Liquid-vapor equilibria and interfacial properties of n-alkanes and perfluoroalkanes by molecular simulation

A molecular dynamics study is presented to assess the performance of a united-atom model in the prediction of liquid-vapor interfacial properties for short-chain perfluoroalkanes and their alkane counterparts. In particular, the ability of this model to discriminate between the surface-energy values of these two types of compounds was investigated over a wide temperature range corresponding to the liquid-vapor region. Comparisons with available experimental data and surface-tension predictions given by other force-field parameterizations, including those based on the more computationally demanding all-atom method, were performed to gauge the viability of this model. It was found that the model used in this study captures qualitatively the expected behavior of surface energy between alkanes and perfluoroalkanes and yields values that are in excellent agreement with experimental data, especially in the high-temperature limit as the critical temperature is approached

Correlates of eye colour and pattern in mantellid frogs

With more than 250 species, the Mantellidae is the most species-rich family of frogs in Madagascar. These frogs are highly diversified in morphology, ecology and natural history. Based on a molecular phylogeny of 248 mantellids, we here examine the distribution of three characters reflecting the diversity of eye colouration and two characters of head colouration along the mantellid tree, and their correlation with the general ecology and habitat use of these frogs. We use Bayesian stochastic character mapping, character association tests and concentrated changes tests of correlated evolution of these variables. We confirm previously formulated hypotheses of eye colour pattern being significantly correlated with ecology and habits, with three main character associations: many tree frogs of the genus Boophis have a bright coloured iris, often with annular elements and a blue-coloured iris periphery (sclera); terrestrial leaf-litter dwellers have an iris horizontally divided into an upper light and lower dark part; and diurnal, terrestrial and aposematic Mantella frogs have a uniformly black iris. Furthermore, the presence of a frenal streak and a dark tympanic patch were associated with each other, with horizontally divided iris colour, and with terrestrial habits. Our study is restricted to the mantellid radiation, and the performed tests detect the simultaneous distribution of independent character states in a tree, rather than providing a measure for phylogenetic independent correlation of these character states. The concentrated changes tests suggest that the evolutionary origin of a bright iris might indeed be correlated to arboreal habits. Yet, rather than testing hypotheses of adaptive evolution of eye colour in anurans, our study serves to formulate hypotheses of convergence more precisely and thus to open perspectives for their further testing in a comparative framework along the anuran tree of life. For instance, a brightly coloured iris and sclera might serve mate recognition or as aposematic defensive strategy especially in tree frogs, and a horizontally divided iris colour might constitute a disruptive defensive strategy in frogs inhabiting the leaf litter stratum

On an efficient k-step iterative method for nonlinear equations

[EN] This paper is devoted to the construction and analysis of an efficient k-step iterative method for nonlinear equations. The main advantage of this method is that it does not need to evaluate any high order Frechet derivative. Moreover, all the k-step have the same matrix, in particular only one LU decomposition is required in each iteration. We study the convergence order, the efficiency and the dynamics in order to motivate the proposed family. We prove, using some recurrence relations, a semilocal convergence result in Banach spaces. Finally, a numerical application related to nonlinear conservative systems is presented. (C) 2016 Elsevier B.V. All rights reserved.This work was supported in part by the project MTM2011-28636-C02-01-{01,02} of the Spanish Ministry of Science and Innovation.Amat, S.; Bermúdez, C.; Hernández-Verón, MA.; Martínez Molada, E. (2016). On an efficient k-step iterative method for nonlinear equations. Journal of Computational and Applied Mathematics. 302:258-271. https://doi.org/10.1016/j.cam.2016.02.003S25827130

Super-attracting periodic orbits for a classical third order method

AbstractWe use a classical third order root-finding iterative method for approximating roots of nonlinear equations. We present a procedure for constructing polynomials so that super-attracting periodic orbits of any prescribed period occur when this method is applied. This note can be considered as the second part of our previous study [S. Amat, S. Busquier, S. Plaza, A construction of attracting periodic orbits for some classical third order iterative methods, J. Comput. Appl. Math. 189(1–2) (2006) 22–33]

Nuevos registros de moscas gigantes (Diptera: Pantophthalmidae) de Colombia

New records of Pantophthalmus planiventris and Pantophthalmus tabaninus in Colombia are reported, map of localities and check-list of pantophthalmid species described and recorded in Colombia is provided.Se presentan nuevos registros geogr\ue1ficos de Pantophthalmus planiventris y Pantophthalmus tabaninus , adem\ue1s un mapa de localidades y la lista preliminar de especies descritas y registradas de pantoft\ue1lmidos en Colombia

Numerical integration rules with improved accuracy close to singularities

Sometimes it is necessary to obtain a numerical integration using only discretised data. In some cases, the data contains singularities which position is known but does not coincide with a discretisation point, and the jumps in the function and its derivatives are available at these positions. The motivation of this paper is to use the previous information to obtain numerical quadrature formulas that allow approximating the integral of the discrete data over certain intervals accurately. This work is devoted to the construction and analysis of a new nonlinear technique that allows to obtain accurate numerical integrations of any order using data that contains singularities, and when the integrand is only known at grid points. The novelty of the technique consists in the inclusion of correction terms with a closed expression that depends on the size of the jumps of the function and its derivatives at the singularities, that are supposed to be known. The addition of these terms allows recovering the accuracy of classical numerical integration formulas even close to the singularities, as these correction terms account for the error that the classical integration formulas commit up to their accuracy at smooth zones. Thus, the correction terms can be added during the integration or as post-processing, which is useful if the main calculation of the integral has been already done using classical formulas. The numerical experiments performed allow us to confirm the theoretical conclusions reached in this paper.Comment: 23 pages, 5 Figures, 3 Table

The internationalisation of the Spanish SME sector

As part of a wider research program, we analysed the theoretical framework and the recent developments of the process of internationalisation (transnationalisation) of the small- and medium-sized enterprises in Spain. The paper highlights the main trends and barriers of this internationalisation process. Methodology included document analyses, interviews, and the analyses of statistical databases