1,721,044 research outputs found
The Reaction of Various Reductants with Oxide Films on Pt Electrodes as Studied by the Surface Interrogation Mode of Scanning Electrochemical Microscopy : Possible Validity of a Marcus Relationship
No full textThe surface interrogation mode of scanning electrochemical microscopy (SI-SECM), an in situ method for the quantification of adsorbed intermediates at electrodes at open circuit, was used to evaluate the rate of reaction of four redox mediators of different reducing power (methyl viologen(+) > Ru(NH3)(6)(2+) > Fe(II)[EDTA](2-) > Fe(CN)(6)(4-)) with electrogenerated platinum oxides (PtOx) at different pHs. The rate constant determined by SI-SECM was sensitive to the nature of the Pt oxide formed at different potentials. A simplified model with finite element method simulation was used to fit the SI-SECM experimental response. The extraction of kinetic constants and their comparison to the potential (reducing power) of the mediator yielded a Marcus-theory type relationship. Although these are clearly not outer sphere reactions, if subjected to the Marcus theory treatment, one can extract an estimated value of lambda = 1.3 +/- 0.3 eV for the reduction of "place exchanged" oxide, which forms with oxide coverage values larger than 0.5 (as PtO). Steady state feedback experiments were also conducted in which the reduced form of the mediators was oxidized at Pt with different oxide coverage, i.e., over a wide range of potentials. A comparison of SI-SECM kinetic analysis with the Pt substrate at open circuit to the case where an electrode bias is applied indicates that for Fe(II)[EDTA](2-), the feedback current follows the oxide coverage at the Pt substrate. We suggest that thin layers of oxide provide a chemical route in which the oxide mediates oxidation of the reduced electrogenerated species; this route is governed by the reactivity of the different species of oxide formed at the electrode and not necessarily by other effects, such as direct electron tunneling through the oxide layer
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Oxidation of Redox Mediators over Oxidized Platinum: Decoupling Heterogeneous Chemical and Electrochemical Kinetics by means of Scanning Electrochemical Microscopy
No full textOxygen Evolution Electrocatalysts Characterization by Scanning Electrochemical Microscopy
No full textScreening of Oxygen Evolution Electrocatalysts by Scanning Electrochemical Microscopy Using a Shielded Tip Approach
No full textOxygen evolution electrocatalysts in acidic media were studied by scanning electrochemical microscopy (SECM) in the substrate generation – tip collection (SG-TC) imaging mode with a 100 m diam tip. Pure IrO2 and Sn1-xIrxO2 combinatorial mixtures were prepared by a sol-gel route to form arrays of electrocatalyst spots. The experimental setup has been developed to optimize screening of electrocatalysts libraries under conditions where the entire array is capable of the oxygen evolution reaction (OER). The activity of individual spots was determined by reducing the interference from the reaction products of neighboring spots diffusing to the tip over the spot of interest. A gold layer deposited on the external wall of the SECM tip was used as a tip shield. In this study the shield was kept at a constant potential to reduce oxygen under mass transfer controlled conditions. The tip shield consumes oxygen coming from the neighbor spots in the array and enables the tip to correctly detect the activity of the spot below the tip. Simulations and experimental results are showed, demonstrating the effectiveness of the tip shield with the SG-TC setup in determining the properties of the composite materials and imaging arrays
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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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