452 research outputs found

    Two sides of the same coin: Opinions and choices of users and non-users related to mobile music listening

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    Mobile music listening has been explored from several perspectives, however, not much is known about the choices mobile music listeners have to make. Moreover, feedback from non-listeners on music listening has only been given anecdotally and not in the context of research. The aim of this thesis is therefore to investigate what motivates listeners to engage with mobile music and to discover more about the social and personal aspects that influence this engagement, as well as to explore views of non-listeners on mobile music listening. Employing a mixed-methods approach, interviews and participant observation were carried out with eleven mobile music listeners to investigate their thoughts and motivations regarding mobile music listening, and to verify these in practice. Eleven people who do not use portable listening devices were also interviewed about their opinions on mobile music listening. The most striking finding of this thesis is that listeners are not always listeners since they sometimes turn off their devices. The interviews with non-users of portable listening devices confirm that mobile music listening is not always seen as positive but has negative aspects as well, which add an important perspective to understanding this behaviour. Results reveal that mobile music listening is a complex cultural practice that connects to many parts of everyday life. Thus, mobile music listening, and similar practices, need to be studied in context to fully grasp everything that is happening. The new method applied in the first study proved to be beneficial in studying everyday behaviour as it occurs. It helps to gain valuable in-depth information in a short amount of time which is useful for future studies of everyday practices. Finally, results show that mobile music listening is simultaneously more sociable than previously assumed but also perceived as unsociable, which contributes a new perspective to studies of urban behaviour

    A gradient index metamaterial

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    Metamaterials--artificially structured materials with tailored electromagnetic response--can be designed to have properties difficult to achieve with existing materials. Here we present a structured metamaterial, based on conducting split ring resonators (SRRs), which has an effective index-of-refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam by a planar slab of the composite metamaterial over a broad range of frequencies. The gradient index metamaterial represents an alternative approach to the development of gradient index lenses and similar optics that may be advantageous, especially at higher frequencies. In particular, the gradient index material we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated

    LDEF Space Plasma-High Voltage Drainage Experiment post-flight results

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    The Space Plasma-High Voltage Drainage Experiment (SP-HVDE) was comprised of two identical experimental trays. With one tray located on the leading (ram facing, B10) edge and the other located on the trailing (wake facing, D4) edge of the Long Duration Exposure Facility (LDEF), it was possible to directly compare the effects of ram and wake spacecraft environments on charged dielectric materials. Six arrays of Kapton dielectric samples of 2 mil, 3 mil, and 5 mil thicknesses maintained at +/- 300, +/- 500, and +/- 1000 voltage bias formed the experimental matrix of each tray. In addition, each tray carried two solar cell strings, one biased at +300 volts and the other at -300 volts, to study current leakage from High Voltage Solar Arrays (HVSA). The SP-HVDE provides the first direct, long-term, in-flight measurements of average leakage current through dielectric materials under electric stress. The experiment also yields information on the long term stability of the bulk dielectric properties of such materials. Data and findings of the SP-HVDE are an extension of those from shorter term flight experiments such as the PIX-1 (Plasma Interaction Experiment) and PIX-2 and are therefore valuable in the design and evaluation of long-lived space systems with high voltage systems exposed to the low earth orbital environment. A summary of the SP-HVDE post flight analysis final report delivered to the LDEF Project Office under contract to the National Aeronautics and Space Administration is presented

    Ac magnetic susceptibility of a molecular magnet submonolayer directly patterned onto a microSQUID sensor

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    We report the controlled integration, via Dip Pen Nanolithography, of monolayer dots of ferritin-based CoO nanoparticles (12 Bohr magnetons) into the most sensitive areas of a microSQUID sensor. The nearly optimum flux coupling between these nanomagnets and the microSQUID improves the achievable sensitivity by a factor 100, enabling us to measure the linear susceptibility of the molecular array down to very low temperatures (13 mK). This method opens the possibility of applying ac susceptibility experiments to characterize two-dimensional arrays of single molecule magnets within a wide range of temperatures and frequencies.Comment: 4 pages 3 figure

    Editorial

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    Deep subcutaneous application of poly-L-lactic acid as a filler for facial lipoatrophy in HIV-infected patients

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    Introduction: Facial lipoatrophy is a crucial problem of HIV-infected patients undergoing highly active antiretroviral therapy (HAART). Poly-L-lactic acid (PLA), provided as New-Fill(R)/Sculptra(TM), is known as one possible treatment option. In 2004 PLA was approved by the FDA as Sculptra(TM) for the treatment of lipoatrophy of the face in HIV-infected patients. While the first trials demonstrated relevant efficacy, this was to some extent linked to unwanted effects. As the depth of injection was considered relevant in this context, the application modalities of the preparation were changed. The preparation was to be injected more deeply into subcutaneous tissue, after increased dilution. Material and Methods: To test this approach we performed a pilot study following the new recommendations in 14 patients. Results: While the efficacy turned out to be about the same, tolerability was markedly improved. The increase in facial dermal thickness was particularly obvious in those patients who had suffered from lipoatrophy for a comparatively small period of time. Conclusion: With the new recommendations to dilute PLA powder and to inject it into the deeper subcutaneous tissue nodule formation is a minor problem. However, good treatment results can only be achieved if lipoatrophy is not too intense; treatment intervals should be about 2 - 3 weeks. Copyright (C) 2005 S. Karger AG, Basel

    Quantum manipulation via atomic-scale magnetoelectric effects

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    Magnetoelectric effects at the atomic scale are demonstrated to afford unique functionality. This is shown explicitly for a quantum corral defined by a wall of magnetic atoms deposited on a metal surface where spin-orbit coupling is observable. We show these magnetoelectric effects allow one to control the properties of systems placed inside the corral as well as their electronic signatures; they provide alternative tools for probing electronic properties at the atomic scale

    Mechanical Metamaterials with Negative Compressibility Transitions

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    When tensioned, ordinary materials expand along the direction of the applied force. Here, we explore network concepts to design metamaterials exhibiting negative compressibility transitions, during which a material undergoes contraction when tensioned (or expansion when pressured). Continuous contraction of a material in the same direction of an applied tension, and in response to this tension, is inherently unstable. The conceptually similar effect we demonstrate can be achieved, however, through destabilisations of (meta)stable equilibria of the constituents. These destabilisations give rise to a stress-induced solid-solid phase transition associated with a twisted hysteresis curve for the stress-strain relationship. The strain-driven counterpart of negative compressibility transitions is a force amplification phenomenon, where an increase in deformation induces a discontinuous increase in response force. We suggest that the proposed materials could be useful for the design of actuators, force amplifiers, micro-mechanical controls, and protective devices.Comment: Supplementary information available at http://www.nature.com/nmat/journal/v11/n7/abs/nmat3331.htm

    Photonic Analogue of Two-dimensional Topological Insulators and Helical One-Way Edge Transport in Bi-Anisotropic Metamaterials

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    Recent progress in understanding the topological properties of condensed matter has led to the discovery of time-reversal invariant topological insulators. Because of limitations imposed by nature, topologically non-trivial electronic order seems to be uncommon except in small-band-gap semiconductors with strong spin-orbit interactions. In this Article we show that artificial electromagnetic structures, known as metamaterials, provide an attractive platform for designing photonic analogues of topological insulators. We demonstrate that a judicious choice of the metamaterial parameters can create photonic phases that support a pair of helical edge states, and that these edge states enable one-way photonic transport that is robust against disorder.Comment: 13 pages, 3 figure
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