36,845 research outputs found

    Non-invasive vibrational mode spectroscopy of ion Coulomb crystals through resonant collective coupling to an optical cavity field

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    We report on a novel non-invasive method to determine the normal mode frequencies of ion Coulomb crystals in traps based on the resonance enhanced collective coupling between the electronic states of the ions and an optical cavity field at the single photon level. Excitations of the normal modes are observed through a Doppler broadening of the resonance. An excellent agreement with the predictions of a zero-temperature uniformly charged liquid plasma model is found. The technique opens up for investigations of the heating and damping of cold plasma modes, as well as the coupling between them.Comment: 4 pages, 4 figure

    Voltage from mechanical stress in type-II superconductors: Depinning of the magnetic flux by moving dislocations

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    Mechanical stress causes motion of defects in solids. We show that in a type-II superconductor a moving dislocation generates a pattern of current that exerts the depinning force on the surrounding vortex lattice. Concentration of dislocations and the mechanical stress needed to produce critical depinning currents are shown to be within practical range. When external magnetic field and transport current are present this effect generates voltage across the superconductor. Thus a superconductor can serve as an electrical sensor of the mechanical stress.Comment: 3 pages, 1 figure

    Experimental Studies for the Detection of Protein in Trace Amounts Quarterly Status Report, 1 Mar. - 31 May 1965

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    Methods for separating inorganic compounds from organic materials in investigation of trace proteins in soil

    Buckets of Water into the Ocean: Non-public Revenue in Public Charter and Traditional Public Schools

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    The funding of K-12 education remains a contentious public policy issue. Questions of funding adequacy and equity across school sectors, school districts and individual schools are prominent in discussions of how to improve educational outcomes, especially for students from disadvantaged backgrounds (Downes & Stiefel 2008; Ladd 2008). Although scholars are divided regarding the extent to which money affects student outcomes in K-12 education (Jackson, Johnson, & Persico 2015; Hanushek, 1997; Burtless 1996), there is basic agreement that more education revenue is better so long as the increased resources are directed towards productive educational activities and programs (Murnane & Levy 1996). If you ask education practitioners, the majority will say that more resources will make their schools better

    Clusterization, frustration and collectivity in random networks

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    We consider the random Erd{\H o}s--R\'enyi network with enhanced clusterization and Ising spins s=±1s=\pm 1 at the network nodes. Mutually linked spins interact with energy JJ. Magnetic properties of the system as dependent on the clustering coefficient CC are investigated with the Monte Carlo heat bath algorithm. For J>0J>0 the Curie temperature TcT_c increases from 3.9 to 5.5 when CC increases from almost zero to 0.18. These results deviate only slightly from the mean field theory. For J<0J<0 the spin-glass phase appears below TSGT_{SG}; this temperature decreases with CC, on the contrary to the mean field calculations. The results are interpreted in terms of social systems.Comment: 10 pages, 6 figures; serious change of result
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