1,721,009 research outputs found
Separation of free fatty acids and acylglycerols
No full textRice bran (RB), a low-value co-product of rice milling, contains about 20 % oil (rice bran oil, RBO). RBO is characterized by a high free fatty acids (FFA) content. This feature makes RBO unsuitable for processing into edible oil; however, it can be a valuable feedstock for the production of chemicals. In fact, a significant number of high-value products require FFA in their manufacturing. The production of FFA by hydrolysis of natural oils and fats is a very important aspect in the economic exploitation of these naturally produced renewable raw materials. Owing to the mild conditions of biocatalyzed processes, enzymatic hydrolysis of RBO appears an attractive approach to preserve the integrity of the oil components. Furthermore, enzyme specificity allows a better control of by-products formation. We here report the separation by flash chromatography of FFA and acylglycerols in a sample of RBO before and after the enzymatic hydrolysis. Results of the separation scale-up are also presented
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
From batch to flow synthesis of 6-substituted purine ribonucleosides by enzymatic transglycosylation
No full textPurine nucleoside phosphorylases (PNPs, EC 2.4.2.1) catalyze the reversible phosphorolysis of the glycosydic bond of purine nucleosides and, upon addition of a second nucleobase, may transfer the glycosyl moiety to stereoselectively form a new nucleoside (transglycosylation).
Because of its wide substrate specificity,[1,2] a PNP from Aeromonas hydrophila (AhPNP) was exploited to catalyze a “one-pot, one-enzyme” batch transglycosylation, resulting in a moderate to high conversion (18-65%) of 6-substituted purine bases into a 23-compound library of 6-substituted purine-9-ribosides.[3] Afterwards, AhPNP was covalently immobilized (50% yield) in a pre-packed stainless steel column by reaction with glutaraldehyde and reduction of the imino groups. The resulting AhPNP-IMER (IMmobilized Enzyme Reactor) was coupled to a HPLC apparatus containing an analytical or semi-preparative chromatographic column associated with a UV-visible detector. This system (Figure 1) was exploited to perform the flow-synthesis of five 6-substituted purine ribonucleosides at a mg scale by transglycosylation. Under optimized (Design of Experiments, DoE) reaction conditions, coupling of transglycosylation with product separation resulted in a fast and efficient process (52-89% conversion) with minimized sample handling.[4]
References:
[1] Ubiali, D. et al. Adv. Synth. Catal. 2012, 354, 96-104.
[2] Calleri, E. et al. J. Chromatogr. B Analyt. Technol. Biomed. Life Sci. 2014, 968, 79-86.
[3] Ubiali, D. et al. Curr. Org. Chem. 2015, 19, 2220-2225.
[4] Calleri, E. et al. Adv. Synth. Catal. 2015, 357, 2520-2528
From batch to flow synthesis of purine ribonucleosides by enzymatic transglycosylation
No full textPurine nucleoside phosphorylases (PNPs, EC 2.4.2.1) catalyze the reversible phosphorolysis of the glycosydic bond of purine nucleosides; upon addition of a second nucleobase, these enzymes may transfer the glycosyl moiety to it, resulting in the chemo-, regio- and stereoselective formation of a new nucleoside (transglycosylation, Scheme 1). This chemoenzymatic process represents an advantageous alternative to conventional chemical strategies which are frequently hampered by several drawbacks such as multistep processes, need for protecting groups, low chemo-, regio- and stereoselectivity.
A PNP from Aeromonas hydrophila (AhPNP) has been recently characterized in terms of substrate specificity [1], also upon immobilization on the inner surface of a silica capillary coupled on-line with a chromatographic column [2].
Because of its wide substrate specificity, AhPNP was then exploited to catalyze the “one-pot, one-enzyme” transglycosylation of 7-methylguanosine iodide with a series of 6-substituted purines, resulting in a moderate to high conversion (18-65%) of the bases into a 23-compound library of 6-substituted purine-9-ribosides. Moreover, AhPNP was covalently immobilized (25 mg immobilized enzyme, 50% yield) in a pre-packed stainless steel column containing aminopropyl silica particles. The resulting AhPNP-IMER (Immobilized Enzyme Reactor) was coupled to a HPLC apparatus containing an analytical or a semi-preparative chromatographic column associated with a UV-visible detector. This system was used to synthesize five 6-substituted purine ribonucleosides at a mg scale by transglycosylation through a “flow-based” approach. Coupling of transglycosylation reaction and product separation resulted in a fast and efficient process (52-89% conversion) with minimized sample handling. To date, AhPNP-IMER completely retained its activity upon 50 reactions in 10 months.
[1] D. Ubiali, C. D. Serra, I. Serra, C. F. Morelli, M. Terreni, A. M. Albertini, P. Manitto, G. Speranza Adv. Synth. Catal. 2012, 354, 96-104
[2] E. Calleri, D. Ubiali, I. Serra, C. Temporini, G. Cattaneo, G. Speranza, C. F. Morelli, G. Massolini J. Chromatogr. B Analyt. Technol. Biomed. Life Sci. 2014, 968, 79-8
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
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