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Using Optical Tweezers for the Characterization of Polyelectrolyte Solutions with Very Low Viscoelasticity
No full textRecently, optical tweezing has been used to
provide a method for microrheology addressed to measure the
rheological properties of small volumes of samples. In this work,
we corroborate this emerging field of microrheology by using
these optical methods for the characterization of polyelectrolyte
solutions with very low viscoelasticity. The influence of
polyelectrolyte (i.e., polyacrylamide, PAM) concentration, specifically
its aging, of the salt concentration is shown. The close
agreement of the technique with classical bulk rheological
measurements is demonstrated, illustrating the advantages of the technique
Dynamics of semiflexible polymer solutions in the tightly entangled concentration regime
Get PDFI corroborate an important experimental evidence reported by Schuldt et al. [ Phys. Rev. Lett. 2016, 117, 197801] revealing the incapability of the current theoretical framework to fully describe the dynamics of semiflexible polymer solutions in the tightly entangled concentration regime. These results have been endorsed here by means of previously published, but overlooked, data by Tassieri et al. [ Phys. Rev. Lett. 2008, 101, 198301; Biophys. J. 2008, 94, 2170]. The ensemble of information provides a strong evidence that the scaling law of the plateau modulus as a function of polymer’s concentration and persistence length, i.e., G0 ∝ cαLpβ, should have both the exponents positive, in contrast with all the existing predictions converging on similar values of α > 0 and β < 0—hence the need of new theoretical models able to better interpret the contribution of the polymer bending rigidity to the viscoelastic properties of the polymer network
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
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