5,378 research outputs found

    Model of the Longitudinal Spin Seebeck Coefficient of InSb in a Magnetic Field

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    We develop a simple theory for the longitudinal spin Seebeck effect in n-doped InSb in an external magnetic field. We consider spin-1/21/2 electrons in the conduction band of InSb with a temperature gradient parallel to the applied magnetic field. In the absence of spin-orbit interactions, a Boltzmann equation approach leads to a spin current parallel to the field and proportional to the temperature gradient. The calculated longitudinal spin Seebeck coefficients oscillates as a function of magnetic field B; the peak positions are approximately periodic in 1/B. The oscillations arise when the Fermi energy crosses the bottom of a Landau band.Comment: 7 pages, 6 figure

    Graphene with adatoms: tuning the magnetic moment with an applied voltage

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    We show that, in graphene with a small concentration of adatoms, the total magnetic moment μT\mu_T can be switched on and off by varying the Fermi energy EFE_F, either by applying a gate voltage or by suitable chemical doping. Our calculation is carried out using a simple tight-binding model described previously, combined with a mean-field treatment of the electron-electron interaction on the adatom. The values of EFE_F at which the moment is turned on or off are controlled by the strength of the hopping between the graphene sheet and the adatom, the on-site energy of the adatom, and the strength of the electron-electron correlation energy U. Our result is in qualitatively consistent with recent experiments by Nair {\it et al.} [Nat.\ Commun.\ {\bf 4}, 2010 (2013)].Comment: 4 Pages, 1 Figur

    Theory of plasmonic waves on a chain of metallic nanoparticles in a liquid crystalline host

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    A chain of metallic particles, of sufficiently small diameter and spacing, allows linearly polarized plasmonic waves to propagate along the chain. In this paper, we describes how these waves are altered when the liquid crystal host is a nematic or a cholesteric liquid crystal (NLC or CLC) with or without an applied magnetic field. We find that, in general, the liquid crystal host, either NLC or CLC, alters the dispersion relations of the transverse (TT) and longitudinal (LL) waves significantly from the dispersion relations for an isotropic host. We show that by altering the director axis of the liquid crystal relative to the long axis of the metallic chain, that the TT branch can be split into two non-degenerate linearly polarized branches (NLC host) or two non-degenerate elliptically polarized branches (CLC host). When an external magnetic field is applied parallel to both the long axis of the metallic particles and the director of the CLC host, we find that the dispersion relations are odd in an exchange in sign for ω\omega for the non-degenerate elliptically polarized TT branches. That is, the application of an external magnetic field leads to the realization of a one-way waveguide.Comment: 9 Pages, 3 Figures. arXiv admin note: text overlap with arXiv:1210.150

    Interactions measurement payload for Shuttle

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    The Interactions Measurement Payload for Shuttle (IMPS) consisted of engineering experiments to determine the effects of the space environment on projected Air Force space systems. Measurements by IMPS on a polar-orbit Shuttle flight will lead to detailed knowledge of the interaction of the low-altitude polar-auroral environment on materials, equipment and technologies to be used in future large, high-power space systems. The results from the IMPS measurements will provide direct input to MIL-STD design guidelines and test standards that properly account for space-environment effects

    Thermodynamic properties in polynomial form for carbon, hydrogen, nitrogen, and oxygen systems from 300 to 15000 K

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    Thermodynamic properties in polynomial form for carbon, hydrogen, nitrogen, and oxygen systems form 300 to 15000

    Doing evolution in economic geography

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    Evolutionary approaches in economic geography face questions about the relationships between their concepts, theories, methods, politics, and policy implications. Amidst the growing but unsettled consensus that evolutionary approaches should employ plural methodologies, the aims here are, first, to identify some of the difficult issues confronting those working with different frameworks. The concerns comprise specifying and connecting research objects, subjects, and levels; handling agency and context; engaging and integrating the quantitative and the qualitative; comparing cases; and, considering politics, policy, and praxis. Second, the purpose is to articulate a distinctive geographical political economy approach, methods, and illustrative examples in addressing these issues. Bringing different views of evolution in economic geography into dialogue and disagreement renders methodological pluralism a means toward improved understanding and explanation rather than an end in itself. Confronting such thorny matters needs to be embedded in our research practices and supported by greater openness; more and better substantiation of our conceptual, theoretical, and empirical claims; enhanced critical reflection; and deeper engagement with politics, policy, and praxis

    Single and Double Nucleophilic-Addition to Coordinated PI-Hydrocarbons - Manganese-Mediated Functionalization of Arenes

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    A range of carbon-donor nucleophiles add to the arene ring in (arene)Mn(CO)2L+ cations to give neutral cyclohexadienyl complexes that liberate monofunctionalized arenes upon oxidative removal of the metal. Treatment of the cyclohexadienyl complexes with the nitrosonium salt NOPF6 affords cationic metal nitrosyl complexes that are attacked by a second nucleophile to give cis- and trans-difunctionalized 1,3-cyclohexadienes. When the metal center is chiral, this procedure provides a route to enantiomerically pure cyclohexadienes. 1. Introduction 2. Mechanism of Nucleophilic Addition 3. Single Nucleophilic Addition 4. Double Nucleophilic Addition 5. Conclusion

    On the Localization of One-Photon States

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    Single photon states with arbitrarily fast asymptotic power-law fall-off of energy density and photodetection rate are explicitly constructed. This goes beyond the recently discovered tenth power-law of the Hellwarth-Nouchi photon which itself superseded the long-standing seventh power-law of the Amrein photon.Comment: 7 pages, tex, no figure
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