1,721,108 research outputs found
Un'applicazione del metodo Qualitometro per la valutazione della qualità di un servizio di prenotazione ospedaliero
No full textThe spectrum of kink-like oscillations of solar photospheric magnetic elements
Full text linkRecently, the availability of new high spatial and temporal resolution observations of the solar photosphere has allowed for the study of the oscillations in small magnetic elements. Small magnetic elements have been found to host a rich variety of oscillations detectable as intensity, longitudinal, or transverse velocity fluctuations that have been interpreted as magneto-hydrodynamic (MHD) waves. Small magnetic elements, at or below the current spatial resolution achieved by modern solar telescopes, are thought to play a relevant role in the energy budget of the upper layers of the Sun's atmosphere, as they are found to cover a significant fraction of the solar photosphere. Unfortunately, the limited temporal length and/or cadence of the data sets or the presence of seeing-induced effects have prevented accurate estimates of the power spectra of kink-like oscillations in small magnetic elements so far. Motivated by this, we studied kink-like oscillations in small magnetic elements, by exploiting very long duration and high cadence data acquired with the Solar Optical Telescope on board the Hinode satellite. In this paper, we present the results of a statistical study of the power spectral density of kink-like oscillations. We found that small magnetic elements exhibit a large number of spectral features in the range 1-12 mHz. Most of these spectral features are not shared among magnetic elements rather they represent a unique signature of each magnetic element itself
Three-minute wave enhancement in the solar photosphere
Full text linkIt is a well-known result that the power of five-minute oscillations is progressively reduced by magnetic fields in the solar photosphere. Many authors have pointed out that this could be due to a complex interaction of many processes: opacity effects, MHD mode conversion, and intrinsically weaker acoustic emissivity in strong magnetic fields. While five-minute oscillations predominate in the photosphere, it has been shown that in the chromosphere three-minute oscillations are more common. Two main theories have been proposed to explain the presence of the latter oscillations based upon resonance filtering in the atmospheric cavity and non-linear interactions. In this work, we show, through the analysis of IBIS observations of a solar pore in the photospheric Fe I 617.3 nm line, that three-minute waves are already present at the height of formation of this line, their amplitude depends on the magnetic field strength, and they are strictly confined to the umbral region
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
On the asymmetry of velocity oscillation amplitude in bipolar active regions
Full text linkThe velocity field in the lower solar atmosphere undergoes strong interactions with magnetic fields. Many authors have pointed out that power is reduced by a factor between two and three within magnetic regions, depending on frequency, depth, the radius, and the magnetic strength of the flux tube. Many mechanisms have been proposed to explain the observations. In this work, Solar Dynamics Observatory (SDO) dopplergrams and magnetograms of 12 bipolar active regions (beta ARs) at a 45-s cadence are used to investigate the relation between velocity fluctuations and magnetic fields. We show that there is an asymmetry within beta ARs, with the velocity oscillation amplitude being more suppressed in the leading polarities than in the trailing polarities. Also, the strongest magnetic fields do not completely suppress the five-minute oscillation amplitude, even in the spot's innermost umbrae
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
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