1,720,956 research outputs found
Nonlinear optical properties of benzylic amide [2] catenanes: a novel versatile photonic material
No full textBenzylic amide catenanes are a class of synthetically-accessible interlocked molecular rings which can rotate one through the other depending on the nature of the local environment. The rings contain four phenyl units each and interlocking also affords their packing in novel, highly interacting ways that may lead to unexpected properties thus opening up the possibility of developing new materials. Third harmonic generation in benzylic amide catenane solutions was measured at a wavelength of γ = 1064 nm, with the fundamental and the harmonic wavelengths in the region of transparency of the material. The thoroughly non resonant value of the hyperpolarisability γ(-3ω; ω, ω, ω) was found to be (6.5 ± 0.7) 10-35 esu with a negligible imaginary part, in agreement with the value of (6.8 ± 0.9) 10-35 esu calculated from a bond-additivity model of hyperpolarisability. The static second order hyperpolarisability predicted by a Molecular Orbital model was about a factor four less than the experimental value. Second hyperpolarizability values of several solvents were also measured at the fundamental wavelength of γ = 1064 nm
Thin films of a Benzylic Amide [2]catenane as a novel versatile photonic material
No full textCatenanes are a new class of potentially interesting materials for application in photonics. Good optical quality thin films of a benzylic amide catenanes were obtained by vacuum evaporation. They exhibit a large transparency range with cut off at around 300 nm and a large refractive index. The propagation losses depend on the wavelength and ar of 2.8 dB/cm, 4.5 dB/cm and 30 dB/cm at 1314 nm, 1550 and 633 nm, respectively. At 633 nm the propagation losses are clearly due to the Raleigh scattering
Benzylic amide [2] catenanes as a novel photonic material
No full textCatenanes are a new class of potentially interesting materials for application in photonics. Good optical quality thin films of a benzylic amide catenanes were obtained by vacuum evaporation. They exhibit a large transparency range with cut off at around 300 nm and a large refractive index. The propagation losses depend on the wavelength and ar of 2.8 dB/cm, 4.5 dB/cm and 30 dB/cm at 1314 nm, 1550 and 633 nm, respectively. At 633 nm the propagation losses are clearly due to the Raleigh scattering. The cubic susceptibility measured by the optical third harmonic generation is of (3.4 +/- 0.4) X 10-13 esu. The as deposited thin films are anisotropic and exhibit second harmonic generation as well as the linear electro-optic effect. However the linear electro-optic coefficient is about two orders of magnitude larger than that expected from SHG measurements, indicating clearly the ring mobility under the applied external electric field
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
Luminescence Lifetime Temperature Sensing Based on Sol-Gels and Poly(acrylonitrile)s Dyed with Ruthenium Metal–Ligand Complexes
No full textTemperature-sensitive materials based on the temperature probe ruthenium-tris-1,10-phenathroline (Ru(phen)) are presented. As its luminescence, the intensity and decay time of which are both temperature sensitive, is quenched by oxygen, Ru(phen) needs to be encapsulated in materials with very low permeability to molecular oxygen. Its incorporation into sol-gels and poly(acrylonitrile)s (PANs) is investigated here and it is shown that the resulting materials can be deposited onto optical fibers for use as temperature optodes
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
- …
