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Matrix effects on a photooxidation reaction of a diol catalyzed by an Fe-porphyrin bonded on MCM-41
No full textSurface characterization of hydrophobic zirconia-silica mixed oxides for clean oxidation catalysis
No full text[nBu4N]4W10O32 inside sol-gel silica: matrix effects on the photocatalytic oxidation of alcohols
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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
Matrix effects on the photocatalytic oxidation of alcohols by [nBu4N]4W10O32 incorporated into sol–gel silica
No full textTwo heterogeneous photocatalysts have been prepared by entrapment of [nBu4N]4W10O32 in a silica matrix, through a sol-gel procedure: SiO2/W30% and SiO2/W10% with 30% and 10% of decatungstate, respectively. They are characterized by the presence of micropores of about 7 Å and 15 Å and mesopores of about 25 Å. Due to different preparation procedures, SiO2/W10% presents a more remarkable porous network than SiO2/W30%. The morphological features of SiO2/W30% and SiO2/W10% differ from those of their parent material SiO2/W0%, indicating that incorporation of the decatungstate induces a significant modification of the porous texture of the siliceous material. These photocatalysts demonstrate good stability in the oxygen-assisted photooxidation of 1-pentanol and 3-pentanol, which have been chosen as models of primary and secondary aliphatic alcohols. In particular, photoexcitation (λ > 290 nm, 25°C, 760 torr of O 2) leads to conversion of these two substrates to pentanal or 3-pentanone, with a mass balance of about 90%. There is a strong effect of the solid support on the reactivity of the two alcoholic substrates. In particular, oxidation of 1-pentanol with SiO2/W10% is about four times faster than with [nBu4N]4W10O32 in homogeneous solution. Preferential adsorption phenomena, due to the hydrophilic character of silica explain the photocatalytic properties of the two heterogeneous systems, because adsorption favours the contact between the photoexcited decatungstate and the primary OH group of 1-pentanol. Moreover, some kind of shape selectivity, due to the microporous structure of the investigated materials, likely contributes to control the conversion yields. © The Royal Society of Chemistry 2010
Fe(III)-porphyrin heterogenized on MCM-41: Matrix effects on the oxidation of 1,4-pentanediol
No full textThe metal complex iron meso-tetrakis (2,6-dichlorophenyl)porphyrin (FeIIIP) has been covalently linked
on the surface of the mesoporous material MCM-41 and of amorphous SiO2 to give the photocatalysts
FeIIIP/MCM-41 and FeIIIP/SiO2 respectively. The effect of porphyrin addition on specific surface area and
porosity of these materials has been evaluated by means of BET and BJH model applied to N2 adsorption/
desorption isotherms. It is seen that the MCM-41 sample presents the largest modification due to
the presence of porphyrin: the pore size changes in average value and distribution, the pores formed in
the presence of porphyrin being smaller and presenting a larger distribution.
The photochemical characterization of FeIIIP/MCM-41 reveals that this is a robust photocatalyst able
to induce the O2-assisted oxidation of 1,4-pentanediol. In particular, photoexcitation of FeIIIP/MCM-41
causes the conversion of 1,4-pentanediol to the aldehyde derivative compound with 70% regioselectivity.
It is noteworthy that this product can be accumulated with no formation of further oxidized compounds.
Due to its high specific surface area, which guarantees a good dispersion of the active centres, FeIIIP/MCM-
41 is about four times more efficient than FeIIIP/SiO2. Moreover, the nature of the support controls the
regioselectivity of the photocatalytic process: this is due to both uptake phenomena and steric effects,
which can control the approach of the diol to the photoactive iron porphyrin
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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