1,947 research outputs found

    High-resolution microwave frequency dissemination on an 86-km urban optical link

    Full text link
    We report the first demonstration of a long-distance ultra stable frequency dissemination in the microwave range. A 9.15 GHz signal is transferred through a 86-km urban optical link with a fractional frequency stability of 1.3x10-15 at 1 s integration time and below 10-18 at one day. The optical link phase noise compensation is performed with a round-trip method. To achieve such a result we implement light polarisation scrambling and dispersion compensation. This link outperforms all the previous radiofrequency links and compares well with recently demonstrated full optical links.Comment: 11 pages, 5 figure

    Symmetric data-driven fusion of diffusion tensor MRI: Age differences in white matter

    Get PDF
    In the past 20 years, white matter (WM) microstructure has been studied predominantly using diffusion tensor imaging (DTI). Decreases in fractional anisotropy (FA) and increases in mean (MD) and radial diffusivity (RD) have been consistently reported in healthy aging and neurodegenerative diseases. To date, DTI parameters have been studied individually (e.g., only FA) and separately (i.e., without using the joint information across them). This approach gives limited insights into WM pathology, increases the number of multiple comparisons, and yields inconsistent correlations with cognition. To take full advantage of the information in a DTI dataset, we present the first application of symmetric fusion to study healthy aging WM. This data-driven approach allows simultaneous examination of age differences in all four DTI parameters. We used multiset canonical correlation analysis with joint independent component analysis (mCCA + jICA) in cognitively healthy adults (age 20-33

    Actors and networks or agents and structures: towards a realist view of information systems

    Get PDF
    Actor-network theory (ANT) has achieved a measure of popularity in the analysis of information systems. This paper looks at ANT from the perspective of the social realism of Margaret Archer. It argues that the main issue with ANT from a realist perspective is its adoption of a `flat' ontology, particularly with regard to human beings. It explores the value of incorporating concepts from ANT into a social realist approach, but argues that the latter offers a more productive way of approaching information systems

    1928-29: Abilene Christian College Bible Lectures - Full Text

    Get PDF
    INTRODUCTION It has been the custom of Abilene Christian College for several years to hold an annual “Lectureship” the last week in February. This is a time of gathering of brethren from all over the state and adjoining states. It is a time of a great spiritual feast. It affords an opportunity for brethren to meet and talk over the work of the Lord. It also enables us to hear again great men of God whose voices have sounded the Word of the Lord in the days of the past in great meetings. In order that those who are not permitted to hear the lectures may enjoy them it has been the custom of Abilene Christian College to publish the lectures in a book at the end of each two years. We feel that these wonderful messages from some of the greatest minds of the church ought to be preserved that they may do good even after the lips of the speakers have become silent. It is with a prayer that great good may come that this volume of lectures of 1928 and 1929 is sent forth. We regret that some of the lectures could not be included in the book. Several of the brethren neglected to send in their manuscripts; some other manuscripts were destroyed by fire, and the brethren did not replace them. Most\u27 of the lectures are in the book. BATSELL BAXTER. DELIVERED IN THE AUDITORIUM OF ABILENE CHRISTIAN COLLEGE ABILENE, TEXAS FEBRUARY 1928-1929 FIRM FOUNDATION PUBLISHING HOUSE 104-106-108 E. 9th Street Austin, Texas

    Multiscale photosynthetic exciton transfer

    Full text link
    Photosynthetic light harvesting provides a natural blueprint for bioengineered and biomimetic solar energy and light detection technologies. Recent evidence suggests some individual light harvesting protein complexes (LHCs) and LHC subunits efficiently transfer excitons towards chemical reaction centers (RCs) via an interplay between excitonic quantum coherence, resonant protein vibrations, and thermal decoherence. The role of coherence in vivo is unclear however, where excitons are transferred through multi-LHC/RC aggregates over distances typically large compared with intra-LHC scales. Here we assess the possibility of long-range coherent transfer in a simple chromophore network with disordered site and transfer coupling energies. Through renormalization we find that, surprisingly, decoherence is diminished at larger scales, and long-range coherence is facilitated by chromophoric clustering. Conversely, static disorder in the site energies grows with length scale, forcing localization. Our results suggest sustained coherent exciton transfer may be possible over distances large compared with nearest-neighbour (n-n) chromophore separations, at physiological temperatures, in a clustered network with small static disorder. This may support findings suggesting long-range coherence in algal chloroplasts, and provides a framework for engineering large chromophore or quantum dot high-temperature exciton transfer networks.Comment: 9 pages, 6 figures. A significantly updated version is now published online by Nature Physics (2012

