1,720,968 research outputs found
Oil structuring: polymer bridging mechanism for structuring soft materials using natural emulsions as templates
Full text linkUsing a bridging flocculation mechanism in the design of oleogels materials constitutes an alternative framework to achieve desired rheological properties of oil-in-water emulsions. Aggregation by polymer bridging generates a droplet network linked together by firmly bound polymer bridges. In this dissertation, we used negatively charged polysaccharides, sodium alginate, xanthan gum, and ι-carrageenan as the structuring agents and soybean oleosomes as the template. Bridging flocculation between polysaccharides and oleosomes was induced by mixing and adjusting the pH to values where both are oppositely charged, leading to electrostatic-driven interactions. Our results indicate that polysaccharides with flexible polymer chains, such as sodium alginate and ι-carrageenan, are effective bridging flocculants.
In contrast, polysaccharides with a more rigid backbone, such as xanthan gum, resulted in depletion flocculation characterized by phase separation between oleosome droplets and xanthan molecules. Bridging flocculation is more effective at an optimum dosage between polysaccharides and oleosomes, expressed as a mass ratio (g polysaccharide/g oleosome) or as an equivalent per droplet surface area (mg/m2). Sodium alginate presented a higher bridging ability than ι-carrageenan, with its optimum bridging ratio at 0.005 g/g and ι-carrageenan at 0.01 g/g. This was confirmed by quantitative analysis of oleosome content upon centrifugation recovery, where sodium alginate yielded more compact and concentrated gels than ι-carrageenan. Differences in structural conformations between sodium alginate and ι-carrageenan account for the difference in bridging ability. Sodium alginate presents a co-block arrangement of alternating charged and uncharged parts. The negatively charged blocks adsorb strongly onto the oleosome interface at several charged units. At the same time, the uncharged parts impart a high degree of flexibility, allowing the polymer chains to bridge several droplets together.
On the other hand, ι-carrageenan is less flexible than alginate, making the individual carrageenan chains more effective for oleosome surface coating but less effective for bridging neighboring droplets. This difference in bridging ability between sodium alginate and ι-carrageenan will influence the structure of the aggregated network and, as a result, will be responsible for the mechanical behavior in rheological measurements. Sodium alginate produced more heterogeneous and interconnected structures, while ι-carrageenan produced smaller and less interconnected clusters. This difference in microstructure and the effect of the structural conformations in the polysaccharide chains becomes relevant at medium and large deformations in amplitude sweeps oscillatory rheology. At deformations between 3- 100%, sodium alginate presented steeper slopes in the moduli G’, indicating sudden microstructure fracture.
In contrast, ι-carrageenan presented less steep slopes indicating yielding rather than fracture behavior in the decrease of the moduli G’. At deformations between 200- 300%, the moduli presented an overshoot indicating a “cage effect” where individual droplets are immobilized due to crowding by surrounding droplets. This effect was more clearly prominent in conditions leading to the densest structures, such as in the compacted gels upon centrifugation performed at the optimum bridging ratios for sodium alginate (0.005 g/g) and ι-carrageenan (0.01 g/g). This study offers many perspectives on how to construct the macroscopic functional properties of oleogels in accordance with their application using the molecular architecture of polysaccharides
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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