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Elaboration of alginate microspheres by emulsification-ionotropic gelation technique containing bioadhesive polymers. A morphological study of the systems.
No full textNatural polymers have great advantages becausethey have good biocompatibility, specificdegradation and the feasibility to incorporatedrugs into their matrices. Amongst the naturalpolymers, alginate has been used by manyworkers as a matrix for the controlled release ofdrugs. It has an ability to cause abioadhesion with mucosal membranes. Drugdelivery in the oral mucosa has many advantagesfor drugs such as local anaesthetics. However,this site of the oral cavity is subjected to theinfluence of the salivation process, that canremove the remanent dosage form from theapplication site. Therefore, the addition of abioadhesive to the bead formulation could avoidthis removing effect.
The most commonly used technique for carrying drugs in an alginate matrix is by extrudingdroplets of alginate drug solution or dispersioninto a calcium chloride bath. Gelation occurs byan ionic interaction between the calcium ionsand the carboxylate anion of G-G blocks ascalcium ions diffuse from the external sourceinto the droplet. An alternative to thesetechniques is the emulsification method, whichallows the encapsulation of the drug in small
beads. Bead formation through emulsion techniques hasnot been adequately investigated withbioadhesive polymers. An emulsion of analginate aqueous solution in oil can be added toCaCl2 solution, and thereby leads to beadformation. However, particle size cannot beeasily controlled and the beads tend to coagulate
into large masses before hardening properly. In the present study, the gelation of alginate-Chitosan (CH) and alginate-Gantrez® solution isachieved through the emulsification of thissolution with the lipophilic phase. In a first stage,a morphological study by SEM has beenrealized, in order to determine the presence orabsence of bead aggregates, and their shape and parameters
Release of diclofenac (salt or acid) from lipid microspheres prepared by ultrasound atomization
No full textThe aim of this work was to elucidate the underlying drug release mechanisms from lipidic matrix microspheres, using two chemical forms of diclofenac (acid or salt) as model drug; and Compritol and Carnauba wax, either alone or together with varying amount (10-30 % w/w) stearic acid. The systems prepared as physical mixtures were obtained as solid dispersion (melting method) in the form of microspheres by atomization assisted by ultrasound. The effects of different formulations on the resulting drug release kinetics in 0.1 N HCl and phosphate buffer pH 7.4 were studied.
Release of acidic diclofenac - Lipid matrix prevents the release of the drug at low pH. The systems contain at least 20% of ionisable diclofenac and pH 7.2 of the buffer should be enough to start its ionization and dissolution, which on the contrary seems to be driven in the presence of stearic acid; in the presence of 30% stearic acid release is complete after 1 h.
Release of the diclofenac salt - The release at acidic pH is null, while the salt is rapidly released from the lipid matrix at pH 7.2 in the presence of compritol; from carnauba wax matrix it needs the presence of stearic acid. In each case the release of the salt is faster than that of the acid, where dissolution had to be mediated by ionization: this reaction rate proved to be slowed down by the proximity of the lipid matrix.
Treating the experimental data in the terms of Peppas equation: Mt/M∞ = ktn, we found n = 0.57 for the release from pure compritol (0.71 for carnauba wax), based on a diffusion mechanism. While in the presence of stearic acid n was found 0.83 (0.75 for carnauba wax), indicating erosion and diffusion operating together for the release of the drug from microspheres, in agreement with the photos taken at SEM
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
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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