2,095 research outputs found

    The potential of Antheraea pernyi silk for spinal cord repair

    Get PDF
    This work was supported by the Institute of Medical Sciences of the University of Aberdeen, Scottish Rugby Union and RS McDonald Charitable Trust. We are grateful to Mr Nicholas Hawkins from Oxford University and Ms Annette Raffan from the University of Aberdeen for assistance with tensile testing. We thank Ms Michelle Gniβ for her help with the microglial response experiments. We also thank Mr Gianluca Limodio for assisting with the MATLAB script for automation of tensile testing’s data analysis.Peer reviewedPublisher PD

    Boundary interactions changing operators and dynamical correlations in quantum impurity problems

    Full text link
    Recent developments have made possible the computation of equilibrium dynamical correlators in quantum impurity problems. In many situations however, one is rather interested in correlators subject to a non equilibrium initial preparation; this is the case for instance for the occupation probability P(t)P(t) in the double well problem of dissipative quantum mechanics (DQM). We show in this paper how to handle this situation in the framework of integrable quantum field theories by introducing ``boundary interactions changing operators''. We determine the properties of these operators by using an axiomatic approach similar in spirit to what is done for form-factors. This allows us to obtain new exact results for P(t)P(t); for instance, we find that that at large times (or small gg), the leading behaviour for g < 1/2} is P(t)eΓtcosΩtP(t)\propto e^{-\Gamma t}\cos\Omega t, with the universal ratio. Ω/Γ=cotπg/2(1g)\Omega/\Gamma = \cot {\pi g}/{2(1-g)}.Comment: 4 pages, revte

    Flow equation analysis of the anisotropic Kondo model

    Full text link
    We use the new method of infinitesimal unitary transformations to calculate zero temperature correlation functions in the strong-coupling phase of the anisotropic Kondo model. We find the dynamics on all energy scales including the crossover behaviour from weak to strong coupling. The integrable structure of the Hamiltonian is not used in our approach. Our method should also be useful in other strong-coupling models since few other analytical methods allow the evaluation of their correlation functions on all energy scales.Comment: 4 pages RevTeX, 2 eps figures include

    The Transition Between Quantum Coherence and Incoherence

    Full text link
    We show that a transformed Caldeira-Leggett Hamltonian has two distinct families of fixed points, rather than a single unique fixed point as often conjectured based on its connection to the anisotropic Kondo model. The two families are distinguished by a sharp qualitative difference in their quantum coherence properties and we argue that this distinction is best understood as the result of a transition in the model between degeneracy and non-degeneracy in the spectral function of the ``spin-flip'' operator.Comment: some typos corrected and a reference adde

    Portraying the hosts: Stellar science from planet searches

    Full text link
    Information on the full session can be found on this website: https://sites.google.com/site/portrayingthehostscs18/We present a compendium of the splinter session on stellar science from planet searches that was organized as part of the Cool Stars 18 conference. Seven speakers discussed techniques to infer stellar information from radial velocity, transit and microlensing data, as well as new instrumentation and missions designed for planet searches that will provide useful for the study of the cool stars

    Movement and Aggregation of Eastern Hudson Bay Beluga Whales (Delphinapterus leucas): A Comparison of Patterns Found through Satellite Telemetry and Nunavik Traditional Ecological Knowledge

