1,721,004 research outputs found
Recommended from our members
Refining The M-Bh-V-C Scaling Relation With H I Rotation Curves Of Water Megamaser Galaxies
Full text linkBlack-hole-galaxy scaling relations provide information about the coevolution of supermassive black holes and their host galaxies. We compare the black-hole mass-circular-velocity (M-BH-V-c) relation with the black-holemass-bulge-stellar-velocity-dispersion (M-BH-sigma(*)) relation to see whether the scaling relations can passively emerge from a large number of mergers or require a physical mechanism, such as feedback from an active nucleus. We present Very Large Array HI observations of five galaxies, including three water megamaser galaxies, to measure the circular velocity. Using 22 galaxies with dynamical M-BH measurements and V-c measurements extending to large radius, our best-fit M-BH-V-c relation, logMBH = alpha +beta log(V-c/200 km s(-1)), yields a = 7.43+0.13 -0.13, beta = 3.68(-1.20)(+1.23), and an intrinsic scatter is an element of(int) = 0.51(-0.09)(+0.11). The intrinsic scatter may well be higher than 0.51, as we take great care to ascribe conservatively large observational errors. We find comparable scatter in the M-BH-sigma(*) relations, is an element of(int) = 0.48(-0.08)(+0.10), while pure merging scenarios would likely result in a tighter scaling with the dark halo (as traced by V-c) properties rather than the baryonic (sigma(*)) properties. Instead, feedback from the active nucleus may act on bulge scales to tighten the M-BH-sigma(*) relation with respect to the M-BH-V-c relation, as observed.McDonald Observator
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
Algorithms, Models, and Methods for SDSS-V Wide-field Robotic Fiber Spectroscopy
No full textThesis (Ph.D.)--University of Washington, 2023The field of astronomy has entered an age of big data, and this being driven by dedicated telescopes and instruments built for the sole purpose of conducting broad surveys to catalog the night sky. The highly successful space-based Gaia mission has already cataloged the broadband colors, 3D locations, and trajectories for nearly 2 billion astronomical sources. The much anticipated Legacy Survey of Space and Time (LSST) is projected to catalog an order of magnitude more objects. Imaging surveys like these are providing an unprecedented number of sources available for spectroscopic followup. Spectroscopy reveals a wealth of astrophysical information that imaging alone cannot, but spectroscopy is an inherently slow process. To spectroscopically observe even a small fraction of what is currently available, observations need to be performed as quickly and efficiently as possible. Robotic fiber positioners are a relatively new technology designed to speed up spectroscopic data collection. The fifth iteration of the Sloan Digital Sky Survey (SDSS-V) has built a pair of instruments each with 500 robots carrying optical fibers for multi-object spectroscopy. The first instrument operates from Apache Point Observatory (APO) in New Mexico and saw first light in December 2021. The second instrument operates from Las Campanas Observatory (LCO) in Chile and saw first light in August 2022. These instruments are designed to perform a spectroscopic survey of 6 million sources in a survey duration of five years. Operationally these instruments are complex, and they are required to perform at very high precision. This work describes the mathematics, algorithms, analysis, and general calibration strategies we have developed to make these instruments operational. A robot's fundamental task is to position a 120 m diameter optical fiber in the focal plane of the telescope to capture light from an astronomical source. A software package {\tt coordio} was developed to perform the calculations for determining where an astronomical source will land in the focal plane of the telescope and how a robot should be moved to collect light from that object. This package defines a series of coordinate systems and transforms and provides a computational backbone for many pieces of SDSS-V's survey operations and infrastructure codes. SDSS-V has chosen a spatially-agressive layout for the robotic fiber positioner array in which the physical workspace for a robot heavily overlaps with its neighbors. This layout grants more sky coverage to each robot but introduces a high risk of collision between robots during reconfiguration. A software package {\tt kaiju} was developed to compute safe paths for every robot while moving from one spectroscopic target to the next. This path planning algorithm was an important success for the project, and it allowed the instrument to realize its full potential in using every available robot in every spectroscopic exposure. When instrument assembly was completed, a period of lab testing and calibration was performed. A lab test camera was used to measure positions of back-lit optical fibers as robots were moved through many reconfigurations. From this process we derive a kinematic model unique to each robot for use in {\tt coordio} routines to accurately predict fiber locations. This period also served to test and tune {\tt kaiju} path planning parameters while operating the robot array at full scale, ensuring proper operation prior to shipping the instrument to the telescope. After lab calibration, each instrument was installed at the telescope where a Fiber View Camera (FVC) is used to measure and adjust fiber positions during array reconfiguration. A series of camera distortion models were derived to reach sufficient FVC measurement accuracy. On-sky instrument commissioning consisted of spectroscopic observations of Gaia sources using a telescope dither technique, which allowed us to estimate on-sky fiber position errors. Analysis of these data informed additional layers of instrument calibration which improved overall fiber positioning accuracy. The instrument at APO was commissioned first, and is currently placing robotic fibers with an RMS error of 21 m relative to astrophysical sources in the focal plane. Spectroscopic targets are generally well centered within the 120 m fiber aperture, and normal survey operations are proceeding. We expect that ongoing efforts will further improve survey efficiencies and fiber positioning performance with an end goal of limiting fiber placement error to 17 m. The instrument at LCO is currently in the commissioning and science verification phase, but initial indications suggest that fiber throughput will be sufficient for achieving SDSS-V science goals. SDSS-V is the third project worldwide to successfully deploy a robotic fiber positioner instrument to conduct a multi-year spectroscopic survey, and several other projects of comparable scale are nearing deployment. Throughout the process of designing, building, and using these instruments, the we have developed a number of strategies and techniques that are directly applicable to contemporary instruments today. Robotic fiber positioner arrays will likely continue to grow in importance, and proposals for building instruments with tens of thousands of robots on large aperture telescopes are already in place. The solutions derived from today's robotic multi-object spectrosopic surveys will directly influence the feasibility and design of future projects
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
