1,076 research outputs found

    Experimental study of ceramic coated tip seals for turbojet engines

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    Ceramic gas-path seals were fabricated and successfully operated over 1000 cycles from flight idle to maximum power in a small turboshaft engine. The seals were fabricated by plasma spraying zirconia over a NiCoCrAlX bond boat on the Haynes 25 substrate. Coolant-side substrate temperatures and related engine parameters were recorded. Post-test inspection revealed mudflat surface cracking with penetration to the ceramic bond-coat interface

    Adapting health behavior measurement tools for cross-cultural use

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    Background: Addressing health disparities in the global community requires awareness of how cultural differences in beliefs, traditions, norms, and values shape health problems and behaviors. Review: This paper reviews methods of assessing health behaviors, how these assessments may be affected by cross-cultural differences, and methods of adaptation of health behaviors across cultures. We describe the methods used in appropriate translation processes and pilot-testing for health behavior assessment tools. We also discuss ways to limit literacy demands and incorporate qualitative interviews

    Hole Doping Effects on Spin-gapped Na2Cu2TeO6 via Topochemical Na Deficiency

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    We report the magnetic susceptibility and NMR studies of a spin-gapped layered compound Na2Cu2TeO6 (the spin gap Δ∼\Delta\sim 250 K), the hole doping effect on the Cu2TeO6 plane via a topochemical Na deficiency by soft chemical treatment, and the static spin vacancy effect by nonmagnetic impurity Zn substitution for Cu. A finite Knight shift at the 125^{125}Te site was observed for pure Na2Cu2TeO6. The negative hyperfine coupling constant 125Atr^{125}A_{tr} is an evidence for the existence of a superexchange pathway of the Cu-O-Te-O-Cu bond. It turned out that both the Na deficiency and Zn impurities induce a Curie-type magnetism in the uniform spin susceptibility in an external magnetic field of 1 T, but only the Zn impurities enhance the low-temperature 23^{23}Na nuclear spin-lattice relaxation rate whereas the Na deficiency suppresses it. A spin glass behavior was observed for the Na-deficient samples but not for the Zn-substituted samples. The dynamics of the unpaired moments of the doped holes are different from that of the spin vacancy in the spin-gapped Cu2TeO6 planes.Comment: 4 pages, 7 figures, to be published in J. Phys. Soc. Jpn. Vol. 75, No. 8 (2006

    Reconstitution of a Minimal DNA Replicase From Pseudomonas Aeruginosa and Stimulation by Non-Cognate Auxiliary Factors

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    DNA polymerase III holoenzyme is responsible for chromosomal replication in bacteria. The components and functions of Escherichia coli DNA polymerase III holoenzyme have been studied extensively. Here, we report the reconstitution of replicase activity by essential components of DNA polymerase holoenzyme from the pathogen Pseudomonas aeruginosa. We have expressed and purified the processivity factor (β), single-stranded DNA-binding protein, a complex containing the polymerase (α) and exonuclease (ϵ) subunits, and the essential components of the DnaX complex (τ3δδ′). Efficient primer elongation requires the presence of αϵ, β, and τ3δδ′. Pseudomonas aeruginosa αϵ can substitute completely for E. coli polymerase III in E. coli holoenzyme reconstitution assays. Pseudomonas β and τ3δδ′ exhibit a 10-fold lower activity relative to their E. coli counterparts in E. coli holoenzyme reconstitution assays. Although the Pseudomonas counterpart to the E. coli ψ subunit was not apparent in sequence similarity searches, addition of purified E. coli χ and ψ (components of the DnaX complex) increases the apparent specific activity of the Pseudomonas τ3δδ′ complex ∼10-fold and enables the reconstituted enzyme to function better under physiological salt conditions

    The influence of pressure on the phase stability of nanocomposite Fe_(89)Zr_7B_4 during heating from energy dispersive x-ray diffraction

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    Nanocomposite materials consisting of small crystalline grains embedded within an amorphous matrix show promise for many soft magnetic applications. The influence of pressure is investigated by in situ diffraction of hammer milled Fe_(89)Zr_(7)B_4 during heating through the α → γ Fe transition at 0.5, 2.2, and 4.9 GPa. The changes in primary and secondary crystallization onset are described by diffusion and the energy to form a critical nucleus within the framework of classical nucleation theory

    NMR characterization of spin-1/2 alternating antiferromagnetic chains in the high-pressure phase of (VO)2P2O7

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    Local-susceptibility measurements via the NMR shifts of 31^{31}P and 51^{51}V nuclei in the high-pressure phase of (VO)2_{2}P2_{2}O7_{7} confirmed the existence of a unique alternating antiferromagnetic chain with a zero-field spin gap of 34 K. The 31^{31}P nuclear spin-lattice relaxation rate scales with the uniform spin susceptibility below about 15 K which shows that the temperature dependence of both the static and dynamical spin susceptibilities becomes identical at temperatures not far below the spin-gap energy.Comment: 6 pages, 5 figures; To be published in J. Phys. Condens. Matte

    Nano granular metallic Fe - oxygen deficient TiO2−δ_{2-\delta} composite films: A room temperature, highly carrier polarized magnetic semiconductor

