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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Communication: Spin densities within a unitary group based spin-adapted open-shell coupled-cluster theory: Analytic evaluation of isotropic hyperfine-coupling constants for the combinatoric open-shell coupled-cluster scheme

We report analytical calculations of isotropic hyperfine-coupling constants in radicals using a spin-adapted open-shell coupled-cluster theory, namely, the unitary group based combinatoric open-shell coupled-cluster (COSCC) approach within the singles and doubles approximation. A scheme for the evaluation of the one-particle spin-density matrix required in these calculations is outlined within the spin-free formulation of the COSCC approach. In this scheme, the one-particle spin-density matrix for an open-shell state with spin S and M{sub S} = + S is expressed in terms of the one- and two-particle spin-free (charge) density matrices obtained from the Lagrangian formulation that is used for calculating the analytic first derivatives of the energy. Benchmark calculations are presented for NO, NCO, CH{sub 2}CN, and two conjugated π-radicals, viz., allyl and 1-pyrrolyl in order to demonstrate the performance of the proposed scheme.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

From closed shells to open shells: Coupled-cluster calculations of atomic nuclei

Coupled-cluster theory is a powerful tool for first-principles calculations of atomic nuclei, enabling accurate predictions of nuclear observables across the Segrè chart. While coupled-cluster computations are especially efficient at shell closures, extensions have been developed to tackle open-shell nuclei, by exploiting the equation-of-motion method or by expanding the coupled-cluster wave function on top of a symmetry-breaking (either deformed or superfluid) reference state. In this study, we provide a comprehensive comparison of these different formulations applied to the calcium and nickel isotopes using nuclear two-and three-body interactions from chiral effective field theory. Here, based on ground-state energies, two-neutron separation energies, and two-neutron shell gaps, different coupled-cluster computations—based on symmetry-broken reference states and equationof-motion techniques— offer consistent descriptions of bulk properties across medium-mass isotopic chains.

Marino, Francesco [Johannes Gutenberg-Universität ↗
DOE OSTI2014

The decays of on-shell and off-shell polarized gauge bosons into massive quark pairs at NLO QCD

We discuss the polar angle decay distribution in the decay of on-shell and off-shell polarized (W, Z) gauge bosons into massive quark pairs. In particular for the off-shell decays in H→(W,Z)+(W{sup ∗},Z{sup ∗})(→q{sub 1}, q-vector {sub 2}) it is important to keep the masses of the charm and bottom quarks at their finite values since the scale of the problem is not set by m{sup 2}{sub W,Z }but by the offshellness of the gauge boson which varies in the range (m {sub 1} + m {sub 2}){sup 2} ≤ q {sup 2} ≤ (m {sub H }− m {sub W,Z }){sup 2}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Dual Functional Ni3S2@Ni Core-Shell Nanoparticles Decorating Nanoporous Carbon as Cathode Scaffolds for Lithium-Sulfur Battery with Lean Electrolytes

Lithium-sulfur batteries are very promising for next-generation energy storage. However, most studies use flooded electrolytes to achieve a high specific capacity at the expense of lowering the specific energy. Understanding lithium-sulfur battery performance with lean electrolytes is highly desirable. Herein, a modified Pechini method is developed to synthesize a nanoporous carbon host decorated with Ni3S2@Ni particles. Such a cathode delivers enhanced specific capacities with extended cycling life in lean electrolytes, due to the dual functions of the Ni3S2 shell, which can both facilitate reaction kinetics and promote electrolyte wetting. This work highlights a strategy to rationally design cathodes for highenergy lithium-sulfur batteries.

Zhang, Yulun↗
DOE OSTI2021

Bioresorbable Primary Battery Anodes Built on Core–Double-Shell Zinc Microparticle Networks

Bioresorbable implantable electronics require power sources that are also bioresorbable with controllable electrical output and lifetime. In this paper, we report a bioresorbable zinc primary battery anode filament based on a zinc microparticle (MP) network coated with chitosan and Al 2 O 3 double shells. When discharged in 0.9% NaCl saline, a Zn MP filament with a 0.17 × 2 mm 2 cross-sectional area exhibited a stable voltage output of 0.55 V at a current of 0.01 mA. Covered by chitosan and Al 2 O 3 double shells, the zinc MP filament exhibited a directional dissolution behavior with a tunable lifetime approximately linear to its length. A stable 200 h discharging time was achieved with a 15 mm Zn MP filament. The maximum output power was found to be 12 μW at 0.03 mA for one filament. The linearity relationship between the current output and the filament cross-sectional area suggested a facile strategy to raise the power output at constant discharging voltage. The filaments could also be connected in series and in parallel to boost its overall voltage and current output, demonstrating their excellent integration capability. Furthermore, this work presents a promising pathway toward bioresorbable transient batteries with controllable lifetime and power output, demonstrating a great potential for powering transient implantable biomedical devices.

