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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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The reaction rates of lanthanide and actinide cations with CO 2 are dictated by the crossing between the potential energy surface (PES) evolving from the ground state reactants (red) and the PES leading to the ground state products (green).
Use of a microextraction device allows for ready sampling of solid substrates, such as cotton swipes, allowing transfer of sub-microgram quantities for multielement ICP-MS analysis.
Great efforts have been made in the last few decades to realize electronic devices based on organic molecules. A possible approach in this field is to exploit the chirality of organic molecules for the development of spintronic devices, an applicative way to implement the chiral-induced spin selectivity (CISS) effect. In this work we exploit enantiopure tetrathiafulvalene (TTF) derivatives as chiral inducers at the nanoscale. The aim is to make use of TTF's well-known and unique semiconducting properties, to be expressed in the fields of enantio-selectivity and the chiral-induced spin selectivity (CISS) effect. Further, the experimental results shown in this paper further demonstrate how chirality and spin are deeply interrelated, as foreseen within the CISS effect theory, paving the way for the application of TTF derivatives in the field of spintronics. In this work, we demonstrate that tetramethyl-bis(ethylenedithio)-tetrathiafulvalene (TM-BEDT-TTF) (1) behaves as an efficient spin filter, as evidenced by magneto-atomic force microscopy (mc-AFM) measurements. Additionally, it is shown to be effective in transferring chirality to CdS/CdSe core–shell nanoparticles, as inferred from the analysis of circularly resolved photoluminescence spectra. This makes 1 a promising candidate for a variety of applications, ranging from plasmonics to quantum computing.
Synergetic interactions between ruthenium and molybdenum oxide weaken H adsorption on ruthenium active sites and hence enhance the electrocatalytic activity towards hydrogen evolution reaction.
Lanthanide reactivity is limited by the energy required to access an electronic configuration with two unpaired non-f electrons.
In this work, two compact, permanent magnet, electron spectrometers have been built to measure the electron beam energy at the Dual Axis Radiographic Hydrodynamic Test facility. Using H - and OH - anions, the spectrometers were calibrated at the Special Technologies Laboratory in Santa Barbara, California (USA). The spectrometers were mounted on a custom drift tube that allows the magnet assemblies to be translated, which increases the path length of the electrons traveling through the magnetic field and therefore increases the upper bound of the measurable electron kinetic energy. The measurable range of electron kinetic energies is between 2.8 MeV–4.1 MeV for the first spectrometer and 14.1 MeV–21.1 MeV for the second spectrometer, with an overall measurement uncertainty of 0.32%.
Amorphous ferromagnetic microwires fabricated by water-quenching have been assessed to show favorable properties for next-generation high-frequency electric machines as compared to those of conventional amorphous magnetic alloys in sheet or ribbon form. Here, water-quenched amorphous Fe 75 Si 10 B 15 microwires were subjected to a range of aging times of up to 5 years in the air at room temperature. While both newer and aged microwires are X-ray amorphous, the aged microwires do exhibit a slight degree of crystallinity, a lower initial susceptibility and a reduced enthalpy change for full devitrification. These small differences (typically < 5%) are attributed to the formation of minor surface oxidation products such as iron oxides and SiO 2 which modify the surface strain state. The resultant stress couples to magnetostriction to promote the formation of radial magnetic domains that impair the magnetic reversal process. These results demonstrate that while amorphous ferromagnetic microwires are essentially stable against aging in the air, consideration of their surface state will be significant for advanced applications.
Abstract Time-resolved ultrafast spectroscopy has emerged as a promising tool to dynamically induce and manipulate non-trivial electronic states of matter out-of-equilibrium. Here we theoretically investigate light pulse driven dynamics in a Kondo lattice system close to quantum criticality. Based on a time-dependent auxiliary fermion mean-field calculation we show that light can dehybridize the local Kondo screening and induce oscillating magnetic order out of a previously paramagnetic state. Depending on the laser pulse field amplitude and frequency the Kondo singlet can be completely deconfined, inducing a dynamic Lifshitz transition that changes the Fermi surface topology. These phenomena can be identified in harmonic generation and time-resolved angle-resolved photoemission spectroscopy spectra. Our results shed new light on non-equilibrium states in heavy fermion systems.
