1,721,048 research outputs found
CONTROLLED PHASE SEPARATION IN CONJUGATED POLYMER BLENDS INDUCED BY THERMOLITHOGRAPHY
No full textThe big interest in conjugated polymers is due to their easy solution processability, which endows them with several prospects, from low-cost processing, to opportunity of creating materials with new properties by simple mixing solutions, so research has focused on to optimize the blends properties in order to enhance optoelectronic device performance. Possibility to rules a phase separation in conjugated polymer blends has wide range of applications in optoelectronics, because both charge transport and charge separation are influenced by presence of phase segregation. Here we present a new method of controlling phase segregation in conjugated polymer blends by using a scanning probe microscope
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
Observation of tip-to-sample heat transfer in near-field optical microscopy using metal-coated fiber probes RID F-3894-2011 RID B-4222-2010
No full textMetal-coated scanning near-field optical microscopy fiber probes can undergo significant heating due to partial absorption of the coupled light by the metallic film covering the apical zone. In this letter we report experimental evidence of tip-to-sample heat transfer on a 7,7',8,8'-tetracyanoquinodimethane molecular crystal. Local melting is observed at nanometric tip-sample distances, when increasing the laser power injected into the fiber above a threshold of 8.8 mW. Hole formation and material displacement are observed, as well as failure of the shear-force-based imaging process, due to partial sticking of the melted material to the probe. (c) 2005 American Institute of Physics
Shape dependent thermal effects in apertured fiber probes for scanning near-field optical microscopy RID B-4222-2010
No full textMetal-coated, "pulled," and conically shaped fiber probes used in scanning near-field optical microscopy (SNOM) typically undergo a thermal expansion when injected with laser light, due to partial energy absorption by the metallic film. Here, we report investigations into the thermal behavior of fiber probes produced by selective chemical etching that in our experience provide high light throughputs (10(-3)-10(-4) vs 10(-6) for the pulled fibers). Unexpectedly, we find a shortening of such probes in response to "high-power" laser injection (>1 mW). Thermal stress due to prolonged high-power laser injection (similar to 9 mW at 325 nm; compared to powers 10 mW at 633 nm). Although the vertical feedback mechanism of the microscope can compensate for dilations/contractions of the probes, these findings are of general importance to the field. More specifically they are significant for the achievement of a detailed understanding of apertured-SNOM operation, for the selection and operation of near-field probes, and for preventing potential artifacts in imaging and lithography, due to uncontrolled alteration of the probe properties and/or light leakage from cracks of the opaque coating induced by thermal fatigue. In addition, our results demonstrate that it is important for probe design to also consider the probe's thermal regime during operation, so as to prevent cracks in the functional parts of the coating and thus spurious, undesired sample illumination from regions other than the probe intended aperture. (C) 2006 American Institute of Physics
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