High Temperature X-ray Diffraction Investigation Of The Beta-(bismuth(2) Oxygen(3))(1-x)(strontium Oxide)(x) Solid Solution

To investigate the controversial {dollar}\beta\sb1\leftrightarrow\beta\sb2{dollar} phase transformation in the {dollar}\beta{dollar}-{dollar}\rm (Bi\sb2O\sb3)\sb{lcub}1-x{rcub}(SrO)\sb{lcub}x{rcub}{dollar} phase, a series of compositions across the phase were prepared by conventional grinding, pressing and firing ceramic techniques. Electrical conductivity measurements demonstrated that the samples were comparable to those used in other laboratories. X-ray diffraction analysis confirmed that the cations are located on a hexagonal sublattice, but details of the anion sublattice could not be resolved, because of the low X-ray scattering factor of {dollar}\rm O\sp{lcub}2-{rcub}.{dollar};The compositional dependence of the lattice parameters of the hexagonal crystal structure of the {dollar}\beta{dollar}-{dollar}\rm (Bi\sb2O\sb3)\sb{lcub}1-x{rcub}(SrO)\sb{lcub}x{rcub}{dollar} phase, which was determined at {dollar}27\sp\circ\rm C{dollar} using X-ray diffraction, revealed two distinct trends. The a and c parameters were both approximately constant for compositions below x = 0.28, whereas for compositions greater than x = 0.28, the c parameter increased progressively with the amount of substituted strontium, while the a parameter showed no significant changes.;An investigation into the temperature dependence of the lattice parameters revealed reversible discontinuities in the a and c lattice parameters at high temperatures, although the basic hexagonal crystal structure was unchanged. The c parameter discontinuity was greatest at low values of x, whereas the a parameter discontinuity was greatest in the middle of the phase and both effects decreased to the detection limit at x {dollar}\u3c{dollar} 0.40. These discontinuities are not caused by changes in the cation sublattice, as the X-ray diffraction peak intensities were not modified on cycling through the transformation. Instead, the discontinuities are attributed to modifications in the {dollar}\rm O\sp{lcub}2-{rcub}{dollar} occupancy of the anion sublattice, or, more precisely, in the distribution of {dollar}\rm O\sp{lcub}2-{rcub}{dollar} vacancies among these sites. The {dollar}\beta\sb1\leftrightarrow\beta\sb2{dollar} phase boundary, omitted from the most recent published phase diagram for the {dollar}\rm Bi\sb2O\sb3{dollar}-SrO system, was found to be asymmetric with respect to composition, in contrast to earlier reports. A revised phase diagram is presented incorporating these results

The ALS-Linked Gene TDP-43 Regulates IFNβIFN\beta Expression through a Novel Mechanism of 3' UTR-Mediated Promoter cis-Regulation

The TAR DNA-binding protein (TDP-43) is a heterogeneous nuclear ribonucleprotein that is involved in multiple stages of RNA processing. Mutations in the TDP-43 gene and mislocalization of TDP-43 protein have been implicated in a growing number of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). Here, we show that TDP-43 negatively regulates innate immune gene expression in response to RNA virus sensing. Perturbation of TDP-43 protein expression leads to an increase in antiviral gene expression in a variety of human and mouse cells. Crosslinked RNA immunoprecipitation (CLIP) experiments revealed that TDP-43 binds to type I interferon (IFN) and interferon stimulated gene (ISGs) transcripts. Using massively parallel 3’ UTR reporter assays coupled with high throughput sequencing (MPRA-seq), we identified polyadenylation signal sequences in the 3' UTRs of innate immune genes to be specifically regulated by TDP-43. Surprisingly, IFN and ISG mRNA decay rates are faster in TDP-43-perturbed cells. Using a metabolic labeling approach to measure nascent transcript generation, we found that perturbation of TDP-43 expression leads to an increase in antiviral gene transcription rates. Additionally, RNA polymerase II (pol II) chromatin immunoprecipitation (ChIP) confirmed that there is greater pol II occupancy on innate immune genes when TDP-43 is depleted. Although TDP-43 perturbation has no effect on an isolated $IFN\beta$ promoter reporter, we found that TDP-43 inhibits $IFN\beta$ promoter activity when the $IFN\beta$ 3' UTR sequence is inserted downstream of the $IFN\beta$ promoter element, suggesting a novel mechanism of 3' UTR-mediated promoter cis-regulation

