1,720,966 research outputs found
Spin State in Homoleptic Iron(II) Terpyridine Complexes Influences Mixed Valency and Electrocatalytic CO2 Reduction
No full textTwo homoleptic Fe(II) complexes in different spin states bearing superbasic terpyridine derivatives as ligands are investigated to determine the relationship between spin state and electrochemical/spectroscopic behavior. Antiferromagnetic coupling between a ligand-centered radical and the high-spin metal center leads to an anodic shift of the first reduction potential and results in a species that shows mixed valency with a moderately intense intervalence-charge-transfer band. The differences afforded by the different spin states extend to the electrochemical reactivity of the complexes: while the low-spin species is a precatalyst for electrocatalytic CO2 reduction and leads to the preferential formation of CO with a Faradaic efficiency of 37%, the high-spin species only catalyzes proton reduction at a modest Faradaic efficiency of approximately 20%.Fil: Suhr, Simon. Universität Stuttgart; AlemaniaFil: Schröter, Nicolai. Universität Stuttgart; AlemaniaFil: Kleoff, Merlin. Freie Universität Berlin; AlemaniaFil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Hunger, David. Universität Stuttgart; AlemaniaFil: Walter, Robert. Universität Stuttgart; AlemaniaFil: Lücke, Clemens. Universität Stuttgart; AlemaniaFil: Stein, Felix. Universität Stuttgart; AlemaniaFil: Demeshko, Serhiy. Universität Göttingen; AlemaniaFil: Liu, Hang. Universität Stuttgart; AlemaniaFil: Reissig, Hans-Ulrich. Freie Universität Berlin; AlemaniaFil: van Slageren, Joris. Universität Stuttgart; AlemaniaFil: Sarkar, Biprajit. Universität Stuttgart; Alemani
Entwicklung von Flussplattform-Designs und deren Anwendung für die Synthese von Naturstoffen, Ferrocenylaziden und Benzotriazolen
No full textIn this work, a modular flow platform was designed and employed in the synthesis of natural products and for two methodology projects. As the established liquid-driven flow shows several disadvantages, in particular the occurrence of dispersion phenomena between solvent and reagent solutions resulting in high reagent losses, the new concept of an argon-driven flow was pursued. In this way, dispersion phenomena were suppressed, opening up new ways for the handling of valuable intermediates in flow on small scale. To avoid common, unsustainable drying protocols of flow reactors, “Schlenk-in-flow” procedures were developed adopting well-established Schlenk techniques to flow chemistry. To realize these concepts, the extensive use of 3D-printing to enable the manufacturing of tailormade equipment turned out as a key technique.
As a proof of concept, two intermediates in natural product synthesis were prepared in reproducible yields slightly higher than in batch. In addition, a new method for the site-selective C–H chlorination of (+)-sclareolide by decatungstate catalysis was developed, allowing improved scalability and higher reaction rates in flow.
Furthermore, a general method for the synthesis of functionalized ferrocenyl azides and amines was developed in batch and flow. By halogen-lithium exchange of ferrocenyl halides and subsequent trapping with tosyl azide, a variety of ferrocenyl azides was obtained. In flow, the halogen-lithium exchange and the reaction with tosyl azide proceeded significantly faster due to improved mixing. Also, the subsequent thermolysis of ferrocenyl triazene intermediates could be accelerated at elevated temperature in flow as a result of the enhanced heat-transfer in tube reactors, while thermal strain of hazardous ferrocenyl azides could be minimized. Precipitating para-tolyl sulfinates were efficiently kept in turbid flow by utilizing a triphasic flow regime. The advantageous safety and scalability profile of the flow process was demonstrated on gram scale. Using a Staudinger protocol, ferrocenyl azides were reduced in consistently good yields to the corresponding ferrocenyl amines.
Employing the flow platform and a selection of the prepared ferrocenyl azides, a protocol for the rapid and scalable synthesis of benzotriazoles via [3+2] cycloaddition of azides and arynes was developed. By making use of the advantages of flow chemistry in the safe handling of potentially explosive azides and the improved reaction control of highly reactive arynes, the process could be performed at elevated temperature providing faster reactions and an increased productivity. The scalability of the flow protocol was demonstrated for the synthesis of an antibacterial and antifungal benzotriazole on gram scale
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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