1,721,005 research outputs found
Scleroglucan/borax: characterization of a novel hydrogel system suitable for drug delivery
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Structural evolution of salt-free aqueous Laponite dispersions: A study based on low-field NMR relaxometry and rheological investigations
No full textThe combination of Low-Field NMR relaxometry (LF-NMR) and rheological analyses was used to investigate the kinetics of aging and structural evolution of salt-free aqueous Laponite dispersions with concentrations ranging from 0.33 to 2.00 wt%. The examination of LF-NMR results reveals that the rate of nanoclay delamination increases with increasing Laponite concentration while its degree decreases. Furthermore, the LF-NMR results were interpreted together with rheological results to assess the kinetics of processes occurring on different length scales reflecting on the time evolution of the three-dimensional structure. The structural evolution is described by the definition and comparison of three different characteristic times. The LF-NMR decay time (tr) designates the time required for Laponite delamination. The induction time (ti) indicates when interparticle edge-face interactions become effective enough for incipient networking. The gelation time (tg) corresponds to sufficiently high degree of interparticle connectivity for the development of a macroscopic gel behavior. The comparison of ti and tg, on one hand, and tr, on the other hand, allows to conclude that for low concentration Laponite dispersions nanoclay delamination is a prerequisite for the formation of the new dispersion structure with a macroscopic gel behavior. Interestingly, the development of the new structure, based on orientation of clay disks into edge-to-face pattern and mutual interparticle attractive interactions, starts when the delamination process is still running
Starch-methylcellulose based edible films: rheological properties of film-forming dispersions
No full textMethylcellulose-starch based edible films: evaluation of functional and physical properties
No full textRheological characterisation of cocoa creams
No full textRheological properties of four commercial cocoa creams (A, B, C and D) were investigated under steady and oscillatory shear conditions in the temperature range 25-45°C. Calorimetric measurements (DSC) were also performed. Samples exhibited marked shear-thinning behaviour characterised by high-viscosity Newtonian plateau at low shear stresses and a complex yielding process. An approach based on three consecutive critical stresses (elastic, static and dynamic yield) was proposed. Large differences in viscosity, yield stresses and flow temperature dependence were observed among samples. Generally, viscosity and yield stress decreased with increasing temperature, and the higher the viscosity of the samples, the greater was the decreasing rate. Mechanical spectra showed gel-like behaviour due to interactions of particle aggregates. Temperature increase determined different changes of linear viscoelastic properties. Relaxation spectra at 25°C ranked samples into two groups (A-B) and (C-D), while all four creams showed similar behaviour at 45°C. No substantial thermal transition occurred in the temperature range investigated
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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