1,721,076 research outputs found
Reactivity in Confined Spaces
No full textThe chemistry that occurs within confined spaces is the product of a collection of forces, often beyond the molecule, and is not easily ascribed to singular factors. There is a breadth of material types that can define a confined space (e.g. macrocycles, interlocked molecules, porous and non-porous crystals, organic and inorganic/coordination cages) which are rarely discussed together. Studies of supramolecular entities in the solution and solid states are also not often compared in the same discussion, even though the concepts are often similar or can be easily transferred between the two.
Chapters in this book combine classical host-guest chemistry with catalysis, reactivity, and modern supramolecular chemistry. They cover the many different technologies used to describe and understand reactivity in confined spaces in one accessible title.
With contributions from leading experts, Reactivity in Confined Spaces will be relevant for graduate students and researchers working in supramolecular chemistry, both organic- and inorganic-based, homogeneous and heterogeneous catalysis, polymer chemistry, and materials science in general
Macrocycles, Catenanes and Rotaxanes
No full textInspired by the myriad enzymes found in living organisms, supramolecular chemists have investigated the cavities of both macrocycles and the related interlocked molecules catenanes and rotaxanes as catalytic and non-catalytic sites of chemical reactions. While macrocycles are typically easier to access synthetically, the interlocked structures of catenanes and rotaxanes offer exciting opportunities, including their innate three-dimensionality, large-amplitude motion of their interlocked components and chirality arising from the mechanical bond
Chapter 11. Stabilising and Characterising Homogeneous Catalysts in MOFs
No full textMetal-organic frameworks (MOFs) provide a crystalline scaffold that can act as a host for guest species. In this chapter, recent advances using MOFs as hosts for catalytic metal complexes are discussed. Particular emphasis is given to MOFs that can tether metal complexes to the framework such that the guests adopt a crystalline arrangement. The structures of the tethered complexes and their reactivity can be studied by a variety of techniques, including X-ray diffraction. We discuss examples of reactive species which are kinetically trapped and structurally characterised within an MOF and reports where tethering catalysts to MOFs can lead to enhanced catalytic performance. Finally, we describe guidelines for developing such approaches and for the use of MOFs to study catalytic processes. </p
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
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