353 research outputs found

    Electron orbital valves made of multiply connected armchair carbon nanotubes with mirror-reflection symmetry: tight-binding study

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    Using the tight-binding method and the Landauer-B\"{u}ttiker conductance formalism, we demonstrate that a multiply connected armchair carbon nanotube with a mirror-reflection symmetry can sustain an electron current of the π\pi-bonding orbital while suppress that of the π\pi-antibonding orbital over a certain energy range. Accordingly, the system behaves like an electron orbital valve and may be used as a scanning tunneling microscope to probe pairing symmetry in d-wave superconductors or even orbital ordering in solids which is believed to occur in some transition-metal oxides.Comment: 4 figures, 12 page

    Direct observation of localized defect states in semiconductor nanotube junctions

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    Scanning tunneling microscopy of semiconductor-semiconductor carbon nanotube junctions with different band gaps was studied. Characteristic features of the wave functions at different energy levels were exhibited in the atomically resolved scanning tunneling microscopy. The experimental observations in terms of the pentagon-heptagon defects in the junction were interpreted.open888

    Local electronic density of states of a semiconducting carbon nanotube interface

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    The local electronic structure of semiconducting single-wall carbon nanotubes was studied with scanning tunneling microscopy. We performed scanning tunneling spectroscopy measurement at selected locations on the center axis of carbon nanotubes, acquiring a map of the electronic density of states. Spatial oscillation was observed in the electronic density of states with the period of atomic lattice. Defect induced interface states were found at the junctions of the two semiconducting nanotubes, which are well-understood in analogy with the interface states of bulk semiconductor heterostructures. The electronic leak of the van Hove singularity peaks was observed across the junction, due to inefficient charge screening in a one-dimensional structure.open111

    Paired gap states in a semiconducting carbon nanotube: Deep and shallow levels

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    Several paired, localized gap states were observed in semiconducting single-wall carbon nanotubes using spatially resolved scanning tunneling spectroscopy. A pair of gap states is found far from the band edges, forming deep levels, while the other pair is located near the band edges, forming shallow levels. With the help of a first-principles study, the former is explained by a vacancy-adatom complex while the latter is explained by a pentagon-heptagon structure. Our experimental observation indicates that the presence of the gap states provides a means to perform local band-gap engineering as well as doping without impurity substitution.open433

    Charity registration and reporting:a cross-Jurisdictional and theoretical analysis of regulatory impact

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    Increasingly governments worldwide regulate charities, seeking to restrict the number of organizations claiming taxation exemptions, reduce abuse of state support and fraud. Under public interest theory governments may increase philanthropy through public trust and confidence in charities. Under public choice theory regulators will maximize political returns, ‘manage’ charity-government relationships, and avoid regulatory capture. Phillips and Smith (2014) suggest that charities’ regulatory regimes should coalesce, despite jurisdictional diversity. We analyse charity regulatory regimes against underlining theories of regulation, and assess regulatory costs and benefits. Thus regulators can reduce regulatory inefficiency, and balance accountability and transparency demands with charities’ abilities to deliver

    Macro-to-Micro Structural Proteomics: Native Source Proteins for High-Throughput Crystallization

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    Structural biology and structural genomics projects routinely rely on recombinantly expressed proteins, but many proteins and complexes are difficult to obtain by this approach. We investigated native source proteins for high-throughput protein crystallography applications. The Escherichia coli proteome was fractionated, purified, crystallized, and structurally characterized. Macro-scale fermentation and fractionation were used to subdivide the soluble proteome into 408 unique fractions of which 295 fractions yielded crystals in microfluidic crystallization chips. Of the 295 crystals, 152 were selected for optimization, diffraction screening, and data collection. Twenty-three structures were determined, four of which were novel. This study demonstrates the utility of native source proteins for high-throughput crystallography

    The construction of the efficient office: scientific management, accountability and the neo-liberal state

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    The office has been a central site of organizational planning, accountability, and control since the 19th century. Yet it has been the subject of relatively little accounting research. Through the dual theoretical lenses of Foucaultian and Labour Process theories, this study employs historical photo‐elicitation methodology to investigate the implementation of management control and accountability in the scientifically managed office which emerged in the United States during the late 19th and early 20th centuries. Our analysis reveals the manner in which accounting records created new modes of disciplinary control and surveillance within the office and how accounting tasks were de‐skilled in a gradually feminized and mechanized office environment. We also witness the role of accounting in the physical structuring of office space through the assembly line arrangement of office furniture to facilitate paper flows and the installation of record‐keeping systems of surveillance. In addition, our visually derived historical account of these transformations in office administration allows us to reflect on some contemporary issues. The production‐line design and efficiency so promoted by scientific management served as a forerunner to today's open‐plan office, as well as influencing contemporary office management philosophies such as Activity‐Based Working. Furthermore, we seek to inform current debates on the role of accounting in contemporary neo‐liberal society. In the history of the scientific office, we gain an early glimpse of the subsequent role that accounting comes to play within a neo‐liberal agenda as a powerful technology of micro‐measurement and micro‐management

    The Neural Basis of Cognitive Efficiency in Motor Skill Performance from Early Learning to Automatic Stages

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