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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

CONSTRAINTS ON VERY HIGH ENERGY EMISSION FROM GRB 130427A

Prompt emission from the very fluent and nearby (z = 0.34) gamma-ray burst GRB 130427A was detected by several orbiting telescopes and by ground-based, wide-field-of-view optical transient monitors. Apart from the intensity and proximity of this GRB, it is exceptional due to the extremely long-lived high-energy (100 MeV to 100 GeV) gamma-ray emission, which was detected by the Large Area Telescope on the Fermi Gamma-Ray Space Telescope for ∼70 ks after the initial burst. The persistent, hard-spectrum, high-energy emission suggests that the highest-energy gamma rays may have been produced via synchrotron self-Compton processes though there is also evidence that the high-energy emission may instead be an extension of the synchrotron spectrum. VERITAS, a ground-based imaging atmospheric Cherenkov telescope array, began follow-up observations of GRB 130427A ∼71 ks (∼20 hr) after the onset of the burst. The GRB was not detected with VERITAS; however, the high elevation of the observations, coupled with the low redshift of the GRB, make VERITAS a very sensitive probe of the emission from GRB 130427A for E > 100 GeV. The non-detection and consequent upper limit derived place constraints on the synchrotron self-Compton model of high-energy gamma-ray emission from this burst.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Effect Modification by Age on the Benefit or Harm of Antihypertensive Treatment for Elderly Hypertensives: A Systematic Review and Meta-analysis

Abstract BACKGROUND The influence of age on balance of benefit vs. potential harm of blood pressure (BP)-lowering therapy for elderly hypertensives is unclear. We evaluated the modifying effects of age on BP lowering for various adverse outcomes in hypertensive patients older than 60 years without specified comorbidities. METHODS All relevant randomized controlled trials (RCTs) were systematically identified. Coronary heart disease, stroke, heart failure (HF), cardiovascular death, major adverse cardiovascular events (MACE), renal failure (RF), and all-cause death were assessed. Meta-regression analysis was used to explore the relationship between achieved systolic BP (SBP) and the risk of adverse events. Random-effects meta-analysis was used to pool the estimates. RESULTS Our study included 18 RCTs (n = 53,993). Meta-regression analysis showed a lower achieved SBP related with a lower risk of stroke and cardiovascular death, but an increased risk of RF. The regression slopes were comparable between populations stratifying by age 75 years. In subgroup analysis, the relative risks of a more aggressive BP lowering strategy were similar between patients aged older or less than 75 years for all outcomes except for RF (P for interaction = 0.02). Compared to treatment with final achieved SBP 140–150 mm Hg, a lower achieved SBP (<140 mm Hg) was significantly associated with decreased risk of stroke (relative risk = 0.68; 95% confidence interval = 0.55–0.85), HF (0.77; 0.60–0.99), cardiovascular death (0.68; 0.52–0.89), and MACE (0.83; 0.69–0.99). CONCLUSIONS To treat hypertension in the elderly, age had trivial effect modification on most outcomes, except for renal failure. Close monitoring of renal function may be warranted in the management of elderly hypertension.

Huang, Chi-Jung↗
DOE OSTI2021

RhizoVision Explorer: open-source software for root image analysis and measurement standardization

Abstract Roots are central to the function of natural and agricultural ecosystems by driving plant acquisition of soil resources and influencing the carbon cycle. Root characteristics like length, diameter and volume are critical to measure to understand plant and soil functions. RhizoVision Explorer is an open-source software designed to enable researchers interested in roots by providing an easy-to-use interface, fast image processing and reliable measurements. The default broken roots mode is intended for roots sampled from pots and soil cores, washed and typically scanned on a flatbed scanner, and provides measurements like length, diameter and volume. The optional whole root mode for complete root systems or root crowns provides additional measurements such as angles, root depth and convex hull. Both modes support providing measurements grouped by defined diameter ranges, the inclusion of multiple regions of interest and batch analysis. RhizoVision Explorer was successfully validated against ground truth data using a new copper wire image set. In comparison, the current reference software, the commercial WinRhizo™, drastically underestimated volume when wires of different diameters were in the same image. Additionally, measurements were compared with WinRhizo™ and IJ_Rhizo using a simulated root image set, showing general agreement in software measurements, except for root volume. Finally, scanned root image sets acquired in different labs for the crop, herbaceous and tree species were used to compare results from RhizoVision Explorer with WinRhizo™. The two software showed general agreement, except that WinRhizo™ substantially underestimated root volume relative to RhizoVision Explorer. In the current context of rapidly growing interest in root science, RhizoVision Explorer intends to become a reference software, improve the overall accuracy and replicability of root trait measurements and provide a foundation for collaborative improvement and reliable access to all.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Pilot testing of CO2 capture from a coal-fired power plant—Part 2: Results from 1-MWe pilot tests

