1,721,086 research outputs found
Study of polyalkylterthiophenes deposition
No full textIn this paper we present the in-situ characterization of poly-3'4'-didodecylterthiophene electrodeposition with the Probe Beam Deflection technique and the Bending Beam Method. Deflectograms revealed anomalous features during the potentiodynamic synthesis of poly-3'4'-didodecylterthiophene for the occurrence of mass fluxes towards the electrode in the cathodic scan of the cyclic voltammetry. The mechanical effects of poly-3'4'-didodecylterthiophene growth onto thin flexible conducting substrates were also detected by means of the Bending Beam Method. The most relevant mechanical effects were observed during the cathodic polarization of the electrode with the verification of tensile stress in the growing polymer. Such results were explained in terms of the changes in the solubilities of the polymerized species when they switch from the oxidized state to the neutral one
Electrochemical Growth of Polyalkylthiophenes. In Situ Characterization of Deposition Processes
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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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Effect of the sample ionic strength on the preconcentration attained in ion exchange voltammetry
No full textAnodic stripping voltammetry in highly-resistive media by electrodes supported on ion-exchange membranes
No full textAn electroanalytical device is described that is suitable for trace metal analyses by anodic stripping voltammetry (ASV) in highly-resistive media in the absence of supporting electrolytes. It consists of a thin mercury film electrodeposited at the glassy carbon-ion-exchange membrane interface obtained by clamping a glassy carbon ring to one surface of a perfluorinated ion-exchange membrane (cationic, Nafion 117, or anionic, Tosflex IE SA48). The inner surface of the membrane is in contact with an electrolyte solution (0.01 M HClO4), containing the counter and reference electrodes. The ion-exchange membrane replaces a conventional supporting electrolyte dissolved in the analyte sample and can be regarded as a solid polymer electrolyte (SPE) confined to the near neighborhood of the working electrode.
This device has been used to perform differential pulse anodic stripping voltammetric (DPASV) analyses of electrolyte-free aqueous synthetic samples containing copper and lead ions. Better results are found at glassy carbon-supported mercury electrodes facing anionic Tosflex membranes, since similar devices assembled with cationic Nafion membranes experience a memory effect associated with blockage of metal ions, due to cation-exchange processes that occur during the stripping redissolution step, even though these processes are able, at the same time, to lead to an increase of DPASV peaks due to metal ion accumulation near the electrode surface. Approximate detection limits of 3.5 x 10(-10) M (0.02 ppb) for Cu2+ and 3 x 10(-10) M (0.05 ppb) for Pb2+ are estimated at Tosflex-equipped devices for a signal-to-noise ratio of 3. Possible modifications aimed at improving the performance of such a device are discussed
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