1,720,957 research outputs found
Structural and solvatochromic studies of a series of tricyanoquinodimethane-based zwitterions
No full textThe synthesis and characterization of three new solvatochromic tricyanoquinodimethane zwitterionic systems is reported. (Z)-{?-[N-(1-Propyl)benzothiazolium-2-yl]-alpha-cyano-4-styryl}dicyanomethanide, C3H7(2)BT3CNQ, (Z)-{?-[ N-(1-propyl)benzothiazolium-2-yl]-alpha-cyano-4-(2,3,5,6-tetrafluorostyr yl)}dicyanomethanide, C3H7(2)BT3CNQF(4), and (Z)-{?-[N-(1-butyl)benzoselenazolium-2-yl]-alpha-cyano-4-styryl}dicya nomethanide, C4H9(2)BS3CNQ, exhibit negative solvatochromism, consistent with a transition from an ionic ground state to a significantly less polar excited state. X-Ray crystallography measurements confirm the zwitterionic ground state of these novel T3CNQ-based chromophores. The solvatochromic properties of these compounds are compared to those of a series of related quinolinium/pyridinium adducts, and also with those of the Reichardt betaine dye
Distorted electron acceptors: an unexpected reaction involving tetramethyl-TCNQ
No full textReactions involving the donors N-methyl-2-methylbenzothiazolium-and N-(1-propyl)-2-methylbenzothiazolium iodide with the acceptor 2,3,5,6-tetramethyl-7,7,8,8-tetracyano-p-quinodimethane (TMTCNQ) in the presence of a suitable base lead to the isolation of novel [(Z)-beta-(N-alkylbenzothiazol-3-ium-2-yl)-alpha-cyano-2,3,5,6-tetrameth yl-4-styryl]dicyanomethanide chromophores. Under prolonged reaction periods, these first examples of charge transfer compounds incorporating the distorted TMTCNQ electron acceptor, undergo further reaction at the acrylonitrile functionality promoting the synthesis of novel thiomorpholine-based charge transfer compounds via a sulfur mediated cyclisation reaction. This second reaction illustrates a fundamentally new type of TCNQ-based chemistry as confirmed by X-ray crystallography and high-resolution mass spectrometry. A possible reaction mechanism for the formation of the thiomorpholine-based chromophores is considered
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
Comparison of the structure property relationships in LB films of zwitterionic TCNQ adducts
No full textSubstitution reactions of TCNQ (7,7,8,8-tetracyanoquinodimethane) with suitable quinolinium and picolinium electron donor moieties yielded an extensive analogous series of alpha-bridged quinolinium and picolinium adducts R(2)Q3CNQ and R(2)P3CNQ respectively of which the long chain (Z)-{beta-[N-(1-hexadecyl)quinolinium-2-yl]-alpha-cyano-4-styryl}-dicyan omethanide (C16H33(2)Q3CNQ) is a typical example. These zwitterionic D-pi-A materials (where D and A are electron donor and acceptor respectively) exhibit properties such as solvatochromism, molecular rectification and second harmonic generation and were compared and contrasted to the existing gamma-bridged adducts. The behaviour of the materials on the water subphase and their resultant Langmuir-Blodgett (LB) film fabrication were studied. The abrupt change in molecular orientation in LB films of the gamma-bridged adducts occurring at R = C15H31 and above was not seen in the more flatly orientated alpha-bridged adducts. Further characterisation of the LB films was performed using reflectance-absorption infra-red spectroscopy (RAIRS) and surface plasmon resonance (SPR). The crystal structure of the long chain adduct, C10H21(2)Q3CNQ, is also reported
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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