1,720,987 research outputs found
HPLC ANALYTICAL STUDY OF METHACRYLIC MONOMERS RELEASED FROM DENTAL COMPOSITE MATERIALS
No full textThe widely used high performance liquid chromatography (HPLC) is an analytical technique based on the crossing of a solvent (mobile phase), under high pressures, through a stainless steel column packed with very small particles (stationary phase). This technique allows a very efficient separation of the components of a mixture and an easy detection with high sensitivity. In the normal phase HPLC, the column is filled with silica particles and the mobile phase has low polarity or it is non-polar. The polar compounds of the mixture passing through the column are retained longer by the polar silica whereas are poorly dissolved into the non-polar mobile phase. The non-polar analytes pass instead more quickly through the column. In the largely used reversed phase HPLC, the silica surface is conversely made non-polar by attaching long hydrocarbon chains. A mixture of water and a polar solvent is used as mobile phase. In this case, the polar molecules of the mixture passing through the column are strongly attracted by the polar solvent but not by the hydrocarbon chains attached to the silica of the stationary phase; the polar molecules will therefore easily move with the solvent through the column. Non-polar compounds will instead tend to interact with the hydrocarbon groups of stationary phase slowing their way through the column. Triethylene glycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) are methacrylic monomers present in dental auto- and photo-polymerizable resins. Many in vitro studies have shown that the polymerization of the above mentioned compounds is never complete and the uncured monomers are released in the oral environment, causing possible local adverse effects. The evaluation of the amounts of the methacrylic monomers released from composite resins is therefore very important and HPLC technique is particularly suitable to this purpose. HPLC is however not limited to qualitative and quantitative analysis of methacrylic monomers but can be also applied to the study of their metabolism. The present work summarizes the recent results about the detection of TEGDMA and HEMA in complex systems like cells and culture media by HPLC, evidencing its key role in the investigations of the substances involved in cytotoxic processes. Moreover the great specificity and sensibility of the used method allow to relate the concentration values of methacrylic monomers to their cytotoxic effects, in particular when such molecules are used in presence of N-acetyl cysteine, helping to clarify its mechanism of detoxification
In vitro evaluation of the cytotoxicity of FotoSanTM light-activated disinfection on human fibroblasts.
No full textRoot canal disinfection needs to be improved because actual techniques are not able to eliminate all microorganisms present in the root canal system. The aim of the present study was to investigate the in vitro cytotoxicity of FotoSan (CMS Dental APS, Copenhagen Denmark), 17% EDTA and 2% chlorhexidine. Fibroblasts of periodontal ligament from healthy patients were cultured. FotoSan (with and without light activation for 30 sec.), 17% EDTA and 2% chlorexidine were used for the cell viability tests. Untreated cells were used as control. The cellular vitality was evaluated by MTT test. The production of reactive oxygen species (ROS) was measured using an oxidation-sensitive fluorescent probe. Results were statistically analyzed by ANOVA, followed by a multiple comparison of means by Student-Newman-Keuls, and the statistical significance was set at p<0.05. MTT tests showed that cytotoxic effects of FotoSan (both photocured and uncured) were statistically lower (p<0.05) than that observed using 2% Chlorhexidine, while no significant differences were found in comparison with 17% EDTA. No alterations in ROS production were detectable in any of the tested materials. Since the toxicity of the FotoSan photosensitizer, both light-activated and not light-activated, is similar to common endodontic irrigants, it can be clinically used with precautions of use similar to those usually recommended for the above-mentioned irrigating solutions
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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