Abstract Using a 1-MWe slipstream pilot plant, solid-sorbent-based post-combustion CO2 capture was tested at a coal-fired power plant. Results from pilot testing were used to develop a preliminary full-scale commercial design. The sorbent selected for pilot-scale evaluation during this project consisted of an ion-exchange resin that incorporated amines covalently bonded to the substrate. A unique temperature-swing-absorption (TSA) process was developed that incorporated a three-stage fluidized-bed adsorber integrated with a single-stage fluidized-bed regenerator. Overall, following start-up and commissioning challenges that are often associated with first-of-a-kind pilots, the pilot plant operated as designed and expected, with a few key exceptions. The two primary exceptions were associated with: (i) handling characteristics of the sorbent, which were sufficiently different at operating temperature than at ambient temperature when design specifications were established with lab-scale testing; and (ii) CO2 adsorption in the transport line between the regenerator and adsorber that preloaded the sorbent with CO2 prior to entering the adsorber. Results from the pilot programme demonstrate that solid-sorbent-based post-combustion capture can be utilized to achieve 90% CO2 capture from coal-fired power plants.

Sjostrom, Sharon↗
DOE OSTI2020

Three new symbiotic crabs of the genus Glassella Campos & Wicksten, 1997 from Atlantic and Gulf of Mexico coasts of Florida, USA (Decapoda: Brachyura: Pinnotheridae)

Abstract New species of the pinnotherid crab genus GlassellaCampos & Wicksten, 1997 are described from western Atlantic waters along the east and west coasts of Florida, with the generic assignment of one being provisional. Glassella chaneyin. sp., Glassella martinin. sp., and Glassella taylorin. sp., all morphologically resemble the long-known species G. floridana (Rathbun, 1918) and overlap part of its distributional range, there occupying similar habitats and at least sometimes found with similar hosts. While genomic DNA sequencing has previously established the generic assignment of G. floridana, small sizes and suboptimal preservation histories of specimens representing the three new species have rendered all sequencing attempts unsuccessful, and thus not allowed their inclusion in molecular phylogenetic analyses. To facilitate present morphological comparisons, a rediagnosis of G. floridana was undertaken, and previously published illustrations were augmented, the latter now including figures of its previously undescribed male first gonopod and gonopodal plate. Comparisons of G. floridana to the three new species reveal striking diagnostic differences between all four species in their male first gonopods and varied configurations in the gonopodal plate or its probable homologs. These characters support the otherwise established separation of G. floridana from its congeners on the basis of its more strongly armed flexor margins of the fourth and fifth pereopods. In G. taylorin. sp., representing the smallest known member of Glassella, development of the third maxilliped and male first gonopod is so exceptional as to suggest the species may warrant eventual assignment to a separate genus.

Marine & Freshwater Biology↗
DOE OSTI2020

Topological nonmagnetic impurity states in topological Kondo insulators

We examine here the presence of nonmagnetic impurities in a hybridization gap model of a Kondo insulator which has band inversion. The model has been used to predict that SmB 6 is a topological insulator. We show that there are two types of nonmagnetic impurity states in a Kondo insulator. The type of states can be categorized as deep impurity states, similar to the impurity states in an ordinary metal, and impurity states which have energies within the hybridization gap. Unlike the deep impurity states which only form if the impurity potential exceeds a critical value of the order of the conduction bandwidth, the in-gap impurity states form for exceptionally small values of the impurity potential comparable to the hybridization gap. This finding may explain why Kondo insulators are found to be exceptionally sensitive to impurities. We demonstrate that these in-gap states are caused by band inversion and have properties similar to those expected for impurities in a topological insulator.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Topological descendants of a multicritical Dirac semimetal with magnetism and strain

The past decades have witnessed a transformation in characterizing condensed matter systems with topology. Aided by a refined understanding of topological band structures with crystalline symmetries that has emerged recently, many electronic phases have been identified, and a plethora of materials have been predicted to host properties and functionalities. A key underlying question, also with respect to future application, is to what extent the related physical features can be manipulated, especially in the context of magnetic order. Here, we describe a paradigmatic semimetal that simultaneously incorporates multiple and sometimes conflicting topology which guarantees gaplessness and leads to an exceptionally rich family of descendent phases on lowering symmetry. We predict that this multicritical phase is realized in EuTl 2 . Starting from the parent semimetallic state, which already separates two topological insulating regimes, the interplay of inherent magnetism and strain allows for an exceptionally rich phase diagram of topological descendant states.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Electronic and structural ground state of heavy alkali metals at high pressure

