1,720,964 research outputs found
Directing the self-assembly of conjugated organic ammonium cations in low-dimensional perovskites by halide substitution
No full textAt present, two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) are drawing significant interest because of their potential use in different optoelectronic applications, that is, photovoltaics and photodetectors. Here, we report on a series of 2D layered HOIPs (Bit-C3)(2)PbX4 (with X = Cl, Br, and I) containing a 2,2'-bithiophene chromophore functionalized with a propylammonium tethering chain as a model molecule. The optical properties, crystal structure, and phase behavior of the 2D layered HOIPs are studied in depth. The crystal structures with the chemical formula (Bit-C3)(2)PbX4 (with X = Cl, and Br) are successfully obtained. Contrastingly, different crystal structures with an inorganic framework containing face- and corner-sharing octahedra were identified for the iodide-based HOIP. The phase diversity and thermal stability of the (Bit-C3)(2)PbX4 (with X = Cl, Br, and I) thin films were investigated via in situ measurements. Here, the presence of lower-dimensional hybrids with reduced electronic dimensionality within the iodide-based thin film is demonstrated. Additionally, we show that the 2D hybrid thermal stability is dependent on the type of lead(II)halide framework employed. We suggest that, via halide substitution from iodide to bromide and chloride, the molecular degrees of freedom of the Bit-C3 ammonium cations are reduced by spatial confinement of a smaller inorganic framework, therefore, limiting the formation of lower-dimensional hybrids besides the targeted 2D layered HOIP. This study illustrates the importance of efficiently utilizing the space supplied by the inorganic framework in which the organic ammonium cations can reside within a 2D layered HOIP. This, in turn, dictates how the organic ammonium cations arrange themselves within the organic layer and influences the adopted crystal structure of the hybrid
Study on the Dynamics of Phase Formation and Degradation of 2D Layered Hybrid Perovskites and Low‐dimensional Hybrids Containing Mono‐functionalized Oligothiophene Cations
No full textLow-dimensional (2D or 1D) hybrid perovskites are receiving increased attention due to their structural flexibility and enhanced stability compared to their 3D counterparts. Understanding the phase formation and degradation behavior of these materials is crucial towards their use in optoelectronic devices, since different crystal phases possess different optical and electronic properties. In this communication, we study the phase formation and degradation of a series of hybrids containing bithiophene, terthiophene and quaterthiophene derivatives. We show that two crystal phases can be formed for each of these systems, depending on the processing conditions. One phase corresponds to a 2D layered perovskite and the other phase has optical properties corresponding to a dimensionality intermediate between a 2D and a 1D hybrid
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
- …
