1,721,017 research outputs found
Organotin(IV) derivatives with 5,7-disubstituted-1,2,4-triazolo [1,5-a]pyrimidine and their cytotoxic activities: The importance of being conformers
No full textThe organotin(IV) compounds Me2SnCl2(dbtp)(1), Me2SnCl2(dbtp)2 (2), Et2SnCl2(dbtp) (3), Et2SnCl2(dbtp)2
(4), Et2SnCl2(dptp) (5), nBu2SnCl2(dbtp)2 (6), nBu2SnCl2(dptp) (7), Ph2SnCl2(dbtp) (8), Ph2SnCl2(EtOH)2
(dptp)2 (9), where dbtp = 5,7-di-tert-butyl-1,2,4-triazolo[1,5-a]pyrimidine and dptp = 5,7-diphenyl-
1,2,4-triazolo [1,5-a]pyrimidine, have been tested by MTT for their cytotoxic activity on three tumor cell
lines, HepG2 (human hepatocellular carcinoma), HeLa (human cervix adenocarcinoma) and MCF-7 (human
breast cancer). Except for 1 and 2, which were ineffective, all compounds significantly showed a dosedependent
anti-proliferative effect against the three cell lines. By calculated IC50 values, the cytotoxicity
of the complexes followed the order nBu > Ph > Et > Me for all the selected tumor cells. The cell death of
HepG2, induced by organotin(IV) compounds 6–9, was considered to be apoptotic by measuring the exposure
of phosphatidylserine to the outer membrane and observing the typical apoptotic morphological
change by acridine orange/ethidium bromide staining. Flow cytometric analysis of propidium iodidestained
cells also demonstrated that organotin(IV) complexes caused apoptosis of HepG2 cells through cell
arrest at G0–G1 phase. The crystal structure of 7, investigated by X-ray diffraction study, exhibited a
distorted trigonal bipyramidal geometry with N, Cl as axial atoms and Cl and butyl groups in the equatorial
plane. The triazolopyrimidine unit coordinates to the Sn atom through N(3) in a monodentate mode. Two
conformational isomers (molecule A and B in the crystallographic independent unit) are co-crystallized in
the solid state, a phenomenon that has been observed only occasionally. Conformational mobility of the
cytotoxic complex 7 can sum up to the ligands ability to form H-bonds and p p stacking, facilitating its
intracellular uptake
Lewis acid-promoted 1,4-addition to chiral imide derivatives in the synthesis of β-amino acids
No full textPentasulfurated Benzene-Cored Asterisks: Relation Between Crystal Structure and Luminescence Properties
No full textRoom temperature phosphorescence by metal-free chromophores is quite a rare phenomenon. Hexasulfurated benzene-cored molecules with phenyl substituents, hereafter named asterisks, display bright green phosphorescence in the solid state at room temperature, while they are not luminescent in solution, because of fast non-radiative decay of the lowest excited state. Some of these asterisks are also among the most phosphorescent compounds. Following a search for structure-property relationships, we report here the synthesis, characterization, crystal structure and optical properties of three pentasulfurated benzene-cored asterisks, carrying at the sixth position of the benzene core a cyano (A5CN), a carboxaldehyde (A5CHO), or a vinyl group (A5CC). The most luminescent compound is A5CN displaying an intense orange phosphorescence in the solid state: our actual aim is to try and correlate the optical properties together with the crystal structure in this series of compounds
Transfer of chirality by dithiophosphate ligands and chiral discrimination in the stereoselective formation of square-planar Ni(II) complexes
No full text
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
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