1,720,968 research outputs found
Structural characterization of bimetallic Pd-Cu vapor derived catalysts
Full text linkPd-Cu bimetallic Solvated Metal Atoms (SMA) were synthesized by metal vapor synthesis technique and supported on PVPy resin. Since the catalytic activity, of the Pd-Cu system turned out to be quite high also compared to the corresponding monometallic system, a structural characterization, using electron microscopy techniques and X-ray Absorption Fine Structure spectroscopy, was performed. HRTEM analysis showed the presence of Pd particles distributed in a narrow range with a mean diameter of about 2.5 nm while the XAFS analysis, confirmed the presence of the Pd nanoparticles but revealed also some alloying with Cu atoms
Solvated Metal Atoms in the Preparation of Supported Gold Catalysts
No full textSeveral reviews appeared in the last years to emphasize the unique properties showed by gold metal, when particle size falls in nanometers range. Au nanoparticles (NPs) have found uses in ceramics, medicine, and other areas. Among them the most exciting and growing field of application is undoubtedly catalysis. Historically, gold was regarded to be catalytically inert, since the discoveries made by Haruta and Hutchings. in the late 1980s: surprisingly, they demonstrated simultaneously and independently that supported gold nanoparticles are the best catalyst for low-temperature CO oxidation and ethyne chlorination to vinylchloride. In recent years, it has been shown that gold becomes active for many novel reactions of synthetic interest when stabilized in the form of nanoparticles deposited on several organic and inorganic supports. Supported Au NPs have found numerous applications as unique catalysts in aerobic oxidative processes, reduction of organic compounds, C-C coupling reactions, etc. Moreover, the ability of gold to coordinate with triple bonds has no parallel with other transition metals. Upon coordination and formation of the corresponding adduct, the alkyne becomes activated and more reactive towards nucleophiles such as alcohols, amines and hydrosilanes.
It was clearly evidenced that particle size play a crucial role in determining catalytic activity of supported gold particles in CO oxidation, as well as in others reactions. On the other hands, it has been also demonstrated that the superficial oxidation state of the metal, the nature of the support, the Au-support interface and the particle morphology may strongly affect catalytic performance of AuNPs. All these findings have increased the efforts made by scientist to investigate how the different preparation methods can affects the above mentioned factors.
In this chapter we intend to provide a synapsis of the synthesis of supported gold catalysts by the metal vapor synthesis (MVS) approach. In particular, the contribution includes the work undertaken till date in our and other research groups pointing out the key factors to control the size of Au nanoparticles by this synthetic method
Characterization of a Poly-4-Vinylpyridine-Supported CuPd Bimetallic Catalyst for Sonogashira Coupling Reactions
No full textCuPd bimetallic solvated metal atoms (SMA) synthesized by metal vapor synthesis (MVS) technique and supported on poly-4-vinylpyridine (PVPy) resin, showed significantly higher catalytic activity in Sonogashira-type carbonâcarbon coupling reactions than the corresponding monometallic Cu and Pd systems as well as their physical mixture. The analysis of the bimetallic catalyst combining transmission electron microscopy techniques and X-ray absorption fine structure (XAFS) spectroscopy revealed the presence of small Pd nanoparticles (dm=2.5 nm) while the analysis of the X-ray absorption data, at the Cu K-edge suggests the formation of thin and incomplete Cu oxide layers around the Pd-rich cores
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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