1,720,988 research outputs found
Distinct Physicochemical Properties of the First Ceria Monolayer on Cu(111)
No full textDiscontinuous ceria layers on Cu(111) represent heterogeneous catalysts with notable activities in water-gas shift and CO oxidation reactions. Ultrathin ceria islands in these catalysts are composed of monolayers of ceria exhibiting CeO2(111) surface ordering and bulklike vertical stacking (O-Ce-O) down to a single ceria monolayer representing the oxide-metal interface. Scanning tunneling microscopy (STM) reveals marked differences in strain buildup and the structure of oxygen vacancies in this first ceria monolayer compared to thicker ceria layers on Cu(111). Ab-initio calculations allow us to trace back the distinct properties of the first ceria monolayer to pronounced finite size effects when the limiting thickness of the oxide monolayer and the proximity of metal substrate cause significant rearrangement of charges and oxygen vacancies compared to thicker and/or bulk ceria
Characterization of innovative Pt-ceria catalysts for PEMFC by means of ex-situ and operando X-Ray Absorption Spectroscopy
Full text linkAs the demand for energy is rising, the role of batteries and fuel cells in everyday life is undeniable, but fuel cell systems are still currently not employed worldwide mainly because of their cost, which is due to the large amount of Pt used in catalyst layers. Recently, it was demonstrated that catalysts composed by low Pt loading (around 10 ?g/cm2) onto ceria (CeOx) matrix are a promising alternative, showing comparable performances with respect to catalysts made by Pt only. Indeed, a strong metal to support interaction between Pt and ceria has been already observed and exploited for application in direct methanol fuel cells. In this context, the aim of the present study is to investigate the stability of innovative Pt-CeOx anode catalyst deposited on two different supports and characterized by means of X-ray Absorption Spectroscopy (XAS). The XANES ex-situ data collected at the Ce L3-edge highlighted the stability of ceria when directly deposited onto the nano-Gas Diffusion Layer (nGDL) whereas it is particularly unstable when deposited onto the so-called Carbon Ionomer Layer (CIL), where Ce was found irreversibly reduced to Ce3+ upon contact with the air. These behaviors are confirmed also by preliminary test experiments conducted in operando conditions, using a modified fuel cell designed on purpose. In addition, EXAFS data collected ex-situ at the Pt L3-edge evidenced an increase in the fraction of Pt2+ as the overall amount of Pt (or the Pt/Ce ratio) is decreasing, in agreement with existing literature. Our results provide an extended picture about characterization of Pt-CeOx catalyst, focusing on the effects of the hosting support, in order to improve the fabrication of more stable Membrane Electrode Assemblies (MEAs) with low Pt contents to be employed with PEMFCs
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
- …