Experimental determination of the residual stresses in a Kraft recovery boiler tube

Neutron diffraction was used to determine the residual stresses in a spiral weld overlay tube used in Kraft recovery boilers by the pulp and paper industry. The specimen was a 2.5 inches OD carbon steel tube covered with a layer of Inconel 625 weld overlay. Residual strains in the carbon steel and weld overlay layers were determined using the ferritic (211) and austenitic (311) reflections, respectively. Residual stresses in each material were derived from the measured strains using Hooke`s law and appropriate elastic constants. Tensile stress regions were found not only in the weld metal but also in the heat affected zone in the carbon steel. The maximum tensile stress was located in the weld overlay layer and was found to be 360 MPa, or about 75% of the yield strength of the weld metal. The experimental data were compared with a finite element analysis based on an uncoupled thermal-mechanical formulation. Overall, the modeling results were in satisfactory agreement with the experimental data, although the hoop strain (stress) appears to have been overestimated by the finite element model. Additional neutron diffraction measurements on an annealed tube confirmed that these welding residual stresses were eliminated after annealing at 900{degrees}C for 20 minutes. 18 refs., 7 figs

Mass spectral characterisation of a polar, esterified fraction of an organic extract of an oil sands process water.

RATIONALE: Characterising complex mixtures of organic compounds in polar fractions of heavy petroleum is challenging, but is important for pollution studies and for exploration and production geochemistry. Oil sands process-affected water (OSPW) stored in large tailings ponds by Canadian oil sands industries contains such mixtures. METHODS: A polar OSPW fraction was obtained by silver ion solid-phase extraction with methanol elution. This was examined by numerous methods, including electrospray ionisation (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) and ultra-high-pressure liquid chromatography (uHPLC)/Orbitrap MS, in multiple ionisation and MS/MS modes. Compounds were also synthesised for comparison. RESULTS: The major ESI ionisable compounds detected (+ion mode) were C15-28 SO3 species with 3-7 double bond equivalents (DBE) and C27-28 SO5 species with 5 DBE. ESI-MS/MS collision-induced losses were due to water, methanol, water plus methanol and water plus methyl formate, typical of methyl esters of hydroxy acids. Once the fraction was re-saponified, species originally detected by positive ion MS, could be detected only by negative ion MS, consistent with their assignment as sulphur-containing hydroxy carboxylic acids. The free acid of a keto dibenzothiophene alkanoic acid was added to an unesterified acid extract of OSPW in known concentrations as a putative internal standard, but attempted quantification in this way proved unreliable. CONCLUSIONS: The results suggest the more polar acidic organic SO3 constituents of OSPW include C15-28  S-containing, alicyclic and aromatic hydroxy carboxylic acids. SO5 species are possibly sulphone analogues of these. The origin of such compounds is probably via further biotransformation (hydroxylation) of the related S-containing carboxylic acids identified previously in a less polar OSPW fraction. The environmental risks, corrosivity and oil flow assurance effects should be easier to assess, given that partial structures are now known, although further identification is still needed

