1,721,197 research outputs found
When defects turn into virtues: the curious case of zirconium-based metal-organic frameworks
Full text linkZirconium-based metal-organic frameworks (Zr-MOFs) are one of the most attractive classes of MOF materials, due to their superior thermal, chemical and mechanical stability. Recently, Zr-MOFs have been shown to feature an unusually high concentration of defects without suffering from severe loss of stability. This feature makes Zr-MOFs unique among MOF materials and is generating additional interest around them. Defects have a significant impact on porosity, thermal properties, mechanical properties, Lewis and Brønsted acidity. Researchers have quickly recognized that defects can be engineered to tune the physical-chemical properties of Zr-MOFs, opening up new avenues for their practical application. The scope of the present review article is to provide a comprehensive account of the progress made in this field since the discovery of defects in Zr-MOFs in 2011 and to point out some relevant controversies and open issues of fundamental nature that need to be addressed to improve the understanding of the very nature of defects
A Simple Synthesis of 3-tributylstannylfuran and 3-lithiofuran
No full text3-Tributylstannylfuran is prepared in two steps from 2-butyne-1,4-diol. © 1985 Georg Thieme Verlag, Stuttgart, Germany. All rights reserved
Synthesis of Pyrazoles by 1,3-Dipolar Cycloaddition under Aqueous Micellar Catalysis
Full text linkEthyl diazoacetate (EDA), which is easily prepared from ethyl glycinate and NaNO2, reacts in situ with alkynes in a water micelle environment without organic solvent to form pyrazoles. The reaction is pH dependent, as in the presence of protic catalysis (H2SO4 4%, pH 3.5) a mixture of 3,5- and 4,5-disubstituted pyrazoles was obtained, while, at pH 5.5, only the 3,5-disubstituted isomer was obtained. The presence of the surfactant TPGS-750-M was crucial to secure clean crude reaction mixtures and high yields of the products. The same protocol was successfully applied to the synthesis of substituted pyrazolines. © 2022 The Author
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
Preparation of Beta-trialkylstannyl and Gamma-trialkylstannyl Alcohols and Thiols By Ring-opening of Oxiranes, Oxetanes, Thiiranes, and Thietanes With Trimethylstannyllithium
No full textAppropriate 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
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