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Lipophilic Cage Ligands: Synthesis, Spectroscopic Properties and Applications
Full text linkLipophilic Cage Ligands: Synthesis, Spectroscopic Properties and Application
NMR Investigation of Lipophilic Cage Ligands. Part 2. Structural Assignments and Conformational Properties of the Ligand 12-hexadecyl-7,17,22,27-tetraoxa-1,4,10,14-tetraazatricyclo (12.5.5.54,10) nonacosane and of its Sodium, Potassium & Silver Complexes
No full textTwo-dimensional homonuclear (COSY, phase-sensitive double quantum filtered COSY) and heteronuclear shift correlated experiments were employed to characterize fully the cylindrical cage ligand 12-hexadecyl-7,17,22,27-tetraoxa-1,4,10,14-tetraazatricyclo[12.5.5.54,10] nonacosane (1) and its sodium, potassium and silver complexes. 13C NMR variable temperature experiments indicated that the free ligand 1 is a mobile molecule in a fast conformational equilibrium at room temperature, whereas its sodium complex is more rigid, some degrees of freedom being allowed in that part of the molecule featuring the longest bridge. The potassium derivative behaves similarly to its sodium counterpart. For the silver complex the differences observed have been attributed to a stronger interaction of the metal ion with nitrogen atoms
New Lipophilic Multidentate Ligands: Effective Complexing Agents for Anions Activation in non Polar Media
No full textNMR analysis of new Lipophilic Multidentate Ligands: Effective Complexing Agents for Anions Activation in non Polar Medi
13C and 1H Two-dimensional NMR Characterization of the Sodium Perchlorate Complex of a New Tetraoxatetraaza Lipophilic Cage Ligand
No full text13C and 1H NMR characterization of the sodium perchlorafe complex of a new tetraoxatetraaza lipophilic cage ligand (1) derived from 1,7-dioxa-4,10-diazacyclododecane has been performed. 1H homonuclear correlated and 1H J-resolved two-dimensional experiments allowed the recognition of resonances due to different types of OCH2CH2N fragments, and of those of the hydrogens of the bridging chains. 13C resonances have been assigned on the basis of a 13C1H heteronuclear correlated two-dimensional experiment, together with the 13C NMR spectra of the synthetic precursors of 1. 13C spin-lattice relaxation times and NOE measurements established that the unique relaxation mechanism is dipole-dipole; the calculated rotational correlation times indicated that molecular reorientation is isotropic. 13C spectra and relaxation times obtained in different solvents showed that specific solute-solvent interactions are absent
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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