1,720,965 research outputs found
Synthesis, physico-chemical studies, non-linear optical properties and DFT calculations of a new non-centrosymmetric compound: (3-ammoniumpyridinium)tetrachloridozincate (II)
No full textA new non-linear optical inorganic–organic hybrid material [H 3 NCH 2 (C 4 H 4 NH)]ZnCl 4 (3-ampH 2 )ZnCl 4 ) has been synthesized and characterized by single-crystal X-ray diffraction, thermal analysis and UV–visible absorption. The compound crystallizes in the non-centrosymmetric orthorhombic space group Cmc2 1 allowing in principle non-linear optical properties. The structure consists of (3-ampH 2 ) 2+ cations disordered in two possible orientations stabilized through Coulombic and hydrogen-bond interactions with isolated ZnCl 42− anions. Intermolecular weak π-π stacking interactions are also observed between pyridine rings. The thermal analysis indicate that (3-ampH 2 )ZnCl 4 starts to melt at 585 K, together with the beginning of its decomposition. UV–visible measurements shows that the material is transparent in a wide range of UV–visible region with a lower cut off wavelength of 261.65 nm. The wide range of transparency in the UV–visible region and the high decomposition temperature make of (3-ampH 2 )ZnCl 4 a good candidate for NLO application. Density functional theory (DFT) calculations indicate that the first-order hyperpolarizability β tot is about 23.38 times more than that of Potassium Dihydrogen Phosphate. (3-ampH 2 )ZnCl 4 is a potential good NLO material
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
Synthesis and crystal structure of 4-fluorobenzylammonium dihydrogen phosphate, [FC6H4CH2NH3]H2PO4
No full textThe asymmetric unit of the title salt, [p-FC6H4CH2NH3]+·H2PO4−, contains one 4-fluorobenzylammonium cation and one dihydrogen phosphate anion. In the crystal, the H2PO4− anions are linked by O—H...O hydrogen bonds to build corrugated layers extending parallel to the ab plane. The FC6H4CH2NH3+ cations lie between these anionic layers to maximize the electrostatic interactions and are linked to the H2PO4− anions through N—H...O hydrogen bonds, forming a three-dimensional supramolecular network. Two hydrogen atoms belonging to the dihydrogen phosphate anion are statistically occupied due to disorder along the OH...HO direction
Synthesis and crystal structure of 4-(2-ammonioethyl)morpholin-4-ium dichloridodiiodidocadmate/chloridotriiodidocadmate (0.90/0.10)
No full textThe crystal structure of the title compound, (C6H16N2O)[CdCl1.90I2.10], a new organic–inorganic hybrid salt synthesized in the form of single crystals, consists of discrete statistically distributed dichloridodiiodidocadmate/chloridotriiodidocadmate anions (occupancy ratio 0.90:0.10) and 4-(2-ammonioethyl)morpholin-4-ium cations, [NH3(CH2)2NH(CH2)4O]2+. The cations are linked by intermolecular N—H...O hydrogen bonds, forming corrugated chains extending parallel to the c axis. The [CdCl1.90I2.10]2− tetrahalidocadmate anions lie between the chains to maximize the electrostatic interactions and are connected with the organic cations via N—H...Cl and C—H...Cl(I) hydrogen bonds developing in the ab plane and leading to the formation of a three-dimensional network structure. The tetracoordinate CdII atom has a distorted tetrahedral conformation, with a τ4 index of 0.87
Crystal structure of non-centrosymmetric bis(4-methoxybenzylammonium) tetrachloridozincate
No full textThe structure of the title non-centrosymmetric organic–inorganic hybrid salt, (C8H12NO)2[ZnCl4], consists of two 4-methoxybenzylammonium cations sandwiched between anionic layers, formed by isolated tetrachloridozincate tetrahedra. The double layers extend parallel to the ac plane. The crystal packing is assured by Coulombic interactions and by a complex N—H...Cl and C—H...Cl hydrogen-bonding system mostly involving the positively charged ammonium groups and the chloride ligands of the isolated tetrahedral [ZnCl4]2− units. One of the methyleneammonium groups is disordered over two sets of sites in a 0.48 (2):0.52 (2) ratio. The crystal investigated was twinned by non-merohedry with a twin component ratio of 0.738 (2):0.262 (2)
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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