1,721,056 research outputs found
Thermal decomposition of tert-butyl o-(phenoxy)- and o-(anilino)phenyliminoxyperacetates
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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
Supported gold nanoparticles catalysts for alkynes hydroamination.
No full textOur research group has previously reported the preparation of gold nanoparticles (AuNPs) supported on different functionalized silica supports. We started using commercial polyethyleneimine-functionalized silica bead [1] and we continued preparing silica nanoparticles functionalized with alkynyl carbamate moieties. [2]
Recently, we have focused on the straightforward synthesis of AuNPs anchored on commercial, micrometric oxide supports (i.e. SiO2, Al2O3, TiO2) previously modified with the di-functional organosilane [3-(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) by a grafting procedure. After being thoroughly characterized by several complementary techniques (XPS, TEM, SSNMR, AAS etc.), the catalytic activity of these systems (Au/OS@Yne) has been evaluated in the oxidation of alcohols both in batch and continuous-flow systems. [3]
Furthermore, we have extended the same synthetic procedure to the preparation of a novel and magnetically recoverable catalyst, consisting of AuNPs supported on functionalized nano-magnetite (Au/Fe3O4@Yne).
We now present the latest results obtained in the study of the catalytic application of Au/SiO2@Yne and Au/Fe3O4@Yne in the alkynes hydroamination reaction, which is considered the most atom efficient process for the formation of a series of nitrogen-containing compounds.
Indeed, this transformation takes place without the formation of any side product and leads to the production of enamine, imine or substituted amines, which have a significant importance as bulk and fine chemicals or building blocks in organic synthesis.
[1] S. Fazzini , D. Nanni , B. Ballarin , M. C. Cassani , M. Giorgetti , C. Maccato, A. Trapananti, G. Aquilanti and S. I. Ahmed, J. Phys. Chem. C. 2012, 116, 25434−25443; M. Giorgetti, G. Aquilanti, B. Ballarin, M. Berrettoni, M. C. Cassani, S. Fazzini, D. Nanni and D. Tonelli, Anal. Chem. 2016, 88, 6873-6880;
[2] S. Fazzini, M. C. Cassani, B. Ballarin, E. Boanini, J. S. Girardon, A.S. Mamede, A. Mignani and D. Nanni, J. Phys. Chem. C. 2014, 118, 24538-24547; M. C. Cassani, B. Ballarin, D. Barreca, E. Boanini, E. Bonansegna, G. Carraro, S. Fazzini, A. Mignani, D. Nanni, D. Pinelli, RSC Adv. 2016, 6, 25780-25788.
[3] B. Ballarin, D. Barreca, E. Boanini, M. C. Cassani, P. Dambruoso, A. Massi, A. Mignani, D. Nanni, C. Parise, A. Zaghi, ACS Sus. Chem. Eng. 2017, 5, 4746-4756
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
Poly-Siloxane Impregnation and Pyrolysis of Basalt Fibers for the Cost-Effective Production of CFCCs
No full textIn this work, the optimisation of basalt fiber CFCCs (Continuous Fiber Ceramic
Composites) production is presented, focusing on the development of a silicon-oxycarbide matrix
by PIP (Polymer Impregnation Pyrolysis). The use of low cost poly-siloxanes and basalt fibers is
particularly promising for transports and constructions, where thermostructural CFCCs would be
interesting for vehicle weight reduction and fire-resistant panels, but only on the condition that
production costs are kept really low. The basalt/SiCO composites are suitable for mechanical
applications up to 600°C and stand up temperatures up to 1200°C, also in oxidative environments.
The key parameters to keep the production costs low are the furnace and moulds type, being steel
probably the best material for both, since it withstands the pyrolysis temperature and can be easily
cleaned, by oxidation, from any residue. Regarding the pyrolysis environment, two conditions were
compared, nitrogen flow and vacuum, being perhaps the vacuum procedure less expensive and so
potentially more appealing for a large scale production. The microstructure and the
thermomechanical characteristics of the obtained composites were compared. Another key
parameter in determining the production costs is the number of PIP steps, which has to be
minimised. The present results support the conclusion that one PIP step in nitrogen or two PIP steps
in vacuum can provide CFCC with satisfactory mechanical characteristics for thermomechanical
applications in oxidative environments
Supported gold nanoparticles catalysts for organic transformations
No full textOur research group has recently developed a convenient method for the anchoring of gold nanoparticles (AuNPs) on different oxide supports (SiO2, Al2O3, TiO2, Fe3O4) previously modified with a propynyl-carbamate organic functionality. The alkynyl-carbamate moieties anchored on the surface of the support are capable of straightforwardly reducing the gold precursor chloroauric acid (HAuCl4) to afford Au/OS@Yne (OS = Oxide Support, Yne = organic functionalization), without the need of additional reducing or stabilising agents.[1,2]
After being thoroughly characterized by several complementary techniques (XPS, TEM, SSNMR, AAS etc.), the catalytic activity of these systems has been evaluated in the oxidation of alcohols and in the hydroamination of alkynes, both in batch and continuous-flow conditions.[1,3
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