1,721,265 research outputs found
Timing Spectroscopy of Quasi-Periodic Oscillations in the Low-Mass X-Ray Neutron Star Binaries
No full textPrecise simultaneous measurements of the frequencies of the two kilohertz quasi-periodic oscillations (referred in the literature as upper and lower kHz QPOs) cast doubts on the validity of the simple beat-frequency interpretation and some of the modifications introduced to explain the results of the varying frequency difference. A new model explains the variation of the frequency difference, suggesting that the upper kHz QPO, namely ν_h, is an upper hybrid frequency of the Keplerian oscillator under the influence of the Coriolis force and the lower kHz QPO is the Keplerian frequency ν_K. Such an oscillator has two branches characterized by a high frequency ν_h (~1 kHz) and by a low frequency ν_L (~50 Hz). The frequency ν_L depends strongly on the angle δ between the normal to the neutron star disk and Ω-the angular velocity of the magnetosphere surrounding the neutron star. In the lower part of the QPO spectrum (~10 Hz), this model identifies the frequency of radial viscous oscillations ν_V (previously called ``extra noise component'') and the break frequency ν_b, which is associated with the diffusive process in the transition region (the innermost part of the disk). According to this model, all frequencies (namely ν_h, ν_L, ν_b, and ν_V) have specific dependences on ν_K. This Letter focuses on the verification of the predicted relations. For the source 4U 1728-34, the best theoretical fit is obtained for δ=8.3^0+/-1.0d, which is slightly larger than the value of δ=5.5^o+/-0.5d previously found for Scorpius X-1. In addition, we show that the theoretically derived power-law relation v_b~nu{^1.61}_V is consistent with the recent observations of other atoll and Z-sources
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
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
Bone Marrow Stromal Cell Assays: In Vitro and In Vivo
No full textPopulations of bone marrow stromal cells (BMSCs, also known as bone marrow–derived “mesenchymal stem cells”) contain a subset of cells that are able to recapitulate the formation of a bone/marrow organ (skeletal stem cells, SSCs). It is now apparent that cells with similar but not identical properties can be isolated from other skeletal compartments (growth plate, periosteum). The biological properties of BMSCs, and these related stem/progenitor cells, are assessed by a variety of assays, both in vitro and in vivo. Application of these assays in an appropriate fashion provide a great deal of information on the role of BMSCs, and the subset of SSCs, in health and in disease
Multipotential cells in the bone marrow stroma: regulation in the context of organ physiology
No full textMultipotential (osteogenic, adipogenic, chondrogenic, and myelosupportive) cells associated with the bone marrow stroma are revealed by in vitro or in vivo differentiation assays. If considered in the context of development, growth, and adaptive changes of bone as an organ, the hierarchical organization, histophysiology, and biological significance of the so-called "stromal system" appear distinct from those predicted from the commonly used analogy with the hematopoietic system, with which the stromal system and its putative "stem" cell are usually compared. The plasticity of differentiated phenotypes and the emergence of individual lineages in a defined temporal succession throughout development and postnatal life reflect the role of the multipotential cells in the stromal system in tissue adaptation and growth, rather than in cell consumption and replacement. This makes the stromal system and its progenitors an interesting paradigm of the biology of an individual cell's flexibility in complex organisms
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