1,721,028 research outputs found
Polydimethylsiloxane/divinylbenzene overcoated fiber and its application to extract and analyse wine volatile compounds by solid-phase microextraction and gas chromatography coupled to mass spectrometry: direct immersion, headspace or both?
No full textIn this study, a comparison of the efficiency of the commercially available polydimethylsiloxane/divinylbenzene (PDMS/DVB) overcoated (OC) fiber used in direct immersion (DI) or in headspace (HS), has been performed by extracting volatiles through solid-phase microextraction (SPME) from a red wine and from a wine model to confirm the results. It was also investigated if a combination of DI followed by HS in a single assay (DI-HS) can provide improvements as compared to the use in DI or in HS only. Furthermore, the use of OC fiber in HS mode was compared with the use of the triphasic phase (TP, in PDMS/CAR/DVB), known to provide good results in this application. To have information also on fiber specificity, the detected analytes were subdivided into three classes depending on their boiling point. Results show that: OC fiber gives slightly better performance as compared to TP fiber, demonstrating a high efficiency of the OC fiber also in HS mode. Then, comparing the use of the commercial OC fiber in HS, DI and in the combined DI-HS mode, explored for the first time in this study to extract volatiles from wine, the combination DI-HS resulted to provide a more balanced efficiency for all the three groups of analytes, thus being a good compromise when the analytes have a broad range of volatility. Principal component analysis (PCA) and the design of experiment (DoE) were exploited to plan experiments and to help interpreting the results, highlighting that the combined DI-HS approach can be successfully applied to the characterization of wines and of other matrices, where analytes of interest have a wide range of volatility
A Simple and Inexpensive Image Analysis Technique to Study the Effect of Disintegrants Concentration and Diluents Type on Disintegration
No full textTablets disintegration is often the result of a size expansion of the tablets. In this study, we quantified the extent and direction of size expansion of tablets during disintegration, using readily available techniques, that is, a digital camera and public domain image analysis software. After validating the method, the influence of disintegrants concentration and diluents type on kinetics and mechanisms of disintegration were studied. Tablets containing diluent, disintegrant (sodium starch glycolate, crospovidone, or croscarmellose sodium), and lubricant were prepared by direct compression. Projected area and aspect ratio of the tablets were monitored using image analysis techniques. The developed method could describe the kinetics and mechanisms of disintegration qualitatively and quantitatively. Sodium starch glycolate and crospovidone acted purely by swelling and shape recovery mechanisms. Instead, croscarmellose sodium worked by a combination of both mechanisms, the extent of which changed depending on its concentration and the diluent type. We anticipate that the method described here could provide a framework for the routine screening of tablets disintegration using readily available equipment
Encapsulation of Flavours and Fragrances into Polymeric Capsules and Cyclodextrins Inclusion Complexes: An Update
Full text linkFlavours and fragrances are volatile compounds of large interest for different applications. Due to their high tendency of evaporation and, in most cases, poor chemical stability, these compounds need to be encapsulated for handling and industrial processing. Encapsulation, indeed, resulted in being effective at overcoming the main concerns related to volatile compound manipulation, and several industrial products contain flavours and fragrances in an encapsulated form for the final usage of customers. Although several organic or inorganic materials have been investigated for the production of coated micro- or nanosystems intended for the encapsulation of fragrances and flavours, polymeric coating, leading to the formation of micro- or nanocapsules with a core-shell architecture, as well as a molecular inclusion complexation with cyclodextrins, are still the most used. The present review aims to summarise the recent literature about the encapsulation of fragrances and flavours into polymeric micro- or nanocapsules or inclusion complexes with cyclodextrins, with a focus on methods for micro/nanoencapsulation and applications in the different technological fields, including the textile, cosmetic, food and paper industries
Zein as a Pharmaceutical Excipient in Oral Solid Dosage Forms: State of the Art and Future Perspectives
No full textZein is the main storage protein of corn and it has several industrial applications. Mainly in the last 10-15 years, zein has emerged as a potential pharmaceutical excipient with unique features. Zein is a natural, biocompatible and biodegradable material produced from renewable sources. It is insoluble, yet due to its amphiphilic nature, it has self-assembling properties, which have been exploited for the formation of micromicroparticle and nanoparticle and films. Moreover, zein can hydrate so it has been used in swellable matrices for controlled drug release. Other pharmaceutical applications of zein in oral drug delivery include its incorporation in solid dispersions of poorly soluble drugs and in colonic drug delivery systems. This review describes the features of zein significant for its use as a pharmaceutical excipient for oral drug delivery, and it summaries the literature relevant to macroscopic zein-based oral dosage forms, i.e. tablets, capsules, beads and powders. Particular attention is paid to the most novel formulations and applications of zein. Moreover, gaps of knowledge as well as possible venues for future investigations on zein are highlighted
A facile and sensitive video-analysis method for tracking floating lag-time and floating rate of gastro-retentive tablets
No full textFloating effervescent tablets are designed to rapidly float in the gastric fluids by gas formation, after an initial lag-time. We developed here a method to characterise these dosage forms. Tablets were prepared containing various concentrations of hydroxypropyl methylcellulose (HPMC), dicalcium phosphate (DCP) and sodium bicarbonate (NB) as gelling agent, high-density model compound and gassing agent, respectively. Videos of the motion of tablets exposed to fluids for 6 h were recorded and then analysed to measure: i) tablet swelling; ii) floating kinetic until lag-time and iii) residual floating rate of the tablets over time. The developed technique was able to precisely track tablet motion and thus describe the floating performance of the dosage forms. Specifically, it was found that floating lag-time and floating fluctuations were influenced by the concentration of NB, more than DCP. Moreover, both swelling volume and residual floating rate over time were not affected by tablet composition, suggesting that density developments of the tablets were similar across formulations. Floating rate also remained constant over the test duration, which correlates well with previous findings on the floating force of HPMC/NB matrices. Overall, we showcase here a simple video-recording and -analysis technique to effectively characterise the performance of floating dosage forms
Temperature: An overlooked factor in tablet disintegration
No full textDisintegration is the first event in the bioavailability cascade after the ingestion of immediate release tablets. Although the influence of various physico-chemical parameters of media on tablet disintegration has been investigated in depth, the role of temperature has received much less attention. Probing the effect of temperature on disintegration is important in order to understand if previous in vitro studies conducted at room temperature can be related to those performed at body temperature. Moreover, from a biorelevant point of view, a tablet could be co-ingested with a cold or hot drink, inducing transient variations of intragastric temperature; state of fever could also elevate body temperature. Here, we studied the effect of temperature on disintegration of directly compressed tablets made of disintegrants alone and in combination with commonly used diluents and binders, using an image analysis technique as well as a compendial disintegration apparatus. Our results indicate that temperature in the range of 23°C to 41°C had a positive effect on disintegration: tablets tested at higher temperatures exhibited up to 2.9-fold faster disintegration than those tested at lower temperatures. The extent of temperature effect on disintegration time was significantly influenced by the composition of the formulations. Overall, the findings of this study suggest that disintegration results obtained in vitro at room temperature can be qualitatively, but not quantitatively, compared to those obtained at body temperature. We also speculate that although temperature had a moderate influence on in vitro disintegration, the magnitude of this effect is unlikely to impact the oral bioavailability in vivo
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
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