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At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on HoB4Ru by Materials Project

HoRuB4 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Ho3+ is bonded in a 2-coordinate geometry to fourteen B+1.50- atoms. There are a spread of Ho–B bond distances ranging from 2.63–2.77 Å. Ru3+ is bonded in a 10-coordinate geometry to ten B+1.50- atoms. There are a spread of Ru–B bond distances ranging from 2.25–2.40 Å. There are four inequivalent B+1.50- sites. In the first B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to four equivalent Ho3+, two equivalent Ru3+, and three B+1.50- atoms. There are a spread of B–B bond distances ranging from 1.75–1.87 Å. In the second B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to four equivalent Ho3+, two equivalent Ru3+, and three B+1.50- atoms. The B–B bond length is 1.84 Å. In the third B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to four equivalent Ho3+, two equivalent Ru3+, and three B+1.50- atoms. There is one shorter (1.74 Å) and one longer (1.76 Å) B–B bond length. In the fourth B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to two equivalent Ho3+, four equivalent Ru3+, and three B+1.50- atoms. The B–B bond length is 1.72 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(HoSe2)2 by Materials Project

Ca(HoSe2)2 crystallizes in the monoclinic P2/m space group. The structure is three-dimensional. Ca2+ is bonded to six Se2- atoms to form CaSe6 octahedra that share corners with six equivalent HoSe6 octahedra, edges with two equivalent CaSe6 octahedra, and edges with six HoSe6 octahedra. The corner-sharing octahedra tilt angles range from 2–5°. There are two shorter (2.95 Å) and four longer (3.00 Å) Ca–Se bond lengths. There are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to six Se2- atoms to form HoSe6 octahedra that share edges with four equivalent CaSe6 octahedra and edges with six HoSe6 octahedra. There are four shorter (2.86 Å) and two longer (2.87 Å) Ho–Se bond lengths. In the second Ho3+ site, Ho3+ is bonded to six Se2- atoms to form HoSe6 octahedra that share corners with six equivalent CaSe6 octahedra, edges with two equivalent CaSe6 octahedra, and edges with six HoSe6 octahedra. The corner-sharing octahedra tilt angles range from 2–5°. There are two shorter (2.82 Å) and four longer (2.89 Å) Ho–Se bond lengths. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three Ho3+ atoms. In the second Se2- site, Se2- is bonded to two equivalent Ca2+ and three Ho3+ atoms to form a mixture of corner and edge-sharing SeCa2Ho3 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Persistent Structure and Frustrated Magnetism in High Entropy Rare-Earth Zirconates

The configurational complexity and distinct local atomic environments of high entropy oxides remain largely unexplored, leaving structure-property relationships and the hypothesis that the family offers rich tunability for applications ambiguous. This work investigates the influence of cation size and materials synthesis in determining the resulting structure and magnetic properties of a family of high entropy rare-earth zirconates (HEREZs, nominal composition RE 2 Zr 2 O 7 with RE = rare-earth element combinations including Eu, Gd, Tb, Dy, Ho, La, or Sc). Here, the structural characterization of the series is examined through synchrotron X-ray diffraction and pair distribution function analysis, and electron microscopy, demonstrating average defect-fluorite structures with considerable local disorder, in all samples. The surface morphology and particle sizes are found to vary significantly with preparation method, with irregular micron-sized particles formed by high temperature sintering routes, spherical nanoparticles resulting from chemical co-precipitation methods, and porous nanoparticle agglomerates resulting from polymer steric entrapment synthesis. In agreement with the disordered cation distribution found across all samples, magnetic measurements indicate that all synthesized HEREZs show frustrated magnetic behavior, as seen in a number of single-component RE 2 Zr 2 O 7 pyrochlore oxides. These findings advance the understanding of the local structure of high entropy oxides and demonstrate strategies for designing nanostructured morphologies in the class.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Discrete theta angles, symmetries and anomalies

Gauge theories in various dimensions often admit discrete theta angles, that arise from gauging a global symmetry with an additional symmetry protected topological (SPT) phase. We discuss how the global symmetry and ’t Hooft anomaly depends on the discrete theta angles by coupling the gauge theory to a topological quantum field theory (TQFT). We observe that gauging an Abelian subgroup symmetry, that participates in symmetry extension, with an additional SPT phase leads to a new theory with an emergent Abelian symmetry that also participates in a symmetry extension. The symmetry extension of the gauge theory is controlled by the discrete theta angle which comes from the SPT phase. We find that discrete theta angles can lead to two-group symmetry in 4d 4 d QCD with SU(N),SU(N)/\mathbb{Z}_k S U ( N ) , S U ( N ) / ℤ k or SO(N) S O ( N ) gauge groups as well as various 3d 3 d and 2d 2 d gauge theories.

