1,720,998 research outputs found
Antioxidant Effects of Rosemary Extract on the Accelerated Degradation of Ethylene‐Propylene‐Diene Monomer
No full textThe influence of natural antioxidants (rosemary extract, capsaicin, quercetin, or oleanolic acid) in ethylene-propylene-diene-monomer (EPDM) thermal behavior has been investigated by the means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). EPDM and EPDM/rosemary (RM) composite are investigated with a thermogravimetric (TG) balance in dynamic heating conditions (25 degrees C-700 degrees C). DSC analysis is also carried out from subambient to better highlight the melting of the polymer and the composite. The obtained DSC and TG values are discussed to have information about the effect of RM content in the polymer stability
Use of the Sol–Gel Method for the Preparation of Coatings of Titanium Substrates with Hydroxyapatite for Biomedical Application
Get PDFAbstract: Hydroxyapatite (HA) was coated onto the surface of commercially pure titanium grade 4
(a material generally used for implant application) by a dip coating method using HA sol.
Hydroxyapatite sol was synthesized via sol–gel using Ca(NO 3 ) 2 ∙4H 2 O and P 2 O 5 as precursors. The
surface of the HA coating was homogeneous, as determined by scanning electron microscopy
(SEM), attenuated total reflectance Fourier transform infrared (ATR-FTIR), and X-ray diffraction
(XRD), which allowed the materials to be characterized. The bioactivity of the synthesized materials
and their efficiency for use as future bone implants was confirmed by observing the formation of a
layer of hydroxyapatite on the surface of the samples soaked in a fluid simulating the composition
of human blood plasma. To verify the biocompatibility of the obtained biomaterial, fibroblasts were
grown on a glass surface and were tested for viability after 24 h. The results of the WST-8 analysis
suggest that the HA systems, prepared by the sol–gel method, are most suitable for modifying the
surface of titanium implants and improving their biocompatibility
Sol–Gel Synthesis of Silica-Based Materials with Different Percentages of PEG or PCL and High Chlorogenic Acid Content
Get PDFImplanted biomedical devices can induce adverse responses in the human body, which can cause failure of the implant—referred to as implant failure. Early implant failure is induced numerous factors, most importantly, infection and inflammation. Natural products are, today, one of the main sources of new drug molecules due to the development of pathogenic bacterial strains that possess resistance to more antibiotics used currently in various diseases. The aim of this work is the sol–gel synthesis of antibacterial biomedical implants. In the silica matrix, different percentages (6, 12, 24, 50 wt %) of polyethylene glycol (PEG) or poly(ε-caprolactone) (PCL) were embedded. Subsequently, the ethanol solutions with high amounts of chlorogenic acid (CGA 20 wt %) were slowly added to SiO2/PEG and SiO2/PCL sol. The interactions among different organic and inorganic phases in the hybrid materials was studied by Fourier transform infrared (FTIR) spectroscopy. Furthermore, the materials were soaked in simulated body fluid (SBF) for 21 days and the formation of a hydroxyapatite layer on their surface was evaluated by FTIR and XRD analysis. Finally, Escherichia coli and Pseudomonas aeruginosa were incubated with several hybrids, and the diameter of zone of inhibition was observed to assessment the potential antibacterial properties of the hybrids
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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