615 research outputs found

    Transport Spectroscopy of Symmetry-Broken Insulating States in Bilayer Graphene

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    The flat bands in bilayer graphene(BLG) are sensitive to electric fields E\bot directed between the layers, and magnify the electron-electron interaction effects, thus making BLG an attractive platform for new two-dimensional (2D) electron physics[1-5]. Theories[6-16] have suggested the possibility of a variety of interesting broken symmetry states, some characterized by spontaneous mass gaps, when the electron-density is at the carrier neutrality point (CNP). The theoretically proposed gaps[6,7,10] in bilayer graphene are analogous[17,18] to the masses generated by broken symmetries in particle physics and give rise to large momentum-space Berry curvatures[8,19] accompanied by spontaneous quantum Hall effects[7-9]. Though recent experiments[20-23] have provided convincing evidence of strong electronic correlations near the CNP in BLG, the presence of gaps is difficult to establish because of the lack of direct spectroscopic measurements. Here we present transport measurements in ultra-clean double-gated BLG, using source-drain bias as a spectroscopic tool to resolve a gap of ~2 meV at the CNP. The gap can be closed by an electric field E\bot \sim13 mV/nm but increases monotonically with a magnetic field B, with an apparent particle-hole asymmetry above the gap, thus providing the first mapping of the ground states in BLG.Comment: 4 figure

    Quantum Hall Effects in Graphene-Based Two-Dimensional Electron Systems

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    In this article we review the quantum Hall physics of graphene based two-dimensional electron systems, with a special focus on recent experimental and theoretical developments. We explain why graphene and bilayer graphene can be viewed respectively as J=1 and J=2 chiral two-dimensional electron gases (C2DEGs), and why this property frames their quantum Hall physics. The current status of experimental and theoretical work on the role of electron-electron interactions is reviewed at length with an emphasis on unresolved issues in the field, including assessing the role of disorder in current experimental results. Special attention is given to the interesting low magnetic field limit and to the relationship between quantum Hall effects and the spontaneous anomalous Hall effects that might occur in bilayer graphene systems in the absence of a magnetic field

    A Burgessian critique of nominalistic tendencies in contemporary mathematics and its historiography

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    We analyze the developments in mathematical rigor from the viewpoint of a Burgessian critique of nominalistic reconstructions. We apply such a critique to the reconstruction of infinitesimal analysis accomplished through the efforts of Cantor, Dedekind, and Weierstrass; to the reconstruction of Cauchy's foundational work associated with the work of Boyer and Grabiner; and to Bishop's constructivist reconstruction of classical analysis. We examine the effects of a nominalist disposition on historiography, teaching, and research.Comment: 57 pages; 3 figures. Corrected misprint

    Fertility, Living Arrangements, Care and Mobility

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    There are four main interconnecting themes around which the contributions in this book are based. This introductory chapter aims to establish the broad context for the chapters that follow by discussing each of the themes. It does so by setting these themes within the overarching demographic challenge of the twenty-first century – demographic ageing. Each chapter is introduced in the context of the specific theme to which it primarily relates and there is a summary of the data sets used by the contributors to illustrate the wide range of cross-sectional and longitudinal data analysed

    Personality preference influences medical student use of specific computer-aided instruction (CAI)

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    BACKGROUND: The objective of this study was to test the hypothesis that personality preference, which can be related to learning style, influences individual utilization of CAI applications developed specifically for the undergraduate medical curriculum. METHODS: Personality preferences of students were obtained using the Myers-Briggs Type Indicator (MBTI) test. CAI utilization for individual students was collected from entry logs for two different web-based applications (a discussion forum and a tutorial) used in the basic science course on human anatomy. Individual login data were sorted by personality preference and the data statistically analyzed by 2-way mixed ANOVA and correlation. RESULTS: There was a wide discrepancy in the level and pattern of student use of both CAI. Although individual use of both CAI was positively correlated irrespective of MBTI preference, students with a "Sensing" preference tended to use both CAI applications more than the "iNtuitives". Differences in the level of use of these CAI applications (i.e., higher use of discussion forum vs. a tutorial) were also found for the "Perceiving/Judging" dimension. CONCLUSION: We conclude that personality/learning preferences of individual students influence their use of CAI in the medical curriculum

    Graduate entry to medicine: widening psychological diversity

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    At Nottingham University more than 95% of entrants to the traditional 5-year medical course are school leavers. Since 2003 we have admitted graduate entrants (GEM) to a shortened (4-year) course to 'widen access to students from more disadvantaged backgrounds'. We have recently shown that the GEM course widens academic and socio-demographic diversity of the medical student population. This study explored whether GEM students also bring psychological diversity and whether this could be beneficial. We studied: a) 217 and 96 applicants to the Nottingham 5- and 4-year courses respectively, applying in the 2002-3 UCAS cycle, and, b) 246 school leavers starting the 5-year course and 39 graduate entrants to the 4-year course in October 2003. The psychological profiles of the two groups of applicants and two groups of entrants were compared using their performance in the Goldberg 'Big 5' Personality test, the Personal Qualities Assessment (PQA; measuring interpersonal traits and interpersonal values), and the Lovibond and Lovibond measure of depression, anxiety and stress. For the comparison of the Entrants we excluded the 33 school leavers and seven graduates who took the tests as Applicants. Statistical analyses were undertaken using SPSS software (version 16.0). Graduate applicants compared to school leaver applicants were significantly more conscientious, more confident, more self controlled, more communitarian in moral orientation and less anxious. Only one of these differences was preserved in the entrants with graduates being less anxious. However, the graduate entrants were significantly less empathetic and conscientious than the school leavers. This study has shown that school leaver and graduate entrants to medical school differ in some psychological characteristics. However, if confirmed in other studies and if they were manifest in the extreme, not all the traits brought by graduates would be desirable for someone aiming for a medical career

    Computational personality recognition in social media

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    A variety of approaches have been recently proposed to automatically infer users' personality from their user generated content in social media. Approaches differ in terms of the machine learning algorithms and the feature sets used, type of utilized footprint, and the social media environment used to collect the data. In this paper, we perform a comparative analysis of state-of-the-art computational personality recognition methods on a varied set of social media ground truth data from Facebook, Twitter and YouTube. We answer three questions: (1) Should personality prediction be treated as a multi-label prediction task (i.e., all personality traits of a given user are predicted at once), or should each trait be identified separately? (2) Which predictive features work well across different on-line environments? (3) What is the decay in accuracy when porting models trained in one social media environment to another

    Welfare assessment protocol App: innovative solutions for on-farm data collection and analyses

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    THE CHALLENGE: Standardization of data collection within EU countries Reduce assessment time Store and analyse welfare data THE SOLUTION: Digital smartphone/tablet applications for data collection and reporting WP1 AWIN scientists developed apps for turkeys, horses and goat
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