1,720,971 research outputs found
Thermally stable, solvent resistant and flexible graphene oxide paper
No full textThe ability of graphene oxide (GO) aqueous suspensions to form robust GO paper is largely improved by basification of the suspension before processing. In particular, casting procedures, which are generally unsuitable for production of robust GO paper, become suitable for basified GO (b-GO) suspensions, leading to dense and free-standing papers, which are also highly flexible. Thermal or microwave treatments of paper from b-GO suspensions (b-GO paper) easily produce loss in stacking order of graphene oxide layers, with maintenance of a high degree of parallelism (0.6 < f ≡ orientation function < 0.7) with respect to the paper surface. Differently from usual GO papers, b-GO papers maintain their dimensional integrity when thermally treated or when dispersed in organic solvents or in aqueous solutions. Many relevant b-GO features (improved film ability by casting, maintenance of film integrity and reduced deoxygenation by heating and improved solvent resistance) can be rationalized by formation of covalent bridges between GO layers. Infrared spectra and simple chemical arguments suggest that these covalent bridges between GO layers could be mainly constituted by ether bonds
Graphite oxide as catalyst for diastereoselective Mukaiyama aldol reaction of 2-(trimethylsilyloxy)furan in solvent free conditions
No full textAbstract Graphite oxide efficiently promotes the stereoselective Mukaiyama aldol reaction of 2-(trimethylsilyloxy) furan in solvent free conditions assuring a good level of diastereoselectivity. The catalyst can be easily recovered and reused making the procedure cheap and sustainable. The GO ability to control the stereochemical pathway opens new scenes for the possible application in other synthetic transformations
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
Efficient Modulation of Polyethylene Microstructure by Proper Activation of (α-Diimine)Ni(II) Catalysts: Synthesis of Well-Performing Polyethylene Elastomers
Full text linkThe activation of a prototypical nickel(II) Brookhart catalyst by either methylalumoxane (MAO) or diethylaluminum chloride (AlEt2Cl) under a variety of conditions showed that a proper choice of the mode of activation is a powerful tool to modulate the polymer microstructure. In particular, use of AlEt2Cl instead of MAO resulted in the production of more branched polyethylenes with a higher content of long chain branches and even some "branches on branches". Characterization of these materials by NMR, thermal, X-ray diffraction, and mechanical analyses provided insight into the relationships between the microstructure and the crystallization behavior and the elasticity of the polymers. For these branched polyethylenes, a transition from plastomeric toward elastomeric behavior occurs for branch concentrations much lower than for ethylene-propylene copolymers and like those observed for ethylene copolymers with bulkier comonomers. For elastomeric materials, reduction of branch concentration implies two relevant advantages: (i) reduction of glass transition temperature becoming closer to that of polyethylene; (ii) more efficient radical cross-linking with reduction of degradation reactions. An additional advantage is, of course, a polymer production process involving only ethylene
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
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