1,720,963 research outputs found
The role of Fibrinogen conformation on platelets activation
No full textAbstract
Platelet adhesion and activation induced by fibrinogen (Fbg) coating on polysaccharide layers of hyaluronic acid (Hyal) and its sulfated derivative (HyalS) were analyzed. Hyal or HyalS was coated and grafted on the glass substrate using a photolithographic method. The Fbg coating was achieved by two different routes: the immobilization of Fbg by means of covalent bond to the polysaccharide layers and the mere adsorption of Fbg to Hyal and HyalS surfaces. Platelet adhesion and activation to the surfaces were evaluated using, respectively, scanning electron microscopy (SEM) and quantifying the release of Platelet Factor 4 by ELISA. The method used for the coating of the surfaces with the Fbg influenced the platelet response. In fact, platelet adhesion and activation took place on surfaces covered by bound Fbg but not on those containing adsorbed Fbg. To explain this difference, the molecular mechanism involved in the Fbg--platelet interaction was investigated blocking platelet membrane receptors by monoclonal antibodies. Because the interaction between Fbg and the GPIIb/IIIa platelet membrane receptor was the only molecular pathway involved, Fbg conformation after the interaction (adsorption or binding) with the Hyal and the HyalS chains and the role of serum proteins adsorbed on the Fbg containing surfaces were accurately analyzed. Both adsorbed and bound Fbg prevented the adsorption of further serum proteins; consequently, a direct interaction between Fbg and platelets was supposed and the different platelet behavior was ascribed to the different conformational changes that occurred after the adsorption and the chemical binding of the Fbg to the Hyal and HyalS surfaces
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
Amidic alginate hydrogel for nucleus pulposus replacement
No full textDegeneration of intervertebral discs is the most common cause of back pain. The first phase of this degenerative process involves the nucleus pulposus (NP). A rapid recovery of this structure can prevent further degradation of the annulus fibrosus. A new amidic derivative of alginate (AAA) was developed to obtain a polysaccharide possessing some of the physical–chemical properties of Hyal (i.e. viscosity) without losing the rigidity of the native alginate structure. The modified polysaccharide was crosslinked using 1.3 diaminopropane as crosslinking agent.
The hydrogel obtained was characterized in terms of water uptake and rheological behavior. In particular, the viscoelastic behavior of the hydrogel was determined in shear stress under dynamic conditions and compared with the behavior of nondegenerated human lumbar NP. We then assessed the effect of the AAA hydrogel on NHC (Normal Human Chondrocyte) cell viability and on the production of important extracellular matrix factors, such as glycosaminoglycans and Type II collagen. In conclusion, the results achieved in this study demonstrated that the amidic alginate based scaffold is a promising material to be utilized in the replacement of NP
Immobilizing Cu, Zn-Superoxide Dismutase in Hydrogels of Carboxymethylcellulose Improves its Stability and Wound Healing Properties.
No full textHydrogels of carboxymethylcellulose (CMC) with 50 and 90% crosslinking degree (CMC50% and CMC90%,
respectively) were prepared and loaded with bovine erythrocyte Cu,Znsuperoxide dismutase (SOD) to obtain two drug
delivery systems: SOD–CMC50% and SOD–CMC90%. Resistance of native SOD to inactivation by H2O2
and the effect
of applying SOD–CMC hydrogels to open wounds of rats’ back skin were examined and compared to that of SOD trapped
into CMC50% and CMC90% hydrogels. Also, the effect of CMC50% and SOD–CMC90% on human fibroblasts prolifer
ation was evaluated at different times. It was found that SOD in the hydrogel was more resistant to H2O2
inactivation than
the native enzyme and at the same time it reduced the time necessary for wound healing. Furthermore, the highest cell pro
liferation value was found for the CMC50% hydrogels, which had a threedimensional structure suitable for gas and nutri
ent exchanges and improving cell life conditions
Low- and high-resolution nuclear magnetic resonance (NMR) characterisation of hyaluronan-based native and sulfated hydrogels
No full textHyaluronan-based hydrogels were synthesised using different crosslinking agents, such as 1,3 diaminopropane (1,3-DAP) and 1,6-diaminohexane (1,6-DAE). The hydrogels were sulfated to provide materials (Hyal-1,3-DAP, Hyal-1,6-DAE, HyalS-1,3-DAP and HyalS-1,6-DAE) that were characterised by both high- and low-resolution nuclear magnetic resonance (NMR) spectroscopy. The 13C NMR spectra of the materials were analysed to identify, characterise and study the crosslinking degree of the hydrogels. The crosslinking degree was also determined by potentiometric titration and the effectiveness of the two techniques was compared. Measurements of longitudinal relaxation times (spin–lattice) and of NOE enhancement were used to study the mobility of the hydrogels. Low-resolution NMR studies allowed the determination of the water transport properties in the hydrogels. In addition, the swelling degree for the various hydrogels was calculated as a function of the longitudinal and transversal relaxation times of the water molecules. Lastly, the self-diffusion coefficients of the water in interaction with the four polysaccharides were measured by the pulsed field gradient spin echo (PFGSE) sequence
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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