Neutron Characterization for Additive Manufacturing

Oak Ridge National Laboratory (ORNL) is leveraging decades of experience in neutron characterization of advanced materials together with resources such as the Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR) shown in Fig. 1 to solve challenging problems in additive manufacturing (AM). Additive manufacturing, or three-dimensional (3-D) printing, is a rapidly maturing technology wherein components are built by selectively adding feedstock material at locations specified by a computer model. The majority of these technologies use thermally driven phase change mechanisms to convert the feedstock into functioning material. As the molten material cools and solidifies, the component is subjected to significant thermal gradients, generating significant internal stresses throughout the part (Fig. 2). As layers are added, inherent residual stresses cause warping and distortions that lead to geometrical differences between the final part and the original computer generated design. This effect also limits geometries that can be fabricated using AM, such as thin-walled, high-aspect- ratio, and overhanging structures. Distortion may be minimized by intelligent toolpath planning or strategic placement of support structures, but these approaches are not well understood and often "Edisonian" in nature. Residual stresses can also impact component performance during operation. For example, in a thermally cycled environment such as a high-pressure turbine engine, residual stresses can cause components to distort unpredictably. Different thermal treatments on as-fabricated AM components have been used to minimize residual stress, but components still retain a nonhomogeneous stress state and/or demonstrate a relaxation-derived geometric distortion. Industry, federal laboratory, and university collaboration is needed to address these challenges and enable the U.S. to compete in the global market. Work is currently being conducted on AM technologies at the ORNL Manufacturing Demonstration Facility (MDF) sponsored by the DOE's Advanced Manufacturing Office. The MDF is focusing on R&D of both metal and polymer AM pertaining to in-situ process monitoring and closed-loop controls; implementation of advanced materials in AM technologies; and demonstration, characterization, and optimization of next-generation technologies. ORNL is working directly with industry partners to leverage world-leading facilities in fields such as high performance computing, advanced materials characterization, and neutron sciences to solve fundamental challenges in advanced manufacturing. Specifically, MDF is leveraging two of the world's most advanced neutron facilities, the HFIR and SNS, to characterize additive manufactured components

Doping Dependence of the Chemical Potential in Cuprate High-TcT_{\rm c} Superconductors I: La2−x_{2-x}Srx_xCuO4_4

The names of the authors, which were inadvertedly lacking in the tex-file submitted two days ago, have been added.Comment: 10 pages, figures on request. Revtex, version 2, Materials Science Center Internal Report Number VSGD.94.6.

Phase transitions in LaFeAsO: structural, magnetic, elastic, and transport properties, heat capacity and Mossbauer spectra

We present results from a detailed experimental investigation of LaFeAsO, the parent material in the series of "FeAs" based oxypnictide superconductors. Upon cooling this material undergoes a tetragonal-orthorhombic crystallographic phase transition at ~160 K followed closely by an antiferromagnetic ordering near 145 K. Analysis of these phase transitions using temperature dependent powder X-ray and neutron diffraction measurements is presented. A magnetic moment of ~0.35 Bohr magnetons per iron is derived from Mossbauer spectra in the low temperature phase. Evidence of the structural transition is observed at temperatures well above the structural transition (up to near 200 K) in the diffraction data as well as the polycrystalline elastic moduli probed by resonant ultrasound spectroscopy measurements. The effects of the two phase transitions on the transport properties (resistivity, thermal conductivity, Seebeck coefficient, Hall coefficient), heat capacity, and magnetization of LaFeAsO are also reported, including a dramatic increase in the magnitude of the Hall coefficient below 160 K. The results suggest that the structural distortion leads to a localization of carriers on Fe, producing small local magnetic moments which subsequently order antiferromagnetically upon further cooling. Evidence of strong electron-phonon interactions in the high-temperature tetragonal phase is also observed.Comment: Revised and expanded magnetization and Mossbauer spectroscopy section. Clarified sample preparation description. This paper contains some results from arXiv:0804.0796. 10 figure

Evidence for Supercurrent Connectivity in Conglomerate Particles in NdFeAsO1-d

Here we use global and local magnetometry and Hall probe imaging to investigate the electromagnetic connectivity of the superconducting current path in the oxygen-deficient fluorine-free Nd-based oxypnictides. High resolution transmission electron microscopy and scanning electron microscopy show strongly-layered crystallites, evidence for a ~ 5nm amorphous oxide around individual particles, and second phase neodymium oxide which may be responsible for the large paramagnetic background at high field and at high temperatures. From global magnetometry and electrical transport measurements it is clear that there is a small supercurrent flowing on macroscopic sample dimensions (mm), with a lower bound for the average (over this length scale) critical current density of the order of 103 A/cm2. From magnetometry of powder samples and local Hall probe imaging of a single large conglomerate particle ~120 microns it is clear that on smaller scales, there is better current connectivity with a critical current density of the order of 5 x 104 A/cm2. We find enhanced flux creep around the second peak anomaly in the magnetisation curve and an irreversibility line significantly below Hc2(T) as determined by ac calorimetry.Comment: 11 pages, 4 figure