1,720,985 research outputs found
Fountain fringe field switching (FFFS) for wide viewing angle LCDs
Full text linkTo reduce or completely remove the viewing angle dependence of liquid crystal (LC) displays
and devices, we have recently introduced a new electrode structure for LC displays. This
electrode structure has openings (holes) in the pixel electrode (PixE) for generating fringe
electric field with azimuthal degenerated distribution of the field lines around each hole,
resembling a fountain. Such a field is promoting azimuthally degenerated switching of the LC
molecules and thus generation of images with 360◦ viewing angle constant contrast when a pair
of crossed circular polarisers are used. A theoretical model of the fountain fringe field,
generated around a single circular hole and plurality of such holes in the PixE, is presented
Wavefront imaging by using an inline holographic microscopy system based on a double-sideband filter
No full textIn this letter, we propose an inline holographic microscopy (ILHM) system, based on the double-sideband technique (DST), for wavefront imaging. The presented optical system shows all the benefits of the previously reported DST (instantaneous removing of ghost images in an inline scheme) but adapted to a microscopic system. The double-sideband filter is implemented by using a transparent liquid crystal (LC) bi-pixel device. Specifically, by addressing the proper phase values to each half of the LC bi-panel, which is located at the Fourier plane of the holographic system, the conjugate image is removed. What is more, by using a high numerical aperture microscope objective, we achieved the microscopic wavefront holography imaging. Finally, the feasibility of the proposed system is testified by obtaining holographic wavefront images of different objects.Fil: Zhang, Haolin. Universidad Autonoma de Barcelona. Facultad de Física; EspañaFil: Monroy Ramírez, Freddy A.. Universidad Nacional de Colombia; ColombiaFil: Lizana, Ángel. Universidad Autonoma de Barcelona. Facultad de Física; EspañaFil: Iemmi, Claudio César. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; ArgentinaFil: Bennis, Noureddine. Military University Of Technology; PoloniaFil: Morawiak, Przemysław. Military University Of Technology; PoloniaFil: Piecek, Wiktor. Military University Of Technology; PoloniaFil: Campos, Juan. Universidad Autonoma de Barcelona. Facultad de Física; Españ
Tunable optical spin Hall effect in a liquid crystal microcavity
No full textThe spin Hall effect, a key enabler in the field of spintronics, underlies the capability to control spin currents over macroscopic distances. The effect was initially predicted by D'Yakonov and Perel1 and has been recently brought to the foreground by its realization in paramagnetic metals by Hirsch2 and in semiconductors3 by Sih et al. Whereas the rapid dephasing of electrons poses severe limitations to the manipulation of macroscopic spin currents, the concept of replacing fermionic charges with neutral bosons such as photons in stratified media has brought some tangible advances in terms of comparatively lossless propagation and ease of detection4–7. These advances have led to several manifestations of the spin Hall effect with light, ranging from semiconductor microcavities8,9 to metasurfaces10. To date the observations have been limited to built-in effective magnetic fields that underpin the formation of spatial spin currents. Here we demonstrate external control of spin currents by modulating the splitting between transverse electric and magnetic fields in liquid crystals integrated in microcavities.</p
Realizing optical persistent spin helix and stern-gerlach deflection in an anisotropic liquid crystal microcavity
No full textSpin-orbit interactions which couple the spin of a particle with its momentum degrees of freedom lie at the center of spintronic applications. Of special interest in semiconductor physics are Rashba and Dresselhaus spin-orbit coupling. When equal in strength, the Rashba and Dresselhaus fields result in SU(2) spin rotation symmetry and emergence of the persistent spin helix only investigated for charge carriers in semiconductor quantum wells. Recently, a synthetic Rashba-Dresselhaus Hamiltonian was shown to describe cavity photons confined in a microcavity filled with optically anisotropic liquid crystal. In this Letter, we present a purely optical realization of two types of spin patterns corresponding to the persistent spin helix and the Stern-Gerlach experiment in such a cavity. We show how the symmetry of the Hamiltonian results in spatial oscillations of the spin orientation of photons traveling in the plane of the cavity
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
Realizing persistent-spin-helix lasing in the regime of Rashba-Dresselhaus spin-orbit coupling in a dye-filled liquid-crystal optical microcavity
No full textIn the presence of Rashba-Dresselhaus coupling, strong spin-orbit interactions in liquid-crystal optical cavities result in a distinctive spin-split entangled dispersion. Spin coherence between such modes gives rise to an optically persistent spin helix. In this paper, we introduce optical gain in such a system, by dispersing a molecular dye in a liquid-crystal microcavity, and demonstrate an optically persistent spin-helix lasing in the Rashba-Dresselhaus regime.</p
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
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