1,721,012 research outputs found
Dust heating in nearby galaxies with 3D radiative transfer modelling
No full textWithin the framework of the DustPedia project we study the effect of cosmic dust on a vast sample of nearby galaxies. Dust radiative transfer (RT) simulations provide us with the unique opportunity to study the heating mechanisms of dust by the stellar radiation field. From 2D FITS images we were able to derive the 3D geometry distributions of stars, a technique, first introduced by De Looze et al. (2014) and followed afterwards by Viaene et al. (2016). This powerful method allows a more realistic description of the complex stellar and dust geometries found in galaxies like asymmetric features or clumpy structures. Our aim is to analyse the contribution of the different stellar populations (old, young & ionising) to the radiative dust heating processes in the nearby face-on barred galaxies NGC1365, M83, M95, and M100 by using high resolution 3D radiative transfer modelling. To model the complex geometries mentioned above, we used SKIRT, a state-of-the-art, 3D Monte Carlo RT code designed to model the absorption, scattering and thermal re-emission of dust in a variety of environments (Nersesian et al.2019, Forthcoming in A&A).</p
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
Studying the effects of interstellar dust in nearby galaxies
Full text linkΣτη παρούσα διατριβή διερευνώ τις ιδιότητες της κοσμικής σκόνης και την αλληλεπίδρασής της με το αστρικό πεδίο ακτινοβολίας (που προέρχεται από διαφορετικούς αστρικούς πληθυσμούς) για 814 γαλαξίες στο κοντινό Σύμπαν (γαλαξίες που βρίσκονται σε απόσταση μικρότερη των 40 Mpc) οι οποίοι έχουν παρατηρηθεί από το διαστημικό τηλεσκόπιο Herschel του Ευρωπαϊκού Οργανισμού Διαστήματος. Για το σκοπό αυτό έγινε χρήση του ευρέως διαδεδομένου κώδικα CIGALE, ο οποίος είναι κατάλληλα διαμορφωμένος ώστε να συμπεριλαμβάνει το προηγμένο μοντέλο για την εκπομπή της σκόνης, THEMIS. Χρησιμοποιώντας τα δεδομένα της βάσης δεδομένων του DustPedia, μου επέτρεψε να προσδιορίσω τις φυσικές ιδιότητες των γαλαξιών, όπως τη μάζα των αστρικών πληθυσμών και της σκόνης, τον ρυθμό σχηματισμού νέων αστέρων, τη συνολική φωτεινότητα κάθε αστρικού πληθυσμού, καθώς και την ενέργεια που απορροφάται εξαιτίας της σκόνης, τόσο για τους γηραιούς (> 200 Myr) όσο και για τους νεαρούς (< 200 Myr) αστρικούς πληθυσμούς. Επιπλέον, ένας από τους κύριους στόχους της διατριβής ήταν η δημιουργία τρισδιάστατων μοντέλων διάδοσης ακτινοβολίας για γαλαξίες με υψηλή διακριτική ικανότητα. Με τη συγκεκριμένη μέθοδο επιχείρησα να λύσω το πρόβλημα διάδοσης της ακτινοβολίας. Από δισδιάστατες εικόνες παρατηρήσεων στα διάφορα μήκη κύματος, παρήγαγα τις τρισδιάστατες κατανομές των αστεριών και της σκόνης. Για να μοντελοποιήσω τις σύνθετες γεωμετρίες, χρησιμοποιήσα το SKIRT, έναν σύγχρονο κώδικα Monte Carlo, τρισδιάστατης διάδοσης ακτινοβολίας που σχεδιάστηκε για να προσομοιώνει την απορρόφηση, τη σκέδαση, και τη θερμική εκπομπή από τη σκόνη για αυθαίρετες τρισδιάστατες κατανομές. Ανέλυσα τη συμβολή των διαφόρων αστρικών πληθυσμών στις διαδικασίες θέρμανσης της σκόνης σε τέσσερις κοντινούς, ραβδωτούς γαλαξίες: NGC1365, M83, M95, και M100; καθώς κι έναν γαλαξία οποίος διαθέτει έναν ενεργό γαλαξιακό πυρήνα: NGC1068. Σκοπός της ανάλυσης αυτής ήταν να ποσοτικοποιήσω το ποσοστό που σχετίζεται άμεσα με τον ρυθμό παραγωγής νέων αστέρων, καθώς και την έκταση της συνεισφοράς του ενεργού γαλαξιακού πυρήνα στη θέρμανση της διάχυτης σκόνης στις τρεις διαστάσεις.The present thesis is investigating the properties of cosmic