9,563 research outputs found

    Generally Covariant Conservative Energy-Momentum for Gravitational Anyons

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    We obtain a generally covariant conservation law of energy-momentum for gravitational anyons by the general displacement transform. The energy-momentum currents have also superpotentials and are therefore identically conserved. It is shown that for Deser's solution and Clement's solution, the energy vanishes. The reasonableness of the definition of energy-momentum may be confirmed by the solution for pure Einstein gravity which is a limit of vanishing Chern-Simons coulping of gravitational anyons.Comment: 12 pages, Latex, no figure

    New Insights into the Design for End-of-life Variability of NBTI in Scaled High-Îş/Metal-gate Technology for the nano-Reliability Era

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    In this paper, a new methodology for the assessment of end-of-life variability of NBTI is proposed for the first time. By introducing the concept of characteristic failure probability, the uncertainty in the predicted 10-year VDD is addressed. Based on this, variability resulted from NBTI degradation at end of life under specific VDD is extensively studied with a novel characterization technique. With the further circuit level analysis based on this new methodology, the timing margin can be relaxed. The new methodology has also been extended to FinFET in this work. The wide applicability of this methodology is helpful to future reliability/variability-aware circuit design in nano-CMOS technology

    Implementation of universal quantum gates based on nonadiabatic geometric phases

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    We propose an experimentally feasible scheme to achieve quantum computation based on nonadiabatic geometric phase shifts, in which a cyclic geometric phase is used to realize a set of universal quantum gates. Physical implementation of this set of gates is designed for Josephson junctions and for NMR systems. Interestingly, we find that the nonadiabatic phase shift may be independent of the operation time under appropriate controllable conditions. A remarkable feature of the present nonadiabatic geometric gates is that there is no intrinsic limitation on the operation time, unlike adiabatic geometric gates. Besides fundamental interest, our results may simplify the implementation of geometric quantum computation based on solid state systems, where the decoherence time may be very short.Comment: 5 pages, 2 figures; the version published in Phys. Rev. Let

    Perennial crops can complement semi-natural habitats in enhancing ground beetle (Coleoptera: Carabidae) diversity in agricultural landscapes

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    Agricultural intensification has caused losses of global biodiversity and associated ecological services. Agroecological landscape assessments are therefore often based on the area of remaining semi-natural habitats due to their ability to promote biodiversity. Due to their structural diversity and often less intensive management in comparison to annual crops, perennial cropland could fulfil similar roles. However, comparisons of the ability of perennial cropland versus semi-natural habitat to maintain agricultural diversity are scarce. Here, we conduct such an assessment, in comparing functional group-specific patterns in ground beetles (Coleoptera: Carabidae) as indicators of anthropogenic land-use impacts on biodiversity and biological pest control. Carabid assemblages were compared between annual cropland (56 plots), perennial cropland (24 plots) and semi-natural habitats (74 plots) of varying plant diversity across nine study regions situated in Eastern China. Our results indicated that perennial crops sustained a greater carabid species richness than semi-natural habitats, whereas assemblages of semi-natural habitats contained greater proportions of large and predatory carabids. Plant species richness positively affected the overall diversity of carabids, with the strongest effects again observed in perennial cropland. Abundance-based and species-based proportions of large carabids were positively linked to plant diversity in perennial cropland and semi-natural habitats, but negatively in annual cropland. A similar response was observed for predatory carabid abundance. Perennial crops might therefore fulfil complementary roles to semi-natural habitats in agricultural biodiversity conservation. Given common trade-offs between biodiversity conservation and agricultural production, promoting perennial cropland in particular in combination with management that increases plant diversity, could enable increases in the sustainability of agricultural production systems particularly in areas with high food demand, but limited availability of arable land. Notwithstanding, semi-natural habitats remain crucial particularly with view of enhancing biological pest control services

    The role of cities in reducing smoking in China

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