5,781 research outputs found

    Socioeconomic impact of photovoltaic power at Schuchuli, Arizona

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    The social and economic impact of photovoltaic power on a small, remote native American village is studied. Village history, group life, energy use in general, and the use of photovoltaic-powered appliances are discussed. No significant impacts due to the photovoltaic power system were observed

    Elastic energy of proteins and the stages of protein folding

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    We propose a universal elastic energy for proteins, which depends only on the radius of gyration RgR_{g} and the residue number NN. It is constructed using physical arguments based on the hydrophobic effect and hydrogen bonding. Adjustable parameters are fitted to data from the computer simulation of the folding of a set of proteins using the CSAW (conditioned self-avoiding walk) model. The elastic energy gives rise to scaling relations of the form RgNνR_{g}\sim N^{\nu} in different regions. It shows three folding stages characterized by the progression with exponents ν=3/5,3/7,2/5\nu = 3/5, 3/7, 2/5, which we identify as the unfolded stage, pre-globule, and molten globule, respectively. The pre-globule goes over to the molten globule via a break in behavior akin to a first-order phase transition, which is initiated by a sudden acceleration of hydrogen bonding

    Magnetic properties of (VO)_2P_2O_7: two-plane structure and spin-phonon interactions

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    Detailed experiments on single-crystal (VO)_2P_2O_7 continue to reveal new and unexpected features. We show that a model composed of two, independent planes of spin chains with frustrated magnetic coupling is consistent with nuclear magnetic resonance and inelastic neutron scattering measurements. The pivotal role of PO_4 groups in mediating intrachain exchange interactions explains both the presence of two chain types and their extreme sensitivity to certain lattice vibrations, which results in the strong magnetoelastic coupling observed by light scattering. We compute the respective modifications of the spin and phonon dynamics due to this coupling, and illustrate their observable consequences on the phonon frequencies, magnon dispersions, static susceptibility and specific heat.Comment: 10 pages, 9 figure

    Magnetic Properties of (VO)_2P_2O_7 from Frustrated Interchain Coupling

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    Neutron-scattering experiments on (VO)_2P_2O_7 reveal both a gapped magnon dispersion and an unexpected, low-lying second mode. The proximity and intensity of these modes suggest a frustrated coupling between the alternating spin chains. We deduce the minimal model containing such a frustration, and show that it gives an excellent account of the magnon dispersion, static susceptibility and electron spin resonance absorption. We consider two-magnon states which bind due to frustration, and demonstrate that these may provide a consistent explanation for the second mode.Comment: RevTeX, 5 pages, 6 figures, compressed from first versio

    Gapped Excitations in the High-Pressure Antiferromagnetic Phase of URu2_2Si2_2

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    We report a neutron scattering study of the magnetic excitation spectrum in each of the three temperature and pressure driven phases of URu2_2Si2_2. We find qualitatively similar excitations throughout the (H0L) scattering plane in the hidden order and large moment phases, with no changes in the ω\hbar\omega-widths of the excitations at the Σ\Sigma = (1.407,0,0) and ZZ = (1,0,0) points, within our experimental resolution. There is, however, an increase in the gap at the Σ\Sigma point from 4.2(2) meV to 5.5(3) meV, consistent with other indicators of enhanced antiferromagnetism under pressure.Comment: 5 pages, 3 figures, 1 tabl

    Globalization, the ambivalence of European integration and the possibilities for a post-disciplinary EU studies

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    Using the work of Manuel Castells as a starting point, this article explores the ambivalent relationship between globalization and European integration and the variety of ways in which the mainstream political science of the EU has attempted to deal with this issue. The analysis here suggests that various 'mainstreaming' disciplinary norms induce types of work that fail to address fully the somewhat paradoxical and counter-intuitive range of possible relationships between globalization and European integration. The article explores critically four possible analytical ways out of this paradox—abandonment of the concept of globalization, the development of definition precision in globalization studies, the reorientation of work to focus on globalization as discourse, and inter- and post-disciplinarity. The argument suggests that orthodox discussions of the relationship require a notion of social geography that sits at odds with much of the literature on globalization and while greater dialogue between disciplines is to be welcomed, a series of profound epistemological questions need to be confronted if studies of the interplay between global and social process are to be liberated from their disciplinary chains
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