1,720,981 research outputs found
Transport of large molecules in hyaluronic acid-based membranes and solution
No full textThe aim of this work was to analyse the hindrance effect of the naturally derived bioactive polymer hyaluronic acid (HA) considered responsible for the interstitium transport regulation. The diffusion coefficient measurements of several macromolecular probes, different for nature and dimension have been performed within HA water solution and HA collagenous gels in order to study the role of HA on the control of macromolecular transport. HA matrices showed less diffusional hindrance then HA water solutions. Moreover, the HA, interpenetrating with the collagen fibres, selectively affected the transport, depending on the HA concentration. These preliminary studies indicate that the biopolymer HA can be employed to design novel biopolymer interpenetrating gels suitable as molecular sieves for membrane permeation and controlled drug delivery
Time and space evolution of transport properties in agarose-chondrocyte constructs
No full textDuring the development of de novo synthesized cartilage tissue engineered constructs, transport and biophysical properties are expected to change in time and space. Monitoring and control of the evolution of these parameters are of crucial importance to process biohybrid constructs in vitro. The aim of this work was to measure fluid and macromolecular transport and evolution of mechanical properties of tissue-engineered cartilage constructs as a function of culture time and extracellular matrix (ECM) production. It was found, in agreement with other literature reports, that mechanical and fluid transport properties of the constructs correlated well with time of culture and glycosaminoglycan (GAG) content. Further, diffusion coefficients of 2 probes, dextran (500 kDa) and bovine serum albumin (BSA), correlated well with GAG production. Diffusion coefficients (D) were measured with high spatial and temporal resolution by fluorescent recovery after photobleaching (FRAP). Diffusivity steadily decreases with time while it does not vary through the thickness of the specimen. On the basis of these results, an empirical relationship between diffusion coefficient and GAG content was proposed for the 2 probes analyzed. The results of this study provide useful information to optimize and control the tissue culture process in vitro
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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