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A [4π+4π] intramolecular photocyclomer of 9-anthroic anhydride: 5,6,11,12-tetrahydro-5,12;6,11-di-o-benzenodibenzo[a,e]cyclooctene-5, 6-dicarboxylic anhydride
No full textThe title compound, C30H18O3, was obtained by light irradiation of a dichloroethane solution of 9-anthroyl chloride and 9-anthroic acid. The molecules, which possess approximately mm2 local symmetry, are packed in columns, the oxygenated moieties facing each other according to the symmetry of a monoclinic lattice. The space group of the crystal is P21/c, with a whole molecule as the asymmetric unit. The structure is compared with those of similar dianthracene derivatives
9-Anthroylacetone and its photodimer
No full text9-Anthroylacetone undergoes a head-to-tail [4π+4π] photo-dimerisation reaction that leads to the formation of 5,11-bis(1,3-diketobutyl)-5,6,11,12- tetrahydro-5,12,6,11-di-o-benzeno-dibenzo[a,e]cyclooctene both in solution and in the solid state when irradiated with different sources (sunlight, tungsten lamp, xenon lamp, UV laser beam 351-364 nm), the reaction being accompanied by a colour variation from bright yellow to colourless. Quantum yields >0.023 mol/Einstein are evaluated for the solid state reaction. Interestingly, the dimer dissociates to give 9-anthroylacetone, both thermally (T>130°C) and photochemically, by short UV wavelength irradiation. The single-crystal X-ray structure of 9-anthroylacetone and its dimer are reported. 9-Anthroylacetone undergoes a head-to-tail [4π+4π] photo-dimerisation reaction both in solution and in the solid state when irradiated with different sources; the dimer reversibly dissociates into 9-anthroylacetone, both thermally and photochemically
Synthesis of 9-Anthrylmethyl-Functionalised Cyclopentadienyl Derivatives of Rhodium(I) and Iridium(I) and Study of their Luminescence Properties
No full textThe compound 9-anthrylmethylcyclopentadiene 1 was prepared by reacting 9-bromomethylanthracene with cyclopentadienylsodium and transformed into its thallium(I) derivative on reaction with thallium ethoxide 3. The 9-anthrylmethylcyclopentadienyl (AnCH2C5H4) derivatives of rhodium(I) and iridium(I) of formula [M(η5-AnCH2C5H4)L2] (M=Rh or Ir; L=C2H4, CO, PPh3, C8H14; L2=C7H8, 1,5-C8H12) 4-6 and 9-11 were obtained in good yields by reacting the corresponding rhodium(I) and iridium(I) chlorides with 3. Both [Rh(η5-AnCH2C5H4)(η2-C2H4)2] (4) and [Rh(η5-AnCH2C5H4)(CO)2] (5) react with triphenylphosphine, at 130°C to give [Rh(η5-AnCH2C5H4)(η2-C2H4)(PPh3)] (7) and [Rh(η5-AnCH2C5H4)(CO)(PPh3)] (8). All complexes were characterised by elemental analysis, mass spectrometry, 1H-NMR and FTIR. The structures of two of them, i.e. [Rh(η5-AnCH2C5H4)(η2-C2H4)2] (4) and [Rh(η5-AnCH2C5H4)(CO)2] (5), were elucidated by single crystal X-ray diffraction. Compound 4 crystallises in the triclinic space group P1̄ with a=11.112(1), b=12.065(1), c=15.982(2) Å; α=99.83(1), β=107.86(1), γ=107.22(1)°. V=1865.6(3) Å3. Z=4, Dcalc=1.475 g cm-1, R1=0.0414 [I>2σ(I)], wR2=0.0953. Compound 5 crystallises in the triclinic space group P1̄ with a=12.232(1), b=13.463(1), c=13.488(1) Å; α=61.25(1), β=68.51(1), γ=67.45(1)°. V=1752.5(2) Å3. Z=4, Dcalc=1.570 g cm-1, R1=0.0313 [I>2σ(I)], wR2=0.0795. The UV-vis spectra (280-700 nm) of 1 and of complexes 4-11 were recorded. The spectra of 4-11 are indicative of important interactions between the anthrylic chromophore and the cyclopentadienyl-metal moiety. When excited at 365 nm, 1 results to be an efficient light-emitting molecule, while its derivatives 4-11 are poorly luminescent compounds. Indeed, all complexes exhibit similar fluorescence spectra which are typical of the anthrylic fluorophore but have extremely low intensity (the one observed for 9-methylanthracene was below 5% and taken as the reference compound). The mechanism of fluorescence quenching in the complexes 4-11 is discussed
Co-agent mediated functionalization of LDPE/iPP mixtures for compatibilization of WEEE-recovered polyvinylchloride
No full textMixtures of low density polyethylene/isotactic polypropylene (LDPE/iPP) 80/20 w/w were functionalized in the melt by using maleic anhydride (MAH) as the functionalizing agent, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (L101) as the peroxide initiator and butyl 3-(2-furyl)propenoate (BFA) as a co-agent suitable to prevent the degradation of iPP and to promote inter-macromolecular reactions. The use of BFA was aimed at favouring the control of radical-induced side reactions and the formation of interfacial graft copolymers. The functionalization degree and the modification of macromolecular architecture, which were evaluated by selective solvent extractions combined with IR, DSC and SEM analyses, were modulated by varying the L101/MAH/BFA ratio in the feed. The optimized product in terms of functionalization degree value and processability was successfully tested as compatibilizer in a polyolefin/polyvinylchloride mixture, where the polyvinylchloride component resulted from the management of waste of electrical and electronic equipment (WEEE)
Polymer surface modification by photografting of functional nitroxides
No full textThe UV-initiated photografting of X-TEMPO onto the surface of ethylene/α-olefin copolymer (EOC) and of styrene-b-(ethylene-co-butene)-b-styrene (SEBS) block copolymer films is here described. In particular, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (BzO-TEMPO), 4-(1-naphthoate)-2,2,6,6-tetramethylpiperidine-1-oxyl (NfO-TEMPO) and 4-(4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononanoate)-2,2,6,6-tetramethylpiperidine-1-oxyl (Fluo-TEMPO) were used as X-TEMPO derivatives to change the surface properties of the two polymer films. Infrared analysis (ATR-FTIR), electron paramagnetic resonance (EPR) and thermogravimetric analysis (TGA) confirmed the covalent immobilization of X-TEMPO onto the polymer surface. The fluorescence emission spectroscopy was used to investigate the optical properties of the NfO-TEMPO functionalized samples, while the contact angle measurements highlighted the wettability features of the surface modified with Fluo-TEMPO. A comparison of the data evidences that the properties of the free X-TEMPO derivatives have been completely transferred to the polymer giving “functional” films by a simple modification technique. Furthermore a discussion about the photografting mechanism as well as of the thermal robustness of the covalent bond between the X-TEMPO and the polymer is proposed
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
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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