Here, alkali metals display unexpected properties at high pressure, including emergence of low symmetry crystal structures, that appear to occur due to enhanced electronic correlations among the otherwise nearly-free conduction electrons. We investigate the high pressure electronic and structural ground state of K, Rb, and Cs using x-ray absorption spectroscopy and x-ray diffraction measurements together with ab initio theoretical calculations. The sequence of phase transitions under pressure observed at low temperature is similar in all three heavy alkalis except for the absence of the oC 84 phase in Cs. Both the experimental and theoretical results point to pressure-enhanced localization of the valence electrons characterized by pseudo-gap formation near the Fermi level and strong spd hybridization. Although the crystal structures predicted to host magnetic order in K are not observed, the localization process appears to drive these alkalis closer to a strongly correlated electron state.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Direct in situ measurement of coupled magnetostructural evolution in a ferromagnetic shape memory alloy and its theoretical modeling

Ferromagnetic shape memory alloys (FSMAs) have shown great potential as active components in next generation smart devices due to their exceptionally large magnetic-field-induced strains and fast response times. During application of magnetic fields in FSMAs, as is common in several magnetoelastic smart materials, there occurs simultaneous rotation of magnetic moments and reorientation of twin variants, resolving which, although critical for design of new materials and devices, has been difficult to achieve quantitatively with current characterization methods. At the same time, theoretical modeling of these phenomena also faced limitations due to uncertainties in values of physical properties such as magnetocrystalline anisotropy energy (MCA), especially for off-stoichiometric FSMA compositions. Here, in situ polarized neutron diffraction is used to measure directly the extents of both magnetic moments rotation and crystallographic twin-reorientation in an FSMA single crystal during the application of magnetic fields. Additionally, high-resolution neutron scattering measurements and first-principles calculations based on fully relativistic density functional theory are used to determine accurately the MCA for the compositionally disordered alloy of Ni 2 Mn 1.14 Ga 0.86 . The results from these state-of-the-art experiments and calculations are self-consistently described within a phenomenological framework, which provides quantitative insights into the energetics of magnetostructural coupling in FSMAs. Furthermore, based on the current model, the energy for magnetoelastic twin boundaries propagation for the studied alloy is estimated to be ~150 kJ/m 3 .

36 MATERIALS SCIENCE↗
DOE OSTI2024

Measurement of the differential cross section for neutral pion production in charged-current muon neutrino interactions on argon with the MicroBooNE detector

We present a measurement of neutral pion production in charged-current interactions using data recorded with the MicroBooNE detector exposed to Fermilab’s booster neutrino beam. The signal comprises one muon, one neutral pion, any number of nucleons, and no charged pions. Studying neutral pion production in the MicroBooNE detector provides an opportunity to better understand neutrino-argon interactions, and is crucial for future accelerator-based neutrino oscillation experiments. Using a dataset corresponding to 6.86 ×10 20 protons on target, we present single-differential cross sections in muon and neutral pion momenta, scattering angles with respect to the beam for the outgoing muon and neutral pion, as well as the opening angle between the muon and neutral pion. Data extracted cross sections are compared to generator predictions. We report good agreement between the data and the models for scattering angles, except for an over-prediction by generators at muon forward angles. Similarly, the agreement between data and the models as a function of momentum is good, except for an underprediction by generators in the medium momentum ranges, 200–400 MeV for muons and 100–200 MeV for pions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

