1,720,964 research outputs found
Orientational ordering of a banana-shaped solute molecule in a nematic calamitic solvent by 2H NMR spectroscopy: an indication of glasslike behavior
No full textThe Saupe ordering matrix of a banana-shaped mesogenic molecule as a solute in a common nematic calamitic solvent has been determined by H-2-NMR spectroscopy as a function of temperature. The temperature dependence of the Saupe ordering matrix element associated with the principal molecular axis is consistent with a glassy behavior in the reorientational motion of this particular solute molecule. The Haller expression, appropriately modified, provides a good fit to the experimental data
Internal Rotation in Alchyl Benzene derivatives: Maximum Entropy and Constrained Maximum Entropy analysis of the Dipolar Couplings of Samples dissolved in a Nematic Liquid Crystal solvent
No full textAtomistic Molecular Dynamics Simulation of Hexa-pentyloxy-triphenylene: Structure and Translational Dynamics of Its Columnar State
No full textAtomistic molecular dynamics simulations have been performed on the columnar state of the discogen hexa-pentyloxy-tryphenilene
Computer simulations of pure and mixed systems of disklike particles interacting with the S-function Corner potential
No full textThe S-function potential for single-site particles has been recently introduced as an extension of the Gay-Berne potential. With the S-function potential, we can model particles of other and, possibly, more realistic shapes than Gaussian overlap ellipsoids and we can simulate mixtures in a systematic manner. As an example of both applications, we have studied via Monte Carlo computer simulation assemblies of cylindrically symmetric disklike particles of two different types. They can be considered complementary perturbations of a disk, with, respectively, a depression (red-cell, R particles) and a protuberance (ufo, U particles) at the center. The former is meant to mimic the average effect of side chains of real diskotics, while the latter is a simple representation of diskotic metallomesogens. Four systems of these kind of particles have been studied as a function of temperature: two pure cases and two 1:2 binary mixtures, so that the combined effects of shape and concentration can be observed. We have found the largest variety of phases in the pure U system where also a nematic phase is present. No such phase is observed when 1/3 of the U particles are replaced by R particles, as well as in the mixture 2/3R-1/3U and in the pure R system. At the lowest temperatures investigated all systems show a lattice phase except the mixture 1/3R- 2/3U, whose organization is better described as a disordered columnar phas
Computer simulation of p-phenyls with interaction potentials from ab-initio calculations
No full textThe potential energy surface (PES) of n-p-phenyls, with n from 2 to 5, has been obtained from ab initio calculations relevant to a few fragments into which the molecule can be decomposed. These PES have been fitted with a single Gay-Berne model that has been used in Monte Carlo NPT and Gibbs ensemble simulations. The results we obtain are in fairly, good agreement with experiment in the case of biphenyl, while only a low density fluid phase (gas) is obtained for p-terphenyl and longer molecules
Computer simulation of mesogens with ab initio interaction potentials - An Application to oligophenyls
No full textMultitechnique investigation of conformational features of small molecules: The case of methyl phenyl sulfoxide
No full textThe conformational distribution of methyl phenyl sulfoxide (a molecule representative of a very important
class of reagents widely used in asymmetric synthesis) has been studied in two different phases of matter
(gas phase and solution) by a comprehensive approach including theoretical calculations, microwave
spectroscopy, liquid crystal NMR experiments, and atomistic molecular dynamics computer simulations. The
aim was to investigate the combined action of intra- and intermolecular interactions in determining the
molecule’s conformational equilibrium, upon which important physicochemical properties (inter alia, the
chemoselectivity) significantly depend. Basically, the results converge in describing the tendency of the molecule
to favor stable conformations governed by intramolecular interactions (in particular, the expected optimization
between steric repulsion and conjugation of ð systems). However, significant solvent effects (whose “absolute”
magnitude is actually difficult to assess, due to a certain “method-dependence” of the results) have been also
detected
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
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