1,720,975 research outputs found
“Selective Oxidation of O-Isopropylidene Derivatives of Diols to 2-Hydroxy Ketones Employing Dioxiranes”
No full textOxyfuncionalization of Non-Natural Targets by Dioxiranes. 5. Selective Oxidation of Hydrocarbons Bearing Cyclopropyl Moieties.”
No full textThe powerful methyl(trifluoromethyl)dioxirane (1b) was employed to achieve the direct oxyfunctionalization of 2,4-didehydroadamantane (5), spiro[cyclopropane-1,2′-adamantane] (9), spiro[2.5]-
octane (17), and bicyclo[6.1.0]nonane (19). The results are compared with those attained in the
analogous oxidation of two alkylcyclopropanes, i.e., n-butylcyclopropane (11) and (3-methyl-butyl)-
cyclopropane (14). The product distributions observed for 11 and 14 show that cyclopropyl activation
ofR-C-H bonds largely prevails when no tertiary C-H are present in the open chain in the tether;
however, in the oxyfunctionalixation of 14 cyclopropyl activation competes only mildly with
hydroxylation at the tertiary C-H. The application of dioxirane 1b to polycyclic alkanes possessing
a sufficiently rigid framework (such as 5 and 9) demonstrates the relevance of relative orientation
of the cyclopropane moiety with respect to the proximal C-H undergoing oxidation. At one extreme,
as observed in the oxidation of rigid spiro compound 9, even bridgehead tertiary C-H’s become
deactivated by the proximal cyclopropyl moiety laying in the unfavorable “eclipsed” (perpendicular)
orientation; at the other end, a cyclopropane moiety constrained in a favorable “bisected” orientation
(as for didehydroadamantane 5) can activate an “R” methylene CH2 to compete effectively with
dioxirane O-insertion into tertiary C-H bonds. Comparison with literature reports describing similar
oxidations by dimethyldioxirane (1a) demonstrate that methyl(trifluoromethyl)dioxirane (1b)
presents similar selectivity and remarkably superior reactivit
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
On the reaction of aminoxyls with dioxiranes.
No full textAbstract: In the reactions of dimethyldioxirane (la) and methyl(trifluoromethyl)dioxirane (Ib) with 2,2,6,6-tetramethylpiperidinyl-1-oxyl (2) (TEMPO) in acetone, the corresponding methoxyamine 1-methoxy-2,2,6,6-tetramethylpiperidine (5) is produced in greater than or equal to 98% yield, both in air and under N-2, and in the absence or presence of a hydrocarbon (adamantane). Kinetic experiments show that aminoxyl 2 triggers the radical decomposition of the dioxirane, in addition to scavenging methyl radicals derived therefrom. The reactions of an aminoxyl less prone to oxidation, namely 1,2-dihydro-2-methyl-2-phenyl-3H-indol-3-one-1-oxyl (4), with dioxiranes la and Ib in acetone have also been studied. In these cases, not only is the corresponding methoxyamine 8a produced (yield 12-16%), but quinoneimine-N-oxides 10 (yield 12-21%) and 11 (yield 18-19%) are also formed. Furthermore, significant amounts (8-14%) of the amine 9 (the product of deoxygenation of 4) can be isolated. These observations provide useful information concerning the free-radical mechanism that follows the initial attack by the aminoxyl at the dioxirane
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