Hsin, Po-Shen↗
NASA NTRS2012

Rapid and Reliable Damage Proxy Map from InSAR Coherence

Future radar satellites will visit SoCal within a day after a disaster event. Data acquisition latency in 2015-2020 is 8 to approx. 15 hours. Data transfer latency that often involves human/agency intervention far exceeds the data acquisition latency. Need interagency cooperation to establish automatic pipeline for data transfer. The algorithm is tested with ALOS PALSAR data of Pasadena, California. Quantitative quality assessment is being pursued: Meeting with Pasadena City Hall computer engineers for a complete list of demolition/construction project 1. Estimate the probability of detection and probability of false alarm 2. Estimate the optimal threshold value.

InSAR↗
DOE OSTI2020

Materials Data on KHoH8RuC6(N3O2)2 by Materials Project

RuKHoC6H4(N3O)2(H2O)2 crystallizes in the orthorhombic Cmcm space group. The structure is two-dimensional and consists of four ruthenium molecules; eight water molecules; and two KHoC6H4(N3O)2 sheets oriented in the (0, 0, 1) direction. In each KHoC6H4(N3O)2 sheet, K1+ is bonded in a 2-coordinate geometry to six N3- and two equivalent O2- atoms. There are four shorter (3.08 Å) and two longer (3.14 Å) K–N bond lengths. Both K–O bond lengths are 2.93 Å. Ho3+ is bonded in a 8-coordinate geometry to six N3- and two equivalent O2- atoms. There are four shorter (2.42 Å) and two longer (2.52 Å) Ho–N bond lengths. Both Ho–O bond lengths are 2.40 Å. There are two inequivalent C+1.33+ sites. In the first C+1.33+ site, C+1.33+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.18 Å. In the second C+1.33+ site, C+1.33+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.18 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a 1-coordinate geometry to one K1+, one Ho3+, and one C+1.33+ atom. In the second N3- site, N3- is bonded in a distorted single-bond geometry to one K1+, one Ho3+, and one C+1.33+ atom. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. O2- is bonded in a distorted water-like geometry to one K1+, one Ho3+, and two equivalent H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Lead compounds for the development of SARS-CoV-2 3CL protease inhibitors

We report the identification of three structurally diverse compounds – compound 4, GC376, and MAC-5576 – as inhibitors of the SARS-CoV-2 3CL protease. Structures of each of these compounds in complex with the protease revealed strategies for further development, as well as general principles for designing SARS-CoV-2 3CL protease inhibitors. These compounds may therefore serve as leads for the basis of building effective SARS-CoV-2 3CL protease inhibitors.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Crystal structures and comparisons of huntite aluminum borates RE Al 3 (BO 3 ) 4 ( RE = Tb, Dy and Ho)

Three huntite-type aluminoborates of stoichiometry RE Al 3 (BO 3 ) 4 ( RE = Tb, Dy and Ho), namely, terbium/dysprosium/holmium trialuminium tetrakis(borate), were synthesized by slow cooling within a K 2 Mo 3 O 10 flux with spontaneous crystallization. The crystal structures were determined using single-crystal X-ray diffraction (SC-XRD) data. The synthesized borates are isostructural to the huntite [CaMg 3 (CO 3 ) 4 ] structure and crystallized within the trigonal R 32 space group. The structural parameters were compared to literature data of other huntite RE Al 3 (BO 3 ) 4 crystals within the R 32 space group. All three borates fit well into the trends calculated from the literature data. The unit-cell parameters and volumes increase linearly with larger RE cations whereas the densities decrease. All of the crystals studied were refined as inversion twins.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Associative nitrogen fixation linked with three perennial bioenergy grasses in field and greenhouse experiments