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    Nano granular metallic iron (Fe) and titanium dioxide (TiO2−δ_{2-\delta}) were co-deposited on (100) lanthanum aluminate (LaAlO3_3) substrates in a low oxygen chamber pressure using a pulsed laser ablation deposition (PLD) technique. The co-deposition of Fe and TiO2_2 resulted in ≈\approx 10 nm metallic Fe spherical grains suspended within a TiO2−δ_{2-\delta} matrix. The films show ferromagnetic behavior with a saturation magnetization of 3100 Gauss at room temperature. Our estimate of the saturation magnetization based on the size and distribution of the Fe spheres agreed well with the measured value. The film composite structure was characterized as p-type magnetic semiconductor at 300 K with a carrier density of the order of 1022/cm3 10^{22} /{\rm cm^3}. The hole carriers were excited at the interface between the nano granular Fe and TiO2−δ_{2-\delta} matrix similar to holes excited in the metal/n-type semiconductor interface commonly observed in Metal-Oxide-Semiconductor (MOS) devices. From the large anomalous Hall effect directly observed in these films it follows that the holes at the interface were strongly spin polarized. Structure and magneto transport properties suggested that these PLD films have potential nano spintronics applications.Comment: 6 pages in Latex including 8 figure

    DNA Polymerase III Holoenzyme From Thermus Thermophilus Identification Expression Purification of Components and use to Reconstitute a Processive Replicase

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    DNA replication in bacteria is performed by a specialized multicomponent replicase, the DNA polymerase III holoenzyme, that consist of three essential components: a polymerase, the β sliding clamp processivity factor, and the DnaX complex clamp-loader. We report here the assembly of the minimal functional holoenzyme from Thermus thermophilus (Tth), an extreme thermophile. The minimal holoenzyme consists of α (pol III catalytic subunit), β (sliding clamp processivity factor), and the essential DnaX (τ/γ), δ and δ′ components of the DnaX complex. We show with purified recombinant proteins that these five components are required for rapid and processive DNA synthesis on long single-stranded DNA templates. Subunit interactions known to occur in DNA polymerase III holoenzyme from mesophilic bacteria including δ-δ′ interaction, δδ′-τ/γ complex formation, and α-τ interaction, also occur within the Tth enzyme. As in mesophilic holoenzymes, in the presence of a primed DNA template, these subunits assemble into a stable initiation complex in an ATP-dependent manner. However, in contrast to replicative polymerases from mesophilic bacteria, Tth holoenzyme is efficient only at temperatures above 50 °C, both with regard to initiation complex formation and processive DNA synthesis. The minimalTth DNA polymerase III holoenzyme displays an elongation rate of 350 bp/s at 72 °C and a processivity of greater than 8.6 kilobases, the length of the template that is fully replicated after a single association event

    Anisotropic low field behavior and the observation of flux jumps in CeCoIn5

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    The magnetic behavior of the heavy fermion superconductor CeCoIn5 has been investigated. The low field magnetization data show flux jumps in the mixed state of the superconducting phase in a restricted range of temperature. These flux jumps begin to disappear below 1.7 K, and are completely absent at 1.5 K. The magnetization loops are asymmetric, suggesting that surface and geometrical factors dominate the pinning in this system. The lower critical field (Hc1), obtained from the magnetization data, shows a linear temperature dependence and is anisotropic. The calculated penetration depth is also anisotropic, which is consistent with the observation of an anisotropic superconducting gap in CeCoIn5. The critical currents, determined from the high field isothermal magnetization loops, are comparatively low (around 4000 A/cm2 at 1.6 K and 5 kOe).Comment: 4 pages 3 figure

    Discovery and Characterization of the Cryptic Psi Subunit of the Pseudomonad DNA Replicase

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    We previously reconstituted a minimal DNA replicase from Pseudomonas aeruginosa consisting of α and ϵ (polymerase and editing nuclease), β (processivity factor), and the essential τ, δ, and δ′ components of the clamp loader complex (Jarvis, T., Beaudry, A., Bullard, J., Janjic, N., and McHenry, C. (2005) J. Biol. Chem. 280, 7890-7900). In Escherichia coli DNA polymerase III holoenzyme, χ and Ψ are tightly associated clamp loader accessory subunits. The addition of E. coli χΨ to the minimal P. aeruginosa replicase stimulated its activity, suggesting the existence of χ and Ψ counterparts in P. aeruginosa. The P. aeruginosa χ subunit was recognizable from sequence similarity, but Ψ was not. Here we report purification of an endogenous replication complex from P. aeruginosa. Identification of the components led to the discovery of the cryptic Ψ subunit, encoded by holD. P. aeruginosa χ and Ψ were co-expressed and purified as a 1:1 complex. P. aeruginosa χΨ increased the specific activity of τ3δδ′ 25-fold and enabled the holoenzyme to function under physiological salt conditions. A synergistic effect between χΨ and single-stranded DNA binding protein was observed. Sequence similarity to P. aeruginosa Ψ allowed us to identify Ψ subunits from several other Pseudomonads and to predict probable translational start sites for this protein family. This represents the first identification of a highly divergent branch of the Ψ family and confirms the existence of Ψ in several organisms in which Ψ was not identifiable based on sequence similarity alone
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