1,721,018 research outputs found
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
Cartographier les fluctuations de brillance des galaxies de la 2D à la 3D : faisabilité de l'interprétation des données à venir
No full textL'étude de l’évolution de la densité du taux de formation d’étoiles (SFRD) dans les galaxies est un champ de recherche clé pour toutes les questions majeures en astrophysique et en cosmologie. Les relevés de galaxies ont été largement utilisés pour retracer l’histoire de la formation d’étoile des galaxies jusqu'à un décalage vers le rouge d'environ z ~ 11. Cependant, ces études ne parviennent pas à capturer l'information complète en raison de la présence de multiples galaxies peu lumineuses et indétectables, en particulier à des z élevés. Pour compléter les relevés traditionnels, la technique dite d’«Intensity Mapping» (IM) est apparue comme une approche intéressante. Elle consiste à mesurer la distribution spatiale de l'émission collective des raies spectrales des galaxies et du milieu intergalactique. Le projet CONCERTO, qui utilise un spectromètre fonctionnant dans la gamme de fréquences 120-310 GHz a pour but de mesurer les fluctuations d'intensité de la raie [CII] provenant de sources à z>5. Ces mesures visent à retracer la formation d'étoiles en exploitant la corrélation étroite entre la raie [CII] et le taux de formation d’étoile dans les galaxies. CONCERTO mesure également en avant-plan les fluctuations d'intensité de la raie CO à z5. This technique aims to trace high-z star formation by exploiting the tight correlation between the [CII] line and SFR in galaxies. The objective of my thesis encompassed two main aspects. Initially, I focused on the development and validation of the Simulated Infrared Dusty Extragalactic Sky (SIDES) simulation, which played a significant role in investigating the feasibility of measuring and extracting physical information from intensity maps and cubes. The SIDES simulation combines a dark-matter halo catalog derived from a N-body cosmological simulation with empirical relations to assign galaxies with various physical properties, including SFR, continuum emission, and the emission of prominent (sub-)millimeter lines such as [CII] and CO. I specifically worked on integrating SIDES with the Uchuu N-body cosmological simulation, ultimately providing a large simulated area spanning approximately 120 square degrees. The power spectrum is a valuable and frequently used estimator that allows us to extract physical information from simulated or observed intensity maps and cubes. It quantifies the probability of encountering a pair of galaxies at a specific separation distance. In my thesis, I quantified and modeled the impact of field-to-field variance on the power spectrum obtained from CONCERTO, as well as from other intensity mapping experiments. This effect emerged as a significant limitation that can eventually influence the resulting physical quantities (e.g., SFR) we aim to obtain. The second aim of my thesis focused on investigating and validating existing models used to interpret the power spectrum of the cosmic infrared background (CIB) and line intensity mapping. These models, collectively known as the "halo model," aim to characterize anisotropies in emissions, such as continuum (CIB) and lines, across all scales. The halo model comprises three components: the 1-halo term, which accounts for small-scale clustering within the same halo, the 2-halo term, which captures clustering on large scales among galaxies in different halos, and the shot noise term, representing uncorrelated anisotropies at all scales. While these widely employed models have demonstrated apparent success in analyzing observational data (e.g., CIB anisotropies observed by the Planck satellite), their validation became crucial, especially prior to employing them for the interpretation of line power spectra. To this end, I employed these models to analyze simulated data from the SIDES-Uchuu simulation and discovered a discrepancy of approximately 20% between the expected and retrieved values. This result exposed weaknesses in the halo model's ability to extract precise physical data. Consequently, I engaged in a discussion regarding the potential sources of these model weaknessesd. Finally, I presented the investigation of a new, previously neglected signal, which is produced by the strong cross-correlation between CO-line intensity and CIB fluctuations and serve as an extra foreground to the already evasive kSZ signa
Probing the gas reservoirs of high-z dusty galaxies using ALMA observations of atomic carbon
No full textLes galaxies poussiéreuses à formation intense d'étoiles (> 500 Msun/an) sont présentes dans l'Univers primitif, et de nombreuses questions concernant leur formation et leur assemblage de masse restent ouvertes. Dans cette thèse, nous étudions une population de telles galaxies à partir de l'échantillon South pole telescope - sub-millimeter galaxies (SPT-SMG) en utilisant le grand réseau millimétrique/sub-millimétrique d'Atacama (ALMA). Nous nous concentrons sur la caractérisation des réservoirs de gaz et du milieu interstellaire de ces galaxies poussiéreuses afin de comprendre leurs taux prodigieux de formation d'étoiles. Nous nous concentrons sur les lignes d'émission du carbone neutre car il s'agit d'un traceur gaz alternatif. Dans la première partie de thèse, nous étudions un échantillon de 29 galaxies. A travers cet échantillon, nous comparons la capacité de [CI], CO, et de la poussière comme traceur des réservoirs de gaz et nous effectuons une calibration croisée de CO, XCI, et GDR. De plus, nous contraignons l'intensité du champ de radiation, les densités et les températures cinétiques de l'ISM en utilisant les rapports de lignes. Dans la deuxième partie de la thèse, nous nous concentrons sur l'imagerie à plus haute résolution de 3 de ces galaxies pour mieux comprendre leurs morphologies et les propriétés résolues de l'ISM afin de mieux étudier la nature des galaxies poussiéreuses à formation intense d'étoiles à haut décalage horaire. Nous trouvons diverses cinématiques de sources dans notre échantillon : SPT0103-45 et SPT2147-50 sont probablement des disques en rotation, tandis que SPT2357-51 est peut-être une fusion majeureIntensely star-forming (> 500 Msun/yr) dusty galaxies are found in the early Universe, and many questions regarding their formation and mass assembly remain open. In this thesis, we study a population of such galaxies from the South pole telescope – sub-millimeter galaxies (SPT-SMG) sample using Atacama large millimeter/sub-millimeter array (ALMA). We focus on characterizing the gas reservoirs and interstellar medium of these dusty galaxies to understand their prodigious star-formation rates. We focus on the neutral carbon emission lines as it is a promising alternative tracer to the traditionally used carbon monoxide lines. In the first part of this thesis, we study a sample of 29 galaxies with a rich ancillary data of multiple emission lines. Through this sample, we compare the ability of [CI], CO, and dust as a tracer of the gas reservoirs in these galaxies. We cross-calibrate the CO, XCI, and GDR and find a good agreement between them. Additionally we constrain the radiation field intensity, densities and the kinetic temperatures of the ISM using line ratios. In the second part of the thesis, we focus on higher-resolution imaging of 3 such galaxies to further understand their morphologies and resolved ISM properties to further investigate on the nature of intensely star-forming dusty galaxies at high-redshifts. We find diverse source kinematics in our sample: SPT0103-45 and SPT2147-50 are likely rotating disks, while SPT2357-51 is possibly a major merge
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
The main sequences of star-forming galaxies and active galactic nuclei at high redshift
Get PDFPRIN INAF; Spanish MINECO [RYC-2013-13256]; I+D project (MINECO/FEDER) [AYA2015-65887-P]; National Science Foundation of China [11503024
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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