1,720,959 research outputs found
Theretical and experimental characterisation of stearic acid based sustained release devices obtained by hot melt co-extrusion
No full textThis study was conducted to develop and characterize a hot melt co-extruded cylindrical system for controlled drug delivery. Different lengths
and configurations (homogeneous, hollow and heterogeneous) co-extrudates were considered. Stearic acid and polyethylene glycol were used as
hydrophobic and hydrophilic components, respectively. Acetaminophen and theophylline were used as model drug. Release kinetics were studied
on the basis of in vitro tests and experimental data were analyzed by a new mathematical model accounting for drug dissolution and diffusion
inside the cylindrical matrix. Surface tension measurements were carried on the two model drugs and the hydrophobic matrix. Experimental results
showed that co-extruded length and configuration sensibly affect release kinetics of both drugs. Additionally, the proposed mathematical model
proved to be reliable and yielded an explanation for the lower acetaminophen release rate with respect to that of theophylline. This behavior could
be explained by the formation of a low permeable layer surrounding the acetaminophen-loaded systems. In addition, surface property analysis
evidenced the higher hydrophobic nature of acetaminophen-loaded systems with respect to theophylline systems
Development and pharmacokinetic evaluation of erythromycin lipidic formulations for oral administratiom in rainbow trout (O. mykiss)
No full textThe aim of this work was to enhance the bioavailability of erythromycin base when administered orally in rainbow trout (Oncorhynchus mykiss). Since erythromycin is normally given in the form of medicated feed, in this study three new types of feed formulation were developed. A self-emulsifying system and two types of double microemulsions (O/W/O) were prepared, characterized and adsorbed on a commercial extruded diet for fish. The three medicated feed were then administered orally by means of a gastric probe to rainbow trout and their relative bioavailability was estimated in comparison with that obtained after oral administration of feed with erythromycin powder. For each medicated feed, 80 fish were tested. Finally, plasma profiles of erythromycin after single administration of medicated feeds were used to predict profiles obtainable by administering once-daily medicated feeds for 7 consecutive days
An innovative oxytetracycline self-emulsifying formulation for fish diets: preparation,characterisation and oral bioavailability in Rainbow Trout (Oncorhyncus mykiss)and in EuropeanSea Bass (Dicentrarchus Labrax)
No full textThe aim of this study was to develop a self-emulsifying system (SES) with practical applications in fish farming. In particular, the lipid vehicle
was developed in order to deliver oxytetracycline hydrocloride to rainbow trout (RT) and European sea bass (ESB) so as to improve the drug’ s
oral bioavailability. The developed formulation was assessed in comparison to an aqueous solution working with two fish species (one fresh-water
and one salt-water), after oral administration with a gastric probe. Results indicated an enhancement of bioavailability of 5.86 and 5.41 times
over the aqueous solution, in RT and ESB, respectively. SES was then used to prepare medicated feed containing the formulation. The pharmacokinetic
of this feed was evaluated after oral administration and compared to that of commercial OTC medicated feed. The bioavailability of OTC
delivered in SES was 3.2 times higher in RT and 2.7 times higher in ESB, than OTC supplied by commercial medicated feed. This bioavailability
enhancement was confirmed when RT were fed by classical administration in fish tanks of single and repeated administration of OTC delivered
in SES and commercial medicated feed, attesting to better absorption of the SES formulation
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
Bi-layered self-emulsifying pellets prepared by co-extrusion and spheronization: influence of formulation variables and preliminary study on the in vivo absorption
No full textThe aim of this work was to produce by co-extrusion–spheronization pellets with two cohesive layers, one of them containing a selfemulsifying system for vinpocetine, a poorly water soluble model drug. Two layers were prepared: an inert layer of microcrystalline cellulose, lactose and water and a second one wetted with the self-emulsifying system. The screening amongst formulations was performed preparing rod extrudates and using the extrusion profiles to assess their suitability for extrusion and to anticipate quality of the spheronized extrudates. Tubular extrudates and co-extrudates/spheronized pellets were then produced. Two types of bi-layered pellets were prepared: type I with the self-emulsifying system internally and the inert matrix externally, whereas type II vice versa. The preliminary technological and pharmacokinetic data demonstrated that co-extrusion/spheronization is a viable technology to produce bi-layered cohesive self-emulsifying pellets of good quality and improved in vivo bioavailability
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
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