1,721,801 research outputs found
Numerical models of the galactic dynamo driven by supernovae and superbubbles
No full textWe calculate the temporal evolution and spatial structure of the large-scale magnetic field in our Galaxy, in the framework of an axisymmetric SN-driven dynamo model. We consider various parameter regimes, allowing for anisotropies in the dynamo parameters, the existence of an effective vertical escape of the field (analogous to a Galactic wind carrying field lines away from the midplane), vertical variations in the Galactic rotation curve... In the linear regime, axisymmetric (m = 0) modes are always easier to excite than bisymmetric (m = 1) modes. Amongst the former, the even (SO) mode often has the larger growth rate, while the odd (AO) mode generally oscillates more readily. Under typical conditions, the SO and AO modes have very similar properties; both grow monotonically with time at an exponential rate similar or equal to 0.45 Gyr(-1), which suggests that the Galactic magnetic field has presently reached a state close to saturation. In the absence of vertical escape, the magnetic field oscillates and only its AO component is amplified. Oscillatory behaviors are also found when the azimuthal alpha-parameter is enhanced by at least a factor of 3 or when the magnetic diffusivities are reduced by a factor > 1.7 with respect to their reference values; in both cases, the switch from monotonous to oscillatory behavior is accompanied by an increase in the growth rate. A height-dependence in the Galactic rotation velocity profoundly modifies the magnetic field morphology and is conducive to oscillatory decay. The nonlinear solutions obtained when the dynamo parameters are forced to decrease with increasing magnetic field strength are generally more spread out in space. For the growing modes, the field amplification saturates when its intensity in the peak region reaches similar to 20 mu G, corresponding to a magnetic pressure of roughly four times the local gas pressure. The time to saturation, which depends on the seed field strength adopted, is typically of the order of a few 10 Gyr. Nonlinear mode interactions may produce long-term changes both in the even vs. odd parity and in the monotonous vs. oscillatory temporal behavior of the large-scale magnetic field
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
Narcissism and the strategic pursuit of short-term mating: Universal links across 11 world regions of the International Sexuality Description Project-2
No full textPrevious studies have documented links between sub-clinical narcissism and the active pursuit of short-term mating strategies (e.g., unrestricted sociosexuality, marital infidelity, mate poaching). Nearly all of these investigations have relied solely on samples from Western cultures. In the current study, responses from a cross-cultural survey of 30,470 people across 53 nations spanning 11 world regions (North America, Central/South America, Northern Europe, Western Europe, Eastern Europe, Southern Europe, Middle East, Africa, Oceania, Southeast Asia, and East Asia) were used to evaluate whether narcissism (as measured by the Narcissistic Personality Inventory; NPI) was universally associated with short-term mating. Results revealed narcissism scores (including two broad factors and seven traditional facets as measured by the NPI) were functionally equivalent across cultures, reliably associating with key sexual outcomes (e.g., more active pursuit of short-term mating, intimate partner violence, and sexual aggression) and sex-related personality traits (e.g., higher extraversion and openness to experience). Whereas some features of personality (e.g., subjective well-being) were universally associated with socially adaptive facets of Narcissism (e.g., self-sufficiency), most indicators of short-term mating (e.g., unrestricted sociosexuality and marital infidelity) were universally associated with the socially maladaptive facets of narcissism (e.g., exploitativeness). Discussion addresses limitations of these cross-culturally universal findings and presents suggestions for future research into revealing the precise psychological features of narcissism that facilitate the strategic pursuit of short-term mating
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
Transverserly Isotropic Saturated Porous Formations: 1. Theoretical Developments And (Quasi) Body Wave Properties
Full text linkUsing the results of homogenization theory, the constitutive equations for an anisotropic
porous formation saturated by a Newtonian viscous fluid are derived. The transverse
isotropy situation is investigated in terms of partial stresses in both phases. It allows
to take into account a transversely isotropic skeleton and/or a transversely isotropic
complex permeability tensor whose axes of symmetry are assumed to coincide. The
wavenumbers equations are solved as part of a cylindrical geometry and general solutions
for the displacement potentials in each phase are presented.
Four dispersive and dissipative waves propagate in a transversely isotropic saturated
porous formation: two quasi compressional waves, a quasi SV wave and aSH
wave. All three quasi body waves approach the isotropic P[subscript 1] wave, slow P[subscript 2] wave, and S wave only as the degree of anisotropy of both the skeleton and the complex permeability tensor vanishes. Simple analytical formuale are derived for vertical and horizontal propagations. The SH-wave only excites the horizontal permeability, whatever its angle of propagation with respect to the vertical. The velocities and attenuations of these four waves are studied as a function of the only transversely isotropic permeability, the anisotropy of the skeleton, and the anisotropy of the mass coupling coefficient.
Whatever the frequency, the quasi P[subscript 1]-wave, quasi SV-wave and SH-wave velocities are primarily governed by the anisotropy of the skeleton. Contrary, the quasi slow P[subscript 2] wave velocity is mostly representative of the complex permeability tensor transverse isotropy. At very high frequencies, when the inertial forces in the saturated porous formation are dominant, an anisotropy of the mass coupling coefficient leads to slightly different quasi BV-wave velocities along the principal directions, contrary to the pure elastic situation. For the quasi PI wave and the quasi BV wave, the degree of anisotropy of the strongly frequency dependent attenuation induced by the two phase character of the material is more important than that of the velocity.Massachusetts Institute of Technology. Full Waveform Acoustic Logging Consortiu
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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