687 research outputs found

    Eleutherodactylus colostichos, a new frog species from the Pramo de los Conejos, in the Venezuelan Andes (Anura: Leptodactylidae)

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    http://deepblue.lib.umich.edu/bitstream/2027.42/57136/1/OP700.pd

    Electrodynamic Limit in a Model for Charged Solitons

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    We consider a model of topological solitons where charged particles have finite mass and the electric charge is quantised already at the classical level. In the electrodynamic limit, which physically corresponds to electrodynamics of solitons of zero size, the Lagrangian of this model has two degrees of freedom only and reduces to the Lagrangian of the Maxwell field in dual representation. We derive the equations of motion and discuss their relations with Maxwell's equations. It is shown that Coulomb and Lorentz forces are a consequence of topology. Further, we relate the U(1) gauge invariance of electrodynamics to the geometry of the soliton field, give a general relation for the derivation of the soliton field from the field strength tensor in electrodynamics and use this relation to express homogeneous electric fields in terms of the soliton field.Comment: 13 pages, 4 figures, Introduction and Section II (Model Lagrangian) rewritten, new chapters concerning electrodynamic limit and discussion of causality inserte

    The architectures of media power: editing, the newsroom, and urban public space

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    This paper considers the relation of the newsroom and the city as a lens into the more general relation of production spaces and mediated publics. Leading theoretically from Lee and LiPuma’s (2002) notion of ‘cultures of circulation’, and drawing on an ethnography of the Toronto Star, the paper focuses on how media forms circulate and are enacted through particular practices and material settings. With its attention to the urban milieus and orientations of media organizations, this paper exhibits both affinities with but also differences to current interests in the urban architectures of media, which describe and theorize how media get ‘built into’ the urban experience more generally. In looking at editing practices situated in the newsroom, an emphasis is placed on the phenomenological appearance of media forms both as objects for material assembly as well as more abstracted subjects of reflexivity, anticipation and purposiveness. Although this is explored with detailed attention to the settings of the newsroom and the city, the paper seeks to also provide insight into the more general question of how publicness is material shaped and sited

    Successful switching of patients with acute schizophrenia from another antipsychotic to brexpiprazole: Comparison of clinicians\u27 choice of cross-titration schedules in a post hoc analysis of a randomized, double-blind, maintenance treatment study

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    © Cambridge University Press 2018. Objective To compare the tolerability and efficacy of different antipsychotic cross-titration schedules, using data from a brexpiprazole study (Equator; NCT01668797).MethodsPatients with schizophrenia were cross-titrated from other antipsychotics to brexpiprazole monotherapy in a 1-4 week open-label conversion phase, then entered a single-blind brexpiprazole treatment phase. Patients were stratified into four conversion groups, according to the amount of time spent in the conversion phase. Discontinuation rates, treatment-emergent adverse events (TEAEs), and efficacy (Positive and Negative Syndrome Scale [PANSS]) were compared between conversion groups.ResultsOf the 404 patients treated with brexpiprazole, the majority (72.0%) spent 22-33 days in the conversion phase. Discontinuation rates due to lack of efficacy or adverse events were low in all conversion groups. Of the 292 patients who successfully switched and completed 8 weeks of brexpiprazole treatment, most were converted to brexpiprazole over 22-33 days (80.1%), and fewer were converted over 1-7 days (2.4%), 8-14 days (6.5%), or 15-21 days (11.0%). The incidence of TEAEs over 8 weeks was lower among those converted over 22-33 days (44.4%) than in other conversion groups (62.5-84.2%), although low patient numbers with shorter conversion times limit the generalizability of this finding. Each conversion group showed comparable improvement in PANSS total score from baseline.ConclusionThe majority of patients were cross-titrated to brexpiprazole over a period of 22-33 days, by investigators\u27 choice. Additional data on shorter conversions may help clinicians to choose a switching paradigm that best meets their patients\u27 needs

    Real-time tomography mooring

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    A real-time tomography system has been developed which combines ocean acoustic tomography with satellite-based time keeping and satellite telemetry. The basis of the system is the acoustic tomography transceiver and its associated acoustic navigation grid. To this basic system, a link to the surface has been added to provide a pathway for telemetry of the tomographic data to shore and a downlink for satellite-derived time which is used to correct the transceiver's clock. The surface buoy contains a GPS receiver, clock comparator, system controller and multiple ID Argos transmitters. Processed tomography signals, transceiver location data time, time drift and surface buoy engineering data are transmitted to satellite using a total of 32 data buffers transmitted every eight minutes. The report describes the real-time tomography system in detail, with particular emphasis on the modifications implemented to convert the standard tomography instrument to a real-time oceanographic tool.Funding was provided by the Office of Naval Technology under Contract No. N000-14-C-90-0098