dust and its interaction with the stellar radiation field (originating from different stellar populations) on global scales, for 814 galaxies in the local Universe, all observed by the Herschel Space Observatory. I took advantage of the widely used fitting code CIGALE, properly adapted to include the state-of-the-art dust model THEMIS. Using the DustPedia photometry I have determined the physical properties of the galaxies, such as the dust and stellar mass, the star-formation rate, the bolometric luminosity, the unattenuated and the absorbed by dust stellar light, for both the old (> 200 Myr) and young (< 200 Myr) stellar populations. In addition, one of the main goals of this thesis, was to construct detailed 3D dust radiative transfer models for spatially resolved, nearby galaxies. From 2D images I have derived the 3D distributions of stars and dust. To model the complex geometries, I have used SKIRT, a state-of-the-art 3D Monte Carlo radiative transfer code designed to self-consistently simulate the absorption, scattering, and thermal re-emission by the dust for arbitrary 3D distributions. By analysing the contribution of the different stellar populations to the radiative dust heating processes in four nearby face-on barred galaxies: NGC1365, M83, M95, and M100; and a galaxy hosting an AGN: NGC1068, has enabled me to quantify the fraction directly related to star-formation, as well as the extent of the contribution of the AGN to the diffuse dust heating in three dimensions
Μελέτη της επίδρασης της μεσοαστρικής σκόνης στους κοντινούς γαλαξίες
No full textThe present thesis is investigating the properties of cosmic dust and its interaction with the stellar radiation field (originating from different stellar populations) on global scales, for 814 galaxies in the local Universe, all observed by the Herschel Space Observatory. I took advantage of the widely used fitting code CIGALE, properly adapted to include the state-of-the-art dust model THEMIS. Using the DustPedia photometry I have determined the physical properties of the galaxies, such as the dust and stellar mass, the star-formation rate, the bolometric luminosity, the unattenuated and the absorbed by dust stellar light, for both the old (> 200 Myr) and young ( 200 Myr) όσο και για τους νεαρούς (< 200 Myr) αστρικούς πληθυσμούς. Επιπλέον, ένας από τους κύριους στόχους της διατριβής ήταν η δημιουργία τρισδιάστατων μοντέλων διάδοσης ακτινοβολίας για γαλαξίες με υψηλή διακριτική ικανότητα. Με τη συγκεκριμένη μέθοδο επιχείρησα να λύσω το πρόβλημα διάδοσης της ακτινοβολίας. Από δισδιάστατες εικόνες παρατηρήσεων στα διάφορα μήκη κύματος, παρήγαγα τις τρισδιάστατες κατανομές των αστεριών και της σκόνης. Για να μοντελοποιήσω τις σύνθετες γεωμετρίες, χρησιμοποιήσα το SKIRT, έναν σύγχρονο κώδικα Monte Carlo, τρισδιάστατης διάδοσης ακτινοβολίας που σχεδιάστηκε για να προσομοιώνει την απορρόφηση, τη σκέδαση, και τη θερμική εκπομπή από τη σκόνη για αυθαίρετες τρισδιάστατες κατανομές. Ανέλυσα τη συμβολή των διαφόρων αστρικών πληθυσμών στις διαδικασίες θέρμανσης της σκόνης σε τέσσερις κοντινούς, ραβδωτούς γαλαξίες: NGC1365, M83, M95, και M100; καθώς κι έναν γαλαξία οποίος διαθέτει έναν ενεργό γαλαξιακό πυρήνα: NGC1068. Σκοπός της ανάλυσης αυτής ήταν να ποσοτικοποιήσω το ποσοστό που σχετίζεται άμεσα με τον ρυθμό παραγωγής νέων αστέρων, καθώς και την έκταση της συνεισφοράς του ενεργού γαλαξιακού πυρήνα στη θέρμανση της διάχυτης σκόνης στις τρεις διαστάσεις
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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