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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Quasi-one-dimensional magnetism in the spin-12 antiferromagnet BaNa 2 Cu(VO 4 ) 2

Here, we report synthesis and magnetic properties of quasi-one-dimensional spin- 1 2 Heisenberg antiferromagnetic chain compound BaNa 2 Cu ( VO 4 ) 2 . This orthovanadate has a centrosymmetric crystal structure, C 2 / c , where the magnetic Cu 2 + ions form spin chains. These chains are arranged in layers, with the chain direction changing by 62 ° between the two successive layers. Alternatively, the spin lattice can be viewed as anisotropic triangular layers upon taking the interchain interactions into consideration. Despite this potential structural complexity, temperature-dependent magnetic susceptibility, heat capacity, electron spin resonance intensity, and nuclear magnetic resonance (NMR) shift agree well with the uniform spin- 1 / 2 Heisenberg chain model with an intrachain coupling of J / k B ≃ 5.6 K. The saturation field obtained from the magnetic isotherm measurement consistently reproduces the value of J / k B . Further, the V 51 NMR spin-lattice relaxation rate mimics the one-dimensional character in the intermediate temperature range, whereas magnetic long-range order sets in below T N ≃ 0.25 K. The effective interchain coupling is estimated to be J ⊥ / k B ≃ 0.1 K. The theoretical estimation of exchange couplings using band-structure calculations reciprocate our experimental findings and unambiguously establish the one-dimensional character of the compound. Finally, the spin lattice of BaNa 2 Cu ( VO 4 ) 2 is compared with the chemically similar but not isostructural compound BaAg 2 Cu ( VO 4 ) 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaNa(PO3)3 by Materials Project

BaNaP3O9 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional. Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.37–2.62 Å. Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.71–3.08 Å. There are three inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent NaO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–63°. There are a spread of P–O bond distances ranging from 1.49–1.66 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent NaO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–61°. There are a spread of P–O bond distances ranging from 1.50–1.62 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent NaO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 49–55°. There are a spread of P–O bond distances ranging from 1.50–1.64 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one Na1+, two equivalent Ba2+, and one P5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Ba2+, and one P5+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the fifth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to one Na1+, one Ba2+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Ba2+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, one Ba2+, and one P5+ atom. In the ninth O2- site, O2- is bonded in a distorted single-bond geometry to one Na1+, two equivalent Ba2+, and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaNa(B3O5)3 by Materials Project

NaBa(B3O5)3 crystallizes in the trigonal R3c space group. The structure is three-dimensional. Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are three shorter (2.34 Å) and three longer (2.54 Å) Na–O bond lengths. Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.85–3.05 Å. There are three inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.48 Å) and two longer (1.49 Å) B–O bond length. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.36–1.40 Å. In the third B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.37 Å) and one longer (1.41 Å) B–O bond length. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ba2+ and two B3+ atoms. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one Ba2+ and two B3+ atoms. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Na1+ and two B3+ atoms. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to one Ba2+ and two B3+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+ and two B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Materials Data on BaNa by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaNa(FeAs)4 by Materials Project

NaBa(FeAs)4 is alpha bismuth trifluoride-derived structured and crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. Na1+ is bonded in a body-centered cubic geometry to eight As3- atoms. All Na–As bond lengths are 3.34 Å. Ba2+ is bonded in a body-centered cubic geometry to eight As3- atoms. All Ba–As bond lengths are 3.34 Å. Fe+2.25+ is bonded to four As3- atoms to form a mixture of corner and edge-sharing FeAs4 tetrahedra. All Fe–As bond lengths are 2.32 Å. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded in a 8-coordinate geometry to two equivalent Na1+, two equivalent Ba2+, and four equivalent Fe+2.25+ atoms. In the second As3- site, As3- is bonded in a 8-coordinate geometry to two equivalent Na1+, two equivalent Ba2+, and four equivalent Fe+2.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Materials Data on BaNa by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reversible hydrogen control of antiferromagnetic anisotropy in α-Fe 2 O 3

Antiferromagnetic insulators are a ubiquitous class of magnetic materials, holding the promise of low-dissipation spin-based computing devices that can display ultra-fast switching and are robust against stray fields. However, their imperviousness to magnetic fields also makes them difficult to control in a reversible and scalable manner. Here we demonstrate a novel proof-of-principle ionic approach to control the spin reorientation (Morin) transition reversibly in the common antiferromagnetic insulator α-Fe 2 O 3 (haematite) - now an emerging spintronic material that hosts topological antiferromagnetic spin-textures and long magnon-diffusion lengths. We use a low-temperature catalytic-spillover process involving the post-growth incorporation or removal of hydrogen from α-Fe 2 O 3 thin films. Hydrogenation drives pronounced changes in its magnetic anisotropy, Néel vector orientation and canted magnetism via electron injection and local distortions. We explain these effects with a detailed magnetic anisotropy model and first-principles calculations. Tailoring our work for future applications, we demonstrate reversible control of the room-temperature spin-state by doping/expelling hydrogen in Rh-substituted α-Fe 2 O 3 .

