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Complex permittivity of FeCl3/AOT/CCl4 microemulsions probed by AC impedance spectroscopy
No full textThe complex permittivity of FeCl3/AOT/CCl4 microemulsions in the 1–105 Hz frequency range has been
measured by the conventional AC complex impedance technique. Measurements as a function of the volume
fraction of the dispersed phase (FeCl3 + AOT) and temperature at fixed salt-to-AOT molar ratio (R,
R = 0.5) show that the entrapment of FeCl3 clusters significantly enhances the local permittivity of the
AOT reverse micelles and the number density of charge carriers resulting from the peculiar state of the
confined inorganic salt. An estimate of the apparent static permittivity of the FeCl3 ionic clusters
entrapped in the core of AOT reverse micelles gives the very high and quite surprisingly value of about
237.
Moreover, a thorough analysis of conductivity data and of their temperature dependence strongly supports
the hypothesis that the charge transport in these systems is mainly sustained by a mechanism of
hopping consisting in the continuous jumping of charged species within supra-micellar aggregates of
AOT reverse micelles whose aggregation is driven by fluctuating opposite charges on contacting micelles
Fast proton conduction in hydrogen bonded microheterogeneous systems: Bis(2-ethylhexyl)phosphoric acid/N-methyl formamide liquid mixtures
No full textStructural and dynamical properties of bis(2-ethylhexyl)phosphoric acid (HDEHP)/N-methyl formamide
(NMF) liquid mixtures in the whole composition range have been investigated by Fourier Transform
Infrared spectroscopy (FT-IR), X-rays Diffraction (XRD), and AC complex impedance spectroscopy. Driven
by hydrogen bond interactions among HDEHP PO4H group and NMF CO and NH groups, and also by steric
effects among the HDEHP alkyl chains, the system microstructure is mainly characterized by the coexistence
of spatially separated hydrophilic and hydrophobic nanodomains showing local organization and
short-range order. The evolution of this structural feature with system composition has been highlighted
by FT-IR and XRD. On the other hand, the thermally activated proton mobility within these hydrophilic
domains, as pointed out by AC complex impedance measurements, emphasizes the occurrence of a percolating
behaviour characterized by percolation threshold at zero. Due to fast proton conduction across
the interconnected network formed by the polar groups, some samples showed very high room-temperature
conductivity up to 10 3 S cm 1
Physico-chemical investigation of nanostructures in liquid phases: Nickel chloride ionic clusters confined in sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles.
No full textThe confinement of finite amounts of nickel chloride in the hydrophilic core of sodium bis(2-ethylhexyl)
sulfosuccinate (AOT) reverse micelles dispersed in n-heptane has been investigated by FT-IR, UV–vis-NIR
and fluorescence spectroscopies. The analysis of experimental data consistently leads to hypothesize that
NiCl2 forms small size ionic clusters stabilized by a monolayer of oriented surfactant molecules. Due to
confinement and interfacial effects, these ionic clusters show peculiar photophysical properties, which
are different from those possessed by the bulk material. From NiCl2/AOT/n-heptane solutions, by evaporation
of the organic solvent, interesting salt/surfactant nanocomposites at various salt concentrations
have been prepared and characterised by WAXS. On the other hand, after mix with Na2S-containing
dry micellar systems, the formation of NiS nanoparticles have been ascertained by UV–vis spectroscopy
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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