1,720,990 research outputs found
Controllable intramolecular motions that generate fluorescent signals for a metal scorpionate complex
Full text linkSimply by changing the pH value, the side chain of complex 1 can be reversibly moved between two positions. Coordination to the metal center through the nitrogen atom of the side chain at moderate pH values is accompanied by a decrease in fluorescence intensity (from IF=100% to IF=60%). A further decrease is observed upon deprotonation of the bound water molecule at higher pH (IF≤2%). Therefore, 1 can be seen as a molecular three-position switch
Anion Recognition by a Dicopper(II) Cryptate
No full textThe dicopper(II) complex of the bistren cage 1, in an aqueous solution buffered at pH = 8, incorporates polyatomic anions (NCO-, NCS-, N-3(-), SO42-, HCO3-, CH3COO-) according to a 1:1 stoichiometry. Log K values range over the 2-5 interval and show a sharp peak selectivity with respect to the anion 'bite', i.e. the distance between the two proximate donor atoms of each anion. The peak maximum lies at about 2.3 Angstrom, a bite length corresponding to the N-3(-) anion. Thus, the dicopper cryptate does not recognize anion size or coordinating tendencies, but simply recognizes the bite length
A ditopic tetradentate pyridyl amine ligand containing an anthracene fragment: fluorescence intensity and ‘closed’ vs. ‘open’ species formation in the presence of Cu2+, as a function of pH
No full textThe compounds 9,10-bis(2-pyridylmethylaminoethyl)anthracene L1 and 9-(2-pyridylmethylaminomethyl)anthracene L2, based on nitrogen donors of the amine and pyridine type, were prepared and their properties examined in aqueous solution (water–1,4-dioxane 1∶4 v/v). The protonation constants of both have been determined by means of potentiometric titrations and the obtained species vs. pH distribution diagrams superimposed on the fluorescence intensity vs. pH profiles. This revealed an ‘off-on-offhair space’ window behaviour: the fluorescence intensity is high only in the pH range in which both free pyridine and protonated amines exist. Moreover, the formation constants of the complex species which form in the presence of 1 or 0.5 (in the case of L1 and L2, respectively) equivalent of CuII have been determined by means of potentiometric titrations. In particular, in the case of the tetradentate ditopic ligand L1 the ‘closed’ two ligand–two metal species [Cu2L12]4+ and [Cu2L12(OH)]3+ form in basic solution, in addition to two ligand–one metal partially protonated ‘open’ complex species. Moreover, a strong variation of the fluorescence intensity of the anthracene fragment signals the formation of the ‘closed’ species with respect to the ‘open’ ones, while a more subtle variation of the fluorescence intensity also allows one to distinguish between [Cu2L12]4+ and [Cu2L12(OH)]3+
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
La platería andina colonial a través de la historia de la familia Sacayco
Full text linkEl platero indio en la colonia ha sido poco estudiado por los investigadores. No solo desde el punto de vista social, sino también económico y tecnológico. Quizás la falta de interés radique en la poca información que aparece en los documentos coloniales hallados hasta el momento sobre estos artesanos, además de la casi imposibilidad de identificar los objetos manufacturados por estos especialistas, en vista de que las piezas carecen de firma. En estas líneas pretendemos mostrar, mediante el uso de documentos históricos y de estudios arqueológicos, cómo es que estos plateros indios buscaron un lugar en la nueva sociedad luego de la conquista europea, y cómo se incorporaron a esta gracias a su destreza y habilidad en el arte de la platería.Colonial Indian silversmiths have been barely studied by researchers. Not only from the social point of view, but also from the economic and technological ones. Perhaps the lack of interest lies in the scarce information about these artisans in the Colonial documents found so far, besides that it is almost impossible to identify the objects manufactured by these specialists due to the lack of signature on the objects. In this paper, we intend to show through the use of historical documents and archaeological studies, how these Indian silversmiths look for a place in the new society after the European Conquest, and how they were incorporated due to their skills and ability as silverware artisans.O ourives índio na colônia tem sido pouco estudado por pesquisadores. Não só desde o ponto de vista social, mas também económico e tecnológico. Talvez a falta de interesse radique na pouca informação que aparece nos documentos coloniais encontrados até o momento sobre esses artesãos, além da quase impossibilidade de identificar os objetos manufaturados pelos especialistas, em vista de que as peças carecem de assinatura. Nestas linhas pretendemos mostrar, mediante o uso de documentos históricos e de estudos arqueológicos, como é que esses ourives índios procuraram um lugar na nova sociedade depois da conquista europeia, e como se incorporaram a esta graças a sua destreza e habilidade na arte da ourivesaria
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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