1,721,001 research outputs found
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
Curcumin‐functionalized gelatin films: Antioxidant materials with modulated physico‐chemical properties
Full text linkIn this paper we used curcumin as a functionalizing agent of gelatin films with the aim to get antioxidant materials with modulated physico‐chemical properties. To this aim, we prepared gelatin films at different contents of curcumin up to about 1.2 wt%. The as‐prepared films, as well as glutaraldehyde crosslinked films, were submitted to several tests: swelling, water solubility, differential scanning calorimetry, X‐ray diffraction, mechanical tests and curcumin release. The radical scavenging activity of the as‐prepared films is similar to that of free curcumin, indicating remarkable antioxidant properties. All the other tested properties vary as a function of curcumin content and/or the presence of the crosslinking agent. In particular, the films exhibit sustained curcumin release in different solvents. Thanks to its biocompatibility, biodegradability and lack of antigenicity, gelatin uses span from food processing to packaging and biomaterials. It follows that the modulated properties exhibited by the functionalized materials developed in this work can be usefully employed in different application fields
α-tricalcium phosphate hydrolysis to octacalcium phosphate: Effect of sodium polyacrylate
No full textα-Tricalcium phosphate (α-TCP) hydrolysis into octacalcium phosphate (OCP) has been investigated in phosphoric acid solution at different concentrations of sodium polyacrylate (NaPA). The hydrolysis process has been followed by powder X-ray diffraction, infrared absorption and scanning electron microscopy analyses. In the absence of the polyelectrolyte, α-TCP undergoes a complete transformation into OCP in 24 h. The presence of polyacrylate in solution inhibits the hydrolysis so that a NaPA concentration of 0.5μM is sufficient to lengthen the time required to complete the hydrolysis to 4 days. The variation of Ca2+ concentration in the soaking solution suggests that the transformation occurs through α-TCP dissolution followed by OCP precipitation. The delayed OCP nucleation and growth in the presence of polyacrylate implies a preferential adsorption of the polyelectrolyte on the growing OCP crystals, which induces an anisotropic reduction of the coherence lengths of the perfect crystalline domains. © 2002 Elsevier Science Ltd. All rights reserved
Strontium-Substituted α-TCP: Structure, Stability, and Reactivity in Solution
Full text link& alpha;-Tricalcium phosphate (& alpha;-TCP) is widelyused as acomponent of bone cements, and many efforts have been made to dopeit with strontium ion (Sr), which is known for its beneficial rolein bone tissue. However, the range of possible substitution of strontiumfor calcium (Ca) into & alpha;-TCP, as well as its effect on the & alpha;-TCPstructure, has not been clarified yet. Herein, we investigate thissubstitution through the examination of & alpha;-TCP synthesized athigh temperatures in the presence of increasing amounts of strontiumaccording to two different routes: 1-step and 2-steps. The results show that Sr can enter into an & alpha;-TCPstructure up to about 10 atom % and substitutes for calcium mostlyat specific cation sites, namely, M(5), M(11), and M(17), characterizedby relatively low bond valence sums and long mean Ca-O distance.Strontium presence stabilizes & alpha;-TCP delaying its transformationinto octacalcium phosphate and hydroxyapatite in H3PO4, as well as in physiological solution. Although the two methodsof synthesis provide similar structural results, the products of 1-step synthesis display a slightly smaller crystallitesize and greater solubility and, as a consequence, a faster hydrolysisreaction.& alpha;-Tricalcium phosphatepreparation through the solid-statereaction is described following two different procedures. The investigationof the range of possible substitution of strontium for calcium into & alpha;-TCP as well as its effect on the & alpha;-TCP structure ispresented. Furthermore, it is shown that strontium presence stabilizes & alpha;-TCP and delays its hydrolysis reaction into octacalcium phosphateand hydroxyapatite
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
alfa-Tricalcium phosphate hydrolysis to octacalcium phosphate: effect of sodium polyacrylate.
No full textAppropriate 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
Role of Aspartic and Polyaspartic Acid on the Synthesis and Hydrolysis of Brushite
No full textDicalcium phosphate dihydrate (DCPD) is one of the mineral phases indicated as possible precursors of biological apatites and it is widely employed in the preparation of calcium phosphate bone cements. Herein, we investigated the possibility to functionalize DCPD with aspartic acid (ASP) and poly-aspartic acid (PASP), as models of the acidic macromolecules of biomineralized tissues, and studied their influence on DCPD hydrolysis. To this aim, the synthesis of DCPD was performed in aqueous solution in the presence of increasing concentrations of PASP and ASP, whereas the hydrolysis reaction was carried out in physiological solution up to three days. The results indicate that it is possible to prepare DCPD functionalized with PASP up to a polyelectrolyte content of about 2.3 wt%. The increase of PASP content induces crystal aggregation, reduction of the yield of the reaction and of the thermal stability of the synthesized DCPD. Moreover, DCPD samples functionalized with PASP display a slower hydrolysis than pure DCPD. On the other hand, in the explored range of concentrations (up to 10 mM) ASP is not incorporated into DCPD and does not influence its crystallization nor its hydrolysis. At variance, when present in the hydrolysis solution, ASP, and even more PASP, delays the conversion into the more stable phases, octacalcium phosphate and/or hydroxyapatite. The greater influence of PASP on the synthesis and hydrolysis of DCPD can be ascribed to the cooperative action of the carboxylate groups and to its good fit with DCPD structure
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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