1,721,033 research outputs found
Damming an electronic energy reservoir: ion-regulated electronic energy shuttling in a [2]rotaxane
No full textWe demonstrate the first example of bidirectional reversible electronic energy transfer (REET) between the mechanically bonded components of a rotaxane. Our prototypical system was designed such that photoexcitation of a chromophore in the axle results in temporary storage of electronic energy in a quasi-isoenergetic “reservoir” chromophore in the macrocycle. Over time, the emissive state of the axle is repopulated from this reservoir, resulting in long-lived, delayed luminescence. Importantly, we show that cation binding in the cavity formed by the mechanical bond perturbs the axle chromophore energy levels, modulating the REET process, and ultimately providing a luminescence read-out of cation binding. Modulation of REET processes represents an unexplored mechanism in luminescent molecular sensor development
Photodriven [2]rotaxane-[2]catenane interconversion
No full textA [2]rotaxane, whose thread component comprises a central dibenzylammonium group and 9-alkoxyanthracene stoppers and is hosted by a 24-dibenzo-8-crown bead, undergoes an efficient photocatenation step resulting in a [2]rotaxane-to-[2]catenane topology interconversion via a fully reversible [4π+4π] photocyclomerization of terminal anthracene groups
Ruthenium(ii) complexes based on tridentate polypyridine ligands that feature long-lived room-temperature luminescence
No full textIntegrating a matched organic chromophore and a Ru(II) complex with optimized tridentate polypyridine ligands instils reversible electronic energy transfer giving an unusually long room temperature luminescence lifetime (42 mu s) without compromising the emission quantum yield
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
Variations 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
Other Photoactive Inorganic Supramolecular Systems: Self-Assembly and Intercomponent Processes
No full text[ES] Se presenta una visión general de una serie de temas de fotoquímica/fotofísica supramolecular inorgánica, complementaria de otros capítulos de esta sección, con especial énfasis en la interacción de especies moleculares discretas. Estos temas incluyen ensamblajes e interacciones no covalentes de moléculas fotoactivas y la consecuencia de la interacción en sus propiedades. Se consideran los procesos fotoinducidos en sistemas supramoleculares, en particular la energía (uni y bidireccional) y la transferencia de electrones, que son de especial relevancia en la comprensión de los procesos biológicos o en las nuevas manifestaciones de separación de cargas fotoinducida en el marco de la fotosíntesis artificial y los materiales inteligentes. Otros temas tratados brevemente son el mecanochromismo, la emisión inducida por agregación y la transferencia supramolecular de quiralidad.[EN] An overview of a range of topics in inorganic supramolecular photochemistry/photophysics is presented, which are complementary to other chapters in this section, with particular emphasis on interacting discrete molecular species. These topics include noncovalent assemblies and interactions of photoactive molecules and the consequence of interaction on their properties. Photoinduced processes in supramolecular systems are considered, notably energy (uni- and bidirectional) and electron transfer, which are of particular relevance in the understanding of biological processes or in new manifestations of photoinduced charge separation in the framework of artificial photosynthesis and smart materials. Other topics briefly discussed include mechanochromism, aggregation induced emission, and supramolecular transfer of chirality.Martí-Centelles, V.; Mcclenaghan, ND. (2022). Other Photoactive Inorganic Supramolecular Systems: Self-Assembly and Intercomponent Processes. En Springer Handbook of Inorganic Photochemistry 2022. Springer Link. 733-763. https://doi.org/10.1007/978-3-030-63713-2_26S73376
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
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