1,720,964 research outputs found
Radial drift in warped protoplanetary disks
Get PDFThe meter-size barrier in protoplanetary disks is a major challenge in planet
formation, for which many solutions were suggested. One of the leading
solutions is dust traps, that halt or slow the inward migration of dust
particles. The source and profile of these traps are still not completely
known. Warped disks are ubiquitous among accretion disks in general and
protoplanetary disks in particular, and the warping could lead naturally to the
formation of dust traps. Dust traps in warped disks could rise not only from
pressure gradients, but also due to different precession rates between gas and
dust. Here we derive analytically the radial drift in warped disks, and
demonstrate derivation for some specific conditions. The radial drift in warped
protoplanetary disks is qualitatively different, and depending on the structure
of the disk, dust traps could form due to the warping. Similar processes could
lead to the formation of traps also in other accretion disks such as AGN disks
Correlation between planet formation rate and gas surface density: an analog of Kennicutt Schmidt law for planet formation
No full textThe efficiency of planet formation is a fundamental question in planetary science, gaining increasing significance as observational data from planet-forming disks accumulates. Here we derive from first principles a correlation between the planet formation rate (PFR) and the gas surface density, i.e. . This relation serves as an analog for the well-established Kennicutt-Schmidt law for star-forming galaxies. We study the different planet formation mechanisms and the density dependence in each one of them, to finally formulate a simple relation. We find that the powerlaw ranges between , depending on the type of the forming planet, when we carry out different analyses for the formation rates of terrestrial planets, gas giants, and also planets formed by gravitational instability. We then compare our results with the available observational data. The relation we derive here aims to shed more light on the interpretation of observational data as well as analytical models, and give a new perspective on the properties of planet formation and its connection to gas.Comments welcome
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Soft no more: gas shielding protects soft binaries from disruption in gas-rich environments
Get PDFBinaries in dense environments are traditionally classified as soft or hard
based on their binding energy relative to the kinetic energy of surrounding
stars. Heggie's law suggests that stellar encounters tend to soften soft
binaries and harden hard binaries, altering their separations. However,
interactions with gas in such environments can significantly modify this
behavior. This study investigates the impact of gas on binary softening and its
consequences. We find that gas interactions can actually harden binaries,
extending the soft-hard boundary to larger separations. This introduces a
"shielding radius" within which binaries are likely to harden due to gas
interactions, surpassing the traditional soft-hard limit. Consequently, a
notable portion of binaries initially classified as "soft" may become "hard"
when both gas and stars are considered. We propose a two-stage formation
process for hard binaries: initial soft binary formation, either dynamically or
through gas-assisted capture, followed by gas-induced hardening before eventual
disruption. In environments with low gas density but high gas content, the
shielding radius could exceed the typical hard-soft limit by an order of
magnitude, leading to a significant fraction of originally soft binaries
effectively becoming hard. Conversely, in high gas-density environments,
gas-induced hardening may dominate, potentially rendering the entire binary
population hard. Gas hardening emerges as a crucial factor in shaping binary
populations in gas-rich settings, such as clusters, star-forming regions, and
possibly AGN disks. This highlights the complex interplay between gas dynamics
and stellar interactions in binary evolution within dense environments.Comment: Comments are welcome
- …