DMFT Reveals the Non-Hermitian Topology and Fermi Arcs in Heavy-Fermion Systems

When a strongly correlated system supports well-defined quasiparticles, it allows for an elegant one-body effective description within the non-Hermitian topological theory. While the microscopic many-body Hamiltonian of a closed system remains Hermitian, the one-body quasiparticle Hamiltonian is non-Hermitian due to the finite quasiparticle lifetime. We use such a non-Hermitian description in the heavy-fermion two-dimensional systems with the momentum-dependent hybridization to reveal a fascinating phenomenon which can be directly probed by the spectroscopic measurements, the bulk “Fermi arcs.” Starting from a simple two-band model, we first combine the phenomenological approach with the perturbation theory to show the existence of the Fermi arcs and reveal their connection to the topological exceptional points, special points in the Brillouin zone where the Hamiltonian is nondiagonalizable. The appearance of such points necessarily requires that the electrons belonging to different orbitals have different lifetimes. This requirement is naturally satisfied in the heavy-fermion systems, where the itinerant c electrons experience much weaker interaction than the localized f electrons. We then utilize the dynamical mean field theory to numerically calculate the spectral function and confirm our findings. We show here that the concept of the exceptional points in the non-Hermitian quasiparticle Hamiltonians is a powerful tool for predicting new phenomena in strongly correlated electron systems.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Quantum Squeezing and Sensing with Pseudo-Anti-Parity-Time Symmetry

The emergence of parity-time (PT) symmetry has greatly enriched our study of symmetry-enabled non-Hermitian physics, but the realization of quantum PT symmetry faces an intrinsic issue of unavoidable symmetry-breaking Langevin noises. Here we construct a quantum pseudo-anti-PT (pseudo-APT) symmetry in a two-mode bosonic system without involving Langevin noises. We show that the spontaneous pseudo-APT symmetry breaking leads to an exceptional point, across which there is a transition between different types of quantum squeezing dynamics; i.e., the squeezing factor increases exponentially (oscillates periodically) with time in the pseudo-APT-symmetric (broken) region. Such dramatic changes of squeezing factors and quantum dynamics near the exceptional point are utilized for ultraprecision quantum sensing. These exotic quantum phenomena and sensing applications can be experimentally observed in two physical systems: spontaneous wave mixing nonlinear optics and atomic Bose-Einstein condensates. Furthermore, our Letter offers a physical platform for investigating exciting APT symmetry physics in the quantum realm, paving the way for exploring fundamental quantum non-Hermitian effects and their quantum technological applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Precision Mass Measurement of the Proton Dripline Halo Candidate 22 Al

Here, we report the first mass measurement of the proton-halo candidate 22 Al performed with the low energy beam ion trap facility’s 9.4 T Penning trap mass spectrometer at facility for rare isotope beams. This measurement completes the mass information for the lightest remaining proton-dripline nucleus achievable with Penning traps. 22 Al has been the subject of recent interest regarding a possible halo structure from the observation of an exceptionally large isospin asymmetry [J. Lee et al ., Large isospin asymmetry in Si22/O22 Mirror Gamow-Teller transitions reveals the halo structure of 22 Al , Phys. Rev. Lett. 125, 192503 (2020).]. The measured mass excess value of ME=18 092.5⁢(3) keV, corresponding to an exceptionally small proton separation energy of 𝑆𝑝=100.4⁢(8) keV, is compatible with the suggested halo structure. Our result agrees well with predictions from 𝑠⁢𝑑-shell USD Hamiltonians. While USD Hamiltonians predict deformation in the 22 Al ground state with minimal 1⁢𝑠 1/2 occupation in the proton shell, a particle-plus-rotor model in the continuum suggests that a proton halo could form at large quadrupole deformation. These results emphasize the need for a charge radius measurement to conclusively determine the halo nature.

binding energy↗
DOE OSTI2025

Reducing heat load density with asymmetric and inclined double-crystal monochromators: principles and requirements revisited

Asymmetric double-crystal monochromators (aDCMs) and inclined DCMs (iDCMs) can significantly expand the X-ray beam footprint and consequently reduce the heat load density and gradient. Based on rigorous dynamical theory calculations, the major principles and properties of aDCMs and iDCMs are presented to guide their design and development, particularly for fourth-generation synchrotrons. In addition to the large beam footprint, aDCMs have very large bandwidths (up to ∼10 eV) and angular acceptance, but the narrow angular acceptance of the second crystal requires precise control of the relative orientations and strains. Based on Fourier coupled-wave diffraction theory calculations, it is rigorously proved that the iDCM has almost the same properties as the conventional symmetric DCM, including the efficiency, angular acceptance, bandwidth, tuning energy range and sensitivity to misalignment. The exception is that, for the extremely inclined geometry that can achieve very large footprint expansion, the iDCM has (beneficially) a larger bandwidth and wider angular acceptance. Inclined diffraction has the `rho-kick effect' that can be cancelled by the second reflection of the iDCM (even with misalignment), except that inhomogeneous strains may cause non-uniform rho-kick angles. At present, fabrication/mounting-induced strains pose low risk since they can be controlled to <0.5 µrad over large areas. The only uncertain challenge is the thermally induced strains, yet it is estimated that these strains are naturally lowered by the large footprint and may be further mitigated by optimized cryogenic cooling to the 1–2 µrad level. Overall, aDCMs and iDCMs have more stringent requirements than normal DCMs, but they are feasible schemes in practice.

