions to the osmotic pressure. For the same model, using a variational approximation for the free energy, we compute both macroion and microion contributions to the osmotic pressure. Within a spherical cell model, which neglects macroion correlations, we solve the nonlinear PB equation to compute microion distributions and osmotic pressures. By comparing the one-component and cell model implementations of PB theory, we demonstrate that the linear-screening approximation is valid for moderately charged microgels. By further comparing cell model predictions with simulation data for osmotic pressure, we chart the cell model’s limits in predicting osmotic pressures of salty dispersions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Composition dependent structural organization in trihexyl(tetradecyl)phosphonium chloride ionic liquid-methanol mixtures

This article reports results from the molecular dynamics simulations on the structural arrangement of the ions and molecules in the mixtures of trihexyl(tetradecyl)phosphonium chloride ([P{sub 666,14}{sup +}][Cl{sup −}]) ionic liquid (IL) and methanol (MeOH) over the entire composition range. Effects of composition on the charge and polarity orderings have been investigated via computation of X-ray scattering structure function, S(q), and by using a partitioning scheme proposed for such multi-component mixtures. Except for the neat methanol liquid, the total S(q) shows two peaks in its intermolecular region for all the mole-fractions. The lowest q peak is dominated primarily by anion-anion, cation-anion, and methanol-anion correlations. Our results signify that the methanol bulk structure, which predominantly has short-distance characteristic correlations and is governed by polar group of methanol, is retained for x{sub IL} ≤ 0.1. Then, the mixture goes through gradual structural changes from methanol-like to the IL-like for 0.1 < x{sub IL} ≤ 0.7. The dipolar interaction between methanol molecules weakens in this range, and the structural landscape of the mixture is steered by strong ion-ion, anion-methanol, and nonpolar interactions. The IL-like structural arrangement is virtually recovered for x{sub IL} > 0.7. At all the compositions studied, while the cation head groups are predominantly solvated by anions and subsequently by methanol molecules, the polar hydroxyl group of methanol is preferentially solvated by the anions. The radial distribution functions of selected pair of atomic species have also confirmed these observations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Absolute and relative emission spectroscopy study of 3 cm wide planar radio frequency atmospheric pressure bio-plasma source

The dynamics of low power atmospheric pressure radio frequency discharge generated in Ar gas in long gap of 3 cm is investigated. This plasma source is characterized and analyzed for possible large scale biomedical applications where low gas temperature and potential-less effluent are required. The discharge forms a homogenous glow-like afterglow in ambient air at input power of 30 W with low gas temperature of 330 K, which is desirable in biomedical applications. With absolute calibrated spectroscopy of the discharge, electron density of 0.4 × 10{sup 18} m{sup −3} and electron temperature of 1.5 eV are obtained from continuum Bremsstrahlung radiation of the source. Time and spatial resolved emission spectroscopy is used to analyze discharge generation mechanism and active species formation. It is found that discharge dynamics strongly correlates with the discharge current waveform. Strong Ar(2p) excited states emission is observed nearby the electrodes surface on a distance up to 200 μm in the plasma sheath region at 10 ns after the current peak, whereas OH(A) emission is uniform along of the interelectrode gap.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Role of structural defects in the ultraviolet luminescence of multiwall boron nitride nanotubes

BN nanotubes (BNNTs) are structurally similar to their carbon counterparts, though much less investigated. New synthesis methods have been recently reported, enabling the production of industrial quantities and stimulating the search of new applications for the BNNTs. In this paper, we investigate the luminescence of multiwall BNNTs. By performing cathodoluminescence experiments on single tubes at 10 K, we show that the tube luminescence is highly heterogeneous (i) from tube to tube and (ii) spatially along a single tube. By combining cathodoluminescence measurements with a nanometer excitation and transmission electron microscopy on the same tube, we correlate luminescence and structural features. We conclude that the near-band-edge luminescence of BNNTs (≈5.4 eV) is related to the presence of extended structural defects, such as dislocations or ruptures in the wall stacking.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Designing high-power, octave spanning entangled photon sources for quantum spectroscopy

