1,720,967 research outputs found
Rapid Static Sensitizer Regeneration Enabled by Ion Pairing
No full textAn anionic CoII complex, [Co(TTT) (NCS)3]− (TTT = 4,4′,4′′-tri-tert-butyl-2,2′:6′,2′′-terpyridine and NCS = isothiocyanate), was synthesized for use in dye-sensitized solar cells (DSSCs). The CoII complex was found to ion-pair with the hexacationic sensitizer [Ru(tmam)2(dcb)]6+ (tmam = 4,4′-bis(trimethylaminomethyl)-2,2′-bipyridine and dcb = 4,4′-(CO2H)2-2,2′-bipyridine) anchored to TiO2 thin films immersed in acetonitrile solution. Visible light excitation of the ion pairs resulted in excited-state injection followed by rapid static regeneration of the oxidized sensitizer (<10 ns). The static component to regeneration gave an ion-pair equilibrium constant of 6000 M–1. This value is an order of magnitude smaller than the equilibrium constant determined for [Ru(tmam)2(deeb)]6+ (deeb = 4,4′-(CO2Et)2-2,2′-bipyridine) dissolved in acetonitrile. DSSC studies employing [Co(TTT) (NCS)3]− or the cationic [Co(DTB)3]2+ (DTB = 4,4′-di-tert-butyl-2,2′-bipyridine) as redox mediators revealed a 3 fold photocurrent increase in the presence of the anionic cobalt complex. As the regeneration step was greatly enhanced through the formation of Coulombic ion pairs, both electron injection and regeneration were complete within 10 ns which is unprecedented for dye-sensitization. The results obtained reveal that ground-state ion-pairing can be a powerful strategy for DSSC optimization
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
The Influence of Non-Covalent Interactions on Photoinduced Electron Transfer at Interfaces and in Fluid Solution
Get PDFPhotoinduced electron transfer is an essential reaction in biology and artificial solar energy conversion. In the dye-sensitized solar cell (DSSC), regeneration of a semiconductor-anchored sensitizer through electron transfer from a solution-based redox mediator is a crucial reaction that is not optimized under operational conditions. Non-covalent interactions offer a way to control and enhance regeneration. This work details efforts in the development of finite control over electron transfer reactions, both at solid-liquid interfaces and in solution. The DSSC is introduced in the context of non-covalent interactions and pertinent electron transfer theory and techniques in Chapter 1.
Chapters 2 and 3 focus on non-covalent enhancement of the regeneration reaction. Chapter 2 describes how a sensitizer’s increased propensity to form halogen bonds with the iodide redox mediator leads to an increase in the regeneration rate constant. The increased rate constant correlated with larger DSSC photovoltages. Chapter 3 demonstrates the importance of frontier molecular orbital overlap for electron transfer. Variation of a single chalcogen atom on a sensitizer showed an order of magnitude increase in regeneration only when the frontier molecular orbital localized on the chalcogen atom.
Chapters 4-8 investigate electron transfer within electrostatic ion pairs. In chapter 4, bromide formed two-consecutive ion pairs with a dicationic ruthenium sensitizer, that yielded a drastic shut-off and then recovery of photoluminescence, which aligns with the Gibbs free energy for electron transfer. Chapters 5-8 utilize a dicationic bipyridyl ligand to increase the cationic charge of ruthenium polypyridyl compounds. In chapter 5, three ruthenium compounds, with 4+, 6+, or 8+ charge, show enhanced ion pairing with iodide in acetonitrile. Chapter 6 characterizes a rare example of ion pairing at the sensitized interface. Regeneration occurred rapidly, k > 108 s-1, within an ion pair between a hexacationic ruthenium and an anionic cobalt redox mediator. Chapter 7 determines the excited-state quenching mechanism of similar ruthenium-cobalt ion pairs through ultrafast transient absorption spectroscopy. Finally, chapter 8 extends the use of ion pairs to excited-state proton-coupled electron transfer (ES-PCET). Direct measurement of the ES-PCET rate constants within the ion pair facilitated the determination of a sequential proton, electron transfer (PT-ET) mechanism.Doctor of Philosoph
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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