1,721,097 research outputs found
Density Functional Theory Study of the Structure and 13C Chemical Shifts of Retinylidene Iminium Salts
No full textWe present a density functional theory calculation of the structure and C-13 chemical shifts of retinylidene molecules which constitute the chromophores of the natural pigments rhodopsin and bacteriorhodopsin. We compare our results with recent X-ray and NMR spectroscopic data on several retinylidene iminium salts characterized by different cation-anion interactions. In agreement with crystallographic data, we find that the amplitude of the bond length alternation between single and double carbon bonds is strongly reduced in the vicinity of the protonated Schiff base nitrogen. The chemical shifts along the carbon chain are in very good agreement with the experimental values for the neutral retinylidene compounds and in fairly good agreement for the charged retinylidene compounds. We find that the C-13 chemical shift is mostly affected by the cation-anion distance and to a lesser extent by the presence of hydrogen bonding interaction between the protonated Schiff base of retinal and the counterion. The correlation between C-13 chemical shift and atomic charge along the conjugated chain of retinals is found to depend strongly on the specific compound. This result suggests some caution in using atomic charges alone to establish the position of the counterion relative to the chromophore in rhodopsin
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
THE SYMPTOM MANAGEMENT MODEL(SMS) TOOL FOR PREDICTION AND ASSESSMENT OF CERTAIN SYMPTOMS THAT AFFECT QUALITY OF LIFE OF PATIENTS WITH SMALL AND NON SMALL CELL LUNG CANCER CANDIDATES FOR RADIOCHEMOTHERAPY
No full textVariations 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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