1,721,008 research outputs found
Weakly nonlocal Poisson brackets, Schouten brackets and supermanifolds
No full textPoisson brackets between conserved quantities are a fundamental tool in the theory of integrable systems. The subclass of weakly nonlocal Poisson brackets occurs in many significant integrable systems. Proving that a weakly nonlocal differential operator defines a Poisson bracket can be challenging. We propose a computational approach to this problem through the identification of such operators with superfunctions on supermanifolds
Projective-geometric aspects of bi-Hamiltonian structures of KdV type
No full textWe introduce the problem of classification of bi-Hamiltonian structures of KdV type under projective reciprocal transformations. This problem
leads naturally to studying the compatibility of a first order localizable homogeneous Hamiltonian operator with a higher order homogeneous Hamiltonian operator. We study the simplest third-order case where the orbit contains a constant operator. Computations with weakly non local Hamiltonian operators have been made by techniques developed in a previous paper
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
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
Glioma cells induce g-glutamyl-transpeptidase activity in cultured blood but not lymphatic endothelial cells
No full textGlial cells have been shown to induce enzyme activities, which are characteristically high in brain capillaries, in cerebral and non cerebral endothelial cells in culture. We evaluated the activity of g -glutamyl transpeptidase (gGT) in freshly isolated (ex vivo) bovine blood (BEC) and lymphatic (LEC) endothelial cells. We also tested the effect of C6 glioma cell conditioned medium (GCM) on gGT activity of BEC and LEC in primary culture. Ex vivo BEC had a high g GT activity, only 9% of which was retained in culture. After exposure to GCM, however, g GT activity of cultured BEC was twofold higher than with
control medium. By contrast g GT activity was extremely low in ex vivo LEC and did not significantly increase in cultured LEC exposed to GCM. These data show that the basal levels of g GT are markedly different in BEC and LEC and also that, unlike BEC, LEC are not capable of producing more g GT in response to glial stimulation
Genesi e significato del riempimento della depressione carsica di Piano Locce sul Gran Sasso d‘Italia (Abruzzo)
No full textWeakly nonlocal Poisson brackets: Tools, examples, computations
Get PDFWe implement an algorithm for the computation of Schouten bracket of weakly nonlocal Hamiltonian operators in three different computer algebra systems: Maple, Reduce and Mathematica. This class of Hamiltonian operators encompass almost all the examples coming from the theory of (1+1)-integrable evolutionary PDEs. Program summary: Program Title: Jacobi (Maple), CDE module cde_weaklynl.red (Reduce, official distribution), nlPVA (Mathematica) CPC Library link to program files: https://doi.org/10.17632/synmrvr74g.1 Developer's repository link: https://gdeq.org/Weakly_nonlocal_Poisson_brackets Licensing provisions: BSD 2-clause Programming language: Maple, Reduce (Rlisp), Mathematica Supplementary material: Example program files in the three languages (Maple, Reduce, Mathematica) Nature of problem: Calculating the Jacobi identity for weakly nonlocal Poisson brackets Solution method: Bringing the Jacobi identity to a canonical form Additional comments including restrictions and unusual features: Use a 2020 Maple or Mathematica version, or a 2021 Reduce snapsho
Flat F-Manifolds, F-CohFTs, and Integrable Hierarchies
Get PDFWe define the double ramification hierarchy associated to an F-cohomological field theory and use this construction to prove that the principal hierarchy of any semisimple (homogeneous) flat F-manifold possesses a (homogeneous) integrable dispersive deformation at all orders in the dispersion parameter. The proof is based on the reconstruction of an F-CohFT starting from a semisimple flat F-manifold and additional data in genus 1, obtained in our previous work. Our construction of these dispersive deformations is quite explicit and we compute several examples. In particular, we provide a complete classification of rank 1 hierarchies of DR type at the order 9 approximation in the dispersion parameter and of homogeneous DR hierarchies associated with all 2-dimensional homogeneous flat F-manifolds at genus 1 approximation
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