    Get PDF
    Traditional Ecological Knowledge (TEK) consists of the collective knowledge, experience, and values of subsistence communities, while Western science relies on hypothesis testing to obtain information on natural processes. Both approaches provide important ecological information, but few studies have directly compared the two. We compared information on movements and aggregation of beluga whales obtained from TEK interview records (n = 3253) and satellite telemetry records of 30 whales tagged in eastern Hudson Bay, Canada, using geographic information system (GIS) approaches that allowed common formatting of the data sets. Estuarine centres of aggregation in the summer were evident in both data sets. The intensive use of offshore areas seen in the telemetry data, where 76% of the locations were more than 15 km from mainland Quebec, was not evident in the TEK data, where only 17% of the records indicated offshore locations. Morisita’s index of similarity indicated that TEK and telemetry data distributions varied with season, with the highest similarity in winter (0.74). Location and movement data from the telemetry study were limited by small sample size and short tag deployment times, while TEK data were biased by spatial coverage and coastal travel habits. Although the two data sets can provide complementary information, both suffer from weaknesses that need to be acknowledged when these data are adapted for use in resource management.Les connaissances écologiques traditionnelles (CÉT) consistent en l’ensemble des connaissances, de l’expérience et des valeurs des communautés de subsistance, tandis que la science occidentale s’appuie sur la mise à l’épreuve d’hypothèses dans le but d’obtenir de l’information sur les processus naturels. Bien que ces deux démarches permettent d’obtenir d’importants renseignements sur l’écologie, peu d’études ont établi une comparaison directe entre ces deux démarches. Nous avons comparé des données sur les mouvements et le rassemblement des bélugas, données obtenues à partir de CÉT prélevées au moyen d’entrevues (n = 3253) ainsi qu’à partir de résultats de télémétrie par satellite sur 30 baleines marquées dans l’est de la baie d’Hudson, au Canada, à l’aide de systèmes d’information géographique (SIG) qui ont permis le formatage commun des ensembles de données. Pendant l’été, les centres de rassemblement en estuaire étaient évidents dans les deux ensembles de données. L’utilisation intensive des zones au large en ce qui a trait aux données de télémétrie, où 76 % des localisations se situaient à plus de 15 km du continent québécois, n’était pas évidente dans le cas des données des CÉT, où seulement 17 % des résultats indiquaient des localisations au large. L’indice de similarité de Morisita indiquait que la répartition des données obtenues par CÉT et par télémétrie variait d’une saison à l’autre, la similarité la plus grande ayant été atteinte l’hiver (0,74). Les données de localisation et de mouvement découlant de l’étude de télémétrie étaient limitées par la petite taille de l’échantillon et les courtes durées de déploiement des étiquettes, tandis que les données provenant des CÉT étaient biaisées par l’espace à couvrir et les habitudes de déplacement sur la côte. Bien que les deux ensembles de données puissent fournir de l’information complémentaire, tous deux possèdent des faiblesses qu’il y a lieu de reconnaître lorsque ces données sont adaptées à des fins de gestion des ressources

    Tax and Development: The Link between International Taxation, The Base Erosion Profit Shifting Project and The 2030 Sustainable Development Agenda.

    Get PDF
    The OECD-G20 project on Base Erosion and Profit Shifting (BEPS) is the largest reform of the international tax architecture in decades. The BEPS project aims to ensure that multinationals pay their taxes in the jurisdictions where they create value and where their economic activity takes place. When it is fully implemented, it will substantially alter the global governance architecture for taxation. This is a commendable goal, yet the BEPS project can be criticized for not sufficiently tailoring to the specific needs of developing countries. While it has made a laudable attempt to be more attentive towards developing countries with the creation of the BEPS inclusive framework, this concerns the implementation phase of BEPS. The agenda-setting and decision-making process only included the G20 and OECD countries. Against this background, it is unclear how and if the BEPS project considered the specific needs of developing countries, especially in light of the Sustainable Development Goals (SDGs). This paper will examine this issue by addressing the following questions: (i) Were the Sustainable Development Goals (SDGs) and the interests of developing countries to attract investment considered throughout the BEPS Process? (ii) What issues of international taxation, beyond BEPS, should be addressed to fulfill developing countries' domestic resource mobilization needs to achieve the 2030 Agenda for Sustainable Development. We conclude with a set of recommendations to the international global tax governance architecture to be more inclusive and responsive to development countries’ needs.Seventh Framework Programme (FP7)758671Grenzen van fiscale soevereinitei

    The Screening Cloud in the k-Channel Kondo Model: Perturbative and Large-k Results

    Full text link
    We demonstrate the existence of a large Kondo screening cloud in the k-channel Kondo model using both renormalization group improved perturbation theory and the large-k limit. We study position (r) dependent spin Green's functions in both static and equal time cases. The equal-time Green's function provides a natural definition of the screening cloud profile, in which the large Kondo scale appears. At large distances it consists of both a slowly varying piece and a piece which oscillates at twice the Fermi wave-vector. This function is calculated at all r in the large-k limit. Static Green's functions (Knight shift or susceptibility) consist only of a term oscillating at 2kF, and appear to factorize into a function of r times a function of T for rT << vF, in agreement with NMR experiments. Most of the integrated susceptibility comes from the impurity-impurity part with conduction electron contributions suppressed by powers of the bare Kondo coupling. The single-channel and overscreened multi-channel cases are rather similar although anomalous power-laws occur in the latter case at large r and low T due to irrelevant operator corrections.Comment: 22 Revtex pages, 12 figure

    Integrable supersymmetric correlated electron chain with open boundaries

    Full text link
    We construct an extended Hubbard model with open boundaries from a RR-matrix based on the Uq[Osp(22)]U_q[Osp(2|2)] superalgebra. We study the reflection equation and find two classes of diagonal solutions. The corresponding one-dimensional open Hamiltonians are diagonalized by means of the Bethe ansatz approach.Comment: latex, 14 page
    corecore