    A Baseline for the Multivariate Comparison of Resting-State Networks

    Get PDF
    As the size of functional and structural MRI datasets expands, it becomes increasingly important to establish a baseline from which diagnostic relevance may be determined, a processing strategy that efficiently prepares data for analysis, and a statistical approach that identifies important effects in a manner that is both robust and reproducible. In this paper, we introduce a multivariate analytic approach that optimizes sensitivity and reduces unnecessary testing. We demonstrate the utility of this mega-analytic approach by identifying the effects of age and gender on the resting-state networks (RSNs) of 603 healthy adolescents and adults (mean age: 23.4 years, range: 12–71 years). Data were collected on the same scanner, preprocessed using an automated analysis pipeline based in SPM, and studied using group independent component analysis. RSNs were identified and evaluated in terms of three primary outcome measures: time course spectral power, spatial map intensity, and functional network connectivity. Results revealed robust effects of age on all three outcome measures, largely indicating decreases in network coherence and connectivity with increasing age. Gender effects were of smaller magnitude but suggested stronger intra-network connectivity in females and more inter-network connectivity in males, particularly with regard to sensorimotor networks. These findings, along with the analysis approach and statistical framework described here, provide a useful baseline for future investigations of brain networks in health and disease

    Public Goods and Public Policy: what is Public Good, and who and what Decides?

    Get PDF
    Higher education is usually seen as serving the public good, especially when funded directly by the state, and because of the ‘social benefit efficiency gains and potential equity effects on opportunity and reduced inequality’ (McMahon, 2009, p. 255). Calhoun (2006, p. 19) argues that public support for higher education is only given and maintained according to its capacity, capability, and willingness, to ‘educate citizens in general, to share knowledge, to distribute it as widely as possible in accord with publically articulated purposes’

    Claims to a nation, dressing the part and other boundary making strategies by skilled migrants in response to ethnic categorization

    Get PDF
    This article is about self-defined social identities, other people's perceptions of us and the potentially conflictual relationship between these two. Building on a Barthian focus on group boundaries, the article takes the interplay between external categorizations and internal group definitions as its point of departure to examine how individuals negotiate the boundaries of their social identities. Based on a case study of skilled migrants with racialized ethnicities in Finland, I look at how they express their self-defined identity as well-to-do, skilled professionals in the face of contradicting categorizations of them as unskilled , lower-class migrant subjects. I identify two types of complementary approaches employed by the skilled migrants in boundary making strategies to their identity negotiations: those de-emphasizing ethnicity (or its importance), and those emphasizing class status. These approaches are two sides of the same coin; coming from different perspectives, they both aim at a more positively viewed identity, and for individuals to be seen as well-to-do, educated, working professionals, rather than as ethnic migrant subjects. As such, the article also highlights the interconnection of class and ethnicity for the social identities of skilled migrants in Finland.This article is about self-defined social identities, other people’s perceptions of us and the potentially conflictual relationship between these two. Building on a Barthian focus on group boundaries, the article takes the interplay between external categorizations and internal group definitions as its point of departure to examine how individuals negotiate the boundaries of their social identities. Based on a case study of skilled migrants with racialized ethnicities in Finland, I look at how they express their self-defined identity as well-to-do, skilled professionals in the face of contradicting categorizations of them as un-skilled, lower-class migrant subjects. I identify two types of complementary approaches employed by the skilled migrants in boundary making strategies to their identity negotiations: those de-emphasizing ethnicity (or its importance), and those emphasizing class status. These approaches are two sides of the same coin; coming from different perspectives, they both aim at a more positively viewed identity, and for individuals to be seen as well-to-do, educated, working professionals, rather than as ethnic migrant subjects. As such, the article also highlights the interconnection of class and ethnicity for the social identities of skilled migrants in Finland.Peer reviewe
    • 

    corecore