604 research outputs found

    The barium iron ruthenium oxide system

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    In the system BaFe(1-x)Ru(x)O(3-y), three phases, separated by immiscibility gaps, are present: an Fe-rich phase (x = 0 to 0.75) with hexagonal BaTiO3 structure (6H; sequence (hcc)2), a Ru-rich phase (x = 0.9) of hexagonal 4H-type (sequence (hc)2), and the pure Ru compounds BaRuO3 with rhombohedral 9R structure (sequence (hhc)3). By vibrational spectroscopic investigations in the 6H phase a transition from n-type semiconduction (Fe-rich compounds with complete O lattice) can be detected. The 4H and 9R stacking polytypes are good, metal-like conductors. The lattice parameters are given

    Improved Semileptonic Form Factor Calculations in Lattice QCD

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    We investigate the computational efficiency of two stochastic based alternatives to the Sequential Propagator Method used in Lattice QCD calculations of heavy-light semileptonic form factors. In the first method, we replace the sequential propagator, which couples the calculation of two of the three propagators required for the calculation, with a stochastic propagator so that the calculations of all three propagators are independent. This method is more flexible than the Sequential Propagator Method but introduces stochastic noise. We study the noise to determine when this method becomes competitive with the Sequential Propagator Method, and find that for any practical calculation it is competitive with or superior to the Sequential Propagator Method. We also examine a second stochastic method, the so-called ``one-end trick", concluding it is relatively inefficient in this context. The investigation is carried out on two gauge field ensembles, using the non-perturbatively improved Wilson-Sheikholeslami-Wohlert action with N_f=2 mass-degenerate sea quarks. The two ensembles have similar lattice spacings but different sea quark masses. We use the first stochastic method to extract O(a){\mathcal O}(a)-improved, matched lattice results for the semileptonic form factors on the ensemble with lighter sea quarks, extracting f_+(0)

    Charmonium spectroscopy and mixing with light quark and open charm states from nF=2 lattice QCD

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    We study the charmonium spectrum including higher spin and gluonic excitations. We determine an upper limit on the mixing of the eta_c ground state with light pseudoscalar flavour-singlet mesons and investigate the mixing of charmonia near open charm thresholds with pairs of (excited) D and anti-D mesons. For charm and light valence quarks and nF=2 sea quarks, we employ the non-perturbatively improved Sheikholeslami-Wohlert (clover) action. Excited states are accessed using the variational technique, starting from a basis of suitably optimised operators. For some aspects of this study, the use of improved stochastic all-to-all propagators was essential.Comment: 23 pages, v2: references updated, correction of an ambiguous statement, minor typos corrected, some figures update

    Charm quark system at the physical point of 2+1 flavor lattice QCD

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    We investigate the charm quark system using the relativistic heavy quark action on 2+1 flavor PACS-CS configurations previously generated on 323×6432^3 \times 64 lattice. The dynamical up-down and strange quark masses are set to the physical values by using the technique of reweighting to shift the quark hopping parameters from the values employed in the configuration generation. At the physical point, the lattice spacing equals a−1=2.194(10)a^{-1}=2.194(10) GeV and the spatial extent L=2.88(1)L=2.88(1) fm. The charm quark mass is determined by the spin-averaged mass of the 1S charmonium state, from which we obtain m_{\rm charm}^{\msbar}(\mu = m_{\rm charm}^{\msbar}) = 1.260(1)(6)(35) GeV, where the errors are due to our statistics, scale determination and renormalization factor. An additional systematic error from the heavy quark is of order αs2f(mQa)(aΛQCD)\alpha_s^2 f(m_Q a)(a \Lambda_{QCD}), which is estimated to be a percent level if the factor f(mQa)f(m_Q a) analytic in mQam_Q a is of order unity. Our results for the charmed and charmed-strange meson decay constants are fD=226(6)(1)(5)f_D=226(6)(1)(5) MeV, fDs=257(2)(1)(5)f_{D_s}=257(2)(1)(5) MeV, again up to the heavy quark errors of order αs2f(mQa)(aΛQCD)\alpha_s^2 f(m_Q a)(a \Lambda_{QCD}). Combined with the CLEO values for the leptonic decay widths, these values yield ∣Vcd∣=0.205(6)(1)(5)(9)|V_{cd}| = 0.205(6)(1)(5)(9), ∣Vcs∣=1.00(1)(1)(3)(3)|V_{cs}| = 1.00(1)(1)(3)(3), where the last error is on account of the experimental uncertainty of the decay widths.Comment: 16 pages, 12 figure

