1,324 research outputs found

    Concrete Encounter with Evil in Gabriel Marcel's Drama

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    Sartre's Last Philosophy: A Feminist Interpretation

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    Transport Mean Free Path for Magneto-Transverse Light Diffusion

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    We derive an expression for the transport mean free path \ell^*_\perp associated with magneto-transverse light diffusion for a random collection of Faraday-active Mie scatterers. This expression relates the magneto-transverse diffusion in multiple scattering directly to the magneto-transverse scattering of a single scatterer.Comment: 5 pages, 1 figure, Latex, accepted for publication in Europhysics Letter

    Structural constraints limit the regime of optimal flux in autocatalytic reaction networks

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    Autocatalytic chemical networks play a predominant role in a large number of natural systems such as in metabolic pathways and in ecological networks. In this work, we present a theoretical framework that identifies the thermodynamic conditions under which autocatalytic networks run optimally in a non-equilibrium stationary state. Our theory shows that the overall reaction associated with the network is aligned with the thermodynamic force that drives the system out of equilibrium. We also demonstrate that the thermodynamic force required to operate at a maximal flux obeys universal constraints that are independent of the kinetics, but solely determined by the stoichiometry of the overall process and by the structural properties of the underlying chemical reaction network.Comment: 27 pages, 5 figures, 1 tabl

    Gallavotti-Cohen-Type symmetry related to cycle decompositions for Markov chains and biochemical applications

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    We slightly extend the fluctuation theorem obtained in \cite{LS} for sums of generators, considering continuous-time Markov chains on a finite state space whose underlying graph has multiple edges and no loop. This extended frame is suited when analyzing chemical systems. As simple corollary we derive in a different method the fluctuation theorem of D. Andrieux and P. Gaspard for the fluxes along the chords associated to a fundamental set of oriented cycles \cite{AG2}. We associate to each random trajectory an oriented cycle on the graph and we decompose it in terms of a basis of oriented cycles. We prove a fluctuation theorem for the coefficients in this decomposition. The resulting fluctuation theorem involves the cycle affinities, which in many real systems correspond to the macroscopic forces. In addition, the above decomposition is useful when analyzing the large deviations of additive functionals of the Markov chain. As example of application, in a very general context we derive a fluctuation relation for the mechanical and chemical currents of a molecular motor moving along a periodic filament.Comment: 23 pages, 5 figures. Correction

    Coherent Backscattering of light in a magnetic field

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    This paper describes how coherent backscattering is altered by an external magnetic field. In the theory presented, magneto-optical effects occur inside Mie scatterers embedded in a non-magnetic medium. Unlike previous theories based on point-like scatterers, the decrease of coherent backscattering is obtained in leading order of the magnetic field using rigorous Mie theory. This decrease is strongly enhanced in the proximity of resonances, which cause the path length of the wave inside a scatterer to be increased. Also presented is a novel analysis of the shape of the backscattering cone in a magnetic field.Comment: 27 pages, 5 figures, Revtex, to appear in Phys. Rev.

    Oxidative stress biomarkers are associated with visible clinical signs of a disease in frigatebird nestlings

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    Infectious diseases are one of the most common threats for both domestic and wild animals, but little is known about the effects on the physiological condition and survival of wild animals. Here, we have tested for the first time in a wild vertebrate facing a viral disease possibly due to herpesvirus (i) whether nestlings with either low levels of oxidative damage or high levels of antioxidant protection are less susceptible to develop visible clinical signs, (ii) whether the disease is associated with the nestlings' oxidative status, (iii) whether the association between the disease and oxidative status is similar between males and females (iv), and whether cloacal and tracheal swabs might be used to detect herpesvirus. To address our questions, we took advantage of a population of Magnificent frigatebirds (Fregata magnificens) whose nestlings have experienced high mortality rates in recent times. Our work shows that (i) blood lipid oxidative damage is associated with observable clinical signs and survival probabilities of nestling frigatebirds, and (ii) that high glutathione levels in red blood cells are associated with the emergence of visible clinical signs of the disease. Our work provides evidence that differences in the oxidative status of nestlings might underlie individual health and survival

    The Dialectic of the Real Erotic and of Eroticism in Kierkegaard's Seducer's Diary

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    The Dialectic of the Real Erotic and of Eroticism in Kierkegaard's Seducer's Diar

    Meta-modelling hybrid formalisms

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    Proceedigns of 2004 IEEE International Symposium on Computer Aided Control Systems DesignPersonal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. S. Lacoste-Julien, H. Vangheluwe J. de Lara, and P. J. Mosterman, "Meta-modelling hybrid formalisms", 2004 IEEE International Symposium on Computer Aided Control Systems Design, Taipei, China, 2004, pp. 65-70This article demonstrates how meta-modelling can simplify the construction of domain-and formalism-specific modelling environments. Using AToM3 (a tool for multi-formalism and meta-modelling developed at McGill University), a model is constructed of a hybrid formalism, HS, that combines event scheduling constructs with ordinary differential equations. From this specification, an HS-specific visual modelling environment is synthesized. For the purpose of this demonstration, a simple hybrid model of a bouncing ball is modelled in this environment. It is envisioned that the future of modelling and simulation in general, and more specifically in hybrid dynamic systems design lies in domain-specific computer automated multi-paradigm modelling (CAMPaM) which combines multi-abstraction, multi-formalism, and meta-modelling. The small example presented in this article demonstrates the feasibility of this approac
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