51,537 research outputs found

    On the Superradiance of Spin-1 Waves in an Equatorial Wedge around a Kerr Hole

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    Recently Van Putten has suggested that superradiance of magnetosonic waves in a toroidal magnetosphere around a Kerr black hole may play a role in the central engine of gamma-ray bursts. In this context, he computed (in the WKB approximation) the superradiant amplification of scalar waves confined to a thin equatorial wedge around a Kerr hole and found that the superradiance is higher than for radiation incident over all angles. This paper presents calculations of both spin-0 (scalar) superradiance (integrating the radial equation rather than using the WKB method) and and spin-1 (electromagnetic/magnetosonic) superradiance, in Van Putten's wedge geometry. In contrast to the scalar case, spin-1 superradiance decreases in the wedge geometry, decreasing the likelihood of its astrophysical importance.Comment: Submitted to The Astrophysical Journal Letter

    Model for the unidirectional motion of a dynein molecule

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    Cytoplasmic dyneins transport cellular organelles by moving on a microtubule filament. It has been found recently that depending on the applied force and the concentration of the adenosine triphosphate (ATP) molecules, dynein's step size varies. Based on these studies, we propose a simple model for dynein's unidirectional motion taking into account the variations in its step size. We study how the average velocity and the relative dispersion in the displacement vary with the applied load. The model is amenable to further extensions by inclusion of details associated with the structure and the processivity of the molecule.Comment: 10 pages, 5 figure

    Development of a mechatronic sorting system for removing contaminants from wool

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    Automated visual inspection (AVI) systems have been extended to many fields, such as agriculture and the food, plastic and textile industries. Generally, most visual systems only inspect product defects, and then analyze and grade them due to the lack of any sorting function. This main reason rests with the difficulty of using the image data in real time. However, it is increasingly important to either sort good products from bad or grade products into separate groups usingAVI systems. This article describes the development of a mechatronic sorting system and its integration with a vision system for automatically removing contaminants from wool in real time. The integration is implemented by a personal computer, which continuously processes live images under the Windows 2000 operating system. The developed real-time sorting approach is also applicable to many other AVI systems

    The Semiclassical Limit for SU(2)SU(2) and SO(3)SO(3) Gauge Theory on the Torus

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    We prove that for SU(2)SU(2) and SO(3)SO(3) quantum gauge theory on a torus, holonomy expectation values with respect to the Yang-Mills measure d\mu_T(\o) =N_T^{-1}e^{-S_{YM}(\o)/T}[{\cal D}\o] converge, as T0T\downarrow 0, to integrals with respect to a symplectic volume measure μ0\mu_0 on the moduli space of flat connections on the bundle. These moduli spaces and the symplectic structures are described explicitly.Comment: 18 page

    String-Inspired Triplet See-Saw from Diagonal Embedding of SU(2)_L in SU(2)_A x SU(2)_B

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    Motivated by string constructions, we consider a variant on the Type II see-saw mechanism involving the exchange of triplet representations of SU(2)_L in which this group arises from a diagonal embedding into SU(2)_A x SU(2)_B. A natural assignment of Standard Model lepton doublets to the two underlying gauge groups results in a bimaximal pattern of neutrino mixings and an inverted hierarchy in masses. Simple perturbations around this leading-order structure can accommodate the observed pattern of neutrino masses and mixings.Comment: 8 pages; uses RevTe

    Unkindest cuts: reflections on destruction and resilience in LGBTQ community-based mental health support

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    This article reflects on the closure of specialist community-based LGBTQ mental health support from the perspective of people who have used or work in such services. The authors discuss the need for community-based specialist support for LGBTQ people who experience mental health problems or work in mental health services
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