1,720,965 research outputs found
Examination of RuO2 single-crystal surfaces: charge storage mechanism in H2SO4 aqueous solution
No full textSystematic voltammetric and impedance studies of RuO2 ‘as-grown’ single crystals were carried out using the (101), (110) and
(002) faces in 0.5 mol dm-3 sulphuric acid solution and applying the hanging electrolyte meniscus technique. The crystal surfaces,
prepared by the vapor transfer technique at high temperature, show well-defined XRD patterns. The dependence of the
voltammetric characteristics on potential scan rate modulations was investigated. The charge storage mechanism was examined in
the following cases for differences: (i) in the anodic surface charge qa* and the atomic distribution of ideal surfaces, (ii) between the total anodic charge qa*tot and the anodic charge associated with the electrochemical process qa** due to the redox couple in the solid state. A systematically higher charge for the (101) face in the same potential range represents a probe for the crystal face specificity of the redox process
The role of surface morphology on the electrocatalytic reduction of organic halides on mono- and polycrystalline silver
No full textThe electrocatalytic reduction of organic halides on silver, assumed to hinge on an attenuated radical intermediate R⋯X⋯Ag, is a reaction of great applicative interest that also provides an example of organic electrocatalytic process particularly convenient for a mechanistic study. The complexity of the problem requires to analyze separately the roles of the many actors involved. The present work focuses on the role of the silver surface morphology, contrasting the reactivity of a series of model halides in systematic CV experiments on (1 1 1), (1 1 0), and (1 0 0) silver monocrystals and on controlled polycrystalline silver surfaces of increasing roughness, in acetonitrile+tetraethylammonium perchlorate medium. The reduction potentials of the alkyl, glycosyl, and benzyl derivatives appear significantly shifted in the positive direction with increasing surface roughness (for polycrystals) or atomic densities and/or surface faceting (for monocrystals) by an extent linked with the molecular structure of the organic halide to be reduced. The addition of strongly specifically adsorbed iodide anions, resulting in surface screening, also results in a leveling effect of the catalytic properties of the different surfaces tested
Surface screening effects by specifically adsorbed halide anions in the electrocatalytic reduction of a model organic halide at mono- and polycrystalline silver in acetonitrile
No full textThe silver surface screening effects by specifically adsorbed halide anions in the electrocatalytic reduction of a model organic bromide (acetobromoglucose) have been studied by cyclic voltammetry on controlled mono- and polycrystalline silver surfaces in acetonitrile+0.1 M tetraethylammonium perchlorate medium as a function of the concentration cX of added TEAX (X = Cl, Br, or I, TEA, tetraethylammonium). The reduction peak potentials, Ep, are regularly shifted in the negative direction with increasing cX, typically tending to an asymptotic value for cX ≈ 0.1 M. Several literature models describing adsorption/desorption equilibria have been applied to justify the above experimental Ep versus c X trends (being logarithmic in the iodide cases) for the three halides and the four silver surfaces tested
Acetonitrile as Adsorbate or Solvent to Probe the Crystal Face Specificity of Metal-Water Interaction at Silver Electrode/Solution Interfaces
No full textThe crystal face specificity of metal–water interaction at Ag electrode/solution interfaces is investigated by using acetonitrile (ACN) as a probe molecule of the water interfacial structure or as a solvent in which water is a solute. Capacitance and voltammetric curves suggest that ACN is weakly adsorbed from aqueous solution on Ag in the order (111) > (100) > (110). Apparent inconsistencies of adsorption parameters are explained by the occurrence of two ACN adsorption modes: (i) directly on the metal surface and (ii) on the water layer adsorbed on the metal surface. Ag surface oxidation in ACN in the presence of variable amounts of water suggests that water has an inhibiting effect on Ag oxidation, the diminution of the water content in ACN leading to free anodic dissolution of the metal surface
A screening of carbon-based electrodes (GC, BDD, F-BDD) as non-catalytic reference materials for investigations in organic electrocatalysis
No full textIn a systematic cyclovoltammetric investigation of electrochemical organic processes, the electrocatalytic effects of the tested electrode materials (i.e., their ability to lower the activation barrier for the process) are conveniently quantified in terms of difference of the peak potential obtained on the catalytic electrode vs. the peak potential obtained on a cathode free of electrocatalytic effects (for the target process). Glassy carbon (GC), which has often been the favorite electrode material for mechanistic investigations of outer-sphere electron transfer processes, is here compared with as prepared, hydrogen-terminated boron-doped diamond (BDD) and fluorinated boron-doped diamond (F-BDD). They are also carbon-based materials but, to a higher degree, terminated with inert groups possibly preventing specific adsorption. Specifically, the comparison is carried out considering the electrocatalytic reduction of model organic halides. While the current densities are comparable, the reduction potentials are regularly shifted in the negative direction, in the sequence GC < BDD < F-BDD, consistently with the decreasing number of O groups and the increasing number of inert H and/or F atoms, the latter species possibly exerting even a repulsing effect towards the reacting halide adsorption
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
- …
