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Gold catalysts for the direct oxidation of aminoalcohols to aminoacids
No full textGold catalysts on different supports, prepared by sol immobilization and deposition-precipitation, were tested in aminoalcohol oxidation for the direct preparation of aminoacids. Nitrogen substitution appeared to be crucial for avoiding parallel reaction pathway, but also the reaction conditions play an important role. Basic conditions and moderate temperature (40 °C) represent a good compromise for enhancing selectivity to aminoacids. TiO 2 represents the most versatile support
Gold-catalyzed liquid phase oxidations for the organic synthesis
No full textGold catalysts prepared by sol immobilisation and deposition-precipitation were tested in aminoalcohol oxidation for direct preparation of aminoacids. Nitrogen substitution appeared to be crucial for avoiding parallel reaction pathway, but also the reaction conditions play an important role. Basic conditions and moderate temperature (40°C) represent a good compromise for enhancing selectivity to aminoacids. Generally sol-prepared catalysts resulted more resistant to deactivation than DP-prepared catalysts, even not always the most active
From renewable to fine chemicals through selective oxidation: The case of glycerol
No full textCatalytic selective oxidation of glycerol is presented in terms of catalytic systems and experimental conditions. Unsupported gold nanoparticles (AuNPs), AuNPs on carbon and on TiO2 were employed and compared in terms of reaction selectivity and activity. The role of the base and the formed hydrogen peroxide has been considered. Gold based catalysts showed selectivity that is strongly dependent of the reaction conditions. In particular C-C scission products increases by increasing the reaction temperature but correlated only partially with the rate of degradation of the H 2O2 formed under the operative conditions. Moreover, under neutral/acidic conditions glycerol can be oxidised also by increasing the temperature slightly, but it leads to a detrimental effect on selectivity and catalyst life
Gold-Ligand Interaction Studies of Water-Soluble Aminoalcohol Capped Gold Nanoparticles by NMR
No full textNovel reproducible preparations of gold nanoparticles capped by aminoalcohols have been set up by reduction of
HAuCl4 with NaBH4 in aqueous solution. The characterization of Au@aminoalcohol nanoparticles performed by 1H
NMR, ATR-FTIR, UV-vis spectroscopies, and TEM microscopy highlighted the binding site and the nature of the
Au-NH bond
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
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