25 ENERGY STORAGE↗
DOE OSTI2013

Single-neutron levels near the N=82 shell closure

The (d, p) reaction was measured with the radioactive ion beams of {sup 126}Sn and {sup 128}Sn in inverse kinematics at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory, utilizing the Super ORRUBA silicon detector array. Angular distributions of reaction protons were measured for several states in {sup 127}Sn and {sup 129}Sn to determine angular momentum transfers and deduce spectroscopic factors. Such information is critical for calculating direct (n,{gamma}) cross sections for the r-process as well as for constraining shell model parameters in the A Almost-Equal-To 130 region. Combined with previous experiments on {sup 130}Sn and {sup 132}Sn, these results will provide a complete set of (d, p) reaction data on even tin isotopes between stable {sup 124}Sn and doubly-magic {sup 132}Sn.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

L-shell spectroscopic diagnostics of radiation from krypton HED plasma sources

X-ray spectroscopy is a useful tool for diagnosing plasma sources due to its non-invasive nature. One such source is the dense plasma focus (DPF). Recent interest has developed to demonstrate its potential application as a soft x-ray source. We present the first spectroscopic studies of krypton high energy density plasmas produced on a 3 kJ DPF device in Singapore. In order to diagnose spectral features, and to obtain a more comprehensive understanding of plasma parameters, a new non-local thermodynamic equilibrium L-shell kinetic model for krypton was developed. It has the capability of incorporating hot electrons, with different electron distribution functions, in order to examine the effects that they have on emission spectra. To further substantiate the validity of this model, it is also benchmarked with data gathered from experiments on the electron beam ion trap (EBIT) at Lawrence Livermore National Laboratory, where data were collected using the high resolution EBIT calorimeter spectrometer.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

LOW MACH NUMBER MODELING OF CONVECTION IN HELIUM SHELLS ON SUB-CHANDRASEKHAR WHITE DWARFS. I. METHODOLOGY

We assess the robustness of a low Mach number hydrodynamics algorithm for modeling helium shell convection on the surface of a white dwarf in the context of the sub-Chandrasekhar model for Type Ia supernovae. We use the low Mach number stellar hydrodynamics code, MAESTRO, to perform three-dimensional, spatially adaptive simulations of convection leading up to the point of the ignition of a burning front. We show that the low Mach number hydrodynamics model provides a robust description of the system.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Reaction Pathway to the Only Open-Shell Transition-Metal Keggin Ion without Organic Ligation: Reaction Pathway to the Only Open-Shell Transition-Metal Keggin Ion without Organic Ligation

Aqueous metal-oxo clusters without organic ligands (including polyoxometalates and group 13 polycations) are useful for energy, environmental and biomolecular applications. While ligands stabilize clusters of different elements, such as open-shell transition metals, they inhibit reactivity and solubility. Therefore a grand challenge is to conceive and execute synthetic strategies to isolate metal-oxo clusters of any composition, without ligation. Here we crystallize and structurally characterize a Cr 3+ dodecamer Keggin ion without organic ligation. Detailed characterization of its formation leads to understanding its reaction pathway, which may translate to isolation of other open-shell transition metal-oxo clusters. We employed electrospray ionization mass spectrometry, Raman spectroscopy and X-ray scattering (small-angle and total) to identify important reaction intermediates and processes. The aqueous synthesis presented here is simple to implement and scalable, producing pure phase materials in gram quantities.

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

Measurement of L-shell transitions in M-shell ions in the laboratory and identification in stellar coronae

Based on laboratory data from the Lawrence Livermore EBIT-I electron beam ion trap and calculations using the relativistic multi-reference Møller-Plesset (MRMP) perturbation theory approach, we identify L-shell transitions of M-shell iron ions in emission spectra of the nearby stars Capella and Procyon. In conclusion, these lines are weaker than the well known, prominent lines from Fe XVII. However, they need to be taken into account when modeling the spectra, especially of cool stars.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2022

Core–Shell Covalently Linked Graphitic Carbon Nitride–Melamine–Resorcinol–Formaldehyde Microsphere Polymers for Efficient Photocatalytic CO 2 Reduction to Methanol

Photocatalytic reduction of CO 2 with light and H 2 O to form CH 3 OH is a promising route to mitigate carbon emissions and climate changes. Although semiconducting metal oxides are potential photocatalysts for this reaction, low photon efficiency and leaching of environmental unfriendly, toxic metals limit their applicability. Here, we report a metal-free, core-shell photocatalysts consisting of graphitic carbon nitride (g-C 3 N 4 , CN) covalently linked to melamine-resorcinol-formaldehyde (MRF) microsphere polymers for this reaction. Cova-lent linkage enabled efficient separation of photo-generated carriers and photocatalysis. Using 100 mg of a photocatalyst containing 15 wt.% CN, a CH 3 OH yield of 0.99 μmol·h -1 was achieved at a reaction temperature of 80 °C and 0.5 MPa with external quantum efficiencies ranging from 5.5% at 380 nm to 1.7% at 550 nm. The yield was about 20 and 10 times higher than that of its components CN and MRF, respectively. Characterization with XPS, TEM, and bulk and surface elemental analyses supported a core-shell structure and charge transfer at C-N bond at the CN-MRF interface between the methoxy group in the 2,4-trishydroxylmethyl-1,3-diphenol part of MRF and the terminal amino groups in the CN. This enhanced ligand-to-ligand charge transfer resulted in 67% of photo-excited internal charge transferred from CN to hy-droxymethylamino group in MRF, whose amino group was the catalytic site for CO 2 photocatalytic reduction to CH 3 OH. Furthermore, this study provides a series of new metal-free photocatalyst designs and insights into the molecular-level structure-mediated photocatalytic response

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

Alginate–peptide amphiphile core–shell microparticles as a targeted drug delivery system

We describe in this work the synthesis of microparticles with a doxorubicin drug conjugated alginate core and a shell of peptide amphiphile nanofibres functionalized for targeting the folate receptor. The spherical geometry of the particle core allows high drug loading per surface area, whereas the nanoscale fibrous shell formed by self-assembly of peptide amphiphiles offers a high surface to volume ratio that is ideal for targeting. Furthermore, the synthesised microparticles have a 60-fold higher cytotoxicity against MDA-MB-231 breast cancer cells compared to non-targeting particles.

77 NANOSCIENCE AND NANOTECHNOLOGY↗