1,720,957 research outputs found
Synthesis and characterisation of the amidine complexes trans-[PtCl(NH3) {HN=C(NH2)R}(2)]Cl (R = Me, Ph, CH2Ph) derived from addition of NH3 to the coordinated nitriles in trans-[PtCl2(N CR)(2)]
No full textThe di-nitrile complexes trans-[PtCl2(NCR)(2)] (R = Me, Ph, CH2Ph) react with an excess of gaseous NH3 in CH2Cl2 at -10 degrees C to form, in high yield, the corresponding di-amidine complexes trans-[PtCl(NH3){HN=C(NH2)R}(2)]Cl in which also one chlorine ligand has been displaced by NH3. The H-1 NMR spectra in DMSO showed the formation of different species which were characterized through NOESY, TOCSY and H-1/C-13 heteronuclear correlations as trans-[Pt(NH3){HN=C(NH2)R}(2)(DMSO)]Cl-2 and trans-[PtCl{HN=C(NH2)R}(2)(DMSO)]Cl. (c) 2005 Elsevier B.V. All rights reserved
Synthesis, characterization and cytotoxic activity of substituted benzyl iminoether Pt(II) complexes of the type cis- and trans-[PtCl2{E-N(H)=C(OMe)CH2-C6H4-p-R}(2)] (R = Me, OMe, F). X-ray structure of trans-[PtCl2{E-N(H)=C(OMe)CH2-C6H4-p-F}(2)]
No full textNew substituted benzyl iminoether derivatives of the type cis- and trans-[PtCl2{E-N(H)=C(OMe)CH2-C6H4-p-R}(2)] (R = Me (1a, 2a), OMe (3a, 4a), F (5a, 6a)) have been synthesized and characterized by elemental analyses, FT-IR spectroscopy and NMR techniques. The iminoether ligands are in the E configuration, which is stable in solution and in the solid state, as confirmed by the H-1 NMR data. Complex trans-[PtCl2{E-N(H)=C(OMe)CH2-C6H4-p-F}(2)] (6a) was also characterized by an X-ray diffraction study. Complexes 1 a-6a have been tested against a panel of human tumor cell lines in order to evaluate their cytotoxic activity. cis-Isomers were significant more potent than the corresponding trans-isomers against all tumor cell lines tested; moreover, complexes la and 5a showed IC50 values from about 2-fold to 6-fold lower than those exhibited by cisplatin, used as reference platinum anticancer drug
Chemistry and Biological Activity of Platinum Amidine Complexes
No full textPlatinum amidine complexes represent a new class of potential antitumor drugs that contain the imino moiety HN[DOUBLE BOND]C(sp2) bonded to the platinum center. They can be related to the iminoether derivatives, which were recently shown to be the first PtII compounds with a trans configuration endowed with anticancer activity. The chemical and biological properties of platinum amidine complexes, and more generally of platinum imino derivatives, can be rationally modified through suitable synthetic procedures with the aim of improving their cytotoxicity and antitumor activity. The addition of protic nucleophiles to nitriles coordinated to platinum in various oxidation states can offer a wide variety of complexes with chemical, structural, and physical properties specifically tuned for a more efficacious biological response
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
A New Class of Antitumor trans-Amine-Amidine-Pt(II) Cationic Complexes: Influence of Chemical Structure and Solvent on in Vitro and in Vivo Tumor Cell Proliferation
No full textThe reactions of cyclopropylamine, cyclopentylamine, and cyclohexylamine with trans-[PtCl2(NCMe)2] afforded the bis-cationic complexes trans-[Pt(amine)2(Z-amidine)2]2+[Cl-]2, 1-3. The solution behavior and biological activity have been studied in different solvents (DMSO, water, polyethylene glycol (PEG 400), and polyethylene glycol dimethyl ether (PEG-DME 500)). The biological activity was strongly influenced by the cycloaliphatic amine ring size, with trans-[Pt(NH2CH(CH2)4CH2)2{N(H) horizontal lineC(CH3)N(H)CH(CH2)4CH2}2]2+[Cl-]2 (3) being the most active compound. Complex 3 overcame both cisplatin and MDR resistance, inducing cancer cell death through p53-mediated apoptosis. Alkaline single-cell gel electrophoresis experiments indicated direct DNA damage, reasonably attributable to DNA adducts of trans-[PtCl(amine)(Z-amidine)2][Cl] species, which can evolve to produce disruptive and nonrepairable lesions on DNA, thus leading to the drug-induced programmed cancer cell death. Preliminary in vivo antitumor studies on C57BL mice bearing Lewis lung carcinoma highlighted that complex 3 promoted a significant and dose-dependent tumor growth inhibition without adverse side effects
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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