Abstract Associative nitrogen (N 2 )‐fixation (ANF) by bacteria in the root‐zone of perennial bioenergy grasses has the potential to replace or supplement N fertilizer and support sustainable production of biomass, but its application in marginal ecosystems requires further evaluation. In this study, we first combined both greenhouse and field experiments, to explore the N 2 fixation effects of three temperate feedstocks Miscanthus × giganteus (giant miscanthus, Freedom), Panicum virgatum (switchgrass, Alamo), and Saccharum sp. (energycane, Ho 02‐147). In field studies across three growing seasons, plant and soil pools of candidate feedstocks were partially composed of N derived from the atmosphere (Ndfa). Energycane, giant miscanthus, and switchgrass were estimated to derive >30%, %Ndfa. Greenhouse studies were also performed to trace isotopically labeled 15 N 2 into plant biomass and soil pools. Evidence for Ndfa was detected in all three feedstock grasses (using reference 15 N of soil, chicory, and sorghum, δ 15 N~+7.0). Isotopically labeled 15 N 2 was traced into biomass (during grass elongation stage) and soil pools. Extrapolation of rates during the 24 hr labeling period to 50 days estimated 30%–55% of plant Ndfa, with the greatest Ndfa for energycane. The findings of the field natural abundance and greenhouse 15 N 2 feeding experiments provided complementary evidence that perennial bioenergy grasses have the potential to support relatively high rates of ANF, and accumulate diazotroph‐derived N into biomass when grown on non‐fertilized soil.

09 BIOMASS FUELS↗
NASA NTRS2008

Review of Tm and Ho Materials; Spectroscopy and Lasers

A review of Tm and Ho materials is presented, covering some fundamental aspects on the spectroscopy and laser dynamics in both single and co-doped systems. Following an introduction to 2- m lasers, applications and historical development, the physics of quasi-four level lasers, energy transfer and modeling are discussed in some detail. Recent developments in using Tm lasers to pump Ho lasers are discussed, and seen to offer some advantages over conventional Tm:Ho lasers. This article is not intended as a complete review, but as a primer for introducing concepts and a resource for further study.

Walsh, Brian M.↗
DOE OSTI2021

CO 2 -selective membranes containing amino acid salts for CO 2 /N 2 separation

In this paper, facilitated transport membranes comprising polyvinylamine (PVAm) as fixed carrier and different amino acid salts (AAS) as mobile carriers were synthesized for post-combustion capture. The AAS carriers were prepared by deprotonating alanine (Ala), lysine (Lys), and proline (Pro) with 2-(1-piperazinyl)ethylamine (PZEA). CO 2 separation performances of the membranes with these AAS carriers were compared, and the AAS effectiveness to facilitate transport of CO 2 was in the order of PZEA-Pro > PZEA-Lys > PZEA-Ala. Here, the membrane comprising 35 wt.% PVAm and 65 wt.% PZEA-Pro at 57 °C rendered a promising CO 2 permeance of 936 GPU and a CO 2 /N 2 mixed gas selectivity of 193. When the PVAm was reduced to 15 wt.%, i.e., its 20 wt.% was replaced by the mobile carrier of PZEA-Sar (sarcosinate), the permeance further improved to 947 GPU with a remarkable CO 2 /N 2 selectivity of 210. Moreover, thermal gravimetric analysis showed a good thermal stability of the membrane, and membrane stability testing also gave stable transport performance. Furthermore, spectroscopic ellipsometry analysis exhibited a uniform membrane selective layer and an excellent agreement on the membrane thickness of ca. 170 nm measured independently by SEM. In addition, the membranes presented in this paper surpassed both the Robeson upper bound and the modified upper bound, indicating a great potential for CO 2 capture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1988

Axions, SN 1987A, and one pion exchange

Nucleon-nucleon, axion bremsstrahlung is the primary mechanism for axion emission from the nascent neutron star associated with SN 1987A, and the rate for this process has been calculated in the one pion exchange approximation (OPE). The axion mass limit which follows from SN 1987A, m sub a less than or approx equal to 10 to the -3 eV, is the most stringent astrophysical bound, and has received much scrutiny. It has been suggested that by using OPE to calculate the cross section for the analog process, pp yields pp + pi sup o, and comparing the result of the experimental data one can test the validity of this approximation, and further, that such a comparison indicates that OPE leads to a value for this cross section which is a factor of 30 to 40 too large. If true, this would suggest that the axion mass limit should be revised upward by a factor of approximately 6. The cross section for pp yields pp + pi sup o using OPE is carefully evaluated, and excellent agreement found (to better than a factor of 2) with the experimental data.

Turner, Michael S.↗
DOE OSTI2023

(2+1)-dimensional compact Lifshitz theory, tensor gauge theory, and fractons

The (2+1)-dimensional continuum Lifshitz theory of a free compact scalar field plays a prominent role in a variety of quantum systems in condensed matter physics and high energy physics. It is known that in compact space, it has an infinite ground-state degeneracy. In order to understand this theory better, we consider two candidate lattice regularizations of it using the modified Villain formalism. We show that these two lattice theories have significantly different global symmetries (including a dipole global symmetry), anomalies, ground-state degeneracies, and dualities. In particular, one of them is self-dual. Given these theories and their global symmetries, we can couple them to corresponding gauge theories. Here, these are two different U(1) tensor gauge theories. The resulting models have excitations with restricted mobility, i.e., fractons. Finally, we give an exact lattice realization of the fracton and lineon-elasticity dualities for the Lifshitz theory, and scalar and vector charge gauge theories.

