1,721,402 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
Constraining some r-n extra-potentials in modified gravity models with LAGEOS-type laser-ranged geodetic satellites
Full text linkWe focus on several models of modified gravity which share the characteristic of leading to perturbations of the Newtonian potential K2 r-2 and K3 r-3. In particular, by using existing long data records of the LAGEOS satellites, tracked on an almost continuous basis with the Satellite Laser Ranging (SLR) technique, we set preliminary constraints on the free parameters K2, K3 in a model-independent, phenomenological way. We obtain |K2|< 2.1× 106 m4 s-2, -2.5× 1012 m5 s-2< K3 < 4.1× 1012 m5 s-2. They are several orders of magnitude tighter than corresponding bounds existing in the literature inferred with different techniques and in other astronomical and astrophysical scenarios. Then, we specialize them to the different parameters characterizing the various models considered. The availability of SLR data records of increasing length and accuracy will allow to further refine and strengthen the present results
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
Probing a r-nmodification of the Newtonian potential with exoplanets
Full text linkThe growing availability of increasingly accurate data on transiting exoplanets suggests the possibility of using these systems as possible testbeds for modified models of gravity. In particular, we suggest that the post-Keplerian (pK) dynamical effects from the perturbations of the Newtonian potential falling off as the square or the cube of the distance from the mass of the host star break the degeneracy of the anomalistic, draconitic and sidereal periods. The latter are characteristic temporal intervals in the motion of a binary system, and all coincide in the purely Keplerian case. We work out their analytical expressions in presence of the aforementioned perturbations to yield preliminary insights on the potential of the method proposed for constraining the modified models of gravity considered. A comparison with other results existing in the literature is made
Gravitomagnetic resonance in the field of a gravitational wave
Full text linkUsing the construction of the Fermi frame, the field of a gravitational wave can be described in terms of gravitoelectromagnetic fields that are transverse to the propagation direction and orthogonal to each other. In particular, the gravitomagnetic field acts on spinning particles and we show that, due to the action of the gravitational-wave field, a new phenomenon - which we call gravitomagnetic resonance - may appear. We give both a classical and a quantum description of this phenomenon and suggest that it can be used as the basis for a new type of gravitational-wave detectors. Our results highlight the effectiveness of collective spin excitations, e.g., spin waves in magnetized materials, in detecting high-frequency gravitational waves. Here we suggest that, when gravitational waves induce a precession of the electron spin, power is released in the ferromagnetic resonant mode endowed with quadrupole symmetry of a magnetized sphere. This offers a possible path to the detection of the gravitomagnetic effects of a gravitational wave
Perturbations of the orbital elements due to the magnetic-like part of the field of a plane gravitational wave
Full text linkIn this paper, we focus on the secular changes of the orbital elements of a planet in the solar system, determined by the magnetic-like part of a gravitational wave field. Using Fermi coordinates, we show that the total force acting on a test particle is made of two contributions: A gravito-electric one and a gravito-magnetic one. While the electric-like force has been thoroughly discussed in the past, the effect of the gravito-magnetic force, which depends on the velocity of the test particle, has not been considered yet. We obtain approximated results to some orders in the orbital eccentricity and show that these effects are much smaller than the corresponding gravito-electric ones
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
Assessing Pragmatic Language Skills in Adults with Major Depressive Disorder: An Exploratory Study
No full textIntroduction: There is increasing evidence that major depressive disorder (MDD) is associated with significant pragmatic language impairments. However, there is a lack of studies that use standardized tools and simultaneously investigate all pragmatic language skills among MDD patients. The aim of this study was to propose a more thorough investigation of all pragmatic language skills in patients with MDD. Methods: Twenty adults (aged 22-65) with a DSM-5 diagnosis of MDD were assessed using BLED Santa Lucia (Batteria sul Linguaggio dell'Emisfero Destro Santa Lucia), a battery designed to evaluate pragmatic language skills (comprehension of inferences, of picture and written metaphors, of indirect requests, of humoristic expressions, and of prosody). The performance of the MDD participants on all BLED Santa Lucia subscales was compared to 20 healthy control subjects (aged 20-60) matched for gender, age, years of education, and employment status. Results: MDD patients performed poorer than controls in comprehension of inferences (p < 0.01), picture metaphors (p < 0.001), written metaphors (p < 0.001), indirect requests (p < 0.01), humoristic expression (p < 0.05), and prosody (p < 0.05). Conclusions: All pragmatic language skills can be significantly impaired in MDD patients. A valid assessment of all pragmatic language skills can allow, for each patient, the definition of a specific profile of risk and protective factors before and during psychotherapy
Angular momentum effects in Michelson - Morley type experiments
Full text linkThe effect of the angular momentum density of a gravitational source on the times of flight of light rays in an interferometer is analyzed. The calculation is made imagining that the interferometer is at the equator of an axisymmetric steadily rotating gravity source. In order to evaluate the size of the effect in the case of the Earth a weak field approximation for the metric elements is introduced. For laboratory scales and non-geodesic paths the correction due to the angular momentum turns out to be comparable with the sensitivity expected in gravitational waves interferometric detectors, whereas it drops under the threshold of detectability when using free (geodesic) light rays
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