1,721,008 research outputs found
Asymptotic evolution of weakly collisional Vlasov-Poisson plasmas
No full textWe study the role of (weak) numerical diffusion on the long time evolution of the Vlasov-Poisson plasma. We consider the classical problem of phase space vortex formation by particle trapping. We show that the asymptotic macroscopic state is not independent of diffusion even if the dissipative length scale is much shorter than any characteristic physical length scale of the system
The Vlasov-Poisson model and the validity of a numerical approach
No full textOur aim in this work is to show that the final macroscopic state of a noncollisional plasma system, computed through numerical simulations, depends on artificial small scale effects induced by the used numerical scheme and/or grid discretization. By using the continuous, Hamiltonian Vlasov-Poisson model, we found significant differences in the nonlinear dynamics when varying the importance of dissipative and/or dispersive (numerical) effects. In particular, such artificial processes are crucial during phase space vortex generation and vortex merging dynamics leading to different irreversible asymptotic states. These results are obtained for numerical grid scale lengths much smaller than any noncollisional physical scale length. (c) 2006 American Institute of Physics
IN VITRO NK CELL DIFFERENTIATION FROM CD34+ HEMATOPOIETIC PROGENITORS SUGGEST A DISTINCT ORIGIN OF THE CD56BRIGHT AND CD56DIM NK CELL SUBSETS
No full text"Echography" of Vlasov codes
No full textCollisionless simulation of nonlinear plasma dynamics is one of the outstanding problems of plasma physics as well as a strong challenge in computational physics. Here, a crucial test for the theoretical study of collisionless plasmas based on large scale numerical simulations is proposed. Plasma echoes are shown to provide a highly selective benchmark for the algorithms adopted in order to follow the collisionless, Hamiltonian dynamics of high temperature, rarefied plasmas described by the Vlasov-Poisson system of equations. The proposed test is more discriminating than those based on the conservation of (a finite set of) Casimir invariants and gives a deeper insight on the numerical dissipative processes at play. (c) 2006 Elsevier B.V. All rights reserved
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
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