Entangled photon spectroscopy is a nascent field that has important implications for measurement and imaging across chemical, biology, and materials fields. Entangled photon spectroscopy potentially offers improved spatial and temporal-frequency resolutions, increased cross sections for multiphoton and nonlinear measurements, and new abilities in inducing or measuring quantum correlations. A critical step in enabling entangled photon spectroscopies is the creation of high-flux entangled sources that can use conventional detectors as well as provide redundancy for the losses in realistic samples. Here, we report a periodically poled, chirped, lithium tantalate platform that generates entangled photon pairs with ~10 -7 efficiency. For a near watt level diode laser, this results in a near μW-level flux. The single photon per mode limit that is necessary to maintain non-classical photon behavior is still satisfied by distributing this power over up to an octave-spanning bandwidth. The spectral–temporal photon correlations are observed via a Michelson-type interferometer that measures the broadband Hong–Ou–Mandel two-photon interference. A coherence time of 245 fs for a 10 nm bandwidth in the collinear case and a coherence time of 62 fs for a 125 nm bandwidth in the non-collinear case are measured using a CW pump laser and, essentially, collecting the full photon cone. We outline in detail the numerical methods used for designing and tailoring the entangled photons source, such as changing center wavelength or bandwidth, with the ultimate aim of increasing the availability of high-flux UV–Vis entangled photon sources in the optical spectroscopy community.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Cr-K EMISSION LINE AS A CONSTRAINT ON THE PROGENITOR PROPERTIES OF SUPERNOVA REMNANTS

We perform a survey of the Cr, Mn, and Fe-K emission lines in young supernova remnants (SNRs) with the Japanese X-ray astronomy satellite Suzaku. The Cr and/or Mn emission lines are detected in 3C 397 and 0519-69.0 for the first time. We also confirm the detection of these lines in Kepler, W49B, N103B, and Cas A. We derive the line parameters (i.e., the line centroid energy, flux, and equivalent width (EW)) for these six sources and perform a correlation analysis for the line center energies of Cr, Mn, and Fe. Also included in the correlation analysis are Tycho and G344.7-0.1 for which the Cr, Mn, and Fe-K line parameters were available in the literature through Suzaku observations. We find that the line center energies of Cr correlate very well with that of Fe and that of Mn. This confirms our previous findings that Cr, Mn, and Fe are spatially co-located, share a similar ionization state, and have a common origin in the supernova nucleosynthesis. We find that the ratio of the EW of the Cr emission line to that of Fe ({gamma}{sub Cr/Fe}{identical_to}EW(Cr)/EW(Fe)) provides useful constraints on the SNR progenitors and on the SN explosion mechanisms: for SNRs with {gamma}{sub Cr/Fe} > 2%, a Type Ia origin is favored (e.g., N103B, G344.7-0.1, 3C 397, and 0519-69.0); for SNRs with {gamma}{sub Cr/Fe} < 2%, they could be of either core-collapse origin or carbon-deflagration Ia origin.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Searches for clustering in the time integrated skymap of the ANTARES neutrino telescope

This paper reports a search for spatial clustering of the arrival directions of high energy muon neutrinos detected by the ANTARES neutrino telescope. An improved two-point correlation method is used to study the autocorrelation of 3058 neutrino candidate events as well as cross-correlations with other classes of astrophysical objects: sources of high energy gamma rays, massive black holes and nearby galaxies. No significant deviations from the isotropic distribution of arrival directions expected from atmospheric backgrounds are observed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Density and magnetic fluctuations in type III-ELM pedestal evolution in JET: experimental and numerical characterization

Density and magnetic fluctuation measurements in low-β type-III ELM discharges are obtained in the Joint European Torus (JET). They are observed during the inter-ELM pedestal evolution, after the LH transition phase, at about 60–70 kHz. Density fluctuations are measured with a correlation reflectometer system installed on the low-field side and they are localized at the pedestal top. Magnetic fluctuations with a spatial scale $k_y\rho_i\sim 0.1$ are measured through a high resolution coil array. The main features and the relations with local plasma parameters are presented. The nature of these fluctuations is discussed along with linear gyrokinetic simulations. Ion temperature gradient (ITG) modes are the dominant instabilities in the frequency range of interest. In terms of radial localization, typical oscillation frequency and qualitative relation with the possible linear drive, ITG modes are consistent with the experimental density fluctuations measurements. Micro-tearing modes (MTMs), found unstable with a lower growth rate, appear a possible explanation for magnetic fluctuations in terms of typical wavenumbers and direction of propagation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Spin-orbit excitons in CoO

