1,721,364 research outputs found
EQCM Analysis of the Insertion Phenomena in a n-Doped Poly-Alkyl-Terthiophene With Regioregular Pattern of Substitution
Full text linkIn the present work, we have undertaken the study of the n-doping process in poly-3,3′′-didodecyl-2,2′:5′,2′′-terthiophene (poly-33′′-DDTT) employing the electrochemical quartz crystal microbalance (EQCM). The present study aims at understanding how cathodic charge in n-doped poly-33′′-DDTT is compensated. For this purpose, the in situ analysis of the variations of the polymeric mass has been considered. Poly-33′′-DDTT was obtained as a thin coating onto a metallic substrate via the anodic coupling of the corresponding monomer 3,3′′-didodecyl-2,2′:5′,2′′-terthiophene (33′′-DDTT). When subjected to electrochemical n-doping in the polarization interval -2.5 ≤ Eappl ≤ 0 V vs. Ag/Ag+, the films of poly-33′′-DDTT varied their mass according to a mechanism of cations insertion during n-doping and cations extraction during polymer neutralization. In fact, the electrochemical doping of polythiophenes requires the accompanying exchange of charged species to maintain the electroneutrality within the structure of the polymer in all states of polarization. At the end of a full electrochemical cycle (consisting of the n-doping and the successive neutralization of poly-33′′-DDTT), the polymer retains a fraction of the mass acquired during n-doping, thus manifesting the phenomena of mass trapping. The combined analysis of electrochemical and microgravimetric data suggests that poly-33′′-DDTT in the n-doped state undergoes (or electrocatalyzes) uncontrolled electrochemical reactions that are not accompanied by mass variations
EQCM analysis of the process of electrochemical insertion in regioregular alkyl-susbtituted polyterthiophene during n-doping
No full textThe material produced through the electrochemical polymerization of 3′4′-DDTT has been characterized with the EQCM during the process of n-doping. The supporting electrolyte (SE) was chosen considering mainly the two characteristics of hydrophobicity (to avoid the presence of water as potential contaminant) and chemical affinity with the alkyl and aromatic moieties present in poly-3′4′-DDTT. On these bases the salt (n-C4H9)4NClO4 was selected as SE since it contains the organic molecular cation (n-C4H9)4N+ that is expected to represent the charge compensating species in poly-3′4′-DDTT during n-doping. The feature of the reversibility of the electrical current profiles originated by the process of injection/extraction of electronic charge carriers in poly-3′ 4′-DDTT, is not encountered in the associated EQCM data. The interpretation of the EQCM data requires the consideration of phenomena of different nature. In the present work a thorough discussion of the factors influencing the EQCM response during polymer n-doping is provided taking into account the spontaneous adsorption of cations, the eventual reorientation of poly-3′4′DDTT on the substrate and the consequences of the chains rearrangement on the electrical polarizability of poly-3′4′-DDTT during the cycles of electrochemical n-doping and undoping
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Walker, Decker F., Back to the Future: The New Conservatism in Education, Educational Researcher, 19(April, 1990), 35-38.
No full textReviews three 1987 books (Finn & Ravitch, Hirsch, Bloom) and notes their ideological perspectives and their non-research bases
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