23,797 research outputs found

    Exciton-polariton emission from organic semiconductor optical waveguides

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    We photo-excite slab polymer waveguides doped with J-aggregating dye molecules and measure the leaky emission from strongly coupled waveguide exciton polariton modes at room temperature. We show that the momentum of the waveguide exciton polaritons can be controlled by modifying the thickness of the excitonic waveguide. Non-resonantly pumped excitons in the slab excitonic waveguide decay into transverse electric and transverse magnetic strongly coupled exciton waveguide modes with radial symmetry. These leak to cones of light with radial and azimuthal polarizations

    Tests of Ocean-Tide Models by Analysis of Satellite-To-Satellite Range Measurements: An Update

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    Seven years of GRACE intersatellite range-rate measurements are used to test the new ocean tide model FES2014 and to compare against similar results obtained with earlier models. These qualitative assessments show that FES2014 represents a marked improvement in accuracy over its earlier incarnation, FES2012, with especially notable improvements in the Arctic Ocean for constituents K(sub 1) and S(sub 2). Degradation appears to have occurred in two anomalous regions: the Ross Sea for the O(sub 1) constituent and the Weddell Sea for M(sub 2)

    Promoting Librarian-Faculty Collaboration to Advance Information Literacy: Hanover College's Pilot Program

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    In 2005, a team from Hanover College (Academic Dean, Library Director, Faculty member) took part in Transformation of the College Library, a workshop offered by The Council of Independent Colleges. The focus of the meeting, advancing Information Literacy, culminated in participating instructions outlining an actionable plan for implementing/improving these important standards on their campus. As a result, the Duggan Library at Hanover College formed a year-long pilot program designed to support faculty wishing to incorporate information literacy concepts into their courses. During the Winter term of 2006, the Library completed a series of classes with topics ranging from research assignment development, to plagiarism and web technology. The remainder of the pilot program includes a session on evaluation followed by a campus-wide forum in January 2007 as Hanover considers the next steps in the Information Literacy initiative

    Effects of virus infection on release of volatile organic compounds from insect-damaged bean, Phaseolus vulgaris

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    Insects can serve as important vectors of plant pathogens, especially viruses. Insect feeding on plants causes the systemic release of a wide range of plant volatile compounds that can serve as an indirect plant defense by attracting natural enemies of the herbivorous insect. Previous work suggests that the Mexican bean beetle (Epilachna varivestis) prefers to feed on plants infected by either of two viruses that it is known to transmit: Southern bean mosaic virus (SBMV) or Bean pod mottle virus (BPMV). A possible explanation for the preferred feeding on virus-infected tissues is that the beetles are attracted by volatile signals released from leaves. The purpose of this work was to determine whether volatile compounds from virus-infected plants are released differentially from those emitted by uninfected plants. To test the hypothesis, common bean plants (Phaseolus vulgaris cv. Black Valentine) were inoculated with either BPMV, SBMV, or a mixture of both viruses, and infected plants were compared to uninfected plants. An Ouchterlony assay was used with SBMVand BPMV-specific antisera to confirm the presence of virus in inoculated plants. RNA blot analysis was performed on tissue from each plant and indicated that a well-characterized defense gene, encoding phenylalanine ammonia-lyase (PAL), was not induced in systemic tissue following virus infection. Plant volatiles were collected—and analyzed via gas chromatography (GC)—from plants that were either undamaged or beetle-damaged. In undamaged plants, there were no measurable differences in profiles or quantities of compounds released by uninfected and virus-infected plants. After Mexican bean beetles were allowed to feed on plants for 48 h, injured plants released several compounds that were not released from undamaged plants. Lower quantities of volatile compounds were released from virus-infected plants suggesting that enhanced release of plant-derived volatile organic compounds is not the cause for attraction of Mexican bean beetles to virus-infected plants

    Casimir forces in a T operator approach

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    We explore the scattering approach to Casimir forces. Our main tool is the description of Casimir energy in terms of transition operators, as presented in Kenneth and Klich, Phys. Rev. Lett. 97, 160401 (2006). We study the convergence properties of the formula and how to utilize it, together with scattering data to compute the force. We illustrate the approach by describing the force between scatterers in 1d and 3d,, and in particular show how it may be applied in order to study the interaction between two spherical bodies at all distances

    Sensing and control in dual-recycling laser interferometer gravitational-wave detectors

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    We introduce length-sensing and control schemes for the dual-recycled cavity-enhanced Michelson interferometer configuration proposed for the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO). We discuss the principles of this scheme and show methods that allow sensing and control signals to be derived. Experimental verification was carried out in three benchtop experiments that are introduced. We present the implications of the results from these experiments for Advanced LIGO and other future interferometric gravitational-wave detectors

    Speech Communication

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    Contains reports on two research projects.National Institutes of Health (Grant MH-04737-03)National Science Foundation (Grant G-16526)National Aeronautics and Space Administration (Grant NsG-496)United States Air Force, Electronic Systems Division (Contract AF19(604)-6102
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