CoO has an odd number of electrons in its unit cell, and therefore is expected to be metallic. Yet, CoO is strongly insulating owing to significant electronic correlations, thus classifying it as a Mott insulator. We investigate the magnetic fluctuations in CoO using neutron spectroscopy. Here, the strong and spatially far-reaching exchange constants reported recently [P. M. Sarte et al., Phys. Rev. B 98, 024415 (2018)], combined with the single-ion spin-orbit coupling of similar magnitude [R. A. Cowley et al., Phys. Rev. B 88, 205117 (2013)] results in significant mixing between jeff spin-orbit levels in the low-temperature magnetically ordered phase. The high degree of entanglement, combined with the structural domains originating from the Jahn-Teller structural distortion at ~300K, make the magnetic excitation spectrum highly structured in both energy and momentum. We extend previous theoretical work on PrTl 3 [W. J. L. Buyers et al., Phys. Rev. B 11, 266 (1975)] to construct a mean-field and multilevel spin-orbit exciton model employing the aforementioned spin exchange and spin-orbit coupling parameters for coupled Co 2+ ions lying on a rocksalt lattice. This parametrization, based on a tetragonally distorted type-II antiferromagnetic unit cell, captures both the sharp low-energy excitations at the magnetic zone center, and the energy broadened peaks at the zone boundary. However, the model fails to describe the momentum dependence of the excitations at high-energy transfers, where the neutron response decays faster with momentum than the Co 2+ form factor. We discuss such a failure in terms of a possible breakdown of localized spin-orbit excitons at high-energy transfers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Poloidal and toroidal plasmons and fields of multilayer nanorings

Composite and janus type metallodielectric nanoparticles are increasingly considered as a means to control the spatial and temporal behavior of electromagnetic fields in diverse applications such as coupling to quantum emitters, achieving invisibility cloaks, and obtaining quantum correlations between qubits. We investigate the surface modes of a toroidal nanostructure and obtain the canonical plasmon dispersion relations and resonance modes for arbitrarily layered nanorings. Unlike particle plasmon eigenmodes in other geometries, the amplitudes of the eigenmodes of tori exhibit a distinct forward and backward coupling. We present the plasmon dispersion relations for several relevant toroidal configurations in the quasistatic limit and obtain the dominant retarded dispersion relations of a single ring for comparison, discuss mode complementarity and hybridization, and introduce two new types of toroidal particles in the form of janus nanorings. The resonance frequencies for the first few dominant modes of a ring composed of plasmon supporting materials such as gold, silver, and aluminum are provided and compared to those for a silicon ring. A generalized Green's function is obtained for multilayer tori allowing for calculation of the scattering response to interacting fields. Employing the Green's function, the scalar electric potential distribution corresponding to individual poloidal and toroidal modes in response to an arbitrarily polarized external field and the field of electrons is obtained. The results are applied to obtain the local density of states and decay rate of a dipole near the center of the torus.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Accessing the Spectral Function in a Current-Carrying Device

The presence of an electrical transport current in a material is one of the simplest and most important realizations of nonequilibrium physics. The current density breaks the crystalline symmetry and can give rise to dramatic phenomena, such as sliding charge density waves, insulator-to-metal transitions, or gap openings in topologically protected states. Almost nothing is known about how a current influences the electron spectral function, which characterizes most of the solid’s electronic, optical, and chemical properties. In this work, we show that angle-resolved photoemission spectroscopy with a nanoscale light spot provides not only a wealth of information on local equilibrium properties, but also opens the possibility to access the local nonequilibrium spectral function in the presence of a transport current. Unifying spectroscopic and transport measurements in this way allows simultaneous noninvasive local measurements of the composition, structure, many-body effects, and carrier mobility in the presence of high current densities. In the particular case of our graphene-based device, we are able to correlate the presence of structural defects with locally reduced carrier lifetimes in the spectral function and a locally reduced mobility with a spatial resolution of 500 nm.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

WE-E-17A-06: Assessing the Scale of Tumor Heterogeneity by Complete Hierarchical Segmentation On MRI

Purpose: In many cancers, intratumoral heterogeneity exists in vascular and genetic structure. We developed an algorithm which uses clinical imaging to interrogate different scales of heterogeneity. We hypothesize that heterogeneity of perfusion at large distance scales may correlate with propensity for disease recurrence. We applied the algorithm to initial diagnosis MRI of rhabdomyosarcoma patients to predict recurrence. Methods: The Spatial Heterogeneity Analysis by Recursive Partitioning (SHARP) algorithm recursively segments the tumor image. The tumor is repeatedly subdivided, with each dividing line chosen to maximize signal intensity difference between the two subregions. This process continues to the voxel level, producing segments at multiple scales. Heterogeneity is measured by comparing signal intensity histograms between each segmented region and the adjacent region. We measured the scales of contrast enhancement heterogeneity of the primary tumor in 18 rhabdomyosarcoma patients. Using Cox proportional hazards regression, we explored the influence of heterogeneity parameters on relapse-free survival (RFS). To compare with existing methods, fractal and Haralick texture features were also calculated. Results: The complete segmentation produced by SHARP allows extraction of diverse features, including the amount of heterogeneity at various distance scales, the area of the tumor with the most heterogeneity at each scale, and for a given point in the tumor, the heterogeneity at different scales. 10/18 rhabdomyosarcoma patients suffered disease recurrence. On contrast-enhanced MRI, larger scale of maximum signal intensity heterogeneity, relative to tumor diameter, predicted for shorter RFS (p=0.05). Fractal dimension, fractal fit, and three Haralick features did not predict RFS (p=0.09-0.90). Conclusion: SHARP produces an automatic segmentation of tumor regions and reports the amount of heterogeneity at various distance scales. In rhabdomyosarcoma, RFS was shorter when the primary tumor exhibited larger scale of heterogeneity on contrast-enhanced MRI. If validated on a larger dataset, this imaging biomarker could be useful to help personalize treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Moist Process Biases in Simulations of the Madden–Julian Oscillation Episodes Observed during the AMIE/DYNAMO Field Campaign

