1,721,308 research outputs found
Benzene and leukemia
No full textBenzene and Leukemia addresses leukemogenic effect of benzene, representing a complex model of chemical carcinogenesis in humans
(2-Pyrene-1-yl-vinyl)pyridine: a highly transparent chromophore with an unexpected large second-order nonlinear optical response
No full textIn the field of electrooptic materials, the rational design and synthesis of chromophores endowed with high transparency together with large second order nonlinear optical (NLO) response is a field of intense research activity. Many organic and metallorganic second order NLO chromophores have been designed according to the ‘‘push-pull’’ strategy, where electron-donating (D) and electron-withdrawing (A) end groups interact through a delocalized -electron bridge to generate an intramolecular charge transfer transition [1]. On the other hand, far less attention has been devoted to low dipole moment chromophores, though in some instance they have been shown to possess large hyperpolarizability [2].
Here we report on the second order NLO properties of (2-pyrene-1-yl-vinyl)pyridine, 1, a chromophore based on the pyrene moiety which is well studied for its outstanding fluorescence properties (long lifetime and high quantum yield) while its derivatives have never been investigated for their NLO response. Preliminary measurements of the second order NLO properties of 1 in solution by the EFISH technique revealed an unexpectedly high and strongly concentration dependent μβ value, comparable to that of benchmark NLO chromophores. At high concentrations the decrease of the second order NLO response seems to point to the formation of centrosymmetric aggregates, a feature that is supported also by the emissive behaviour of 1. Interestingly 1 is quite transparent, a relevant property for potential technological applications. These experimental results have been supported by theoretical investigation performed at DFT and Time Dependent DFT level, which has allowed an analysis of the electronic origin of the NLO response.
[1] T. Verbiest, et al. J. Mater. Chem. 7, 1997, 2175.
[2] J. Gradinaru, A. Forni, et al. Inorg. Chem. 46, 2007, 884
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
Use of Chiral Diamines in the Synthesis of ‘Half Unit’ Schiff Base Cu(II) Trinuclear Complexes: A Possibility of Chirality Induction
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