357 research outputs found

    Exact relations between damage spreading and thermodynamic functions for the N-color Ashkin-Teller model

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    Exact results are derived relating quantities computable by the so-called damage spreading method and thermodynamic functions for the N-color Ashkin-Teller model. The results are valid for any ergodic dynamics. Since we restrict our analysis to the ferromagnetic case the results are also valid for any translational invariant lattice. The derived relations should be used in order to determine numerically the N-color Ashkin-Teller critical exponents with better accuracy and less computational efforts than standard Monte Carlo simulations.Comment: 6 pages, to be published in JSTAT (Journal of Statistical Mechanics: Theory and Experiment). The results of a computer simulation were included for N=3 as an example on how to use the analytical relations derived in the paper as a guide to obtain the critical temperature and critical exponent

    Dirichlet boundary value problem for Chern-Simons modified gravity

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    Chern-Simons modified gravity comprises the Einstein-Hilbert action and a higher-derivative interaction containing the Chern-Pontryagin density. We derive the analog of the Gibbons-Hawking-York boundary term required to render the Dirichlet boundary value problem well-defined. It turns out to be a boundary Chern-Simons action for the extrinsic curvature. We address applications to black hole thermodynamics.Comment: 4 pages, revtex4, v2: added Refs., made one statement stronger, added footnote and added paragraph on single field inflatio

    Lorentz-violating contributions of the Carroll-Field-Jackiw model to the CMB anisotropy

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    We study the finite temperature properties of the Maxwell-Carroll-Field-Jackiw (MCFJ) electrodynamics for a purely spacelike background. Starting from the associated finite temperature partition function, a modified black body spectral distribution is obtained. We thus show that, if the CMB radiation is described by this model, the spectrum presents an anisotropic angular energy density distribution. We show, at leading order, that the Lorentz-breaking contributions for the Planck's radiation law and for the Stefan-Boltzmann's law are nonlinear in frequency and quadratic in temperature, respectively. Using our results, we set up bounds for the Lorentz-breaking parameter, and show that Lorentz violation in the context of the MCFJ model is unable to yield the known CMB anisotropy (of 1 part in 105)10^{5})

    Equilibrium moisture content and heat of desorption of garlic

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    Desorption isotherms for 1 mm thick garlic slices were determined by a static gravimetric method at temperatures between 5 and 45ÂşC, in the relative humidity range from 11 to 98%. The experimental desorption data obtained in this study was fitted to BET and GAB equations to predict the desorption behavior of garlic. It was found that the GAB model was the most satisfactory model for representation of the sorption data. The results obtained in this study, are now being used in the development of a drying unit for garlic, by a suitable technique

    Evaluation of self-perception of awake bruxism in dentistry students : clinical case series

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    Abstract in proceedings of the Fourth International Congress of CiiEM: Health, Well-Being and Ageing in the 21st Century, held at Egas Moniz’ University Campus in Monte de Caparica, Almada, from 3–5 June 2019.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.info:eu-repo/semantics/publishedVersio

    Three Questions on Lorentz Violation

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    We review the basics of the two most widely used approaches to Lorentz violation - the Stardard Model Extension and Noncommutative Field Theory - and discuss in some detail the example of the modified spectrum of the synchrotron radiation. Motivated by touching upon such a fundamental issue as Lorentz symmetry, we ask three questions: What is behind the search for Lorentz violation? Is String Theory a physical theory? Is there an alternative to Supersymmetry?Comment: 16 pages; invited luecture at DICE2006 - Piombino, Italy - September 200

    A New Method for the Preparation of Non-Terminal Alkynes: Application to the Total Syntheses of Tulearin A and C

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    Lactones are known to react with the reagent generated in situ from CCl4 and PPh3 in a Wittig-type fashion to give gem-dichloro-olefin derivatives. Such compounds are now shown to undergo reductive alkylation on treatment with organolithium reagents RLi to furnish acetylene derivatives bearing the substituent R at their termini (R=Me, n-, sec-, tert-alkyl, silyl); the reaction can be catalyzed with either Cu(acac)2 or Fe(acac)3/1,2-diaminobenzene. Two alkynol derivatives prepared in this way from readily accessible lactone precursors served as the key building blocks for the total syntheses of the cytotoxic marine macrolides tulearin A (1) and C (2). The assembly of these fragile targets hinged upon ring closing alkyne metathesis (RCAM) followed by a formal trans-reduction of the resulting cycloalkynes via trans-hydrosilylation/protodesilylation

    Effects of Urbanization and the Sustainability of Marine Artisanal Fishing: A Study on Tropical Fishing Communities in Brazil

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    Marine fishing occurs along the coast and oceanic islands within the Exclusive Economic Zone of Brazil and is practiced mainly in an industrial fashion in the southern and southeastern regions of the country as well as in an artisanal fashion in the northern and northeastern regions. Artisanal marine fishing is practiced by fishermen who use sailing rafts or mid-size motorboats in daily fishing activities or activities that surpass 20 days at sea. To face the ocean and extract sustenance and income, the majority of artisanal fishermen do not have advanced fishing technologies, but rather empirical knowledge passed from one generation to another, which has allowed fishermen to maintain their activities for hundreds of years. The shared knowledge with regard to fishing and gear as well as fishing territories and the discovery of new territories allows artisanal fishermen to maintain catches while resources have become scarce. However, different factors in urban areas have been contributing to changes in artisanal marine fishing, such as the facility to education and jobs in other sectors of the economy. The aim of the present study was to investigate the experiences of artisanal fishermen in traditional communities of northeastern Brazil in the occurrence of urbanization. Traditionally in artisanal fishing, the transmission of knowledge occurs in the family, generally from father to son. However, this traditional transmission of knowledge is being lost in urban fishing communities. The urban environment facilitates access to formal education and provides opportunities for both formal and informal jobs, leading to income in more attractive sectors to the sons of fishermen than the activity of fishing. This is caused by changes in schooling and has triggered the avoidance of youths with regard to fishing activities. Moreover, urban pressures, such as the loss of areas of embarkation and landing, further hinder the maintenance of fishing in such areas. Thus, issues related to urbanization have been changing the structure of fishing communities and compromising the maintenance and sustainability of marine artisanal fishing activities in urban areas
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