1,720,962 research outputs found
SILK FIBROIN/POLYURETHANE SCAFFOLDS: IN VITRO INTERACTIONS WITH HUMAN ADULT FIBROBLASTS
No full textStuttgart (Germany
Silk fibroin-polyurethane scaffolds for tissue engineering
No full textSilk ribroin (SF)-based or -coated biomaterials are likely to be endowed with properties fitting tissue engineering applications. In this work we investigated the interactions between SF-coated polyurethane (PU) membranes and foams, and four different strains of normal human adult fibroblasts (HAF). In parallel, the same cell strains were grown on polystyrene plates and uncoated PU scaffolds. With respect to the uncoated homologues, cell adhesion to SF-coated PU membranes was two-fold within 3 h and cell numbers were 2.5-fold higher after 30 days in culture; SF-coated PU foams were found to harbor 1.39-fold more cells after 30 days in vitro (p < 0.01). This enhanced cell growth was coupled with a more intense uptake of glucose and a higher secretion rate of lactate, but with similar consumption of glutamine. In addition, cells on SF-coated membranes exhibited a higher secretion rate of interleukin-6. HAF cultured on all types of substrates were never found to secrete any ELISA-assayable amount of the main pro-inflammatory cytokines IL-1/spl beta/, TNF-/spl alpha/, and TGF-/spl beta/1. The rate of the extracellular assembly of collagen type I fibers, measured by the release of procollagen C-peptide, was found to be somewhat higher on both 2D and 3D SF-coated PU scaffolds. On the whole, these results show that SF-coated PU substrates constitute a novel type of composite biomaterial that promotes cell adhesion and growth, and the performance of specific metabolic tasks of normal HAF without inducing any secretion of some of the most relevant proinflammatory cytokines
Silk Fibroin-Coated Three-Dimensional Polyurethane Scaffolds for Tissue Engineering: Interactions with Normal Human Fibroblasts
No full textSilk fibroin (SF)-based or -coated biomaterials hold structural and surface properties that render them suitable for biomedical applications. In this work, we investigated the behavior of four strains of normal human adult fibroblasts (HAFs) seeded onto polyurethane foam, uncoated (PUF) or SF coated (PUF/SF). HAF adhesion within 3 h to PUF/SF was 2-fold that of adhesion to PUF. After 30 days of incubation in vitro, 37% more HAFs had grown on PUF/SF than on PUF. Taking 105 cells as a basis for comparisons, HAFs on PUF/SF exhibited initially higher glucose consumption rates, but persistently lower glutamine uptake rates than on PUF, whereas the rates of lactate and interleukin 6 release and of extracellular assembly of type I collagen fibers were alike on either substrate. Moreover,
HAFs on both PUF/SF and PUF never secreted any ELISA-assayable amounts of interleukin 1, tumor necrosis factor , and transforming growth factor 1. Hence, PUF/SF scaffolds embody a novel class of biomaterials favoring the adhesion, proliferation, and performance of specific metabolic tasks by HAFs without eliciting any concurrent secretion of the chief proinflammatory cytokines
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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