924 research outputs found

    TMRT observations of 26 pulsars at 8.6 GHz

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    Integrated pulse profiles at 8.6~GHz obtained with the Shanghai Tian Ma Radio Telescope (TMRT) are presented for a sample of 26 pulsars. Mean flux densities and pulse width parameters of these pulsars are estimated. For eleven pulsars these are the first high-frequency observations and for a further four, our observations have a better signal-to-noise ratio than previous observations. For one (PSR J0742-2822) the 8.6~GHz profiles differs from previously observed profiles. A comparison of 19 profiles with those at other frequencies shows that in nine cases the separation between the outmost leading and trailing components decreases with frequency, roughly in agreement with radius-to-frequency mapping, whereas in the other ten the separation is nearly constant. Different spectral indices of profile components lead to the variation of integrated pulse profile shapes with frequency. In seven pulsars with multi-component profiles, the spectral indices of the central components are steeper than those of the outer components. For the 12 pulsars with multi-component profiles in the high-frequency sample, we estimate the core width using gaussian fitting and discuss the width-period relationship.Comment: 33 pages, 49 figures, 5 Tables; accepted by Ap

    Observation of non-Hermitian antichiral edge currents

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    Non-Hermitian topological photonics is of great interest in bridging topological matter with gain/dissipation engineering in optics. A key problem in this direction is the interplay between the effective gauge potential and the non-Hermiticity. Here we tackle this problem in a synthetic non-Hermitian Hall ladder and experimentally observe antichiral edge currents (ACECs) of photons, by tuning the locally uniform effective magnetic flux and the on-site gain/loss. Such ACECs provide a topological method to probe the signatures of the non-Hermitian skin effect (NHSE) from steady-state bulk dynamics. The universality of this method is verified by its generalization to three dimensions. This study paves a way to investigate exotic non-Hermitian topological physics and has potential applications in topological photonics engineering

    Orthotopic and heterotopic tracheal transplantation model in studying obliterative bronchiolitis

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    AbstractBackgroundSeveral animal models have been established to investigate the mechanisms of obliterative bronchiolitis after lung transplantation. In this study, we compared three prevalent murine models of obliterative bronchiolitis in terms of several basic pathologic changes in a relatively short span of time after transplantation.MethodsEach of the recipient mice simultaneously received orthotopic, intra-omental and subcutaneous tracheal transplantation in both syngeneic and allogeneic settings. No immunosuppressive treatment was administered. Tracheal grafts were harvested on Day 14, 21 and 28 after transplantation for histological and immunohistochemical analyses.ResultsSyngeneic tracheal grafts from different transplant sites retained normal histologic structures, while their corresponding allografts demonstrated more occlusion of the airway lumen as well as more infiltration of CD4+/CD8+ mononuclear cells and myofibroblasts, but less regenerative epithelium and neovascularized vessels at indicated times (P<0.05). Compared with two heterotopic allografts, orthotopic allografts had less occlusion of the tracheal lumen as well as less infiltration of CD4+/CD8+ mononuclear cells and myofibroblasts, but more regenerative epithelium and neovascularized vessels (P<0.05).ConclusionsOrthotopic tracheal transplantation in mice can be considered as a model to study early stages of obliterative bronchiolitis, and heterotopic tracheal transplantation can be a model for late stages of obliterative bronchiolitis
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