1,720,991 research outputs found
Polymer-dispersed liquid crystals: effects of photorefractivity and local heating on holographic recording
No full textInfluence of the ions on the dynamical response of a nematic cell submitted to a DC voltage
No full textThe influence of the ions present in a liquid crystal on the dynamical response of a nematic slab submitted to a dc voltage is studied. The evolution of the system toward the equilibrium state is investigated by solving the continuity equation for the electric charge, taking into account the current of drift and of diffusion. Our analysis shows that the formation of the double layers close to the electrodes strongly modifies the distribution of the electric field across the sample. We evaluate the surface polarization due to the ions movements and the contribution to the anisotropic part of the surface energy having a dielectric origin. We show also that, even if the optical response of the liquid crystal is a slow phenomenon, the distribution of the ionic charge is rather fast. Consequently, the presence of the ions cannot be neglected in the determination of the flexoelectric coefficients when the nematic sample is submitted to a square wave having a period of the order of one second
Spectrograph Based on a Single Diffractive Element for Real- Time Measurement of Circular Dichroism
No full textIn this study, a novel and simple diffractive spectrographic method for
real-time measurements of circular dichroism (CD) is considered from a
theoretical and experimental approach. A demonstrator prototype of the
CD spectrograph has been developed and its performance has been
compared with a commercial phase-modulation CD spectrometer. The
main element of the device is a polarization holographic grating, recorded
in a thin photosensitive organic film, by two interfering opposite circularly
polarized beams. A peculiarity of this grating is that the amplitude of the
þ1 (1) order of diffraction is proportional to the right (left) circular
polarization component of the incoming beam. Here we demonstrate that
the CD spectrum of a specimen can be easily evaluated from the intensities
of the diffracted beams. A white light beam passing through the specimen
is diffracted from the grating and the intensities of the 6 1 orders of
diffraction are measured. Due to the spectral selectivity of the grating, the
CD at each wavelength can be evaluated at the same time using two linear
array detectors
Molecular reorientation dynamics due to direct current voltage-induced ion redistribution in undoped nematic planar cell
Full text linkInvestigation of photorefractive effect in dye doped PDLC: TBC experiments and photoinduced currents measurements
No full text
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
Probing Cavitand−Organosilane Hybrid Bilayers via Sum-Frequency Vibrational Spectroscopy
No full textQuinoxaline cavitands (QxCav) are transferred by Langmuir-Schaefer method on self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS) and N,N-dimethyl-N-octadecyl-3-aminopropyltrimethoxysilyl chloride (DMOAP) on fused silica substrates. The molecular architectures of both the hydrophobic SAMs templates and the hybrid cavitand-organosilanes bilayers at the solid−air
interface are investigated and correlated by sum-frequency vibrational spectroscopy. The results show that QxCav are always in the closed vase configuration and orient with their principal axis normal to the substrates. The role of the alkyl chains density in the SAM templates on the QxCav transfer ratio is pointed out
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