Two Madden–Julian oscillation (MJO) episodes observed during the 2011 Atmospheric Radiation Measurement Program MJO Investigation Experiment (AMIE)/DYNAMO field campaign are simulated using a regional model with various cumulus parameterizations, a regional cloud-permitting model, and a global variable-resolution model with a high-resolution region centered over the tropical Indian Ocean. Model biases in relationships relevant to existing instability theories of MJO are examined and their relative contributions to the overall model errors are quantified using a linear statistical model. The model simulations capture the observed approximately log-linear relationship between moisture saturation fraction and precipitation, but precipitation associated with the given saturation fraction is overestimated especially at low saturation fraction values. This bias is a major contributor to the excessive precipitation during the suppressed phase of MJO. After accounting for this bias using a linear statistical model, the spatial and temporal structures of the model-simulated MJO episodes are much improved, and what remains of the biases is strongly correlated with biases in saturation fraction. The excess precipitation bias during the suppressed phase of the MJO episodes is accompanied by excessive column-integrated radiative forcing and surface evaporation. A large portion of the bias in evaporation is related to biases in wind speed, which are correlated with those of precipitation. Furthermore, these findings suggest that the precipitation bias sustains itself at least partly by cloud radiative feedbacks and convection–surface wind interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Develop and Test TXM Battery Cells

Summary of the specific research and project accomplishments: The team combined their knowledge and expertise in x-ray science and electrochemistry to quantify lithium concentration gradients for commercially relevant metal oxide cathodes at rates up to 6C. Completion of the project required several significant technical developments including new x-ray experimental methodologies, high-speed and high-accuracy sample multiplexers and a new class of x-ray compatible cells. The results from thin and thick electrodes demonstrated that both spatial heterogeneity and concentration gradients through the thickness of the cathode may be present. The relevance of either phenomena appears to be correlated to aspects of the electrode such as calendaring in addition to the configuration of the experiment (e.g. force between the anode and cathode).

25 ENERGY STORAGE↗
DOE OSTI2016

MultiDimChemImaging v1.30

The purpose of this software is to correlate and visualize multidimensional chemical images where the different modalities were collected with different resolution and/or offset. List of features: - change dimension of data stored in XYZ (XYcoordinate, value) or Comma Separated Values (CSV) formats via bipolar or bicubic interpolation - determine and apply offset between different modalities - create a multimodal image file from multiple single modalities in Tab Separate Values (TSV) or TissueViewTM (industry standard for chemical image visualization) formats - visualize and save (whole or partial) composite chemical images made of multiple (up to 3 at once) modalities Specific application: correlated multidimensional chemical imaging by AFM-based nano-thermal (nano-TA) analysis coupled to spectroscopy and mass spectrometry for spatially resolved surface analysis. In case of a phase separated polymer film, the modalities were: 1. topography image 203. IR images collected at two different wavelengths 4-5. mass spectral chemical images of two different m/z values.

Kertesz, Vilmos↗
DOE OSTI2012

Diagnostic performance of the beam emission spectroscopy system on the National Spherical Torus Experiment

The beam emission spectroscopy system on the National Spherical Torus Experiment measures localized density fluctuations on the ion gyroscale. Optical sightlines provide core to edge radial coverage, and the sightlines are aligned to typical pitch angles to maximize cross-field spatial resolution. Sightline images are 2-3 cm, and point spread function calculations indicate image distortion from pitch angle misalignment and atomic state finite lifetimes is minor with a 15% increase in the image size. New generation photodetectors achieve photon noise limited measurements at frequencies up to 400 kHz with refrigerant cooling at -20 Degree-Sign C. Measurements near the pedestal show broadband turbulence up to 100 kHz, and poloidal correlation lengths are about 10 cm. Plasma turbulence signals can be 2-3 orders of magnitude above photon noise and amplifier thermal noise.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