14,812 research outputs found

    Tunable Hydrogen Storage in Magnesium - Transition Metal Compounds

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    Magnesium dihydride (\mgh) stores 7.7 weight % hydrogen, but it suffers from a high thermodynamic stability and slow (de)hydrogenation kinetics. Alloying Mg with lightweight transition metals (TM = Sc, Ti, V, Cr) aims at improving the thermodynamic and kinetic properties. We study the structure and stability of Mgx_xTM1x_{1-x}H2_2 compounds, x=[0x=[0-1], by first-principles calculations at the level of density functional theory. We find that the experimentally observed sharp decrease in hydrogenation rates for x0.8x\gtrsim0.8 correlates with a phase transition of Mgx_xTM1x_{1-x}H2_2 from a fluorite to a rutile phase. The stability of these compounds decreases along the series Sc, Ti, V, Cr. Varying the transition metal (TM) and the composition xx, the formation enthalpy of Mgx_xTM1x_{1-x}H2_2 can be tuned over the substantial range 0-2 eV/f.u. Assuming however that the alloy Mgx_xTM1x_{1-x} does not decompose upon dehydrogenation, the enthalpy associated with reversible hydrogenation of compounds with a high magnesium content (x=0.75x=0.75) is close to that of pure Mg.Comment: 8 pages, 5 figure

    Relativity and EPR Entanglement: Comments

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    Recent experiment by Zhinden et al (Phys. Rev {\bf A} 63 02111, 2001) purports to test compatibility between relativity and quantum mechanics in the classic EPR setting. We argue that relativity has no role in the EPR argument based solely on non-relativistic quantum formalism. It is suggested that this interesting experiment may have significance to address fundamental questions on quantum probability.Comment: 6 pages, no figure; Submitted to Phys. Rev.

    Radiative and non-radiative effects of a substrate on localized plasmon resonance of particles

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    Experiments have shown strong effects of some substrates on the localized plasmons of metallic nano particles but they are inconclusive on the affecting parameters. Here we have used Discrete Dipole Approximation in conjunction with Sommerfeld integral relations to explain the effect of the substrates as a function of the parameters of incident radiation. The radiative coupling can both quench and enhance the resonance and its dependence on the angle and polarization of incident radiation with respect to the surface is shown. Non-radiative interaction with the substrate enhances the plasmon resonance of the particles and can shift the resonances from their free-space energies significantly. The non-radiative interaction of the substrate is sensitive to the shape of particles and polarization of incident radiation with respect to substrate. Our results show that plasmon resonances in coupled and single particles can be significantly altered from their free-space resonances and are quenched or enhanced by the choice of substrate and polarization of incident radiation.Comment: 14 pages, 4 figure

    Classical Electron Model with Negative Energy Density in Einstein-Cartan Theory of Gravitation

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    Experimental result regarding the maximum limit of the radius of the electron \sim 10^{-16} cm and a few of the theoretical works suggest that the gravitational mass which is a priori a positive quantity in Newtonian mechanics may become negative in general theory of relativity. It is argued that such a negative gravitational mass and hence negative energy density also can be obtained with a better physical interpretation in the framework of Einstein-Cartan theory.Comment: 12 Latex pages, added refs and conclusion

    Evaluating the Chinese Revised Controlling Behaviors Scale (C-CBS-R)

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    The present study evaluated the utility of the Chinese version of the Revised Controlling Behaviors Scale (C-CBS-R) as a measure of controlling behaviors in violent Chinese intimate relationships. Using a mixed-methods approach, in-depth, individual interviews were conducted with 200 Chinese women survivors to elicit qualitative data about their personal experiences of control in intimate relationships. The use of controlling behaviors was also assessed using the C-CBS-R. Interview accounts suggested that the experiences of 91 of the women were consistent with the description of coercive control according to Dutton and Goodman’s (2005) conceptualization of coercion. Using the split-half validation procedure, a receiver operating characteristics (ROC) curve analysis was conducted with the first half of the sample. The area under the curve (AUC) for using the C-CBS-R to identify high control was .99, and the cutoff score of 1.145 maximized both sensitivity and specificity. Applying the cutoff score to the second half gave a sensitivity of 96% and a specificity of 95%. Overall, the C-CBS-R has demonstrated utility as a measure of controlling behaviors with a cutoff score for distinguishing high from low levels of control in violent Chinese intimate relationships