1,720,957 research outputs found
Electrodeposition of lead dioxide from methanesulfonate solutions
No full textLead dioxide electrodeposition from methanesulfonic media and physicochemical properties of the resulting oxide were studied in this work to improve anodic process at PbO2/Pb2+ electrode of flow battery. The presence of methanesulfonate ions in the electrodeposition solution causes only a quantitative difference in the PbO2 electrodeposition process without apparently changing the reaction mechanism. In methanesulfonic media PbO2 electrodeposition rate is higher than in nitrate solutions. Current efficiency of PbO2 formation depends on electrode potential (or deposition current density), electrolyte composition (concentration of Pb2+ and methanesulfonate ions), hydrodynamic conditions, pH and temperature of the solution. It is important to note that thick PbO2 coatings (up to 2 mm) with good mechanical properties and adhesion to the substrate can be deposited in a wide range of current density (2-100 mA cm-2). © 2008 Elsevier B.V. All rights reserved
Nitrite oxidation on RuO2 electrodes
No full textAn electrochemical kinetic investigation of nitrite oxidation to nitrate on RuO2 is discussed. The process is studied by cyclic voltammetry, steady-state measurements and potential step measurements. The overall oxidation reaction is a two-electron process where the first step involves a reversible charge transfer: NO 2- ⇔ NO2 + e - The one-electron oxidation of nitrite yields adsorbed NO 2 which is further oxidized to adsorbed (NO2)+ and subsequently desorbed via a chemical reaction. In the general case, fit of experimental data is obtained with adsorption described by a Temkin isotherm unless the electrode is pre-treated at a cathodic potential where the (NO 2)ads is removed. This treatment lowers the degree of coverage by intermediates but not the nature of the slow step. © 2008 MAIK Nauka
Kinetics of lead dioxide electrodeposition from nitrate solutions containing colloidal TiO2
No full textThe influence of particles of colloidal titanium dioxide on lead dioxide electrodeposition from nitrate electrolytes was studied in the work. Addition of the nanostructured T{cyrillic}iO2 particles to the electrolyte increases the rate of lead dioxide formation. This enhancement is ascribed to extra nucleation sites contributed by Ti-O{radical dot} radicals generated at the TiO2 surface by OH{radical dot} species, in turn formed by discharge of water. A four stages kinetics scheme is proposed for description of the process of lead dioxide electrodeposition in presence of oxides of the valve metal in colloidal solutions. It is suggested that the presence of TiO2 nanoparticles influences crystallization, charge transfer and diffusion stages. © 2009 Elsevier B.V. All rights reserved
Nafion effect on the lead dioxide electrodeposition kinetics
No full textElectrodeposition of lead dioxide in the presence of Nafion in solution is described by a four-stage kinetic scheme. The limiting stage at low polarizations is that of the second-electron transfer, and at high polarizations, the stage of delivery of lead compounds to the electrode surface. Nafion adsorption at the oxide profoundly affects the process kinetics. © Nauka/Interperiodica 2007
Composite PbO2-TiO2 materials deposited from colloidal electrolyte: electrosynthesis and physicochemical properties
No full textElectrodeposition of PbO2 from nitrate solutions in the presence of TiO2 nanoparticles leads to composite PbO2-TiO2 films. The content of the dispersed oxide which is finally occluded into the composite PbO2 film depends on electrodeposition conditions such as pH, the value of the electrodeposition constant current or potential, the amount of added TiO2 and on temperature. It also depends strongly on the presence of anionic additives such as sodium dodecyl sulfate (SDS) whose adsorption decreases the positive charge on the surface of the TiO2 particles. The photo-electrocatalytic activity of the prepared materials has been tested in the oxidation of oxalic acid and benzyl alcohol. Electrodes showed a photoresponse to illumination at λ > 320 nm confirming literature reports on synergistic effects of illumination in electro-oxidation processes at PbO2-based anodes. We also established that the life service of these electrodes increases by a factor of about 3 with respect to traditional P..
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
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