433,548 research outputs found

    Proton strange form factors and SAMPLE experiments

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    We study the chiral models such as the Skyrmion and chiral bag to investigate the baryon strange form factors associated with the SAMPLE experiments.Comment: 3 page

    Emission of Axions in strongly magnetized star

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    We show that the axion decay constant does not get any correction at any order by external magnetic fields. On the other hand, in the context of the Wilsonian effective action under external magnetic fields, the axial currents get a finite correction. We then calculate the effect of strong magnetic fields B>1018GB>10^{18}G on the axion-nucleon coupling and find that if B≳1020 GB\gtrsim 10^{20}~G in strongly magnetized neutron and white dwarf stars, the emission rate of axions is enhanced by several orders of magnitude.Comment: 11 pages, RevTeX, 4 Postscript figures, uses epsf.st

    Monte-Carlo Simulations of Spin-Crossover Phenomena Based on a Vibronic Ising-like Model with Realistic Parameters

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    Materials with spin-crossover (SCO) properties hold great potentials in information storage and therefore have received a lot of concerns in the recent decades. The hysteresis phenomena accompanying SCO is attributed to the intermolecular cooperativity whose underlying mechanism may have a vibronic origin. In this work, a new vibronic Ising-like model in which the elastic coupling between SCO centers is included by considering harmonic stretching and bending (SAB) interactions is proposed and solved by Monte Carlo simulations. The key parameters in the new model, k1k_1 and k2k_2, corresponding to the elastic constant of the stretching and bending mode, respectively, can be directly related to the macroscopic bulk and shear modulus of the material in study, which can be readily estimated either based on experimental measurements or first-principles calculations. The convergence issue in the MC simulations of the thermal hysteresis has been carefully checked, and it was found that the stable hysteresis loop can be more readily obtained when using the SAB model compared to that using the Wajnflasz-Pick model. Using realistic parameters estimated based on first-principles calculations of a specific polymeric coordination SCO compound, [Fe(pz)Pt(CN)4_4]â‹…\cdot2H2_2O, temperature-induced hysteresis and pressure effects on SCO phenomena are simulated successfully.Comment: 8 pages, 8 figure

    Porosity and Micro-Hardness of Shrouded Plasma Sprayed Titanium Coatings

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    Titanium and its alloys are often used as key materials for corrosion protection. A promising approach to optimize both mechanical properties and corrosion resistance is the use of coating technologies. In this paper, shrouded plasma spray was used as a useful technology to produce low oxide containing titanium coatings. A solid shroud was used to plasma spray titanium coatings to reduce the oxide content. The titanium coatings were assessed by optical microscope, scanning electron microscopy and Vickers microhardness testing. The results showed that the shrouded titanium coatings exhibited an enhanced microstructure. The presence of the shroud and shroud gas flow led to a significant reduction in coating porosity because the reduction in air entrainment with the shroud resulted in better heating of the particles. The shrouded titanium coatings had a lower value of Vickers microhardness and a relative lower standard deviation than the air plasma sprayed titanium coatings
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