1,721,006 research outputs found
Spontaneous formation of a polariton condensate in a planar GaAs microcavity
No full textWe report on polariton condensation in a planar GaAs microcavity under nonresonant optical excitation. Angularly resolved photoluminescence measurements demonstrate polariton condensation for temperature up to 40 K. Numerical simulations using Boltzmann equations give an overall description of the observed condensation for various detunings and temperatures. This model highlights the importance of the polariton relaxation rate as compared to the polariton decay for condensation to occur on the lowest energy polariton states
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
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
Rashba-Dresselhaus spin-orbit coupling in topological physics and exciton-polariton fluids
No full textDes degrés de liberté supplémentaires enrichissent la physique des systèmes et fournissent les leviers de contrôle supplémentaires nécessaires à la réalisation d'applications. Par exemple, en incluant le spin de l'électron dans la description du transport électronique dans les solides, tout le domaine de la spintronique a émergé, lequel compte désormais de nombreuses applications, telles que les dispositifs de stockage de mémoire magnétique, les capteurs magnétiques, les DEL et lasers polarisés en spin, les transistors à spin, etc. Dans le domaine de la physique topologique, l'inclusion du spin a donné naissance aux isolants et supraconducteurs de Hall quantique de spin, aux semi-métaux de Weyl, ainsi qu'à d'autres phases topologiques intéressantes de la matière.Le cœur de nombreux de ces effets réside dans le couplage spin-orbite, le lien entre le spin de l'électron et son mouvement. En général, le couplage spin-orbite électronique est décrit par une superposition des contributions de Rashba et de Dresselhaus. Sous une fabrication et un réglage appropriés des paramètres, ces deux contributions peuvent être équilibrées, donnant lieu à un régime particulier de couplage spin-orbite de Rashba-Dresselhaus (RDSOC). Il se trouve que le même type de couplage spin-orbite équilibré peut être réalisé dans les systèmes photoniques et les gaz atomiques, où le rôle du spin est joué par la polarisation de la lumière dans le cas des photons et par deux niveaux hyperfins dans le cas des atomes. L'étude des effets possibles provenant du RDSOC est l'objectif principal de cette thèse théorique.Tout d'abord, nous examinons comment l'incorporation du RDSOC peut induire ou modifier la topologie de différents systèmes. Nous commençons par construire une description générique et appropriée des liaisons fortes dans des réseaux en présence de RDSOC. Nous distinguons deux régimes fournis par le RDSOC : les régimes de contrôle de l'amplitude et de la phase des coefficients de couplage. Le premier nous permet de démontrer le contrôle topologique de la chaîne de Su-Schrieffer-Heeger. Le second ouvre la voie à la réalisation du modèle de Harper-Hofstadter. Nous élargissons ensuite notre étude aux systèmes non-Hermitiens. En introduisant la non-Hermiticité dans le système, l'effet tunnel devient non-réciproque. Dans le cas d'une chaîne de monomères, cela donne lieu à l'effet de peau non-Hermitien de spin, où la chaîne de monomères se divise en deux copies orthogonalement polarisées, chacune réalisant le modèle de Hatano-Nelson. Un effet similaire se produit pour une chaîne SSH avec RDSOC, conduisant à une correspondance anormale entre le volume et les bords.Dans cette thèse, nous nous concentrons sur une réalisation particulière du RDSOC dans une microcavité planaire à cristaux liquides nématiques. Ce système offre une grande flexibilité de la structure de bande, de vastes capacités d'ingénierie, y compris par lithographie, il possède tous les avantages des systèmes photoniques, tels que l'accès direct aux états propres, le couplage lumière-matière, des propriétés non linéaires uniques et, enfin, il offre une voie vers la physique non-Hermitienne en raison de la nature ouverte des systèmes photoniques. Nous montrons que les effets suggérés ci-dessus peuvent être réalisés dans des microcavités avec cristaux liquides, et certains ont déjà été réalisés après nos propositions.Enfin, nous consacrons la dernière partie de cette thèse à la description des fluides d'exciton-polaritons sous RDSOC. Nous proposons une nouvelle approche pour confirmer le couplage fort dans un système à structure de bande modulable. Nous appliquons cette approche aux résultats expérimentaux obtenus dans une microcavité hybride cristaux liquides-polymère organique. Nous poursuivons l'étude de ce système dans le régime condensé, en démontrant et en étudiant la phase « stripes » du fluide polaritonique, une caractéristique emblématique de la supersolidité.Additional degrees of freedom enrich the physics of systems and provide the supplementary control knobs necessary for achieving applications. For example, by including the electron spin in the description of electron transport in solids, the whole field of spintronics has emerged, which now counts many applications, such as magnetic memory storage devices, magnetic sensors, spin-polarized LEDs and lasers, spin transistors, etc. In the domain of Topological Physics, the inclusion of the spin gave rise to the quantum spin Hall insulators and superconductors, Weyl semimetals, and other interesting topological phases of matter.The core of many of these effects lies in the spin-orbit coupling, the link between electron spin and its motion. Generically, electronic spin-orbit coupling is described by a superposition of Rashba and Dresselhaus contributions. Under proper fabrication and tuning of parameters, these two contributions can be balanced, giving rise to a particular regime of Rashba-Dresselhaus spin-orbit coupling (RDSOC). It turns out that the same type of balanced spin-orbit coupling is possible to realize in photonics and atomic gases, where the role of spin is played by the light polarization in the case of photons and two hyperfine levels in the case of atoms. The investigation of possible effects originating from RDSOC is the main scope of this theoretical thesis.First, we investigate how the incorporation of RDSOC can induce or modify the topology of different systems. We start by constructing a proper generic tight-binding description of lattices in the presence of RDSOC. We distinguish two regimes provided by RDSOC: tunneling amplitude and phase control regimes. The first allows us to demonstrate the topology control of the Su-Schrieffer-Heeger chain. The second paves the way towards realization of the Harper-Hofstadter model. We then extend our study to non-Hermitian systems. By adding a non-Hermiticity into the system, the tunneling becomes non-reciprocal. In the case of a monomer chain, it gives rise to the spin non-Hermitian skin effect, where the monomer chain splits into two orthogonally-polarized copies, each realizing the Hatano-Nelson model. A similar effect happens for an SSH chain with RDSOC, with the addition of anomalous bulk-boundary correspondence.In this thesis, we focus on a particular realization of the RDSOC in a nematic liquid crystal planar microcavity. This system provides a fine tunability of band structure, vast engineering capabilities, including lithography, it possesses all the advantages of photonic systems, such as direct access to the eigenstates, light-matter coupling, unique nonlinear properties, and, finally, it offers a path towards non-Hermitian physics due to the open nature of photonic systems. We show that the effects suggested above can be realized in the liquid crystal microcavities, and some of them have already been realized after our proposals.Finally, we devote the last part of this thesis to the description of exciton-polariton fluids under RDSOC. We suggest a new approach for the strong coupling confirmation in a system with a tunable band structure. We apply this approach to the experimental results obtained in a hybrid liquid crystal - organic polymer microcavity. We further investigate this system in the condensed regime, demonstrating and studying the stripe phase of the polariton fluid, a hallmark of the supersolidity
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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