1,720,983 research outputs found
Sol-Gel Processing for new silica based materials functionalized with chlorogenic acid
No full textThe aim of the present study was to synthetize new phenol-based materials through the sol gel approach. 5-O-ceaffeoyl quinie acid, a natural antioxidant better known as chlorogenic acid (CGA), was incorporated within silica matrix obtaining orange colored hybrid materials, characterized by Fourier Transform InfraRed (FTIR) and Ultra Violet-Visible (UV-Vis) spectroscopic techniques. In vitro soaking tests in simulated body fluid (SI3F) was performed to evaluate the new materials' bioactivity and the formation of a hydroxyapatite layer was observed on the hybrid surface by SEM/EDX analysis. Moreover, CGA-based materials were biocompatible to murine and mammalian cells as assessed by tetrazolium dye (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)-based microtitration assay (MIT assay) and exerted antioxidant capability by scavenging DPPH and ARTS(+) radicals
A multi-technique approach to characterize bioactive silicate composites
No full textIn the present work the ternary SiO2·CaO·P2O5composite, which differ in the Ca/P molar ratio, were synthesized by means of a sol-gel route. In order to investigate the influence of the relative amount of each phase the thermal properties of the synthesized gel-glass materials were studied as a function of the Ca/P molar ratio using thermogravimetric and differential thermal analysis (TG/DTA). After dehydration (in a single step), described from a kinetic point of view as a simple water evaporation without rupture of chemical bonds, all gels undergo a complex multi-step decomposition with endo and exothermic effects, followed by crystallization of calcium silicate phases at about 950°C. Furthermore, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning Electron Microscopy, coupled with energy dispersive spectroscopy (SEM/EDS), allowed us to detect the chemical modifications induced by modifying the Ca/P molar ratio and the sintering. This process is obtained by thermal treatment of the materials after analyzing their thermal behavior in the temperature range 600-1000°C, with the aim of making them suitable for their applications. The results revealed that when temperature is up to 900°C, crystallization occurs and pseudowollastonite and wollastonite were formed. Finally, the amount of pseudowollastonite decreased with increasing the sintering temperature, while that of wollastonite increased
Thermal and biological properties of several composite materials prepared by sol-gel method.
Full text linkGoing 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
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