asymmetric monochromator↗
DOE OSTI2017

Distributed Workflows for Modeling Experimental Data

Modeling helps explain the fundamental physics hidden behind experimental data. In the case of material modeling, running one simulation rarely results in output that reproduces the experimental data. Often one or more of the force field parameters are not precisely known and must be optimized for the output to match that of the experiment. Since the simulations require high performance computing (HPC) resources and there are usually many simulations to run, a workflow is very useful to prevent errors and assure that the simulations are identical except for the parameters that need to be varied. These workflows are usually distributed because the simulations require HPC, but the optimization and steps to compare the simulation results and experimental data are done on a local workstation. We will present results from force field refinement of data collected at the Spallation Neutron Source using Kepler, Pegasus, and Beam workflows and discuss what we have learned from using these workflows.

Lynch, Vickie E.↗
DOE OSTI2021

A Novel State-Constrained Primary Control for Grid-Forming Inverters

The problem of operating an AC microgrid with purely inverter-based generating units is considered, and a novel vector control for the constrained grid-forming (GFM) inverters is proposed. The design aims to achieve the primary control objectives of the GFM inverters: voltage establishment, synchronization, and voltage/frequency regulation. It is novel that the proposed control also ensures all operational variables constrained both real-time and for all the time except for low voltage during the period of grid forming. The constraints include frequency, output AC voltage, input DC power, and active/reactive power injections to the grid. Here, in this paper, outcomes of a detailed simulation are presented to demonstrated that the above design objectives are met and that the overall performance is superior due to its unique ability of simultaneously controlling the whole vectors of the inverter state and output.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2023

Using Synchronization as an Indicator of Controllability in a Fleet of Water Heaters

Peak reduction is an important concern that can help reduce the growing stress on distribution grid and allow to defer investments in new capacity. However, the growing concern for customer privacy and comfort may impact the performance of load control for residential devices. Water heaters represent a convenient way of reducing peak due to their ability to store thermal energy for future use. In this paper, we developed a methodology to help utilities gain more insight with respect to the impact of load control efforts for shaving peak with no necessary information about the water heaters except the device status (on/off). To this end, we use a fleet of water heaters in a controlled residential neighborhood in Atlanta, GA. Our findings show that convergence in device status can serve as a proxy for peak shifting during hours of the evening peak.

demand response↗
DOE OSTI2020

Effects of cold stress on metabolic regulation in the overwintering larvae of the Chinese white pine beetle, Dendroctonus armandi

Abstract The Chinese white pine beetle, Dendroctonus armandi Tsai & Li (Coleoptera: Curculionidae, Scolytinae), is considered the most destructive forest pest in the Qinling and Bashan Mountains of China. In recent years, winter temperature has dropped in these regions, and extremely low temperatures are hard to survive for insects. Cold hardiness becomes a crucial strategy because temperature change often leads to fluctuations in insect abundance, and the metabolism rate is a key index of resistance to cold in overwintering insects. Therefore, we investigated the relationship between the change in respiratory rate and the activity of metabolism‐related mitochondrial enzymes in D. armandi larvae under cold conditions. We found that the respiratory rate decreased, and it was matched with the activity of glutamate dehydrogenase, aconitase, and lipase during overwintering. Among the various test times under cold conditions, the respiratory rate also decreased with decreasing temperature and increased under very low temperatures. At all cold stress periods, glutamate dehydrogenase and lipase showed increased activity at higher temperatures and decreased activity under lower temperatures, but the activity of NAD‐malic enzyme, NADP‐malic enzyme, mitochondrial isocitrate dehydrogenase, and aconitase were contrary. Under all low temperatures, the activity of enzymes – except for NADP‐malic enzyme, glutamate dehydrogenase, and lipase – increased in short‐term cold stress and decreased in long‐term cold stress at 4, 0, −4, −6, −8, and −10 °C. However, at −2 °C, the activity of enzymes showed a decreasing trend in short‐term treatments and an increasing trend in long‐term treatments, except for mitochondrial isocitrate dehydrogenase. The results not only improve our understanding of the metabolic mechanism of cold adaptation in D. armandi , but also provide an important experimental basis for further study and biological pest control.

Fu, Danyang↗