1,720,970 research outputs found
On the acidity of liquid and solid acid catalysts. Part 3. Esterification of benzoic and mesitoic acids
No full textMethyl esters of benzoic and mesitoic acid have been prepared with high yields (>98 wt%) from the corresponding carboxylic acids
+ methanol in aprotic solvents over samples of H2SO4/SiO2 at 60 C. The results show a high catalytic efficiency of the solids but
also suggest an acid strength comparable to that observed in concentrated aqueous H2SO4 (range >90 wt%) when the acid requirements
for the esterification of analogous compounds in aqueous acid solutions are taken into account. Indeed, different reacting species, i.e.,
ArC(OH)+2 from benzoic acid and 2,4,6-triMe-ArC=O+ from mesitoic acid are involved in the esterification, but the mesitoyl cation
can be formed and esterified in the acidity ranges between 92 and 98 wt% H2SO4
On the acidity of liquid and solid acid catalysts: Part 1. A thermodynamic point of view
No full textThe protonation equilibria of weak bases (B) in solid acids (HClO4/SiO2, CF3 SO3H/SiO2, H2SO4/SiO2) were studied by UV
spectroscopy and the results were compared to those obtained for analogous compounds in concentrated aqueous solutions of strong
acids (HClO4, CF3SO3H, H2SO4). The behaviour of B in liquid (L) and solid (S) phase was analysed by titration curves, log[BH+]=[B]
ratios and thermodynamic pKBH+ values. It has been shown that the proton transfer process acid ! base (i.e., from (H+A..)(L,S) to
(BH+A..)(L,S)) can be described by the relationship observed between the activity coefficient terms that are to be taken into account for
acid–base equilibria occurring in nonideal systems (..log(fBfH+=fBH+)(L,S) = ..nBA log(fA..fH+=fHA)(L,S)) and can be estimated
by the nBA values. Two “activity coefficient functions” (i.e., Mc(B) = ..log(fBfH+=fBH+) and Mc(s) = ..log(fA..fH+=fHA)) were
used to describe, respectively, the equilibria of B and the equilibria of the acids in concentrated aqueous solutions and the meaning of
terms “activity coefficient function” and “protonating ability of an acid” were discussed. The difference between “acidity functions”,
determined for solutes (Ac(i)) and solvents (Ac(s)) in aqueous acids, and the Hx acidity functions, the latter developed for solutes in
analogous media by the Hammett procedure, was also show
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
