2,212 research outputs found

    A characterization of those automata that structurally generate finite groups

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    Antonenko and Russyev independently have shown that any Mealy automaton with no cycles with exit--that is, where every cycle in the underlying directed graph is a sink component--generates a fi- nite (semi)group, regardless of the choice of the production functions. Antonenko has proved that this constitutes a characterization in the non-invertible case and asked for the invertible case, which is proved in this paper

    Rate-dependent propagation of cardiac action potentials in a one-dimensional fiber

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    Action potential duration (APD) restitution, which relates APD to the preceding diastolic interval (DI), is a useful tool for predicting the onset of abnormal cardiac rhythms. However, it is known that different pacing protocols lead to different APD restitution curves (RCs). This phenomenon, known as APD rate-dependence, is a consequence of memory in the tissue. In addition to APD restitution, conduction velocity restitution also plays an important role in the spatiotemporal dynamics of cardiac tissue. We present new results concerning rate-dependent restitution in the velocity of propagating action potentials in a one-dimensional fiber. Our numerical simulations show that, independent of the amount of memory in the tissue, waveback velocity exhibits pronounced rate-dependence and the wavefront velocity does not. Moreover, the discrepancy between waveback velocity RCs is most significant for small DI. We provide an analytical explanation of these results, using a system of coupled maps to relate the wavefront and waveback velocities. Our calculations show that waveback velocity rate-dependence is due to APD restitution, not memory.Comment: 17 pages, 7 figure

    Canine sterile steroid-responsive lymphadenitis in 49 dogs

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    OBJECTIVES:To report clinical and laboratory features, treatment responses and outcome in dogs diagnosed with sterile steroid-responsive lymphadenitis in the United Kingdom. MATERIALS AND METHODS:Medical records of dogs diagnosed with sterile steroid-responsive lymphadenitis from 2009 to 2016 at six specialist referral centres were evaluated retrospectively. RESULTS:The study included 49 dogs. Springer spaniels appeared to be over-represented (16 of 49 dogs). Young dogs (median age: 3 years and 9 months) and females (31 of 49) were frequently affected. Clinical presentation was variable, with pyrexia (39 of 49), lethargy (35 of 49) and anorexia (21 of 49) the most commonly reported clinical signs. Lymph node cytology or histopathology demonstrated neutrophilic, pyogranulomatous, granulomatous or necrotising lymphadenitis without a detectable underlying cause in all cases. Because a sterile immune-mediated aetiology was suspected, all dogs received prednisolone, which was followed by rapid resolution of clinical signs and lymphadenopathy in most cases. CLINICAL SIGNIFICANCE:Sterile steroid-responsive lymphadenitis should be considered in dogs with pyrexia of unknown origin with inflammatory lymphadenopathy if no underlying cause can be found and often responds well to immunosuppressive corticosteroid therapy

    Tunneling through a multigrain system: deducing the sample topology from the nonlinear conductance

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    We study a current transport through a system of a few grains connected with tunneling links. The exact solution is given for an arbitrarily connected double-grain system with a shared gate in the framework of the orthodox model. The obtained result is generalized for multigrain systems with strongly different tunneling resistances. We analyse the large-scale nonlinear conductance and demonstrate how the sample topology can be unambiguously deduced from the spectroscopy pattern (differential conductance versus gate-bias plot). We present experimental data for a multigrain sample and reconstruct the sample topology. A simple selection rule is formulated to distinguish samples with spectral patterns free from spurious disturbance caused by recharging of some grains nearby. As an example, we demonstrate experimental data with additional peaks in the spectroscopy pattern, which can not be attributed to coupling to additional grains. The described approach can be used to judge the sample topology when it is not guaranteed by fabrication and direct imaging is not possible.Comment: 13 pages (including 8 figures

    Renormalization group approach to energy level statistics at the integer quantum Hall transition

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    We extend the real-space renormalization group (RG) approach to the study of the energy level statistics at the integer quantum Hall (QH) transition. Previously it was demonstrated that the RG approach reproduces the critical distribution of the {\em power} transmission coefficients, i.e., two-terminal conductances, Pc(G)P_{\text c}(G), with very high accuracy. The RG flow of P(G)P(G) at energies away from the transition yielded the value of the critical exponent, ν\nu, that agreed with most accurate large-size lattice simulations. To obtain the information about the level statistics from the RG approach, we analyze the evolution of the distribution of {\em phases} of the {\em amplitude} transmission coefficient upon a step of the RG transformation. From the fixed point of this transformation we extract the critical level spacing distribution (LSD). This distribution is close, but distinctively different from the earlier large-scale simulations. We find that away from the transition the LSD crosses over towards the Poisson distribution. Studying the change of the LSD around the QH transition, we check that it indeed obeys scaling behavior. This enables us to use the alternative approach to extracting the critical exponent, based on the LSD, and to find ν=2.37±0.02\nu=2.37\pm0.02 very close to the value established in the literature. This provides additional evidence for the surprising fact that a small RG unit, containing only five nodes, accurately captures most of the correlations responsible for the localization-delocalization transition.Comment: 10 pages, 11 figure

    Breadwinners and Homemakers: Migration and Changing Conjugal Expectations in Rural Bangladesh

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    The literature on marriage norms and aspirations across societies largely sees the institution as static – a tool for the assertion of masculinities and subordination of women. The changing meanings of marriage and conjugality in the contemporary context of globalisation have received scant attention. Based on research in rural Bangladesh, this article questions the usefulness of notions of autonomy and dependence in understanding conjugal relations and expectations in a context of widespread migration for extended periods, especially to overseas destinations, where mutuality is crucial for social reproduction, though in clearly genderdemarcated domains
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