1,721,019 research outputs found
Orientational ordering studies of fluorinated thermotropic liquid crystals by NMR spectroscopy
No full textInteraction of Azole Compounds with DOPC and DOPC/Ergosterol Bilayers by Spin Probe EPR Spectroscopy: Implications for Antifungal Activity
No full textCharacterization of an amylose-graft-poly(n-butyl methacrylate) copolymer obtained by click chemistry by EPR and SS-NMR spectroscopies
No full textWe present an investigation of the main chemical and physico-chemical properties of a graft copolymer of amylose and poly(n-butyl methacrylate), Am-g-PBMA, amphiphilic and able to self-assemble in water, prepared by coupling end azide-functionalized PBMA and alkyne-functionalized amylose under convenient click conditions. A deep knowledge of these properties is necessary in the perspective of real applications of the copolymer. To this aim we combined a basic characterization through FT-IR, TGA, ICP-OES and SEM with an extensive EPR and Solid State NMR investigation. It was possible to characterize the main structural and dynamic properties of Am-g-PBMA and highlight the presence of residual copper (Cu(II)) from the catalyst, even after an extensive purification procedure. We could identify two main species of Cu(II): Cu(II) complexes coordinated to the N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) ligand from the catalyst and to the copolymer triazole nitrogens and multi-nuclear or clustered Cu(II) species likely coordinated to amylose hydroxyl groups
Liquid Crystals Showing a Molecular Rearrangement: A Dynamic NMR Study of a 2-Acyloxytropone Mesogen and Two Related Compounds
No full textInteraction of cisplatin and two potential antitumoral platinum(II) complexes with a model lipid membrane: a combined NMR and MD study
Full text linkIn this study, the interaction of cisplatin (1) and two potential antitumoral Pt(II) complexes (2 and 3) with a model DMPC bilayer was investigated by multinuclear NMR spectroscopy and MD simulations in order to understand its implication on the different antitumoral properties shown by the three complexes. In particular, 31P, 13C and 2H solid state NMR experiments were performed to obtain information on the phase structure, phase transitions and structural and dynamic changes in the phospholipid bilayer upon interaction with the platinum complexes. On the other hand, MD calculations yielded free energy profiles for the different complexes across the bilayer; the results were analysed to obtain MD predictions on complex distribution with respect to the bilayer, as well as to establish their effects on the conformational equilibrium of the DMPC acyl chains. The combination of NMR and MD approaches highlighted that, whereas the more hydrophilic cisplatin tends to remain in the polar head group region, causing a decrease in flexibility of the bilayer, the two new complexes enter into the bilayer. In particular, complex 2 is preferentially located relatively close to the surface, only slightly affecting the bilayer structure and mobility, while complex 3 penetrates more deeply, strongly perturbing the bilayer and giving rise to lateral phase separation
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
Orientational order of two fluoro- and isothiocyanate-substituted nematogens by combination of ^{13}C NMR spectroscopy and DFT calculations
Full text linkOrientational order properties of two nematogens containing a fluoro- and isothiocyanate-substituted biphenyl moiety have been investigated by means of 13C NMR spectroscopy. 13C NMR spectra acquired on static samples under high-power 1H- decoupling allowed both 13C chemical shift anisotropies and 13C−19F couplings to be measured. These data were used to determine the local principal order parameter and biaxiality for the different rigid fragments of the molecules. To this aim, advanced DFT methods for the calculation of geometrical parameters and chemical shift tensors were used. The orientational order parameters obtained by NMR have been critically compared with those obtained by dielectric spectroscopy. Trends of order parameters with temperature have been analyzed in terms of both mean field theory and the empirical Haller equatio
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