1,721,005 research outputs found
Unexpected chromogenic properties of the 1,3,3-trimethylspiro[indoline-2,3’-[3H]naphtho [2,1-b][1,4]oxazine] in solid phase: photochromism, piezochromism and acidichromism
No full textNew chromogenic properties of a spirooxazine {1,3,3- trimethylspiro(indoline-2,3′-[3H]naphtho[2,1-b][1,4]-oxazine), SO} are presented in this work. This molecule was found to be photochromic and piezochromic in the pure microcrystalline solid phase and also exhibited acidichromism when kept in contact with a hydrogen-donating solid phase. Photochromism was observed under continuous UV irradiation. Biexponential thermal bleaching followed the interruption of irradiation. Piezochromism was detected by applying a mechanical force to the solid powder, using either a hydraulic press or manual crushing. After discontinuing pressure, biexponential bleaching kinetics were observed. The biexponential nature of the fading processes is interpreted in terms of merocyanine (M) micro-spot formation inside the crystalline phase. The third chromogenic property of the solid spirooxazine, acidichromism, is due to the extraction of protons from an acidic solid matrix, alpha zirconium phosphate [α-Zr(HPO4) 2·H2O]. Proton transfer to SO in the solid phase causes the appearance of a purple colour. The spectral evolution is qualitatively similar to that observed in CH3CN solution when HClO4 is added at room temperature and in the dark. Temporal evolution of the colour bands, in both solid and liquid phases, is interpreted in terms of an initial protonation, inducing ring-opening, and a second protonation, leading to a colourless produc
Modern Painted Palimpsests. Deciphering the Artworks of Osvaldo Licini
No full textUna campagna di indagini non invasive sui dipinti di Osvaldo Licini, basata sulla integrazione dei risultati ottenuti con tecniche di imaging e con tecniche spettroscopiche puntuali, ha permesso di precisare la tavolozza dell'artista, le modalità operative e l'abitudine di reimpiegare supporti già dipinti
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
Monitoraggio ambientale del microclima, degli inquinanti gassosi e della contaminazione microbica nella Galleria Nazionale dell'Umbria. Ecosistemi urbani.
No full textDispelling 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
New insights into the fading mechanism of Geranium lake in painting matrix”
No full textGeranium lake is an eosin-derived organic pigment highly employed by Van Gogh and his contemporaries. Its elusive behavior, observed in a large number of post-impressionism masterpieces, is of current concern for both conservators and heritage scientists. Herein, the lightfastness of Geranium lake within oil matrix has been investigated by means UV–Vis spectroscopic techniques and HPLC-DAD-HRMS with the final aim of understanding the degradation mechanism behind its marked bleaching. Accelerated photo-aging experiments irradiating with mono/polychromatic light have been carried out on oil paint models prepared with lead eosin-based lakes, in-house synthesized for this purpose according to available historical recipes, alone and in admixture with different white pigments namely, zinc oxide and basic lead carbonate. The aging experiment not only reproduced the fugitive nature of Geranium lake but also evidenced a reversible behavior during the preliminary stages of the light exposure. Succeeding targeted experiments employing monochromatic light as well as a simplified eosin-oil system in solution, corroborated by the wide literature regarding the photophysics of xanthene dyes, allowed us to propose a reasonable fading mechanism of eosin-based lakes, based on the key role played by linseed oil and environmental oxygen
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