1,720,982 research outputs found
Effects of the reaction conditions on 3-(perfluorohexyl)prop-1-ene formation from perfluorohexyl iodide and allyl chloride
No full textThe addition of perfluorohexyl iodide to allyl chloride leads to the formation of 3-(perfluorohexyl)prop-1-ene in addition to the expected iodine-containing adduct. This reaction was studied under different conditions in order to determine their influence on the formation of the polyfluoro-olefin. The reaction conditions varied in the experiments were: molar ratio of reactants, weight percent of initiator, temperature and reaction time, and their effect on the formation of 3-(perfluorohexyl)prop-1-ene and by-products was determined
Experimental surface activity measurements of some fluorinated compounds in a non-aqueous medium
No full textPreparazione di trifluorometossibenzene da anisolo
No full textIl trfluorometossibenzene è prodotto per fotoclorurazione dell'anisolo da cui si ottiene il triclorometossibenzene quindi mediante reazione di scambio del cloro con il fluoro ad opera dell'acido fluoridrico, la reazione è condotta in autoclave a 70°C a 28atm
Catalytic chlorofluorination of fluoroacyl fluorides: hypochlorites synthesis
No full textA new procedure fo synthetizing the hypochlorittes CF3CF2OCl, CF2BrCF2OCl, and CF2HCF2OCl is reported. In the proposed method hypochlorites can be produced by a continous addition of chlorine monofluoiride (ClF) to an appropriate carbonyl compound
Liquid-phase fluorination of aromatic compounds by elemental fluorine
No full textThe fluorination of aromatic compounds (benzene, toluene, phenol and benzoic acid) by elemental fluorine diluted with nitrogen has been investigated in various solvents (Freon 11, chloroform, methanol, trifluoroacetic acid, 2,2,2-trifluoroethanol, water) in order to define the influence of the experimental conditions on the reaction. Experiments have been carried out by varying the temperature, the substrate concentration in solution, the molar ratio of fluorine to substrate, and the concentration of fluorine in the fluorine/nitrogen mixture. In all cases, the effects on the yield of fluorinated products were studied. Monofluorinated compounds were mainly found in the reaction mixture, the isomers formed being in accord with the mechanism for electrophilic substitution. The highest yield of monofluorinated products was obtained with polar solvents and the following order was found: CFCl3 < CHCl3 < CH3OH < CF3CH2OH < CF3COOH. Interesting results were also found using particular additives (for instance, KOH or C4F9SO3Na in methanol) or water as the solvent. A direct relationship was observed between the yield of monofluorinated compounds and the molar ratio of fluorine to substrate, which has to be less than one in order to obtain high yields. In contrast, low selectivity, expressed as the yield ratio of ortho to para (or metal isomers, was found
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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