1,721,033 research outputs found
Thermal valorization and elemental composition of industrial tannin extracts
No full textDue to their natural origin and broad availability, industrial tannin extracts are extending their application field
from the classical, and still principal, application in tannery, to oenology, pharmacy, adhesives and material
science. Despite the growing interest, not much is known about the thermal valorization of these biomolecules. In
this article we present the thermal properties of the eight most common commercial tannin extracts and their
elemental chemical composition to shed light on the end-life of the bio-materials based on these polyphenols.
Results have shown that hydrolysable tannins can be managed similarly to wood, while condensed tannins have
higher heating values but also generally higher chlorine content. Sumac and gambier leaf extracts registered
contained heating values and significant amounts of ashes rich in calcium and sulfur. The high chlorine content
observed for the extracts of mimosa (Acacia Mearnsii) does not hinder the combustion of its derived products
which can still be thermally valorized. Mimosa tannin-based materials can also be added up to 2% to wood
pellets and briquettes without significantly affecting the overall quality of the biofuels according to the in-force
standards
Comparing condensed and hydrolysable tannins for mechanical foaming of furanic foams
Full text linkThis study examined the potential of hydrolysable tannin in comparison to condensed tannins for the production of furanic foams. The results indicate that chestnut tannin presents lower reactivity and requires a stronger acid for the polymerization. Additionally, foamability and density were found to be dependent on both surfactant concentration and tannin type, allowing lower densities for mimosa tannin and lower thermal conductivities for chestnut-based foams. Mimosa tannin was found to have the highest compression strength, followed by quebracho and chestnut, promising thermal conductivity of around 50 mW/m·K for 300 kg/m3 foams, which suggests that chestnut foams have the potential to performing highly when the density is reduced. Chemical analysis revealed that the methylene moieties of the furanics are non-specific and produces new covalent bonds with nucleophilic substrates: -OH groups and free-positions in the flavonoids. Overall, this study opens new perspectives for the application of hydrolysable tannins in polymer and material science
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
Fully Biobased Polyhydroxyalkanoate/Tannin Films as Multifunctional Materials for Smart Food Packaging Applications
Full text linkFully biobased and biodegradable materials have attracteda growinginterest in the food packaging sector as they can help to reduce thenegative impact of fossil-based plastics on the environment. Moreover,the addition of functionalities to these materials by introducingactive molecules has become an essential requirement to create modernpackaging able to extend food's shelf-life while informingthe consumer about food quality and freshness. In this study, we presentan innovative bioplastic formulation for food packaging based on poly-(hydroxybutyrate-co-valerate) (PHBV) and tannins as multifunctional additives.As a proof of concept, PHBV/tannin films were prepared by solventcasting, increasing the tannin content from 1 to 10 per hundred ofresin (phr). Formic acid was used to reach a homogeneous distributionof the hydrophilic tannins into hydrophobic PHBV, which is remarkablychallenging by using other solvents. Thanks to their well-known properties,the effect of tannins on the antioxidant, UV protection, and gas barrierproperties of PHBV was evaluated. Samples containing 5 phr bioadditiverevealed the best combination of these properties, also maintaininggood transparency. Differential scanning calorimetry (DSC) investigationsrevealed that films are suitable for application from the fridge topotentially high temperatures for food heating (up to 200 degrees C).Tensile tests have also shown that Young's modulus (900-1030MPa) and tensile strength (20 MPa) are comparable with those of thecommon polymers and biopolymers for packaging. Besides the improvementof the PHBV properties for extending food's shelf-life, itwas also observed that PHBV/tannin could colorimetrically detect ammoniavapors, thus making this material potentially applicable as a smartindicator for food spoilage (e.g., detection of fish degradation).The presented outcomes suggest that tannins can add multifunctionalproperties to a polymeric material, opening up a new strategy to obtainan attractive alternative to petroleum-based plastics for smart foodpackaging applications
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