1,721,051 research outputs found
Introducing Hydrogen Bond Networks in the Self-Assembly of Chitin Nanocrystals: Strong and Flexible Bioactive Films Containing Natural Polyphenols
Full text linkFree-standing, highly transparent and flexible films are obtained from solvent casting of aqueous colloidal dispersions of surface-deacetylated chitin nanocrystals. The Young's modulus and the water absorption of the films is further modulated by the addition of three natural polyphenols, i.e., epigallocatechingallate, tannic acid and one lignosulfonate, which differ one another in terms of molecular weight, and overall amount of hydroxy, phenolic and catecholic functionalities. The polyphenolic molecules create an extensive network of hydrogen bonds with the nanocrystals, thus controlling interfacial interactions. Therefore, they act as crosslinkers exerting a reinforcing and structuring action and hampering water absorption. The films do not show dissolution in water upon 7 days of incubation at room temperature, and the release profiles of the polyphenols in aqueous media evidence hindered Fickian diffusion kinetics confirming the presence of interactions with the nanostructured matrix. Lastly, the developed films possess bioactive properties, as they show both radical scavenging and antimicrobial activity. These characteristics are enhanced by the phenolic and, most importantly, catecholic moieties present in tannins (and to a lesser extent in lignins), allowing to reach bactericidal effects as high as 99.99% against both Gram-positive and Gram-negative strains
Introducing Hydrogen Bond Networks in the Self‐Assembly of Chitin Nanocrystals: Strong and Flexible Bioactive Films Containing Natural Polyphenols
No full textFree-standing, highly transparent and flexible films are obtained from solvent casting of aqueous colloidal dispersions of surface-deacetylated chitin nanocrystals. The Young's modulus and the water absorption of the films is further modulated by the addition of three natural polyphenols, i.e., epigallocatechingallate, tannic acid and one lignosulfonate, which differ one another in terms of molecular weight, and overall amount of hydroxy, phenolic and catecholic functionalities. The polyphenolic molecules create an extensive network of hydrogen bonds with the nanocrystals, thus controlling interfacial interactions. Therefore, they act as crosslinkers exerting a reinforcing and structuring action and hampering water absorption. The films do not show dissolution in water upon 7 days of incubation at room temperature, and the release profiles of the polyphenols in aqueous media evidence hindered Fickian diffusion kinetics confirming the presence of interactions with the nanostructured matrix. Lastly, the developed films possess bioactive properties, as they show both radical scavenging and antimicrobial activity. These characteristics are enhanced by the phenolic and, most importantly, catecholic moieties present in tannins (and to a lesser extent in lignins), allowing to reach bactericidal effects as high as 99.99% against both Gram-positive and Gram-negative strains
Simple Strategies to Modulate the pH-Responsiveness of Lignosulfonate-Based Delivery Systems
Full text linkThe extensive use of non-degradable microplastics in a wide plethora of daily life products is causing serious pollution problems. More ecofriendly solutions are therefore urgently needed. In this context, the use of lignin, a largely available aromatic polymer, may represent a viable option. Due to the self-assembly ability of its molecules, lignin is in fact an ideal matrix for the fabrication of nanostructures. In this study, lignosulfonate microcapsules containing a limonene core were prepared and characterized in terms of their dimensions and of the physicochemical characteristics of the capsule-forming lignosulfonate molecules. The main purpose is to elucidate the key properties governing the pH-responsive behavior of the capsules to be able to achieve better control over the release kinetics of the entrapped compound(s). The results demonstrate that both the molecular weight and the concentration of sulfonate groups are the most important factors in this respect. Based on these findings, two strategies were followed to further tailor the capsules’ behavior: (i) fractionation of the starting lignosulfonate by solvent extraction and (ii) introduction of a specific additive in the formulation. The first approach permitted to fabricate highly resistant capsules both in acidic, as well as in alkaline conditions, while in the second case the chemical structure of the additive, the diester diveratryl sebacate, allowed for fast kinetics of release, as values above 70% were reached after 24 h of incubation at pH 4 and pH 12
Novel biobased amines
No full textThe present invention relates to a method for producing an amidoamine by reacting a triacid derivative (I) with at least one amine (A), the at least one amine (A) being selected from diethylene triamine and a diamine (II). The molar ratio of the triacid derivative (I) to the at least one amine (A) is in the range of 1 : 2 to 1 : <3. The present invention further relates to the amidoamine as such,and to the use of said amidoamine as a cross-linking agent
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
Sustainable Strategies in the Synthesis of Lignin Nanoparticles for the Release of Active Compounds: A Comparison
No full textThe preparation of nanoparticles represents a powerful tool for lignin valorization, as it combines easy methodologies with high application potential. Different synthetic strategies and various lignin sources have been employed in the process. However, the great variability in the lignin structure prevents a direct comparison of the so far reported lignin nanoparticles (LNPs), especially as regards their physicochemical and functional properties. To this purpose, two green protocols, that is, solvent-antisolvent and hydrotropic, were optimized and used to generate LNPs from the same softwood kraft lignin. The nanomaterials were fully characterized to extrapolate structure/property relationships and reveal any differences in the mechanism of self-assembly. Furthermore, tests on methylene blue entrapment capacity and release behavior at two different pH values (2.0 and 7.4) evidenced a clear dependence on the LNPs characteristics and thus on the strategy adopted for their production
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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