1,720,982 research outputs found
Photoresponsive properties of optically active (meth)acrylic homopolymers with pendant L-lactic acid or L-alanine residues connected to 4-amino-azobenzene
No full textThe photochromic behaviour and photoisomerization kinetics of optically active homopolymers of trans-(S)-4-N-(2-methacryloyloxypropanoyl)aminoazobenzene and trans-(S)-4-N-(2-acryloyloxypropanoyl)aminoazobenzene were studied by u.v. spectroscopy under irradiation at 366 nm. The resulting data are compared with those obtained for the corresponding low molecular weight structural models trans-(S)-4-N-(2-pivaloyloxypropanoyl)aminoazobenzene and trans-(S)-4-N-(2-isobutyroyloxypropanoyl)aminoazobenzene. The photoresponsive behaviour of the above polymeric systems was also investigated by circular dichroism measurements at various extents of photoisomerization. The results are discussed in terms of the structural requirements of the macromolecules
Novel monomers with N-methyl-D-glucamine segments and their application in structured porous materials for arsenic capture
Full text linkThe N-methyl-D-glucamine moieties exhibit high ability and selectivity toward arsenate ions in water by a complexation mechanism that involves their hydroxyl groups. In this work, the syntheses of two monomers containing N-methyl-D-glucamine, namely 4-vinylbenzyl-N-methyl-D-glucamine (VbNMDG), and N-methyl-D-glucamine methacrylamide (MNMDG) were studied. Different synthetic routes were considered in order to obtain liquid monomers able to polymerize and selectively capture arsenic. Furthermore, the incorporation of protective groups like trimethylsilyl moieties in the molecular structure was assessed to prevent transfer reactions during further polymerization. After polymerization, hydroxyl groups were deprotected using hydrofluoric acid. Following this methodology, structured microporous polymeric films based on colloidal crystal templates were prepared. NMR and FTIR techniques were used to follow the reactions and to determine the chemical structure of the obtained products. The morphology of materials was characterized by SEM. The performances of the developed polymeric films to selectively capture arsenic were determined. Films showed an improved and reproducible sensitivity to arsenic detection exhibiting high values of arsenic capturing capability (around 90%)
Influence of hydro-soluble polymeric stabilizers in nano-catalysis: molecular weight effect
No full textMagnetic nanomaterials coated by N-methyl-D-glucamine based polymers for wastewater treatment
No full textOptically active polymers containing side-chain azobenzene moieties. Synthesis and chiroptical properties of copolymers of (-)-menthyl acrylate with trans-4-(phenylazo)-1-naphthyl acrylate and trans-4-(naphthylazo)-1-phenyl acrylate
No full textPhotochromic behavior and photoisomerization kinetics of optically active copolymers of trans-N-(4-azobenzene) maleimide (ABM) with (-)-menthyl vinyl ether (MtVE) and (+)(S) -2-methylbutyl vinyl ether were studied by UV spectroscopy under irradiation at 348 nm. The resulting data have been compared with those of the corresponding copolymers containing also trans-N-( 4-azobenzene) maleamic acid co-units as well as of low molecular weight model compounds. The photoresponsive behavior has been also investigated by circular dichroism measurements at various extents of photoisomerization. The results are discussed in terms of structural requirements of the macromolecules
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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