1,721,029 research outputs found
Heterobimetallic rollover derivatives
No full textHeterobimetallic complexes with metal centers connected by a small delocalized ligand constitute an interesting class of compounds. Here we report that starting from the mononuclear platinum(II) rollover complexes [Pt(bipy-H)(L)Cl] (bipy-H = 2,2′-bipyridine C(3′)-N cyclometalated, L= DMSO, PPh3) a second rollover cyclometalation may produce a series of Pt(II)/Pd(II) heterobimetallic complexes where the two metals are linked by the planar, highly delocalized, doubly deprotonated 2,2′-bipyridine
Solution, solid-state, and computational analysis of agostic interactions in a coherent set of low-coordinate rhodium(III) and iridium(III) complexes
Full text linkA homologous family of low-coordinate complexes of the formulation trans-[M(2,2′-biphenyl)(PR3)2][BArF4] (M=Rh, Ir; R=Ph, Cy, iPr, iBu) has been prepared and extensively structurally characterised. Enabled through a comprehensive set of solution phase (VT 1H and 31P NMR spectroscopy) and solid-state (single crystal X-ray diffraction) data, and analysis in silico (DFT-based NBO and QTAIM analysis), the structural features of the constituent agostic interactions have been systematically interrogated. The combined data substantiates the adoption of stronger agostic interactions for the IrIII compared to RhIII complexes and, with respect to the phosphine ligands, in the order PiBu3>PCy3>PiPr3>PPh3. In addition to these structure–property relationships, the effect of crystal packing on the agostic interactions was investigated in the tricyclohexylphosphine complexes. Compression of the associated cations, through inclusion of a more bulky solvent molecule (1,2-difluorobenzene vs. CH2Cl2) in the lattice or collection of data at very low temperature (25 vs. 150 K), lead to small but statistically significant shortening of the M−H−C distances
Essential oils from three species of Mentha harvested in Sardinia : chemical characterization and evaluation of their biological activity
Full text linkThe chemical composition, antimicrobial activity and antioxidant activity of Mentha (M.) requienii, M. pulegium L. and M. aquatica (L.) Huds from Sardinia, Italy were tested. The chemical composition was determined by Gas Chromatography-Mass Spectrometry (GC-MS) and GC-Flame Ionization Detector (GC-FID) analysis. The antiradical activity was assessed by DPPH and ABTS assay and minimal inhibition concentration was determined by microdilution broth analysis. The major components found in M. requienii EO were pulegone, menthone and limonene; similarly the major components of M. pulegium EO were pulegone and iso-menthone. By contrast, the major components of the EO from M. aquatica are terpinyl acetate and eucalyptol. The antioxidant activity of M. aquatica EO was higher than that of M. requienii and M. pulegium. The EO from M. requienii had good antifungal and antioxidant activity. In the concentration range tested, the mint EOs did not show any antibacterial activity against Staphylococcus aureus 20231 DSMZ, Salmonella enterica subsp. bongori serovar 66:z41:- 13772 DSMZ and four strains of Listeria monocytogenes. Lactic acid bacteria strains were not inhibited by the EOs tested, with the exception of Lactobacillus brevis which showed slight sensitivity to M. pulegium and M. requenii EOs. Yeast strains were in general sensitive to the different Mentha EOs tested and was species and strain dependent;generally, the EOs of M. pulegium and M. requenii were found to be more active than that of M. aquatica
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
Profiling and simultaneous quantitative determination of anthocyanins in wild myrtus communisL. berries from different geographical areas in Sardinia and their comparative evaluation
Full text linkIntroduction
Myrtus communis L. (Myrtaceae) is a self-seeded shrub, widespread in Sardinia, with anti-inflammatory, antiseptic, antimicrobial, hypoglycemic and balsamic properties. Its berries, employed for the production of sweet myrtle liqueur, are characterised by a high content of bioactive polyphenols, mainly anthocyanins. Anthocyanin composition is quite specific for vegetables/fruits and can be used as a fingerprint to determine the authenticity, geographical origin and quality of raw materials, products and extracts.
Objective
To rapidly analyse and determine anthocyanins in 17 samples of Myrtus communis berries by developing a platform based on the integration of UHPLC–MS/MS quantitative data and multivariate analysis with the aim of extracting the most information possible from the data.
Methodology
UHPLC-ESI-MS/MS methods, working in positive ion mode, were performed for the detection and determination of target compounds in multiple reaction monitoring (MRM) mode. Optimal chromatographic conditions were achieved using an XSelect HSS T3 column and a gradient elution with 0.1% formic acid in water and 0.1% formic acid in acetonitrile. Principal component analysis (PCA) was applied to the quantitative data to correlate and discriminate 17 geographical collections of Myrtus communis.
Results
The developed quantitative method was reliable, sensitive and specific and was successfully applied to the quantification of 17 anthocyanins. Peonidin-3-O-glucoside was the most abundant compound in all the extracts investigated.
Conclusion
The developed methodology allows the identification of quali-quantitative differences among M. communis samples and thus defines the quality and value of this raw material for marketed products. Moreover, the reported data have an immediate commercial value due to the current interest in developing antioxidant nutraceuticals from Mediterranean plants, including Sardinian Myrtus communis. Copyright © 2016 John Wiley & Sons, Ltd
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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