2-dimensional systems↗
DOE OSTI2020

Materials Data on HoTl(MoO4)2 by Materials Project

HoTl(MoO4)2 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.29–2.56 Å. Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.76–1.87 Å. Tl1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Tl–O bond distances ranging from 2.77–3.02 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ho3+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Ho3+, one Mo6+, and one Tl1+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and two equivalent Tl1+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS2014

2-Micron Coherent Doppler Lidar Instrument Advancements for Tropospheric Wind Measurement

Knowledge derived from global tropospheric wind measurement is an important constituent of our overall understanding of climate behavior [1]. Accurate weather prediction saves lives and protects properties from destructions. High-energy 2-micron laser is the transmitter of choice for coherent Doppler wind detection. In addition to the eye-safety, the wavelength of the transmitter suitably matches the aerosol size in the lower troposphere. Although the technology of the 2-micron laser has been maturing steadily, lidar derived wind data is still a void in the global weather database. In the last decade, researchers at NASA Langley Research Center (LaRC) have been engaged in this endeavor, contributing to the scientific database of 2-micron lidar transmitters. As part of this effort, an in depth analysis of the physics involved in the workings of the Ho: Tm laser systems have been published. In the last few years, we have demonstrated lidar transmitter with over1Joule output energy. In addition, a large body of work has been done in characterizing new laser materials and unique crystal configurations to enhance the efficiency and output energy of the 2-micron laser systems. At present 2-micron lidar systems are measuring wind from both ground and airborne platforms. This paper will provide an overview of the advancements made in recent years and the technology maturity levels attained.

Petros, Mulugeta↗
DOE OSTI2020

Materials Data on Ho6Mn4Al43 by Materials Project

Ho6Mn4Al43 crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. Ho is bonded in a 6-coordinate geometry to one Ho, one Mn, and fifteen Al atoms. The Ho–Ho bond length is 3.41 Å. The Ho–Mn bond length is 3.49 Å. There are a spread of Ho–Al bond distances ranging from 3.04–3.42 Å. There are two inequivalent Mn sites. In the first Mn site, Mn is bonded in a cuboctahedral geometry to twelve Al atoms. There are six shorter (2.65 Å) and six longer (2.80 Å) Mn–Al bond lengths. In the second Mn site, Mn is bonded in a 10-coordinate geometry to two equivalent Ho and ten Al atoms. There are a spread of Mn–Al bond distances ranging from 2.53–2.65 Å. There are seven inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to one Ho, two Mn, and nine Al atoms. There are a spread of Al–Al bond distances ranging from 2.70–2.95 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent Ho, one Mn, and nine Al atoms. There are a spread of Al–Al bond distances ranging from 2.71–2.95 Å. In the third Al site, Al is bonded in a 12-coordinate geometry to four equivalent Ho and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.76–3.09 Å. In the fourth Al site, Al is bonded in a 12-coordinate geometry to two equivalent Ho, one Mn, and nine Al atoms. There are a spread of Al–Al bond distances ranging from 2.72–2.98 Å. In the fifth Al site, Al is bonded in a 10-coordinate geometry to two equivalent Ho, one Mn, and seven Al atoms. There are one shorter (2.74 Å) and two longer (2.81 Å) Al–Al bond lengths. In the sixth Al site, Al is bonded in a 2-coordinate geometry to two equivalent Mn and ten Al atoms. Both Al–Al bond lengths are 2.75 Å. In the seventh Al site, Al is bonded to three equivalent Ho and nine Al atoms to form a mixture of face and corner-sharing AlHo3Al9 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoTl(WO4)2 by Materials Project

HoTl(WO4)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ho3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ho–O bond distances ranging from 2.27–2.32 Å. W6+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing WO6 octahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of W–O bond distances ranging from 1.83–2.14 Å. Tl1+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Tl–O bond distances ranging from 2.88–3.14 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent W6+ and two equivalent Tl1+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Ho3+, one W6+, and one Tl1+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ho3+, two equivalent W6+, and one Tl1+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ho3+, one W6+, and one Tl1+ atom.

36 MATERIALS SCIENCE↗