New Family of Robust 2D Topological Insulators in van der Waals Heterostructures

We predict a new family of robust two-dimensional (2D) topological insulators in van der Waals heterostructures comprising graphene and chalcogenides BiTeX (X=Cl, Br and I). The layered structures of both constituent materials produce a naturally smooth interface that is conducive to proximity induced new topological states. First principles calculations reveal intrinsic topologically nontrivial bulk energy gaps as large as 70-80 meV, which can be further enhanced up to 120 meV by compression. The strong spin-orbit coupling in BiTeX has a significant influence on the graphene Dirac states, resulting in the topologically nontrivial band structure, which is confirmed by calculated nontrivial Z2 index and an explicit demonstration of metallic edge states. Such heterostructures offer an unique Dirac transport system that combines the 2D Dirac states from graphene and 1D Dirac edge states from the topological insulator, and it offers new ideas for innovative device designs

Van der Waals heterostructures

Research on graphene and other two-dimensional atomic crystals is intense and likely to remain one of the hottest topics in condensed matter physics and materials science for many years. Looking beyond this field, isolated atomic planes can also be reassembled into designer heterostructures made layer by layer in a precisely chosen sequence. The first - already remarkably complex - such heterostructures (referred to as 'van der Waals') have recently been fabricated and investigated revealing unusual properties and new phenomena. Here we review this emerging research area and attempt to identify future directions. With steady improvement in fabrication techniques, van der Waals heterostructures promise a new gold rush, rather than a graphene aftershock

Spatio-Temporal Progression of Grey and White Matter Damage Following Contusion Injury in Rat Spinal Cord

Cellular mechanisms of secondary damage progression following spinal cord injury remain unclear. We have studied the extent of tissue damage from 15 min to 10 weeks after injury using morphological and biochemical estimates of lesion volume and surviving grey and white matter. This has been achieved by semi-quantitative immunocytochemical methods for a range of cellular markers, quantitative counts of white matter axonal profiles in semi-thin sections and semi-quantitative Western blot analysis, together with behavioural tests (BBB scores, ledged beam, random rung horizontal ladder and DigiGait™ analysis). We have developed a new computer-controlled electronic impactor based on a linear motor that allows specification of the precise nature, extent and timing of the impact. Initial (15 min) lesion volumes showed very low variance (1.92±0.23 mm3, mean±SD, n = 5). Although substantial tissue clearance continued for weeks after injury, loss of grey matter was rapid and complete by 24 hours, whereas loss of white matter extended up to one week. No change was found between one and 10 weeks after injury for almost all morphological and biochemical estimates of lesion size or behavioural methods. These results suggest that previously reported apparent ongoing injury progression is likely to be due, to a large extent, to clearance of tissue damaged by the primary impact rather than continuing cell death. The low variance of the impactor and the comprehensive assessment methods described in this paper provide an improved basis on which the effects of potential treatment regimes for spinal cord injury can be assessed

Sources of Increasing Returns and Regional Innovation in the UK

This empirical paper investigates the impact of different sources of increasing returns on firm innovative behaviour in different regions of the UK. Of the different sources of increasing returns, the impact of intermediation and the emergence of specialized markets on the probability of innovation is of particular interest to this analysis. The existing literature on regional development in the UK strongly suggests that the South East has many features that may characterize an economy growing with a greater division of labour. These are less evident in the Industrial Heartland region of northern England. Other influences on innovation such as the impact of regional public R&D and dynamic economies to scale due to learning within a firm are also considered. Cet article empirique cherche à examiner l'impact des sources différentes des rendements croissants sur l'innovation des entreprises situées dans diverses régions au Royaume-Uni. Parmi les différentes sources des rendements croissants, il s'avère que les conséquences de l'intermédiation et l'émergence des marchés spécialisés sur la probabilité de l'innovation sont à noter pour ce qui est de cette analyse. La documentation disponible au sujet du développement régional au Royaume-Uni laisse vivement supposer que le Sud-est montre beaucoup des traits qui caractérisent une économie qui croît avec une division du travail plus importante. Ces traits-làsont moins évidents dans le berceau industriel qui est le nord du pays. D'autres facteurs qui influent sur l'innovation, tels l'impact de la recherche-développement publique régionale et les économies d'échelles dynamiques dues à l'apprentissage intra-entreprise, sont aussi considérés. Dieser empirische Aufsatz untersucht die Auswirkung verschiedener Quellen wachsenden Profits dank innovativem Firmenverhalten in verschiedenen Regionen des Vereinigten Königreichs. Von den verschiedenen Quellen vermehrten Gewinns sind das Aufkommen spezialisierter Märkte und die Auswirkung der 'Intermediation' auf die Wahrscheinlichkeit der Innovation von besonderem Interesse fur diese Analyse. Die bereits vorliegende Literatur über regionale Entwicklung im UK legt es entschieden nahe, daß sich im Südosten des Landes vielerlei Anzeichen finden, die fur eine Wirtschaft mit stärkerer Arbeitsteilung charakteristisch sein könnten. In der Region des industriellen Kernlandes im Norden Englands sind sie weniger zu beobachten. Darüberhinaus werden auch andere Einflüsse auf Innovation in Betracht gezogen, wie die Auswirkung regionaler öffentlicher Forschung und Entwicklung, sowie dynamische Einsparungen durch erhöhte Produktion dank Wissenserwerb in einer Firma.Increasing Returns And Growth, Specialized Markets Public, R And D Innovation, By Firms, Regional Innovation, Regional Development,