1,721,160 research outputs found
Catalytic activity of Fe3O4/CeO2 nanocomposites prepared by a microwave-assisted solvothermal method: imine formation from benzyl alcohol and aniline
No full textIn cafalysis, nanoceria has been used as efficient catalysi for aerobic oxidation reactions due to its oxygen storage capability [1], although its recovery at the end of the catalytic cycle cannot be carried out by simple filtration, because of its too tiny texture [2]. A method to overcome this disadvantage is to cover magnetite (Fe304) with nanoceria [3], in order to remove the whole material easily from the reaction mixture by using an external magnet.
The focus of this contribution is to verify, whether: i) the nanoceria deposition process changes the pristine morphology of the magnetite nanoparticles, ii) the different morphologies of magnetite seeds synthesized using various organic stabilizer (polyvinyIpyrrolidone, trisodium citrate dihydrate or oleic acid) during the preparation of the catalyst can influence its catalytic activity in the imine formation from benzyl alcohol and aniline
Reactions of alpha-Ionone Oxide with Aminium Salts, Brønsted and Lewis Acids. Synthesis of New Therminal Group Synthons
No full textStille coupling reactions catalysed by a polymer supported palladium complex
No full textThe coupling between aryl iodides and bromides with organostannanes (Stille reaction) has been investigated in the presence of a
polymer supported palladium catalyst. The reaction could be performed in air without any activating ligand and with non-dried
solvents. The catalyst, which acts by releasing controlled amounts of soluble active species, could be recycled several times in the
coupling between Sn(CH3)4 or nBu3SnPh with iodoarenes or activated bromoarenes
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
Random Poly(fluorenylene-vinylene)s Containing 3,7-Dibenzothiophene-5,5-dioxide Units: Synthesis, Photophysical, and Electroluminescence Properties
No full textThe synthesis of new random poly(arylene-vinylene)s containing the electron withdrawing 3,7-dibenzothiophene-5,5-dioxide unit was achieved by the Suzuki-Heck cascade polymerization reaction. The properties of poly[9,9-bis(2-ethylhexyl)-2,7-fluorenylene-vinylene-co-3,7-dibenzothiophene-5,5-dioxide-vinylene] (50/50 mol/mol, P1) and poly[1,4-bis(2-ethylhexyloxy)-2,5-phenylene-vinylene-co-3,7-dibenzothiophene-5,5-dioxide-vinylene] (50/50 mol/mol, P2) were compared with those of terpolymers obtained by combining the fluorene, dibenzothiophene, and 1,4-bis(2-ethylexyloxy)benzene in 20/40/40 (P3), 50/25/25 (P4), and 80/10/10 (P5) molar ratios. The polymers were characterized by (1)H NMR and IR, whereas their thermal properties were investigated by TGA and DSC. Polymers P1-5 are blue-green emitters in solution (lambda(em) between 481 and 521 nm) whereas a profound red shift observed in the solid state is emission (lambda(em) from 578 to 608 nm) that can be attributed both to the charge transfer stabilization exerted by the polar medium and to intermolecular interactions occurring in the solid state. Cyclic voltammetry permitted the evaluation of the ionization potentials and also revealed a quasi-reversible behavior in the reduction scans for the polymers (P1-4) containing the higher amounts of 3,7-dibenzothiophene-5,5-dioxide units. Electroluminescent devices with both ITO/PEDOT-PSS/P1-5/Ca/Al (Type 1) and ITO/PEDOT-PSS/P1-5/Alq(3)/Ca/Al (Type 11) configuration were fabricated showing a yellow to yellow-green emission. In the case of P4, a luminance of 1835 cd/m(2) and an efficiency of 0.25 cd/A at 14 V were obtained for the Type II devices. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2093-2104, 200
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
Random terpolymers for electroluminescent devices: synthesis and characterization of new cyano–containing poly(fluorenylene–vinylene)s
No full textThe synthesis of new random poly(2,7-fluorenylene-vinylene)s was
achieved by a Suzuki–Heck cascade polymerization reaction. The poly(fluorenylenevinylene)
base structure was modified by the regio-random incorporation of 1-cyano-
2,5-phenylene as electron withdrawing unit (CN-PFV1) and its properties were compared
with terpolymers also embodying 1,4-dioctyloxy-2,5-phenylene (CN-PFV2) or
3,6-N-octylcarbazole (CN-PFV3) as electron-donating moieties. Thermal analysis
revealed a high thermal stability (Td [ 389 8C) and the absence of glass transitions
for all polymers. Cyclic voltammetry indicated a high electron affinity of the materials
(2.96–3.21 eV) attributed to the presence of the cyano-containing comonomer. In
dilute solutions, the copolymers showed a broad green fluorescence with quantum
yields ranging from 0.42 to 0.79, while in the solid state, a relatively narrow emission
centered at 560 nm, governed by the low-energy segments within the p-conjugated
backbone, was observed. The electroluminescence properties of the materials
were tested in OLED devices of ITO/PEDOT-PSS/CN-PFV1-3/Ca/Al or ITO/PEDOTPSS/
CN-PFV1-3/Alq3/Ca/Al configurations, showing a bright green-yellow emission
that, in the case of CN-PFV2, reached 1403 cd/m2 with efficiencies as high as 0.13
cd/A
Influencing the spectral stability and the electroluminescence behavior of new blue-emitting bifluorene-based materials by the 7,7′-functionalization of the core
No full textThis study concerns the preparation of novel monodispersed organic materials based on a tetrahexyl-bifluorene
core linked to end-groups by double or triple bonds. The molecules were designed aiming at tuning their
HOMO-LUMO levels without remarkably changing their optical properties. The syntheses were carried out
through a convergent-divergent approach by reaction of a 7,7¢-diiodobifluorene building block with 2-fluoren-
7-yl-ethynyl (BF1), 2-carbazol-3-yl-ethynyl (BF2), 2-fluoren-7-yl-ethenyl (BF3), and 2-carbazol-3-yl-ethenyl
(BF4) moieties. The analysis of the optical properties evidenced for BF1-4 an efficient blue emission in
solution. Their emission profile is preserved also in the solid state, except for that of BF4, the PL spectrum
of which showed the appearance of a green band deriving from aerobic degradation. The HOMO value of
-5.00 eV, measured for BF4 by cyclic voltammetry, suggested a correlation of the spectral instability with
its low ionization potential. This hypothesis was confirmed by the photoluminescence behavior of BF1-3
upon UV photoirradiation showing a correlation between spectral stability and ionization potential. OLED
devices of ITO/PEDOT-PSS/BF1-4/Ca/Al configuration exhibited a blue electroluminescence. Fair
performances were obtained for the carbazole-containing BF2 (1000 cd/m2 with a current efficiency of 0.039
cd/A at 10 V) and BF4 (1431 cd/m2 and 0.027 cd/A at 14 V) presumably due to a more balanced transport
of charge carriers in the active layer. The results obtained in devices embodying 7.5 nm of a hole-blocking
layer (BCP) between the calcium cathode and the emitting material showed a remarkable enhancement of
current efficiencies for all devices and confirmed a more balanced transport of charge carriers in the carbazolecontaining
molecules. The figures of merit obtained for the carbazole-containing BF2 (1088 cd/m2 and 0.070
cd/A at 10 V) represent one of the best results for blue-emitting materials embodying ethynyl groups
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