1,720,987 research outputs found
Kinetic Investigation of the Solvent-Free Hydrogenation of Dehydroisophytol
No full textIsophytol is a key intermediate in the industrial synthesis of vitamins, produced by selective hydrogenation of dehydroisophytol. This work presents a study of the kinetics of this process in the absence of any solvent. The experimental data were modeled using power-law kinetic expressions and mechanistic models based on Langmuir–Hinshelwood kinetics. The hypothesis of noncompetitive adsorption between hydrogen and organics was chosen in order to describe the changes in the reactivity of the system at varying temperatures (313–353 K) and pressures (5.0–9.0 bar). A simplified approach was used to describe the kinetics of the overhydrogenation reaction to the corresponding alkane. A list of the relevant kinetic and adsorption parameters, the result of an optimization procedure, is reported. The mathematical model, successfully validated, allows the prediction of the influence of the operating conditions and of the addition of quinoline, as reaction modifier, on the selectivity of the process
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
Kinetics and mass transfer of the hydrogenation of 2-methyl-3-butyn-2-ol in a structured Pd/ZnO/Al2O3 reactor
No full textThis work presents a study of the hydrogenation of 2-methyl-3-butyn-2-ol in flow over a structured catalyst. A porous tubular metal structure is coated with a layer of ZnO/Al2O3 and impregnated with palladium. This reactor is operated with recirculation of the process liquid and continuous supply of hydrogen with co-current upward flow. A Langmuir-Hinshelwood mechanism based on noncompetitive adsorption of hydrogen and organics is used to model the experimental results. The kinetic and adsorption parameters governing the process are estimated in the kinetic regime by means of a numerical optimization procedure. The extension of the model to the mass transfer limited regime, at lower hydrogen flowrates, allows the estimation of an overall mass transfer coefficient Kov. The reaction appears to be strongly dependent on the hydrogen flowrate with estimated Kov lower than 0.25 s−1 in the range of flowrates 0.1–0.5 nL min−1. The mathematical model, successfully validated, is able to accurately predict the concentration profiles of the species involved in the system at varying temperatures, in both kinetic and mass transfer limited regimes
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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