1,720,998 research outputs found
Biological evaluation of zirconia/PEG hybrid materials synthesized via sol-gel technique
No full textThe objective of the following study has been the synthesis via sol-gel and the characterization of novel organic-inorganic hybrid materials to be used in biomedical field. The prepared materials consist of an inorganic zirconia matrix containing as organic component the polyethylene glycol (PEG), a water-soluble polymer used in medical and pharmaceutical fields. Various hybrids have been synthesized changing the molar ratio between the organic and inorganic parts. Fourier transform spectroscopy suggests that the structure of the interpenetrating network is realized by hydrogen bonds between the Zr-OH group in the sol-gel intermediate species and both the terminal alcoholic group and ethereal oxygen atoms in the repeating units of polymer The amorphous nature of the gels has been ascertained by X-ray diffraction analysis. The morphology observation has been carried out by using the Scanning Electron Microscope and has confirmed that the obtained materials are nanostructurated hybrids. The bioactivity of the synthesized system has been shown by the formation of a hydroxyapatite layer on the surface of samples soaked in a fluid simulating the human blood plasma. The potential biocompatibility of hybrids has been assessed as performing indirect MTT cytotoxicity assay towards 3T3 cell line at 24, 48, and 72 h exposure times.The objective of the following study has been the synthesis via sol-gel and the characterization of novel organic-inorganic hybrid materials to be used in biomedical field. The prepared materials consist of an inorganic zirconia matrix containing as organic component the polyethylene glycol (PEG), a water-soluble polymer used in medical and pharmaceutical fields. Various hybrids have been synthesized changing the molar ratio between the organic and inorganic parts. Fourier transform spectroscopy suggests that the structure of the interpenetrating network is realized by hydrogen bonds between the Zr-OH group in the sol-gel intermediate species and both the terminal alcoholic group and ethereal oxygen atoms in the repeating units of polymer The amorphous nature of the gels has been ascertained by X-ray diffraction analysis. The morphology observation has been carried out by using the Scanning Electron Microscope and has confirmed that the obtained materials are nanostructurated hybrids. The bioactivity of the synthesized system has been shown by the formation of a hydroxyapatite layer on the surface of samples soaked in a fluid simulating the human blood plasma. The potential biocompatibility of hybrids has been assessed as performing indirect MTT cytotoxicity assay towards 3T3 cell line at 24, 48, and 72 h exposure times. © 2014 Elsevier B.V. All rights reserved
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
Influence of the polymer amount on bioactivity and biocompatibility of SiO2/PEG hybrid materials synthesized by sol-gel technique
No full textSiO2/PEG organic-inorganic hybrid materials, which differ in polyethylene glycol (PEG) content, were synthesized by sol-gel technique and the characterization of their structure and biological properties was carried out in order to evaluate the possible use in biomedical field. FT-IR spectroscopy detected that the two components of the hybrids (SiO2 and PEG) are linked by hydrogen bonds between the Si-OH groups of the inorganic phase and the terminal alcoholic groups and/or the ethereal oxygen atoms in the repeating units of polymer. X-ray diffraction analysis ascertained the amorphous nature of the gels and the observation of their morphology by SEM microscopy confirmed that the interpenetration of the two phases (organic and inorganic) occurs on nanometric scale. The biological characterization was carried out as a function of the polymer amount to study its influence on material behavior. The results showed that the synthesized materials were bioactive and biocompatible. The formation of a hydroxyapatite layer, indeed, was observed on their surface by SEM/EDX analysis after soaking in simulated body fluid. Moreover, the biocompatibility of SiO2/PEG hybrids was assessed performing MTT and SRB cytotoxicity tests on fibroblast cell NIH 3T3 after 24 and 48h of exposure, as well as Trypan Blue dye exclusion test. The response to the presence of the investigated materials was positive. The cell growth and proliferation showed dependence on polymer amount and time of exposure to the material extracts. Therefore, the obtained results are encouraging for the use of the obtained hybrids in dental or orthopedic applications.SiO2/PEG organic-inorganic hybrid materials, which differ in polyethylene glycol (PEG) content, were synthesized by sol-gel technique and the characterization of their structure and biological properties was carried out in order to evaluate the possible use in biomedical field. FT-IR spectroscopy detected that the two components of the hybrids (SiO2 and PEG) are linked by hydrogen bonds between the Si-OH groups of the inorganic phase and the terminal alcoholic groups and/or the ethereal oxygen atoms in the repeating units of polymer. X-ray diffraction analysis ascertained the amorphous nature of the gels and the observation of their morphology by SEM microscopy confirmed that the interpenetration of the two phases (organic and inorganic) occurs on nanometric scale. The biological characterization was carried out as a function of the polymer amount to study its influence on material behavior. The results showed that the synthesized materials were bioactive and biocompatible. The formation of a hydroxyapatite layer, indeed, was observed on their surface by SEM/EDX analysis after soaking in simulated body fluid. Moreover, the biocompatibility of SiO2/PEG hybrids was assessed performing MTT and SRB cytotoxicity tests on fibroblast cell NIH 3T3 after 24 and 48 h of exposure, as well as Trypan Blue dye exclusion test. The response to the presence of the investigated materials was positive. The cell growth and proliferation showed dependence on polymer amount and time of exposure to the material extracts. Therefore, the obtained results are encouraging for the use of the obtained hybrids in dental or orthopedic applications
Cytotoxicity and apoptosis inducing activity of an apolar Laurus nobilis leaf extract towards three neuronal cell lines
No full textVariations 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
Synthesis and chemical characterization of new silica polyethylene glycol hybrid nanocomposite materials for controlled drug delivery
No full textA series of inorganic organic hybrid nanocomposite materials, containing indomethacin (IND) as a model drug, were synthesized using an inorganic precursor (tetraethoxysilane, TEOS) and an organic precursor (polyethylene glycol, PEG 400) through sol-gel chemistry. The various synthesized hybrids differed in PEG weight percentage (0, 6, 12, 24, and 50% wt). On an equal PEG percentage, different amounts of the non-steroidal anti-inflammatory drug were loaded (5, 10, and 15% wt). The bonding characteristics of the various composites were investigated via FT-IR spectroscopy, which suggests the formation of H-bonds between hybrids components. X-ray diffraction (XRD), used for the investigation of their atomic organization, and scanning electron microscopy (SEM) analysis confirmed the amorphous and nanocomposite structure of synthesized materials, which appeared morphologically homogeneous. The in vitro bioactivity evaluation was carried out by analyzing the apatite layers produced on the hybrid materials using SBF as incubation medium. The apatite formation was analyzed using SEM coupled to energy-dispersive electron X-ray spectroscopy. The in vitro release of indomethacin from the new drug-loaded bioactive materials was investigated by HPLC-UV-ESIMS/MS analysis. Data obtained allowed us to state that the drug release was markedly affected by the PEG percentage in investigated hybrid materials.A series of inorganic organic hybrid nanocomposite materials, containing indomethacin (IND) as a model drug, were synthesized using an inorganic precursor (tetraethoxysilane, TEOS) and an organic precursor (polyethylene glycol, PEG 400) through sol-gel chemistry. The various synthesized hybrids differed in PEG weight percentage (0, 6, 12, 24, and 50% wt). On an equal PEG percentage, different amounts of the non-steroidal anti-inflammatory drug were loaded (5, 10, and 15% wt). The bonding characteristics of the various composites were investigated via FT-IR spectroscopy, which suggests the formation of H-bonds between hybrids components. X-ray diffraction (XRD), used for the investigation of their atomic organization, and scanning electron microscopy (SEM) analysis confirmed the amorphous and nanocomposite structure of synthesized materials, which appeared morphologically homogeneous. The in vitro bioactivity evaluation was carried out by analyzing the apatite layers produced on the hybrid materials using SBF as incubation medium. The apatite formation was analyzed using SEM coupled to energy-dispersive electron X-ray spectroscopy. The in vitro release of indomethacin from the new drug-loaded bioactive materials was investigated by HPLC-UV-ESIMS/MS analysis. Data obtained allowed us to state that the drug release was markedly affected by the PEG percentage in investigated hybrid materials
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
- …
