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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 OSTI2016

Interleukin-15 promotes intestinal dysbiosis with butyrate deficiency associated with increased susceptibility to colitis

Dysbiosis resulting in gut-microbiome alterations with reduced butyrate production are thought to disrupt intestinal immune homeostasis and promote complex immune disorders. However, whether and how dysbiosis develops before the onset of overt pathology remains poorly defined. Interleukin 15 (IL-15) is upregulated in distressed tissue and its overexpression is thought to predispose susceptible individuals to and play a role in the pathogenesis of celiac disease and inflammatory bowel disease (IBD). While the immunological roles of IL-15 have been largely studied, its potential impact on the microbiota remains unexplored. Analysis of 16S rRNA-based inventories of bacterial communities in mice overexpressing IL-15 in the intestinal epithelium (v-IL-15tg mice) shows distinct changes in the composition of the intestinal bacteria. While some alterations are specific to individual intestinal compartments, others are found across the ileum, cecum, and feces. In particular, IL-15 overexpression restructures the composition of the microbiota with a decrease in butyrate producing bacteria that is associated with a reduction in luminal butyrate levels across all intestinal compartments. Fecal microbiota transplant experiments of wild-type and v-IL-15tg microbiota into germ-free mice further indicate that diminishing butyrate concentration observed in the intestinal lumen of v-IL-15tg mice is the result of intrinsic alterations in the microbiota induced by IL-15. This reconfiguration of the microbiota is associated with increased susceptibility to dextran sodium sulfate induced colitis. Altogether, this study reveals that IL-15 impacts butyrate-producing bacteria and lowers butyrate levels in the absence of overt pathology, which represent events that precede and promote intestinal inflammatory diseases.

autoimmunity↗
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 OSTI2016

Gas gain stabilisation in the ATLAS TRT detector

The ATLAS (one of two general purpose detectors at the LHC) Transition Radiation Tracker (TRT) is the outermost of the three tracking subsystems of the ATLAS Inner Detector. It is a large straw-based detector and contains about 350,000 electronics channels. The performance of the TRT as tracking and particularly particle identification detector strongly depends on stability of the operation parameters with most important parameter being the gas gain which must be kept constant across the detector volume. The gas gain in the straws can vary significantly with atmospheric pressure, temperature, and gas mixture composition changes. This paper presents a concept of the gas gain stabilisation in the TRT and describes in detail the Gas Gain Stabilisation System (GGSS) integrated into the Detector Control System (DCS). Operation stability of the GGSS during Run-1 is demonstrated.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Early Transcriptomic Changes in the Ileal Pouch Provide Insight into the Molecular Pathogenesis of Pouchitis and Ulcerative Colitis

Background: Ulcerative colitis (UC) only involves the colonic mucosa. Yet, nearly 50% of patients with UC who undergo total proctocolectomy with ileal pouch anal anastomosis develop UC-like inflammation of the ileal pouch (pouchitis). By contrast, patients with familial adenomatous polyposis (FAP) with ileal pouch anal anastomosis develop pouchitis far less frequently. We hypothesized that pathogenic events associated with the development of UC are recapitulated by colonic-metaplastic transcriptomic reprogramming of the UC pouch. Methods: We prospectively sampled pouch and prepouch ileum mucosal biopsies in patients with UC with ileal pouch anal anastomosis 4, 8, and 12 months after their pouch was in continuity. Mucosal samples were also obtained from patients with FAP. Transcriptional profiles of the UC and FAP pouch and prepouch ileum were investigated via RNA sequencing and compared with data from a previously published microarray study. Results: Unlike patients with FAP, subjects with UC exhibited a large set of differentially expressed genes between the pouch and prepouch ileum as early as 4 months after pouch functionalization. Functional pathway analysis of differentially expressed genes in the UC pouch revealed an enhanced state of immune/inflammatory response and extracellular matrix remodeling. Moreover, >70% of differentially expressed genes mapped to published inflammatory bowel diseases microarray data sets displayed directional changes consistent with active UC but not with Crohn's disease. Conclusions: The UC pouch, well before histologic inflammation, already displays a systems-level gain of colon-associated genes and loss of ileum-associated genes. Patients with UC exhibit a unique transcriptomic response to ileal pouch creation that can be observed well before disease and may in part explain their susceptibility to the development of pouchitis.

familial adenomatous polyposis↗
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 OSTI2017

Natural polyreactive IgA antibodies coat the intestinal microbiota

Large quantities of immunoglobulin A (IgA) are constitutively secreted by intestinal plasma cells to coat and contain the commensal microbiota, yet the specificity of these antibodies remains elusive. In this paper, we profiled the reactivities of single murine IgA plasma cells by cloning and characterizing large numbers of monoclonal antibodies. IgAs were not specific to individual bacterial taxa but rather polyreactive, with broad reactivity to a diverse, but defined, subset of microbiota. These antibodies arose at low frequencies among naïve B cells and were selected into the IgA repertoire upon recirculation in Peyer’s patches. This selection process occurred independent of microbiota or dietary antigens. Furthermore, although some IgAs acquired somatic mutations, these did not substantially influence their reactivity. In conclusion, these findings reveal an endogenous mechanism driving homeostatic production of polyreactive IgAs with innate specificity to microbiota.

59 BASIC BIOLOGICAL SCIENCES↗