1,720,963 research outputs found
Pier Luigi Nordio Festschrift, Structure, Dynamics and Liquid Crystals - Proceedings of the seminar held in memory of Pier Luigi Nordio - Palazzo del Bo, Padova, Italy - January 11-12, 2002 - Part I of II - Foreword
No full textAngular dependence of 2H-NMR longitudinal spin relaxation in aligned nematic 4-n-pentyl-4'-cyanobiphenyl: molecular rotation and director fluctuations
No full textThe longitudinal (spin-lattice) relaxation in nuclear magnetic resonance (NMR) experiments on 4-n-pentyl-4'-cyanobiphenyl (5CB) mesogen, deuteriated in the alpha-position, has been investigated by changing the orientation of the phase director with respect to the instrumental magnetic field through the application of a competing alternating electric field. The angular-dependent profiles of the corresponding rotational spectral densities were fitted and interpreted by invoking a model for single-molecule reorientational dynamics and fluctuations of the local director with respect to the average direction of alignment. The relative contribution of the two processes to the longitudinal relaxation rate has been estimated, and values of the principal components of the rotational diffusion tensor of the 5CB molecule were obtained from the data fit. The work focuses mainly on the methodological grounds, by pointing out the increase in the extent of achievable information when passing from standard NMR experiments performed at the canonical orientation of the sample (that is an alignment collinear to the magnetic field) to measurements on arbitrarily oriented samples
On the flexoelectric coefficients of liquid crystal monomers and dimers: a computational methodology bridging length-scales
No full textNematic cyanobiphenyl dimers have been found to exhibit a
strong flexoelectric coupling, whose molecular origin is not
obvious; we can explain such behaviour and clearly identify the
role of different molecular features using a computational
approach which combines a molecular level model and the
elastic continuum theory
Angular dependence of 2H-NMR longitudinal spin relaxation in aligned nematic 4-n-pentyl-4'-cyanobiphenyl: molecular rotation and director fluctuations
No full textThe longitudinal (spin-lattice) relaxation in nuclear magnetic resonance (NMR) experiments on 4-n-pentyl-4'-cyanobiphenyl (5CB) mesogen, deuteriated in the alpha-position, has been investigated by changing the orientation of the phase director with respect to the instrumental magnetic field through the application of a competing alternating electric field. The angular-dependent profiles of the corresponding rotational spectral densities were fitted and interpreted by invoking a model for single-molecule reorientational dynamics and fluctuations of the local director with respect to the average direction of alignment. The relative contribution of the two processes to the longitudinal relaxation rate has been estimated, and values of the principal components of the rotational diffusion tensor of the 5CB molecule were obtained from the data fit. The work focuses mainly on the methodological grounds, by pointing out the increase in the extent of achievable information when passing from standard NMR experiments performed at the canonical orientation of the sample (that is an alignment collinear to the magnetic field) to measurements on arbitrarily oriented samples
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
Monte Carlo simulations of orientational ordering of solutes in a nematic solvent: comparison with mean-field models
No full textMonte Carlo simulations were used to study orientational ordering of solutes in a nematic phase. Nematogens were modelled as hard prolate ellipsoids with an axis ratio of 5:1. Solutes were also modelled as hard prolate ellipsoids, with a variety of sizes and shape anisotropies. Solute order parameters and singlet orientational distribution functions were analysed using several mean-field models. The results confirm that these empirical mean-field potentials are closely linked to the anisotropic short-range repulsive forces that are crucial for the formation of the nematic phase.PT: J; CR: ADAMS DJ, 1987, MOL PHYS, V61, P1575 ALEJANDRE J, 1994, J CHEM PHYS, V101, P7027 ALLEN MP, 1993, ADV CHEM PHYS, V136, P1 EMERSON APJ, 1992, MOL PHYS, V76, P241 FERRARINI A, 1992, MOL PHYS, V77, P1 FRENKEL D, 1984, PHYS REV LETT, V52, P287 FRENKEL D, 1985, MOL PHYS, V55, P1171 FRENKEL D, 1987, MOL PHYS, V60, P1 LUCKHURST GR, 1990, LIQ CRYST, V8, P451 LUCKHURST GR, 1993, MOL PHYS, V80, P233 PALKE WE, 1994, MOL PHYS, V82, P177 PATEY GN, 1983, CHEM PHYS LETT, V99, P271 PHOTINOS DJ, 1992, J PHYS CHEM-US, V96, P8176 PHOTINOS DJ, 1993, J CHEM PHYS, V98, P10009 SAMBORSKI A, 1994, MOL PHYS, V81, P263 SNIJDERS JG, 1983, ISRAEL J CHEM, V23, P269 VANDEREST AJ, 1987, MOL PHYS, V60, P397 VIEILLARDBARON J, 1972, J CHEM PHYS, V56, P4729 WILSON MR, 1991, MOL CRYST LIQ CRYST, V198, P465 WILSON MR, 1992, LIQ CRYST, V12, P157 ZIMMERMAN DS, 1990, MOL PHYS, V69, P1059 ZIMMERMAN DS, 1991, MOL CRYSTALS LIQ CRY, V203, P61 ZIMMERMAN DS, 1993, MOL PHYS, V78, P687; NR: 23; TC: 15; J9: MOL PHYS; PG: 16; GA: UT951Source type: Electronic(1
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
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