36 MATERIALS SCIENCE↗
DOE OSTI2020

A missense variant remote from the active site impairs stability of human phosphoglucomutase 1

Abstract Missense variants of human phosphoglucomutase 1 (PGM1) cause the inherited metabolic disease known as PGM1 deficiency. This condition is categorised as both a glycogen storage disease and a congenital disorder of glycosylation. Approximately 20 missense variants of PGM1 are linked to PGM1 deficiency, and biochemical studies have suggested that they fall into two general categories: those affecting the active site and catalytic efficiency, and those that appear to impair protein folding and/or stability. In this study, we characterise a novel variant of Arg422, a residue distal from the active site of PGM1 and the site of a previously identified disease‐related variant (Arg422Trp). In prior studies, the R422W variant was found to produce insoluble protein in a recombinant expression system, precluding further in vitro characterisation. Here we investigate an alternative variant of this residue, Arg422Gln, which is amenable to experimental characterisation presumably due to its more conservative physicochemical substitution. Biochemical, crystallographic, and computational studies of R422Q establish that this variant causes only minor changes in catalytic efficiency and 3D structure, but is nonetheless dramatically reduced in stability. Unexpectedly, binding of a substrate analog is found to further destabilise the protein, in contrast to its stabilising effect on wild‐type PGM1 and several other missense variants. This work establishes Arg422 as a lynchpin residue for the stability of PGM1 and supports the impairment of protein stability as a pathomechanism for variants that cause PGM1 deficiency. Synopsis Biochemical and structural studies of a missense variant far from the active site of human PGM1 identify a residue with a key role in enzyme stability.

Stiers, Kyle M.↗
DOE OSTI2020

Fecal microbiota transplant rescues mice from human pathogen mediated sepsis by restoring systemic immunity

Death due to sepsis remains a persistent threat to critically ill patients confined to the intensive care unit and is characterized by colonization with multi-drug-resistant healthcare-associated pathogens. Here we report that sepsis in mice caused by a defined four-member pathogen community isolated from a patient with lethal sepsis is associated with the systemic suppression of key elements of the host transcriptome required for pathogen clearance and decreased butyrate expression. More specifically, these pathogens directly suppress interferon regulatory factor 3. Fecal microbiota transplant (FMT) reverses the course of otherwise lethal sepsis by enhancing pathogen clearance via the restoration of host immunity in an interferon regulatory factor 3-dependent manner. This protective effect is linked to the expansion of butyrate-producing Bacteroidetes. Taken together these results suggest that fecal microbiota transplantation may be a treatment option in sepsis associated with immunosuppression.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Differential Expression of Core Metabolic Functions in Candidatus Altiarchaeum Inhabiting Distinct Subsurface Ecosystems

Candidatus Altiarchaea are widespread across aquatic subsurface ecosystems and possess a highly conserved core genome, yet adaptations of this core genome to different biotic and abiotic factors based on gene expression remain unknown. Here, we investigated the metatranscriptome of two Ca. Altiarchaeum populations that thrive in two substantially different subsurface ecosystems. In Crystal Geyser, a high-CO2 groundwater system in the USA, Ca. Altiarchaeum crystalense co-occurs with the symbiont Ca. Huberiarchaeum crystalense, while in the Muehlbacher sulfidic spring in Germany, an artesian spring high in sulfide concentration, Ca. A. hamiconexum is heavily infected with viruses. We here mapped metatranscriptome reads against their genomes to analyse the in situ expression profile of their core genomes. Out of 537 shared gene clusters, 331 were functionally annotated and 130 differed significantly in expression between the two sites. Main differences were related to genes involved in cell defence like CRISPR-Cas, virus defence, replication, transcription and energy and carbon metabolism. Our results demonstrate that altiarchaeal populations in the subsurface are likely adapted to their environment while influenced by other biological entities that tamper with their core metabolism. We consequently posit that viruses and symbiotic interactions can be major energy sinks for organisms in the deep biosphere.

archaea↗
DOE OSTI2020

Manufacturing Process of Electrode Films

Rotating disk electrode (RDE) experiments form a key experimental characterization technique for measuring electrocatalyst performance and durability. While standard RDE testing protocols have been documented, it has been noted that catalyst film quality can skew measurements. Furthermore, the impact of relative humidity on drying is studied in an effort to produce consistent, high quality catalyst films for RDE experiments, which shows that high quality catalyst films can be manufactured repeatedly in a controlled environment, such as inside an environmental chamber as described.

08 HYDROGEN↗
NASA NTRS1973

Silica RSI entry simulation tests

Simulated reentry heating of the all-silica surface insulation material under a variety of conditions including arc jet and radiant lamp facilities for up to 100 simulated flight cycles has demonstrated consistent thermal performance capability. Consistent predictability along with demonstrated coating integrity and dimensional stability to 1645 K validates the earlier selection of the all-silica material for the RSI application.

Banas, R. P.↗
NASA NTRS1974

Electron beam, laser beam and plasma arc welding studies

This program was undertaken as an initial step in establishing an evaluation framework which would permit a priori selection of advanced welding processes for specific applications. To this end, a direct comparison of laser beam, electron beam and arc welding of Ti-6Al-4V alloy was undertaken. Ti-6Al-4V was selected for use in view of its established welding characteristics and its importance in aerospace applications.

Banas, C. M.↗
NASA NTRS1972

High Power Laser Welding

A review of recent developments in high power, carbon dixoide laser welding is presented. Deep penetration welding in stainless steel to 0.5-in. thick, high speed welding in thin gage rimmed steel and gas shielded welding in Ti-6Al-4V alloy are described. The effects of laser power, power density, focusing optics, gas-shielding techniques, material properties and weld speed on weld quality and penetration are discussed. It is shown that laser welding performance in thin materials is comparable to that of electron beams. It is further shown that high quality welds, as evidenced by NDT, mechanical and metal-lographic tests, can be achieved. The potential of the laser for industrial welding applications is indicated.

Banas, C. M.↗