1,720,980 research outputs found
Partial hydrogenation of a C18:3-rich FAME mixture over Pd/C
No full textThe study focuses on the partial hydrogenation of a C18:3-rich FAME mixture (a-linolenate/linoleate:
~3.5:1 mol/mol) taken as a model of FAME materials obtainable from alternative non-edible oils deriving
from non-food biomass, which are suitable feedstocks for 2nd generation biodiesel. High C18:1 yield and
selectivity required an accurate control of reaction time and temperature because of stearate generation
through consecutive reactions C18:3/C18:2/C18:1/C18:0. In n-heptane, under mild conditions
(50 °C, 0.1 MPa H2, 1 h), the FAME mixture was converted over Pd(5%)/C into C18:1 selectively (97.8%),
with high yield (81.1%). The final mixture was C18:3-free (0.1%) and showed a low content of stearate
(2.0%). Also the C18:2 component was markedly reduced (21.5%/16.7%). The content of trans-C18:1-
monoenes was 39.0%. A lower content of trans-C18:1 (16.4%) was attained at 0 °C (1.5 h). Under the
latter conditions, stearate and C18:3 in the final product were, respectively, 3.3% and 1.5%. Remarkably,
Pd/C can act as a tunable catalyst being able to promote effectively the full hydrogenation of the FAME
mixture to stearate under uncommon very mild conditions (0 °C, 0.1 MPa) within a relatively short time
(6 h). Under solventless conditions or in polar solvents (MeOH, THF, dimethyl carbonate), hydrogenation
was slower and less selective than in n-heptane
Partial hydrogenation of FAMEs with high content of C18:2 dienes. Selective hydrogenation of tobacco seed oil-derived biodiesel
Full text linkThe study reports on Pd(5%)/C-catalyzed partial hydrogenation of two C18:2-rich FAME mixtures (66.9 and 75.1 mol% C18:2) respectively prepared by esterification of technical linoleic acid and transesterification of tobacco seed oil. The mixtures were taken as representatives of C18:2-rich FAMEs obtainable from a variety of non-edible oils, which have potential as alternative feedstocks for the development of 2nd-generation biodiesel. In n-heptane, under mild conditions (15 °C; 0.1 MPa H2; 45–60 min; Pd/C, 2.1–5.7 wt%), the FAME mixtures were converted to C18:1 with high yield (83–92%) and selectivity (93–95%). Stearate abundance in the hydrogenated mixture was kept in acceptable limits (5.5–8.1%); E-C18:1 formation and C[dbnd]C scattering were respectively in the ranges 20.3–34.8% and 15–24%. At 0 °C, under moderate H2 pressure (1 MPa), the formation of trans-C18:1 monoenes and C[dbnd]C scrambling were less pronounced and respectively equal to 9.0% and 7% after 45 min, using a lower catalyst load (1.0 wt%): under the latter conditions the C18:2-component was markedly curtailed (66.9 → 13.6%) in the final product, while stearate abundance was still quite modest (9.3%). Geometric and positional isomerization increased over time with the progress of C18:2 conversion and were favored by higher temperature and catalyst load. Under solventless conditions hydrogenation was slower than in n-heptane; moreover, both cis → trans isomerization and C[dbnd]C bond scattering were larger than in the hydrocarbon solvent. Remarkably, Pd/C can act as a versatile catalyst, being able to effectively promote the conversion of the FAME mixtures to stearate under uncommon very mild conditions
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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