1,720,977 research outputs found
Mechanistic insights into the BINOL-derived phosphoric acid-catalyzed asymmetric allylboration of aldehydes
Full text linkBINOL-derived phosphoric acids catalyze the asymmetric allylboration of aldehydes. DFT and QM/MM hybrid calculations showed that the reaction proceeds via a transition state involving both a hydrogen-bonding interaction from the catalyst hydroxyl group to the pseudoaxial oxygen of the cyclic boronate and a stabilizing interaction from the phosphoryl oxygen of the catalyst to the formyl hydrogen of the aldehyde. These interactions lower the energy of the transition structure and provide extra rigidity to the system. This mechanistic pathway is consistent with the experimentally observed enantioselectivity except in one case. We have used our model’s predictions to guide our own experimental work. The conflict is resolved in favor of our calculations.Fil: Grayson, Matthew N.. University of Cambridge; Reino UnidoFil: Pellegrinet, Silvina Carla. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Goodman, Jonathan M.. University of Cambridge; Reino Unid
RSC CICAG Open Chemical Science meeting: integrating chemical data from two symposia and a series of workshops
No full textIn November
2020 the Royal Society of Chemistry Chemical Information and Computer
Applications interest group (RSC CICAG) ran a five-day meeting entitled Open
Chemical Science (https://www.rsc.org/events/detail/42090/open-chemical-science). This event had three intertwined themes, Open
Data, Open Access publishing and a series of workshops highlighting a variety
of Open-Source tools for chemistry. The online event proved to be enormously
popular, with attendees from 45 different countries. The challenges involved in
converting what was planned as a three-day physical event into a five day virtual
event with three intertwined strands was recognised by the RSC with the award
of the “2021 Inspirational Committee Award” (https://www.rsc.org/prizes-funding/prizes/2021-winners/rsc-chemical-information-and-computer-applications-group/). The workshops in particular proved to be
enormously popular and spawned a year long series of further workshops</p
Dial-a-molecule workshop: computational prediction of reaction outcomes and optimum synthetic routes
No full textComputational prediction of reaction outcomes and optimum synthetic routes was a two-day meeting and workshop organised by the EPSRC Dial-a-molecule grand challenge network. Forty delegates discussed computer predictions of synthetic routes and reactions, and considered their relevance to contemporary chemistr
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
Synthesis of 2,3-O-benzyl-ribose and xylose and their equilibration
No full textThe preparation and NMR analysis of 2,3-di-O-benzyl D-ribose and 2,3-di-O-D-xylose are described. In DMSO-d(6) the sugars adopt a conformation in which the hydroxyl groups are in an equatorial position. In CDCI3 and CD2Cl2 the sugars adopts a conformation in which intramolecular hydrogen bonding plays an important role in determining the equilibrium composition. These findings were also confirmed by DFT studies and, in the solid phase, by X-ray single crystal diffractio
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
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