1,720,958 research outputs found
Systematic Evaluation of the Mesh Size of Poly(ethylene glycol)-based Hydrogels for Biomedical Applications
No full textPoly(ethylene glycol) (PEG) hydrogels are one of the most widely utilized biomaterial systems, thanks to their intrinsic resistance to protein adsorption and the ability to be covalently linked to multiple functional moieties. This opens a wide range of design options for the synthesis of substrates with tunable chemistry and bioactivity. Moreover, the hydrogel mesh size can be finely controlled to regulate the molecular trafficking within the polymer matrix. The primary objective of this work was to explore the mesh size of poly(ethylene glycol) diacrylate (PEGDA)-based hydrogels obtained by photo- crosslinking. Aqueous solutions differing for polymer concentration and type of photoinitiator were crosslinked by ultraviolet (UV) expo- sure for different time lengths. Free swelling and uniaxial compression measurements were performed to evaluate the hydrogel mesh size, based on classical theoretical models of swelling and rubber elasticity. The calculated values of mesh size were then experimentally validated by protein diffusion studies. Further aim of this work was to assess the gradual increase of the mesh size resulting from hydrolytic degradation, upon incubation at 37°C for 10 weeks. The experimental results showed that, for the hydrogel formulations tested, the mesh size could be reliably estimated by both swelling and mechanical measurements. Remarkably, the evaluation of the mesh size following hydrolysis al- lowed detection of significant differences in the degradation rate of the samples, while providing pivotal information on the dynamic change of their diffusive properties. Such a systematic evaluation of the mesh size allows the careful design of PEG-based hydrogels for medium to long- term biomedical applications
Functional Characterization of a Novel Protocol for Encapsulation of Pancreatic Islets within a Conformal Layer of Poly(Ethylene Glycol)-Based Hydrogel
No full textType 1 Diabetes is an autoimmune disease with no currently available therapies for a definitive reversal of the pathological phe- notype. Among available therapies, pancreatic islet transplantation is a promising strategy, although the requirement of life-long systemic immunosuppression and the limited number of islet donors reduces its widespread application. In this context, islet encapsulation is a promising strategy to create a physical barrier to prevent islet de- struction by the recipient immune system. Furthermore, the encap- sulation material can be exploited as a substrate to conjugate immunomodulatory antibodies or bioactive molecules in order to enhance the immunoprotection activity and to drive targeted im- munosuppression. In this study we developed a protocol for coating murine islets with a conformal layer of poly(ethylene glycol) (PEG)- based hydrogel by employing a photopolymerization method that leads to single islet encapsulation and provides a suitable substrate for targeted functionalization. To validate the biocompatibility of our approach, we assessed encapsulated islet viability and functionality in vitro, and we analysed possible gene expression variations. Our encapsulation protocol preserved islet viability and did not affect significantly expression of apoptotic and hypoxic marker genes. The physiological responsiveness of encapsulated islets to glucose- stimulated insulin secretion was confirmed both at mRNA and pro- tein level. Moreover, effects of the coating on islet architecture were investigated by analysing cytoskeletal morphology and expression of cell-cell and cell-matrix interaction marker genes, observing no substantial differences between encapsulated and control islets. Concluding, our encapsulation protocol provides a safe and bio- compatible approach to encapsulate pancreatic islets, thus suitable for targeted functionalization
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
Photo-crosslinked poly(ethylene glycol) diacrylate (PEGDA) hydrogels from low molecular weight prepolymer: Swelling and permeation studies
No full textThe aim of this work was to assess the diffusive properties of poly(ethylene glycol) diacrylate (PEGDA)-based hydrogels, derived from low MW prepolymers, in view of potential biomedical applications. Several hydrogels were synthesized through UV irradiation of PEGDA solutions for different exposure times. Swelling measurements in distilled water were performed to estimate the yielded crosslink density, while swelling tests at 37 °C in selected media allowed to analyze the mesh size changes induced by various pH and ionic strength (IonS) conditions. The transport of glucose and insulin through thin hydrogel membranes was finally assessed in a modified Ussing chamber at physiological values of pH and IonS (7.4 and 150 mM, respectively). Results showed that the swelling was dependent on the IonS (with swelling reductions up to 20–30% for IonS increases in the range 0–300 mM) and, to a lesser extent, on the pH of the surrounding medium (with swelling increments of about 10% for increasing pH in the range 2.5–11). All hydrogels were also permeable to glucose and insulin, which displayed comparable diffusion coefficients (in the order of 10−6 cm2/s). Specific interactions between glucose and the polymer chains were evidenced by values of the partition coefficient higher than unity
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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