1,720,955 research outputs found
A multimembrane enzyme reactor operating in an electric field.
No full textA multimembrane enzyme reactor, operating under an electric field, is described. This reactor is based on the concept of isoelectric traps, by which a pair of membranes, of appropriate pi value, are able to trap the enzyme, the buffering ions (which have to be amphoteric), the substrate and, if needed, cofactors. Charged reaction products can thus leave the enzyme chamber and be recovered in other chambers where they are trapped by the same isoelectric mechanism (if amphoteric). The unique advantages of such reactors are absence of enzyme inhibition by a feed-back mechanism and reaction yields approaching 100 %. Examples of a urease and a trypsin/casein reactor are given
Isoelectrically trapped enzymatic bioreactors in a multimembrane cell coupled to an electric field: theoretical modelling and experimental validation with urease.
No full textA novel type of immobilized enzyme reactor operating under an electric field is here reported: a multicompartment immobilized enzyme reactor (MIER). In this experimental set-up, the enzyme and zwitterionic buffering ions are trapped in between two isoelectric membranes, having isoelectric point (pl) values so far apart as to trap the enzyme by an isoelectric mechanism, while allowing operation at pH optima, even when the latter pH value is quite removed from the enzyme pl. As an example, urease (pl 4.9) is trapped between a pl 4.0 and a pl 8.0 membranes, thus permitting operation (via suitable amphoteric ions buffering at pH 7.5) at the pH of optimum of activity (pH 7.5). The charged product (ammonium ions) quickly leaves the enzyme chamber under the influence of the electric field, thus allowing sustained activity for much longer time periods than in conventional reactors. As an example, while in a batch reactor 90% of original enzyme activity is lost in 200 min, only 2% activity is lost in the same period in the MIER reactor. As an additional bonus, the MIER reactor allows conversion rates of approximately 95% in a wide range of substrate concentrations, whereas batch-type reactors rarely achieve better than 50% conversion under comparable experimental conditions
Continuous enzymatic hydrolysis of ß-casein and isoelectric collection of some of the biologically active peptides in an electric field.
No full textAmong the milk proteins, bovine beta-casein has the peculiarity of containing in its sequence some peptides liable to interfere in mineral nutrition and some peptides with opioid (casomorphines), antihypertensive, and immunomodulatory activities. In this work we propose a novel type of multicompartment enzyme reactor, operating under an electric field, for the continuous hydrolysis of milk proteins such as beta-casein. The enzyme trypsin is trapped, with zwitterionic buffering ions and its substrate beta-casein, in solution between two isoelectric membranes having pI values encompassing the isoelectric point of the enzyme. Additionally, beta-casein is captured inside the same reaction chamber with the aid of sieving membranes, since its pI is too far away from the pI of trypsin. This setup permits the continuous operation at the pH of optimum of activity. The peptides, arising from tryptic hydrolysis of beta-casein, are removed under the influence of the electric field and collected in different chambers in which they are isoelectric and isoionic as well. The purity of the peptides collected is ascertained by capillary zone electrophoresis and their identity confirmed by N-terminal sequencing and MALDI-TOF mass spectrometry. This setup allows continuous harvesting of some biologically-active peptides in a pure form. The major advantages of such a reactor system over conventional batch reactors are the great increase in enzyme utilization efficiency and the overall reactor productivity
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
- …
