1,720,974 research outputs found
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
Manipulation of ultracold atomic mixtures using microwave techniques
No full textWe used microwave radiation to evaporatively cool a mixture of of Cs-133 and Rb-87 atoms in a magnetic trap. A mixture composed of an equal number (around 10(4)) of Rb and Cs atoms in their doubly polarized states at ultracold temperatures was prepared. We also used microwaves to selectively evaporate atoms in different Zeeman states
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
Model for collisions in ultracold-atom mixtures
No full textWe present a model for the collisional properties of a mixture of Cs-133 and Rb-87 atoms in a magnetic trap at mu K temperatures. The experimental sequence we model corresponds to a selective evaporation of the Rb atoms using a radio-frequency field, leading to sympathetic cooling of the Cs atoms or, if selective evaporation is carried out fast, to a difference in temperature between the two atomic species. In the latter case, the two atomic clouds reached an equilibrium temperature starting from an Rb temperature lower than that of Cs. By supposing that each atomic cloud was in thermal equilibrium we modeled this rethermalization process through differential equations for the two atomic temperatures. An alternative approach was based on the Monte Carlo simulations of the individual collisional processes. The sympathetic cooling and the rethermalization were analyzed in terms of the inter-species collisional cross-section
Sympathetic cooling and collisional properties of a Rb-Cs mixture
No full textWe report on measurements of the collisional properties of a mixture of Cs-133 and Rb-87 atoms in a magnetic trap at mu K temperatures. By selectively evaporating the Rb atoms using a radio-frequency field, we achieved sympathetic cooling of Cs down to a few mu K. The interspecies collisional cross section was determined through rethermalization measurements, leading to good agreement with a theoretical prediction of 595a(0) for the triplet s-wave scattering length for Rb in the parallel to F=2,m(F)=2 > and Cs in the parallel to F=4,m(F)=4 > magnetic states. We briefly speculate on the prospects for reaching the Bose-Einstein condensation of Cs inside a magnetic trap through sympathetic cooling
Manipulation of ultracold atomic mixtures using microwave techniques
No full textWe used microwave radiation to evaporatively cool a mixture of of Cs-133 and Rb-87 atoms in a magnetic trap. A mixture composed of an equal number (around 10(4)) of Rb and Cs atoms in their doubly polarized states at ultracold temperatures was prepared. We also used microwaves to selectively evaporate atoms in different Zeeman states. (c) 2005 Elsevier B.V. All rights reserved
Erratum to “Manipulation of ultracold atomic mixtures using microwave techniques” [Opt. Commun. 257 (2) (2006) 340–348]
No full textTwo-photon ionization of cold rubidium atoms
No full textTwo-photon ionization cross sections from the rubidium ground state have been measured with both a cw 421-nm laser and a combination of cw 421- and 1002-nm lasers. The measurements were performed within a high-vacuum magneto-optical trap while the trapping lasers were switched off, exploiting the long trap lifetime and also the trap laser confinement. The two-photon cross sections were determined for the blue laser near resonance with the 6P(1/2) and 6P(3/2) states and compared with the estimates of a theoretical model. In near resonance with the 6P states, large two-photon photoionization cross sections were measured
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