1,720,966 research outputs found
Effect of the incomplete interaction on the nematic-isotropic transition at the nematic-wall interface
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Impedance spectroscopy analysis of an electrolytic cell limited by Ohmic electrodes: the case of ions with two different diffusion coefficients dispersed in an aqueous solution
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Measurement of the impedance of aqueous solutions of KCl: An analysis using an extension of the Poisson-Nernst-Planck model
No full textWe investigate the frequency dependence of the real and imaginary parts of the electric impedance of a cell with titanium electrodes, filled with aqueous solution of KCl in different concentrations. Our experimental data are interpreted by means of an extension of the Poisson-Nernst-Planck model, assuming that the electrodes are not blocking and well described by Ohmic boundary conditions, and that two groups of ions are responsible for the electric conduction. One group is due to the dissociation of KCl in water (majority carriers), the other to the impurities dissolved in water or present in KCl (minority carriers), whose bulk density is very small with respect to first group. The agreement between the experimental data and the theoretical predictions is good, taking into account the small number of free parameters entering in the model. In particular, the diffusion coefficient for the potassium and chloride ions well comparer with those reported in literature. According to our analysis, the role of the carriers related to the impurities present in the solution play a fundamental role in the fit of the experimental data in the low frequency region. The presented model where two groups of ions are present, with the assumption of equal mobilities for positive and negative charges in a group, is motivated by the experimental evidence that in aqueous solution of KCl, K+, and Cl- have approximately the same mobilities. Since the PNP model for an electrolytic solution of the case considered by us predicts an electric response similar to that of an electrolytic solution where the positive and negative ions have different mobility, a comparison with the results reported recently by Macdonald is presented [J. R. Macdonald, Electrochim. Acta, 123, 535 (2014)]. Alternative interpretation of our experimental results related to the assumption of non-blocking electrodes is also discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dielectric dispersion of water in the frequency range from 10 mHz to 30 MHz
No full textWe investigate the dielectric dispersion of water, specially in the low-frequency range, by using the impedance spectroscopy technique. The frequency dependencies of the real R and imaginary Z parts of the impedance Could not be explained by means of the Usual description of the dielectric properties of the water as all insulating liquid containing ions. This is due to the incomplete knowledge of the parameters entering in the fundamental equations describing the evolution of the system, and oil the mechanisms regulating the exchange of charge of the cell with the external circuit. We propose a simple description of our experimental data based on the model of Debye, by invoking a dc conductivity of the cell, related to the nonblocking character of the electrodes. A discussion on the electric Circuits able to simulate the cell under investigation, based oil bulk and Surface elements, is also reported. We find that the simple circuit formed by a series of two parallels of resistance and capacitance is able to reproduce the experimental data concerning the real and imaginary part of the electrical impedance of the cell for frequency larger than 1 Hz. According to this description, one of the parallels takes into account the electrical properties of interface between the electrode and water, and the other of the bulk. For frequency lower than 1 Hz, a good agreement with the experimental data is obtained by simulating the electrical properties of the interface by means of the constant phase element.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPqFAPESPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)INC
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