Sawtooth crashes on tokamak plasmas exhibit relaxation much faster than resistive time scales via a mechanism not fully understood. Using core magnetic measurements from the Radial Interferometer-Polarimeter (RIP) diagnostic on the DIII-D tokamak, Grad–Shafranov equilibria constrained by internal magnetic measurements that have high time resolution (<1μs) can be computed, allowing analysis of how equilibrium parameters such as safety factor q, current density J, and parallel electric field E ∥ , particularly on-axis, evolve. At the sawtooth crash, on-axis safety factor q 0 is observed to rise by 5% but remain below 1 throughout the cycle, and on-axis current density J 0 is observed to drop by 5%. On-axis parallel electric field E ∥ (0) is found to be balanced by ηJ 0 (resistivity times on-axis current density) except during the 200 µs crash period, where E ∥ (0) reaches 22 V m –1 , exceeding ηJ 0 by a factor of more than 2000. These first measurements in tokamak plasmas verify that generalized Ohm's law is not balanced during the crash by resistive effects alone; this is a finding expected due to the relaxation being much faster than resistive timescales. As a result, measurement of the electric field during the tokamak sawtooth serves to illuminate the physical mechanisms at work.
Spherical tokamaks (STs) have been shown to possess properties desirable for a fusion power plant such as achieving high plasma β and having increased vertical stability. To understand the confinement properties that might be expected in the conceptual design for a high β ST fusion reactor, a 1 GW ST plasma equilibrium was analyzed using local linear gyrokinetics to determine the type of micro-instabilities that arise. Kinetic ballooning modes and micro-tearing modes are found to be the dominant instabilities. The parametric dependence of these linear modes was determined and, from the insights gained, the equilibrium was tuned to find a regime marginally stable to all micro-instabilities at θ 0 = 0.0. This work identifies the most important micro-instabilities expected to generate turbulent transport in high β STs. The impact of such modes must be faithfully captured in first-principles-based reduced models of anomalous transport that are needed for predictive simulations.
One of the primary shortcomings of the surface nuclear magnetic resonance (NMR) freeinduction decay (FID) measurement is the uncertainty surrounding which mechanism controls the signal’s time dependence. Ideally, the FID-estimated relaxation time T$*\atop{2}$ that describes the signal’s decay carries an intimate link to the geometry of the pore space. In this limit the parameter T$*\atop{2}$ is closely linked to a related parameter T 2 , which is more closely linked to pore-geometry. If T$*\atop{2}$ T 2 the FID can provide valuable insight into relative pore-size and can be used to make quantitative permeability estimates. However, given only FID measurements it is difficult to determine whether T$*\atop{2}$ is linked to pore geometry or whether it has been strongly influenced by background magnetic field inhomogeneity. If the link between an observed T$*\atop{2}$ and the underlying T 2 could be further constrained the utility of the standard surface NMR FID measurement would be greatly improved. We hypothesize that an approach employing an updated surface NMR forward model that solves the full Bloch equations with appropriately weighted relaxation terms can be used to help constrain the T$*\atop{2}$ –T 2 relationship. Weighting the relaxation terms requires estimating the poorly constrained parameters T 2 and T 1 ; to deal with this uncertainty we propose to conduct a parameter search involving multiple inversions that employ a suite of forward models each describing a distinct but plausible T$*\atop{2}$ –T 2 relationship. We hypothesize that forward models given poor T 2 estimates will produce poor data fits when using the complex-inversion, while forward models given reliable T 2 estimates will produce satisfactory data fits. By examining the data fits produced by the suite of plausible forward models, the likely T$*\atop{2}$ –T 2 can be constrained by identifying the range of T 2 estimates that produce reliable data fits. Synthetic and field results are presented to investigate the feasibility of the proposed technique.
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