1,721,018 research outputs found
Vortex-lattice interaction in Pulsar Glitches
No full textIn this proceeding we present a quantitative model to study the pinning interaction between a neutron vortex and the nuclear lattice in the inner crust of a neutron star, which is formed by nuclear clusters immersed in a superfluid neutron gas. This is one of the most important quantities in the vortex model for pulsar glitches, where the sudden variations of the rotation velocity observed in some neutron stars are explained in terms of pinning-depinning processes between vortices and the nuclear lattice. The study has been done through an actual counting of the number of pinning sites between the vortex and the nuclear lattice. Moreover, it has been recognized that the vortices can have a generic orientation with respect to the lattice and thus the simple pinned-unpinned scenario (that is characteristic of the aligned case and has been assumed in previous qualitative models) is not acceptable for a realistic calculation. The forces that we have found are more than two orders of magnitude smaller than those calculated so far in the literature, and of the same order as what suggested to explain real Vela-like glitches. They can thus be applied to quantitative models for the vortex dynamics, in order to better simulate and understand these remarkable astrophysical phenomena
PROPRIETA' DELLA MATERIA SUPERFLUIDA IN PRESENZA DEL RETICOLO NUCLEARE NELLA CROSTA INTERNA DELLE STELLE DI NEUTRONI
Full text linkIn this thesis I study three different properties of superfluid nuclear matter in the inner crust of neutron stars, which is formed by nuclear clusters immersed in a superfluid neutron gas and ultrarelativistic electrons.
In the first part the cluster structure is calculated in the self-consistent HFB approach at zero temperature. The mean field and the pairing correlations of the inner crust nuclear matter are described, respectively, by a Skyrme-type effective interaction and by a zero range density dependent pairing force. The inner crust matter is treated in the Wigner-Seitz approximation. The properties of the Wigner-Seitz cells, i.e., their neutron to proton ratio and their radius at a given baryonic density, are obtained from the energy minimization at beta equilibrium. We have found that the Wigner-Seitz cells have a much smaller number of protons compared to the previous HF or HF+BCS calculations.
In the second part the specific heat of the nuclear matter is calculated with the same HFB formalism used in the first part, but at finite temperature. This study represent a considerable improvement respect to the specific heats that are generally used in the literature on which the superfluid corrections to the specific heat were calculated in the BCS approach and considering the matter as homogeneous neutron gas. Using the HFB approach, in fact, it is possible to calculate directly the specific heat of the nuclear matter considering at the same time the composition, the interaction between particles, the clusters structure and the pairing properties. We have then used this specific heat in the study of the thermalization process in the cooling of a neutron star and we have found that the nuclear clusters have a non-negligible influence on the time evolution of the surface
temperature of neutron stars.
Finally, in the third part we have used numerical simulations of interaction of vortex with lattice to study the pinning force per unit length that binds a vortex to the nuclear lattice, one of the most important quantities in the vortex model for pulsar glitches, i.e. sudden variation of the rotation velocity of some neutron stars. The forces that we have found are almost two order of magnitude smaller than those reported in the literature and of the same order of those that have been suggested to explain the peculiar behaviour of real pulsar glitches. They can thus be applied in a quantitative model of the vortex dynamics in order to reproduce those phenomena
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
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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