1,721,021 research outputs found
Bis(cyclopentadienyl)dihydrido Mo and W complexes as Lewis’ bases. A computational study about their adducts with BX3 (X = F, Cl) and Al(CH3)3
No full textTheoretical conformational analysis of Boc-Gly-Val-Gly-Gly-Leu-OMe, a building block of prototype elastomeric peptide
No full textNon-symmetrical aryl- and arylethynyl-substituted thioalkyl-porphyrazines for optoelectronic materials: synthesis, properties, and computational studies
No full textA series of novel non-symmetrically substituted mono β-aryl and β-arylethynyl (alkylsulfanyl)porphyrazines and the corresponding Ni(II) complexes have been prepared by the Suzuki–Miyaura and Sonogashira cross-coupling reactions with the aim to investigate substituent effects on their electronic and aggregation properties. Spectroscopic, electrochemical and computational investigations show that in both aryl and arylethynyl compounds efficient electron transfer between the aryl and macrocycle moieties occurs.
The highest perturbation of the porphyrazine π-electron core is provided by strong electron-donating (NMe2) and electron withdrawing (NO2) aryl substituents, which increase and decrease the macrocycle electron density, respectively. Moreover, while in most of the compounds the LUMOs and HOMOs are mainly localized on the porphyrazine ring, in the amino-substituted derivatives the HOMO is localized on the peripheral aryl moieties and the LUMO is localized on the macrocycle. Charge-transfer electronic excitations give rise to absorptions in UV-Vis spectra of both amino- and nitro-substituted compounds. In the former such excitations occur from aryl-localized to macrocycle-localized orbitals, while backward excitations occur in the latter. Therefore, the porphyrazine ring shows an ambivalent behavior, acting as an electron acceptor in the case of the NMe2 substituted compounds and as an electron donor in the NO2-substituted derivative. In these derivatives, even macrocycle mono-substitution provides unconventional “push–pull” systems suitable for NLO. Columnar discotic mesophases are also shown by thio-octyl arylethynyl derivatives, allowing us to envisage the possibility to achieve compounds both suitable for optoelectronic applications and endowed with self-aggregation properties
Discotic Mesomorphism of 2,3,7,8,12,13,17,18-octakis (alkyl-thio) 5,10,15,20 Tetraaza Porphyrin and Its Complexes With Some Divalent Transition-metal Ions - Synthesis and Characterization
No full textElectronic Properties, Spectroscopic Properties and Monomolecular Isomerization Processes of Prototype OLED Compound Aluminum Tris(Quinolin-8-olate) Facial and Meridianal Isomers
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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
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