585 research outputs found

    Riemann Surfaces of genus g with an automorphism of order p prime and p>g

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    The present work completes the classification of the compact Riemann surfaces of genus g with an analytic automorphism of order p (prime number) and p > g. More precisely, we construct a parameteriza- tion space for them, we compute their groups of uniformization and we compute their full automorphism groups. Also, we give affine equations for special cases and some implications on the components of the singular locus of the moduli space of smooth curves of genus g.Comment: 28 pages, 5 figure

    On hydrogen bond correlations at high pressures

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    In situ high pressure neutron diffraction measured lengths of O H and H O pairs in hydrogen bonds in substances are shown to follow the correlation between them established from 0.1 MPa data on different chemical compounds. In particular, the conclusion by Nelmes et al that their high pressure data on ice VIII differ from it is not supported. For compounds in which the O H stretching frequencies red shift under pressure, it is shown that wherever structural data is available, they follow the stretching frequency versus H O (or O O) distance correlation. For compounds displaying blue shifts with pressure an analogy appears to exist with improper hydrogen bonds.Comment: 12 pages,4 figure

    Abnormal left ventricular wall rotation in patients with complete left bundle branch block: analysis using magnetic resonance imaging tagging images

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    The ideal vaccine is a simple and stable formulation which can be conveniently administered and provides life-long immunity against a given pathogen. The development of such a vaccine, which should trigger broad and strong B-cell and T-cell responses against antigens of the pathogen in question, is highly dependent on tailored vaccine delivery approaches. This review addresses vaccine delivery in its broadest scope. We discuss the needs and challenges in the area of vaccine delivery, including restrictions posed by specific target populations, potentials of dedicated stable formulations and devices, and the use of adjuvants. Moreover, we address the current status and perspectives of vaccine delivery via several routes of administration, including non-or minimally invasive routes. Finally we suggest possible directions for future vaccine delivery research and development. (C) 2012 Elsevier B.V. All rights reserved

    Constraining symmetron fields with atom interferometry

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    We apply the new constraints from atom-interferometry searches for screening mechanisms to the symmetron model, finding that these experiments exclude a previously unexplored region of the parameter space. We discuss the possibility of networks of domain walls forming in the vacuum chamber, and how this could be used to discriminate between models of screening

    L-infinity algebra connections and applications to String- and Chern-Simons n-transport

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    We give a generalization of the notion of a Cartan-Ehresmann connection from Lie algebras to L-infinity algebras and use it to study the obstruction theory of lifts through higher String-like extensions of Lie algebras. We find (generalized) Chern-Simons and BF-theory functionals this way and describe aspects of their parallel transport and quantization. It is known that over a D-brane the Kalb-Ramond background field of the string restricts to a 2-bundle with connection (a gerbe) which can be seen as the obstruction to lifting the PU(H)-bundle on the D-brane to a U(H)-bundle. We discuss how this phenomenon generalizes from the ordinary central extension U(1) -> U(H) -> PU(H) to higher categorical central extensions, like the String-extension BU(1) -> String(G) -> G. Here the obstruction to the lift is a 3-bundle with connection (a 2-gerbe): the Chern-Simons 3-bundle classified by the first Pontrjagin class. For G = Spin(n) this obstructs the existence of a String-structure. We discuss how to describe this obstruction problem in terms of Lie n-algebras and their corresponding categorified Cartan-Ehresmann connections. Generalizations even beyond String-extensions are then straightforward. For G = Spin(n) the next step is "Fivebrane structures" whose existence is obstructed by certain generalized Chern-Simons 7-bundles classified by the second Pontrjagin class.Comment: 100 pages, references and clarifications added; correction to section 5.1 and further example to 9.3.1 adde

    Elastomeric spring actuator using nylon wires

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    Medical devices are designed for collaboration with the human body, which makes the steps to create them increasingly more complex if the device is to be implanted. Soft robots have the unique potential of meeting both the mechanical compliance with the interacting tissues and the controlled functionality needed for a repair or replacement. Soft devices that fulfill fundamental mechanical roles are needed as parts of soft robots in order to carry out desired tasks. As the medical devices become increasingly low-profile, soft devices must feature multi-functionality that is embedded in the structure. A device embedded with nylon actuators allows for the controlled collapsing of an elastomeric spring by compression alone or compression and twisting. In this paper we present the concept of a novel elastomeric spring, its fabrication and mechanical characterization

    Strong time operators associated with generalized Hamiltonians

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    Let the pair of operators, (H,T)(H, T), satisfy the weak Weyl relation: Te−itH=e−itH(T+t)Te^{-itH} = e^{-itH}(T + t), where HH is self-adjoint and TT is closed symmetric. Suppose that g is a realvalued Lebesgue measurable function on \RR such that g∈C2(RK)g \in C^2(R K) for some closed subset K \subset \RR with Lebesgue measure zero. Then we can construct a closed symmetric operator DD such that (g(H),D)(g(H), D) also obeys the weak Weyl relation.Comment: 10 page

    Systematic characterization of upper critical fields for MgB2_2 thin films using the two-band superconducting theory

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    We present experimental results of the upper critical fields Hc2H_{\rm c2} of various MgB2_2 thin films prepared by the molecular beam epitaxy, multiple-targets sputtering, and co-evaporation deposition apparatus. Experimental data of the Hc2(T)H_{\rm c2}(T) are successfully analyzed by applying the Gurevich theory of dirty two-band superconductivity in the case of Dπ/Dσ>1D_{\pi}/D_{\sigma}>1, where DπD_{\pi} and DσD_{\sigma} are the intraband electron diffusivities for π\pi and σ\sigma bands, respectively. We find that the parameters obtained from the analysis are strongly correlated to the superconducting transition temperature TcT_{\rm c} of the films. We also discuss the anormalous narrowing of the transition width at intermediate temperatures confirmed by the magnetoresistance measurements.Comment: 7 pages, 7 figures, submitted to Phys. Rev.
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