1,721,169 research outputs found
The Dulmage-Mendelsohn permutation in seismic tomography
No full textSeismic tomography inverse problems are among the largest high-dimensional parameter estimation tasks in Earth science. Although iterative algorithms can be used to efficiently solve these problems, their size gives rise to several issues such as the intractability of the computation of the model resolution and the model posterior covariance matrices that provide the means of assessing the robustness of the solution. In this work, we utilize methods from combinatorics and graph theory to study the structure of typical regional seismic body-wave tomography problems, and to effectively decompose them into subsets that can be solved efficiently by means of the least squares method. In combination with recent high performance direct sparse algorithms, this reduction in dimensionality allows for an efficient computation of the model resolution and covariance matrices using limited resources. We apply this methodology to a moderate size imaging of the structure of the crust and the upper mantle beneath Japan using deep local earthquakes recorded by the High Sensitivity Seismograph Network stations. Among the prominent features that are being imaged is a strong low-velocity region beneath the subducting Pacific slab along the entire Japan trench
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
Stellar-gas kinematic misalignments in eagle: enhanced SMBH growth in misaligned galaxies
No full textStellar-gas kinematic misalignments are a transient phenomenon observed in ∼11 per cent of the local galaxy population. According to current models, misaligned gas is expected to lose angular momentum and relax into the galactic plane on timescales of ∼0.1 Gyr, driving gas toward the central regions of the galaxy. Recent observational studies have found a higher incidence of active galactic nuclei in misaligned galaxies. We use the eagle simulation to explore the connection between stellar-gas misalignments and enhanced central black hole (BH) activity between 0 < z < 1. We use a sample of ∼5600 galaxies with a stellar mass of M* ≥ 109.5 M⊙ that feature long-lived stellar-gas alignment, counter-rotation, and unstable misalignments (non-coplanarity). Over time windows of 0.5 Gyr, we find that galaxies experiencing an unstable misalignment have systematically enhanced BH growth during relaxation. Galaxies with long-term counter-rotation show little difference in BH growth compared to aligned galaxies. We suggest that this enhanced BH growth is driven by loss of angular momentum in unstable misaligned gas discs which is able to drive gas inward toward the vicinity of the BH. At z = 0.1, we find a greater incidence of overmassive BHs in galaxies that have spent a greater fraction of time with unstable stellar-gas kinematic misalignments over the preceding ≈2 Gyr compared to control samples of aligned galaxies. In agreement with observations, we conclude that BH activity is enhanced in misaligned systems in eagle and suggest that the presence of overmassive BHs may be indicative of a past stellar-gas kinematic misalignment
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
Investigating the effects of fresh gas on the Active Galactic Nuclei luminosity of early- and late-type galaxies
Full text linkThe main fuelling processes for Active Galactic Nuclei (AGN) are currently unknown. Previous work showed that galaxies with a large kinematic misalignment between their stellar and gas reservoirs have a higher AGN fraction than galaxies without misalignment. Such misalignment is a strong indication of a past galaxy interaction or an external accretion event. In this work we use integral field spectroscopy data from the SAMI and MaNGA surveys to investigate the AGN luminosity as a function of kinematic misalignment angle. Our sample of AGN exhibit bolometric luminosities in the range 1040 to 1043 erg s−1, indicative of low to moderate luminosity AGN. We find no correlation between AGN luminosity as a function of misalignment for AGN host galaxies from both surveys. We find some differences between the AGN luminosity of early- and late-type AGN host galaxies (ETGs, LTGs). AGN in LTG hosts have a wider luminosity range, with most LTG hosts showing aligned stellar to gas kinematics. AGN in ETG hosts have a luminosity range that does not depend on misalignment angle, suggesting AGN in ETG hosts are consistent with being fuelled by external accretion events, irrespective of their stellar to gas kinematic misalignment. While all the AGN in ETGs in our sample are consistent with being activated and fuelled by external gas, the range of observed AGN luminosities is likely caused by secondary factors such as the amount of fresh gas brought into the galaxy by the external interaction
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
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