1,720,976 research outputs found
Metal-promoted synthesis of amidines containing the model nucleobases 1-methylcytosine and 9-methyladenine
Full text linkThe amidine complexes cis-[L2PtNH[double bond, length as m-dash]C(R){1-MeCy(-2H)}]NO3 (R = Me, 1a; Ph, 1b, Me3C, 1c; Ph2(H)C, 1d) and cis-[L2PtNH[double bond, length as m-dash]C(R){9-MeAd(-2H)}]NO3 (R = Me, 2a; Ph, 2b; Me3C, 2c; Ph2(H)C, 2d), are formed when cis-[L2Pt(μ-OH)]2(NO3)2 (L = PPh3) reacts with 1-methylcytosine (1-MeCy) and 9-methyladenine (9-MeAd) in solution of MeCN, PhCN, Me3CCN and Ph2(H)CCN. Reaction of 1a,b and 2a,b with HCl affords the protonated amidines [NH2[double bond, length as m-dash]C(R){1-MeCy(-H)}]NO3 (R = Me, 3a; Ph, 3b) and [NH2[double bond, length as m-dash]C(R){9-MeAd(-H)}]NO3 (R = Me, 4a; Ph, 4b) and cis-(PPh3)2PtCl2 in quantitative yield. Treatment of 3b and 4b with NaOH allows the isolation of the neutral benzimidamides NH2-C(Ph){1-MeCy(-2H)} (5b) and NH2-C(Ph){9-MeAd(-2H)} (6b). In the solid state 3b shows a planar structure with the hydrogen atom on N(4) cytosine position involved in a strong H-bond with the NO3− ion. Intermolecular H-bonds between the oxygen of the cytosine ring and one of the H atoms of the amidine-NH2 group allow the dimerization of the molecule. A detailed analysis of the spectra of 3b in DMF-d7 at −55 °C indicates the presence of an equilibrium between the species [NH2[double bond, length as m-dash]C(R){1-MeCy(-H)}]NO3 and [NH2[double bond, length as m-dash]C(R){1-MeCy(-H)}]2(NO3)2, exchanging with trace amounts of water at 25 °C. [15N,1H]-HMBC experiments for 5b and 6b indicate that the amino tautomer H2N-C(Ph){nucleobase(-2H)}, is the only detectable in solution and such structure has been confirmed in the solid state. The reaction of 5b and 6b with cis-L2Pt(ONO2)2 (L = PPh3), in chlorinated solvents, determines the immediate appearance of a pale yellow colour due to the coordination of the neutral amidine, likely in its imino form HN[double bond, length as m-dash]C(Ph){nucleobase(-H)}, to give the adducts cis-[L2PtNH[double bond, length as m-dash]C(Ph){nucleobase(-H)}]2+. In fact, addition of “proton sponge” leads to the immediate deprotonation of the amidine ligand with formation of the starting complexes 1b and 2b
Structural characterization of two solid state forms of the complex bis(1,1'-bis(diphenylphosphino)ferrocene) rhodium(I) tetraphenylborate.
No full textThis paper describes a work aimed at determining the molecular structure of a rhodium(I) complex along an experimental track in which a conventional X-ray single crystal structural analysis was accidentally preceded by a powder X-ray diffractometric investigation. The complex [Rh(dppf)(2)]BPh(4) (dppf=1,1'-bis(diphenylphosphino)ferrocene) was obtained from dichloroethane in two crystalline forms, hereafter referred to as alpha and beta, which are different in colour and in the content of lattice-entrapped solvent. Conventional and synchrotron powder wide angle X-ray diffractometry (WAXS), FT-IR, P-31 and H-1 NMR spectroscopy demonstrate that alpha and beta are dimorphic forms of the same molecular entity. The observed WAXS spectrum of the alpha form was computationally fitted (R=11.3%) with that calculated for [Rh(dppf)(2)]BPh(4), upon assuming that the molecular geometry of the title complex was identical to that of the already determined iridium analogue, i.e. square-planar with a pronounced tetrahedral distortion. X-ray single crystal structural analysis confirmed this conclusion. FT-IR, DSC and TG analyses have also been employed for a solid state characterization of the two species
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
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