1,720,973 research outputs found
Development of nitrile-functionalized ionic liquids for C-C coupling reactions: Implication of carbene and nanoparticle catalysts
No full textA series of nitrile-functionalized imidazolium salts (many of which are liquid at room temperature) have been prepared. The reactivity of these salts with PdCl(2) has been studied, resulting in salts containing a tetrachloropalladate dianion or compounds in which the nitrile substituent coordinates to the palladium center. Further derivation of the latter compounds affords carbenes. All the new compounds have been characterized by spectroscopic methods and nine of them by single-crystal X-ray diffraction. The catalytic activity of the different palladium salts in Suzuki, Stille, and Heck reactions has been evaluated in some of the nitrile-functionalized ionic liquids (ILs) and compared with that of nonfunctionalized ILs, providing insights into the nature of the actual catalyst. In some instances, palladium nanoparticles have been identified, but the nature of the catalyst strongly depends on the IL employed
In vitro and in vivo evaluation of ruthenium(II)-arene PTA complexes
No full textThe antitumor activity of the organometallic ruthenium(II)-arene complexes, RuCl2(è6-arene)-
(PTA), (arene ) p-cymene, toluene, benzene, benzo-15-crown-5, 1-ethylbenzene-2,3-dimethylimidazolium
tetrafluoroborate, ethyl benzoate, hexamethylbenzene; PTA ) 1,3,5-triaza-7-
phosphaadamantane), abbreviated RAPTA, has been evaluated. In vitro biological experiments
demonstrate that these compounds are active toward the TS/A mouse adenocarcinoma cancer
cell line whereas cytotoxicity on the HBL-100 human mammary (nontumor) cell line was not
observed at concentrations up to 0.3 mM, which indicates selectivity of these ruthenium(II)-
arene complexes to cancer cells. Analogues of the RAPTA compounds, in which the PTA ligand
is methylated, have also been prepared, and these prove to be cytotoxic toward both cell lines.
RAPTA-C and the benzene analogue RAPTA-B were selected for in vivo experiments to evaluate
their anticancer and antimetastatic activity. The results show that these complexes can reduce
the growth of lung metastases in CBA mice bearing the MCa mammary carcinoma in the
absence of a corresponding action at the site of primary tumor growth. Pharmacokinetic studies
of RAPTA-C indicate that ruthenium is rapidly lost from the organs and the bloodstream
Influence of Hydrogen-Bonding Substituents on the Cytotoxicity of RAPTA Compounds
No full textA new series of organometallic ruthenium(II)-arene compounds of the type RuCl2(è6-arene)(phosphine)
(phosphine ) 1,3,5-triaza-7-phosphaadamantane, PTA, and 3,7-diacetly-1,3,7-triaza-5-phosphabicyclo-
[3.3.1]nonane, DAPTA) with different potential hydrogen-bonding functionalities on the arene ligand
have been prepared and studied for their antitumor activity. Cell viability studies using the TS/A mouse
adenocarcinoma cancer cell line and the nontumorigenic HBL-100 human mammary cell line, combined
with uptake determinations, are compared to the nonfunctionalized analogues, previously shown to be
active on solid metastasizing tumors. The reactivity of the functionalized RAPTA compounds with a
14-mer oligonucleotide (established by mass spectrometry) has been rationalized by DFT calculations,
which indicate that environmental factors are important
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
Searching for molecular arene hydrogenation catalysis in ionic liquids
No full textArene hydrogenation by homogeneous catalysts is a highly controversial area of research, with many of the mononuclear complexes shown to catalyse the reaction, being found to be pre-catalysts to nanoparticles, on closer examination. The solvent properties of ionic liquids, i.e., low nucleophilicity and high polarity, make them ideal, at least in principal, for homogeneous arene hydrogenation catalysts. In this paper, we described our attempts to prepare and study such systems, using either simple metal halides or ruthenium complexes including trinuclear ruthenium clusters as catalyst precursors. (c) 2005 Elsevier B.V. All rights reserved.LCO
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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