1,721,017 research outputs found
The impact of a stochastic background of primordial magnetic fields on scalar contribution to cosmic microwave background anisotropies
No full textThe scalar, vector and tensor contributions of a stochastic background of magnetic fields to cosmic microwave background anisotropies
No full textWe study the contribution of a stochastic background (SB) of primordial magnetic fields (PMFs) on the anisotropies in temperature and polarization of the cosmic microwave background (CMB) radiation. A SB of PMF modelled as a fully inhomogeneous component induces non-Gaussian scalar, vector and tensor metric linear perturbations. We give the exact expressions for the Fourier spectra of the relevant energy–momentum components of such a SB, given a power-law dependence parametrized by a spectral index nB for the magnetic field power spectrum cut at a damping scale kD. For all the values of nB considered here, the contribution to the CMB temperature pattern by such a SB is dominated by the scalar contribution and then by the vector one at higher multipoles. We also give an analytic estimate of the scalar contribution to the CMB temperature pattern
Impact of stochastic primordial magnetic fields on the scalar contribution to cosmic microwave background anisotropies
No full textWe study the impact of a stochastic background of primordial magnetic fields on the scalar contribution
of cosmic microwave background (CMB) anisotropies and on the matter power spectrum. We give the
correct initial conditions for cosmological perturbations and the exact expressions for the energy density
and Lorentz force associated to the stochastic background of primordial magnetic fields, given a powerlaw
for their spectra cut at a damping scale. The dependence of the CMB temperature and polarization
spectra on the relevant parameters of the primordial magnetic fields is illustrated
Territorio e logistica: un binomio ancora tutto da inventare
Full text linkLa velocità di adattamento alle situazioni è quel concetto che sta alla base del nuovo modo di fare e vivere il territorio. Esso accomuna sia gli aspetti di urgenza legati all’esigenza di trasformazione delle strutture territoriali per far sì che esse possano confrontarsi in maniera competitiva con territori che sempre di più devono aggiornare la propria immagine ed organizzazione per far fronte ai nuovi dettami e strategie imposti dalla globalizzazione, sia gli aspetti più strettamente economici e della produzione i quali, nelle sfide lanciate dalla mondializzazione dei mercati e dall’impellenza della sostenibilità - intesa nella sua accezione più ampia - risentono in maniera sempre più pressante della necessità di un aggiornamento o di una trasformazione continui
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
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