1,720,967 research outputs found
Maximising the learning potential of brain injured patients
No full textSIGLEAvailable from British Library Document Supply Centre-DSC:DX190493 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Silicon sensitisation using light harvesting layers
Full text linkLangmuir–Blodgett monolayers of a cyanine dye mixed with stearic acid were deposited on glass and silicon substrates with spacer layers of pure stearic acid monolayers or silicon dioxide films deposited by PECVD. By using the time correlated single photon counting technique, time resolved emission spectra (TRES) and decay curves were measured to characterise the dependence of energy transfer rate on the separation between the dye monolayer and the silicon surface and also for the dye concentrations in the monolayers. We observe interlayer energy transfer between monomers, dimers and higher aggregates present in the monolayer deposited on glass but also competing directly with energy transfer to silicon at close distances. We find that the fluorescence lifetime of the dye monolayer is significantly shortened when deposited close to the silicon surface signifying efficient energy transfer. The dissipation of the excitation energy near silicon is explained using the classical theory developed for metals and a deviation is observed for monolayers deposited at distances close to the silicon surfac
Light harvesting in silicon (111) surfaces using covalently attached protoporphyrin IX dyes
Full text linkWe report the photosensitization of crystalline silicon via energy transfer using covalently attached protoporphyrin IX (PpIX) derivative molecules at different distances via changing the diol linker to the surface. The diol linker molecule chain length was varied from 2 carbon to 10 carbon lengths in order to change the distance of PpIX to the Si(111) surface between 6Å and 18Å. Fluorescence quenching as a function of the PpIX-Si surface distance showed a decrease in the fluorescence lifetime by almost two orders of magnitude at the closest separation. The experimental fluorescence lifetimes are explained theoretically by a classical Chance-Prock-Silbey model. At a separation below 2 nm, we observe for the first time, a Förster-like dipole-dipole energy transfer with a characteristic distance of Ro = 2.7 nm
Photon collection efficiency of fluorescent solar collectors
Full text linkPhoton collection efficiency of fluorescent collectors is examined experimentally and by modelling, with a
view to assess the potential of this attractive solar energy technology. The edge fluorescence of single dye collectors
based on Rhodamine 6G and Coumarin 540A, manufactured by a simple fabrication technique, is investigated
in detail. A novel technique for determination of the collection efficiency is presented based on the traditional model
of fluorescent collectors but extended to allow spectral analysis. We show that these results agree well with direct
solar cell measurements. General conclusions are presented about fundamental loss mechanisms and about the
role of re-absorption of fluorescent light. It is shown that substantial improvements in collector efficiency can be
made with the use of photonic fluorescence confinement rather than by total internal reflection
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
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