1,720,965 research outputs found
Functionalized poly(organophosphazenes)
No full textIn this paper we highlight the general strategies established over the time for the functionalization of poly(organophosphazenes) in order to modify both the chemical structures and the chemicophysical properties of these substances. These modifications have been obtained by reacting poly(dichlorophosphazene) with difunctional nucleophiles thus introducing selected chemical functions into the polyphosphazene substrates or by carrying out suitable functionalization processes on pre-synthesized phosphazene macromolecules. Particular attention has been paid to the chemical modification of polyphosphazenes containing 2,2,2-trifluoroethoxy, phenoxy, 4-ethylphenoxy, 4-sec-butylphonoxy and 4-methoxyphenoxy substituents as these groups were attached to phosphazene homopolymers and copolymers that have been considered in the past for industrial development
cyclic phosphazene derivatives containing benzene groups on the substituents at the phosphorus
No full textCyclic aryloxy- or arylamino-substituted phosphazine derivatives containing photoinitiator groups substituted at the phosphorus formed from benzene derivatives of different types so as to give rise to radical polymerisation reactions for vinyl monomers under light or induce photo-crosslinking phenomena in both preformed polymers which include particularly reactive centres and unsaturated acrylic resins of various kinds
Cyclic and polymeric phosphazenes containing Bengal Red or other colouring agents suitable for use as sensitizers for photooxidation
No full textCyclic and polymeric phosphazenes suitable for the photosensitized production of singlet oxygen having the general formula: in which X, X', (w + y + z) have the meanings defined in the text, containing Bengal Red or other colouring agents of the 9-phenyl-xanthene series which are bound to the cyclic or polyphosphazene matrix by reaction between the carboxylate group present in the dye and an [alpha]- bromomethylene group introduced into the phosphazene substrate
Phosphazene-bound Rose Bengal: A novel photosensitizer for singlet oxygen generation
No full textIn this paper we report the synthesis and the characterization of cyclo- and polyphosphazenes supporting Rose Bengal. These substrates are suitable for the photosensitized generation of singlet oxygen, both in homogeneous and in heterogeneous phase. The efficiency of1O2 production has been measured in homogeneous solution using, as photosensitizer, the cyclophosphazene-bound Rose Bengal and considering, as testing reaction, the oxidation of 1,3-diphenylisobenzofuran; it was found comparable to that of free Rose Bengal in the same experimental conditions
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
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