1,721,170 research outputs found
The Role of supramolecular interactions in magnetic systems: 1,8-Napthalimides and other π-containing species
No full textSupramolecular chemistry is a rapidly expanding area of research having seen the award of two Nobel prizes within the last 30 years. Whilst this means the phenomenon is well known, the important role it plays within inorganic structural chemistry is only beginning to be fully appreciated. The most common supramolecular interaction utilized is hydrogen bonding, which is fundamental for all life by allowing liquid water to exist over a wide range of temperatures and pressures. In addition to hydrogen bonding, there are other intermolecular interactions such as π-π, van der Waals, and the less common halogen, chalcogen, tetrel, or pnictogen bonds. The prevalence of hydrogen bond donors and acceptors in most systems can lead to unpredictability of the long-range structure, making rational design of specific supramolecular architectures a complex task. In a similar vein, halogen, chalcogen, tetrel, and pnictogen bonds can often prove unwieldy or challenging to work with as they typically require specialist design. The use of π-π interactions is however an attractive idea; these systems are typically easy to work with, stable, and able to be incorporated into many systems. Magnetically interesting compounds have had a large success over the same time frame, with the first single molecule magnet (SMM) being produced in the early 1990s. This field has continued to grow and recently, in 2018, reached a major milestone with the first reported system which retains the slow magnetic relaxation required of an SMM compound above the temperature of liquid nitrogen. The result has long been thought to be the first step on the route to incorporating SMMs into working components such as data processing and storage devices, as current SMM devices require expensive and finite liquid helium. Whilst the definition of a single molecule magnet is “a molecule that shows slow relaxation of the magnetisation of purely molecular origin”, researchers have recently begun to believe that the SMM properties can be modulated by the non-local environment in a similar manner to another magnetic phenomenon, spin crossover. This research explores the use of supramolecular design and control within magnetochemistry by producing a series of 1,8-naphthalimide based complexes to investigate their structure directing properties, with a view for inclusion into existing SMM architectures. The 1,8-naphthalimide system allows for a wide variety of components and simple synthesis resulting in a wide library of available ligands for almost any purpose. This organic species also provides a rigid framework for building πbased supramolecular architectures given the predictability of the interactions between the naphthalimide molecules. We detail how the predictability of the system allowed us to build layered networks which demonstrate SMM characteristics, although not in the frequency region of a standard SQUID magnetometer. This research also investigates stronger π-based interactions using radical enhanced pancake-like bonds. The 9,10-phenanthrenequinone system used here provided a facile route to the 9,10-phenanthrenesemiquinone radical via an in situ reduction. When combined with the presence of Ln(III) ions, the radical ligands form intramolecular π-bonds with an exceptionally short distance encapsulating two lanthanide ions in a cage consisting of four ligands. The exceptional strength of this pancake bond effectively forces the two lanthanide ions together, resulting in a strong electrostatic interaction which appears to quench the quantum tunnelling of magnetisation relaxation pathway. Further demonstrating the use of π-based interactions in SMM research. The future roadmap for modification to include supramolecular pancake-like bonds is provided in the future work section
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Structural and magnetic properties of novel dinuclear Cu(II) complexes featuring triazolyl-naphthalimide ligands
No full textVariations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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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