    Surface Modification of Polycrystalline Diamond Compacts by Carbon Ion Irradiation

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    Selective modification (e.g. defect creation and amorphization) of diamond surfaces is of interests for functional diamond-based semiconductors and devices. Bombarding the diamond surface with high energy radiation sources such as electron, proton, and neutrons, however, often result in detrimental defects in deep bulk regions under the diamond surface. In this study, we utilized high energy carbon ions of 3 MeV to bombard the polycrystalline diamond compact (PDC) specimen. The resultant microstructure of PDCs was investigated using micro Raman spectroscopy. The results show that the carbon bombardment successfully created point defects and amorphization in a shallow region of ∼500 nm deep on the diamond surface. The new method has great potential to allow diamond-based semiconductor devices to be used in numerous applications

    Biomarker qualification at the European Medicines Agency: a review of biomarker qualification procedures from 2008 to 2020

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    Regulatory qualification of biomarkers facilitates their harmonised use across drug developers, enabling more personalised medicine. This study reviews various aspects of the European Medicines Agency's (EMA) biomarker qualification procedure, including frequency and outcome, common challenges, and biomarker characteristics. Our findings provide insights into EMA's biomarker qualification process and will thereby support future applications. All biomarker-related "Qualification of Novel Methodologies for Medicine Development" procedures that started from 2008 to 2020 were included. Procedural data were extracted from relevant documents and analysed descriptively. In total, 86 biomarker qualification procedures were identified, of which 13 resulted in qualified biomarkers. Whereas initially many biomarker qualification procedures were linked to a single company and specific drug development program, a shift was observed to qualification efforts by consortia. Most biomarkers were proposed (n=45) and qualified (n=9) for use in patient selection, stratification, and enrichment, followed by efficacy biomarkers (37 proposed, 4 qualified). Overall, many issues were raised during qualification procedures, mostly related to biomarker properties and assay validation (in 79% and 77% of all procedures, respectively). Issues related to the proposed context of use and rationale were least common, yet, were still raised in 54% of all procedures. While few qualified biomarkers are currently available, procedures focus increasingly on biomarkers for general use instead of those linked to specific drug compounds. The issues raised during qualification procedures illustrate the thorough discussions taking place between applicants and regulators - highlighting aspects that need careful consideration and underlining the importance of an appropriate validation strategy

    Design of a five-axis ultra-precision micro-milling machine—UltraMill. Part 1: Holistic design approach, design considerations and specifications

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    High-accuracy three-dimensional miniature components and microstructures are increasingly in demand in the sector of electro-optics, automotive, biotechnology, aerospace and information-technology industries. A rational approach to mechanical micro machining is to develop ultra-precision machines with small footprints. In part 1 of this two-part paper, the-state-of-the-art of ultra-precision machines with micro-machining capability is critically reviewed. The design considerations and specifications of a five-axis ultra-precision micro-milling machine—UltraMill—are discussed. Three prioritised design issues: motion accuracy, dynamic stiffness and thermal stability, formulate the holistic design approach for UltraMill. This approach has been applied to the development of key machine components and their integration so as to achieve high accuracy and nanometer surface finish

    Nucleotide sequence of cDNA encoding the precursor of the 23 kDa photosystem II protein of tomato

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43431/1/11103_2004_Article_BF00019216.pd
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