1,720,967 research outputs found
BIOMACROMOLECULES IN RADICAL PROCESSES: INNOVATIVE STRATEGIES FOR THE SYNTHESIS OF BIOMATERIALS
No full textNatural polymers, such as polysaccharides and proteins, are materials extensively investigated due to their biocompatibility, biodegradability and non-toxic and non-immunogenic characteristics. Enclosing the biomacromolecules, in a complex structure, these features can be transferred to a biomaterial in order to extend the performance of the device. Basically, the synthesis of bioconjugates, by insertion of natural polymers in a macromolecular network by radical polymerization processes, can be achieved employing two different synthetic approaches. The first method involves the chemical modification of the biomacromolecules to introduce functionality able to undergo radical polymerization reactions. In addition, polysaccharides and proteins, without any functional changes, can take part in graft radical polymerization reactions that involve the heteroatoms of the substrates. Both synthetic approaches allows to prepare biocompatible bioconjugates showing improved physico-chemical and mechanical properties respect to the starting natural species. Furthermore, radical polymerization of biomacromolecules with monomeric species bearing specific functionality, carry out to the synthesis of polymeric network that undergo a phase transition process in response to external stimuli changes (temperature, pH, magnetic and electric field). These findings showed that the radical polymerization techniques, improving the performance of natural polymer, represent an innovative tools for the preparation of macromolecular devices potentially useful in pharmaceutical and biomedical field
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
Innovative antioxidant thermo-responsive hydrogels by radical graftingof cathechin on inulin chain
No full textThe synthesis of thermo-sensitive antioxidant hydrogels by grafting of an antioxidant molecule and athermo-responsive monomer into inulin, in the presence of a crosslinker. In particular, catechin andNIPAAm, as antioxidant and thermo-responsive species, respectively, were inserted in a polymeric networkemploying a redox pair as an eco-friendly radical initiator system. Calorimetric, FT-IR, UV–Vis andfluorescence analyses were performed to verify both the formation of the inulin–antioxidant covalentbond and the insertion of bioactive molecules and monomers in the network. The hydrogels showed transitiontemperatures in the range 31.3–33.1 ◦C and a water affinity depending on the temperature of thesurrounding medium. The antioxidant activity of the conjugates was evaluated measuring the scavengerproperties of the hydrogels against the 2,2-diphenyl-1-picrylhydrazyl radical and the total flavonoid contentat different temperatures. The thermo-responsive antioxidant properties of the hydrogels confirmedthe efficiency of the proposed synthetic strategy and demonstrated as the antioxidant–carbohydratethermo-responsive conjugates possess peculiar features for specific applications in the food industry
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
Antioxidant Polymers by Free Radical Grafting on Natural Polymers
No full textThis chapter presents an overview of the different antioxidant polymeric materials, based on natural macromolecules, which can be obtained by employing the free radical grafting procedure. Free radical grafting is a straightforward method which allows the covalent insertion of the antioxidant molecules onto the polymer backbone without the use of organic solvents or toxic radical initiators. Chitosan, starch, inulin and alginate are examples of polysaccharides widely used to obtain these kind of systems, while some gelatin-antioxidant materials will also be presented as representative examples of protein-based conjugates. The advantages to having these systems consist of their high stability, biocompatibility and good biological properties. All these characteristics make them suitable systems for several pharmaceutical and food applications, such as delivery devices of drugs, as preservatives and for food packaging
Grafted gelatin microspheres as potential pH-responsive devices
No full textThis study describes the synthesis of polymericmicrospheres by reversed-phase graft polymerization ofnative gelatin (GL) and sodium methacrylate, which areuseful as stimuli-responsive drug delivery devices. Bymeans of varying the GL/functional monomer ratios(2.0–0.5 w/w), formulations with different crosslinkingdegrees, dimensional distributions, and water affinities were synthesized. The hydrogels showed spherical shape,porous surface, and high water affinity at neutral pH value with respect to the acidic conditions, with the ratio between the swellings, at pH 7.0 and 1.0, being in the range 3.7–5.1. In vitro release studies, using iclofenac sodium salt, in neutral and acidic media, simulating biological fluids, were performed. For all formulations, low amounts of drug (Mt/M0 percent \20.0%) are released in acidic medium.When the pH is 7.0, the swelling of the network increases, and the drug molecules diffuse through the polymeric structure. By means of semi-empirical equations, the release mechanism was studied, and the diffusional contribute was evaluated
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