1,721,064 research outputs found
Recent development in the synthesis of eco-friendly polymeric antioxidants
No full textThe growing impact of environmental concerns of industrial processes carried out to the development of the socalled “Green Chemistry” approaches. By these technologies, the use of any hazardous substances within the synthesis of chemicals, nutraceuticals or therapeutics, is avoided, and considerable safety and biocompatibility advantages are raised.Among the different products prepared by Green Chemistry, high molecular weight antioxidants show remarkable appeal within the scientific community by virtue of their advantageous chemical and biological properties. These functional materials have been prepared by different synthetic strategies, classified in condensation methods, radical grafting and enzymatic catalysis. This review summarizes the chemical mechanisms of these strategies, and elucidates some of the most significant applications of the obtained products.- See more at: http://www.eurekaselect.com/124858/article#sthash.FYdLDiDb.dpu
Flavonoid-based pH-responsive hydrogels as carrier of unstable drugs in oxidative conditions
No full textIn this study, pH-responsive hydrogels, synthesized by the coupling reaction of polyacrylic acid and catechin, are proposed as carriers of oxidable drugs toward the GI tract. The presence of polyphenolic moieties in the network gives the polymers properties suitable for the release of unstable drugs in oxidative conditions. The characterization of the hydrogels is obtained by means of morphological and physico-chemical analyses, antioxidant assays and evaluation of the swelling behavior in media simulating the gastric (pH 1.0) and the intestinal (pH 7.4) tracts. The hydrogels are tested as pH-responsive carriers in in vitro release studies of folic acid and thiamine, two model drugs easily degraded by oxidative conditions simulated by UV irradiation and t-butyl hydroperoxide treatment, respectively. Results show that catechin-based carriers are able to control the release of drugs at different pH values, giving a remarkable improvement in the stability of the therapeutics
Application of LC with Evaporative Light Scattering detector for biogenic amines determination in fair tradee cocoa-based products
No full textIn this study, the separation of eight biogenic
amines (cadaverine, serotonin, histamine, spermidine,
spermine, tyramine, putrescine and β-phenylethylamine) by
a liquid chromatography (LC) method with evaporative light
scattering detection (ELSD) was performed. The LC–ELSD
method was validated by comparison of the results with those
obtained through LC–ultraviolet (UV) determination, based
on a pre-column dansyl chloride derivatisation step, and the
recorded data showed as both analytical methods can be interchangeably
used for biogenic amines determination. LC–
ELSD methodology showed good precision and permitted to
achieve, for standard solutions, limits of detection (LOD)
ranging from 0.01 to 0.02 μg ml−1 and limits of quantitation
(LOQ) ranging from 0.03 to 0.05 μg ml−1. The whole methodology,
comprehensive of the homogenization–extraction
process and LC–ELSD analysis, has been applied in the analysis
of several samples of fair trade cocoa derivatives. The
most abundant amine found was histamine for a total amount
of biogenic amines in the range 5.81–38.82 μg g−1. The
highest amounts of biogenic amines (BAs) were found in the
most processed products but never representing a possible risk
for consumer health, according to the toxicity levels reported
in literature and regarded as acceptable
Molecularly Imprinted Polymers Based On Amidic Functional Monomers For Selective Recognition Of Cholesterol In Aqueous Media
No full textThe aim of this work was to investigate the possibility of employing
amidic functional monomers for the preparation of Molecularly
Imprinted Polymers (MIPs) able to bind selectively cholesterol in aqueous
media. For this purpose, Acrylamide and N,N-Dimethylacrylamide were
employed in order to maximize the hydrogen bound forming both in
pre-polymerization complex and in rebinding experiments which were
performed in polar solvents; in particular, an acetonitrile:water (7:3 v/
v) mixture was employed. The so obtained matrices showed a good
binding capacity towards the template molecule, they bound, indeed,
much more cholesterol than the corresponding non-imprinted ones.
Finally, the polymers affinity for cholesterol and its selectivity using two
steroids quite similar to cholesterol such as progesterone and
hydrocortisone. The synthesized materials, showed a good selectivity,
because they recognised less effectively the two analogues
Biogenic amines as quality marker in organic and fair-trade cocoa-based products
No full textIn this study, the quantitative determination of eight biogenic amines (cadaverine, serotonin, histamine, spermidine, spermine, tyramine, putrescine and β-phenylethylamine) by an liquid chromatography method with evaporative light scattering detection was performed. The analysis of several samples of conventional, organic and fair trade cocoa-derivatives showed that organic and fair trade samples always contain much lower amine concentrations in comparison with their conventional counterparts, supporting the idea that biogenic amines can be regarded as cocoa quality markers. Irrespective of the kind of sample, results also showed that the most abundant amines were histamine, tyramine, spermidine, putrescine and spermine while β-phenylethylamine, cadaverine and serotonine have been found more rarely, all the amines never reaching dangerous amounts for consumer health. With the aim to confirm the experimental results, clustering analysis was performed on samples and instrumental results using principal component analysis
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
Cambiamenti nel profilo di ammine biogene durante il periodo di conservazione di campioni di bottarga
No full textCambiamenti nel profilo di ammine biogene durante il periodo di conservazione di campioni di bottarg
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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