    The Ontology of Intentional Agency in Light of Neurobiological Determinism: Philosophy Meets Folk Psychology

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    The moot point of the Western philosophical rhetoric about free will consists in examining whether the claim of authorship to intentional, deliberative actions fits into or is undermined by a one-way causal framework of determinism. Philosophers who think that reconciliation between the two is possible are known as metaphysical compatibilists. However, there are philosophers populating the other end of the spectrum, known as the metaphysical libertarians, who maintain that claim to intentional agency cannot be sustained unless it is assumed that indeterministic causal processes pervade the action-implementation apparatus employed by the agent. The metaphysical libertarians differ among themselves on the question of whether the indeterministic causal relation exists between the series of intentional states and processes, both conscious and unconscious, and the action, making claim for what has come to be known as the event-causal view, or between the agent and the action, arguing that a sort of agent causation is at work. In this paper, I have tried to propose that certain features of both event-causal and agent-causal libertarian views need to be combined in order to provide a more defendable compatibilist account accommodating deliberative actions with deterministic causation. The ‘‘agent-executed-eventcausal libertarianism’’, the account of agency I have tried to develop here, integrates certain plausible features of the two competing accounts of libertarianism turning them into a consistent whole. I hope to show in the process that the integration of these two variants of libertarianism does not challenge what some accounts of metaphysical compatibilism propose—that there exists a broader deterministic relation between the web of mental and extra-mental components constituting the agent’s dispositional system—the agent’s beliefs, desires, short-term and long-term goals based on them, the acquired social, cultural and religious beliefs, the general and immediate and situational environment in which the agent is placed, etc. on the one hand and the decisions she makes over her lifetime on the basis of these factors. While in the ‘‘Introduction’’ the philosophically assumed anomaly between deterministic causation and the intentional act of deciding has been briefly surveyed, the second section is devoted to the task of bridging the gap between compatibilism and libertarianism. The next section of the paper turns to an analysis of folk-psychological concepts and intuitions about the effects of neurochemical processes and prior mental events on the freedom of making choices. How philosophical insights can be beneficially informed by taking into consideration folk-psychological intuitions has also been discussed, thus setting up the background for such analysis. It has been suggested in the end that support for the proposed theory of intentional agency can be found in the folk-psychological intuitions, when they are taken in the right perspective

    Low Temperature Static and Dynamic Behavior of the Two-Dimensional Easy-Axis Heisenberg Model

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    We apply the self-consistent harmonic approximation (SCHA) to study static and dynamic properties of the two-dimensional classical Heisenberg model with easy-axis anisotropy. The static properties obtained are magnetization and spin wave energy as functions of temperature, and the critical temperature as a function of the easy-axis anisotropy. We also calculate the dynamic correlation functions using the SCHA renormalized spin wave energy. Our analytical results, for both static properties and dynamic correlation functions, are compared to numerical simulation data combining cluster-Monte Carlo algorithms and Spin Dynamics. The comparison allows us to conclude that far below the transition temperature, where the SCHA is valid, spin waves are responsible for all relevant features observed in the numerical simulation data; topological excitations do not seem to contribute appreciably. For temperatures closer to the transition temperature, there are differences between the dynamic correlation functions from SCHA theory and Spin Dynamics; these may be due to the presence of domain walls and solitons.Comment: 12 pages, 14 figure

    Static solitons with non-zero Hopf number

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    We investigate a generalized non-linear O(3) σ\sigma-model in three space dimensions where the fields are maps S3↦S2S^3 \mapsto S^2. Such maps are classified by a homotopy invariant called the Hopf number which takes integer values. The model exhibits soliton solutions of closed vortex type which have a lower topological bound on their energies. We explicitly compute the fields for topological charge 1 and 2 and discuss their shapes and binding energies. The effect of an additional potential term is considered and an approximation is given for the spectrum of slowly rotating solitons.Comment: 13 pages, RevTeX, 7 Postscript figures, minor changes have been made, a reference has been corrected and a figure replace

    Nonlinear stability of oscillatory wave fronts in chains of coupled oscillators

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    We present a stability theory for kink propagation in chains of coupled oscillators and a new algorithm for the numerical study of kink dynamics. The numerical solutions are computed using an equivalent integral equation instead of a system of differential equations. This avoids uncertainty about the impact of artificial boundary conditions and discretization in time. Stability results also follow from the integral version. Stable kinks have a monotone leading edge and move with a velocity larger than a critical value which depends on the damping strength.Comment: 11 figure
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