1,720,968 research outputs found
Constraining sulfur isotope abundances in molecular clouds: A meteoritic perspective
Get PDFMade available in DSpace on 2018-08-17T16:09:15Z (GMT). No. of bitstreams: 2
3173.pdf: 15447 bytes, checksum: fadb22e3c5dd9550ee7db7ebb484f2ca (MD5)
license.txt: 4802 bytes, checksum: 58353f9dd6876860dd5221f3d7872a95 (MD5)
Previous issue date: 6Made available in DSpace on 2018-12-12T22:37:34Z (GMT). No. of bitstreams: 4
3173.pdf.txt: 1035 bytes, checksum: b01d268601f14817dd8a2f81b42dac9e (MD5)
license.txt: 4802 bytes, checksum: 58353f9dd6876860dd5221f3d7872a95 (MD5)
3173.pdf: 15447 bytes, checksum: fadb22e3c5dd9550ee7db7ebb484f2ca (MD5)
1164491.pptx: 5107190 bytes, checksum: 4eced22f76d2e2ff20120bf3fd2efd1d (MD5)
Previous issue date: 6Carbonaceous chondrite class meteorites exhibit isotopic enrichments in deuterium, 13C, 15N, and possibly 33S, implying interstellar origins. To study possible sulfur enrichments, we have been conducting observations of SO in molecular clouds to determine abundance ratios between 32S, 34S, and 33S. The N=2-1 3mm transitions of SO have been measured towards W51M, DR21, G34.3, W3(OH), and NGC7538 using the ARO 12m telescope. The sulfur isotope ratios are currently being calculated and will be compared to meteoritic samples (Bose et al. 2017). The results presented will help to determine the connection between molecular cloud and meteoritic materials
CONSTRAINING SULFUR ISOTOPE ABUNDANCES IN MOLECULAR CLOUDS: A METEORITIC PERSPECTIVE
No full textCarbonaceous chondrite class meteorites exhibit isotopic enrichments in deuterium, C, N, and possibly S, implying interstellar origins. To study possible sulfur enrichments, we have been conducting observations of SO in molecular clouds to determine abundance ratios between S, S, and S. The N=2-1 3mm transitions of SO have been measured towards W51M, DR21, G34.3, W3(OH), and NGC7538 using the ARO 12m telescope. The sulfur isotope ratios are currently being calculated and will be compared to meteoritic samples (Bose et al. 2017). The results presented will help to determine the connection between molecular cloud and meteoritic materials
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
Isotopic and Elemental Compositions of Stardust and Protosolar Dust Grains in Primitive Meteorites
Get PDFThis dissertation presents the results and implications of the isotopic and elemental analyses of presolar silicate grains from the primitive chondrites, Acfer 094, SAH 97096, and ALHA77307. Oxygen-anomalous, C-anomalous, and N-anomalous grains were identified by O, C, and N isotopic imaging, respectively, using the NanoSIMS 50. Subsequently, the elemental compositions of the grains carrying the anomalous isotopic signatures were acquired in the PHI 700 Auger Nanoprobe. Some silicate grains with unique O isotopic compositions were measured for Si and Fe isotopes. The isotopic analyses indicate that a majority of the silicate and oxide grains are 17O-rich with solar to sub-solar 18O/16O ratios and come from less than 2.2Mï Red Giant or Asymptotic Giant Branch stars. The second most abundant fraction of grains show large 18O excesses and come from core collapse supernovae. The next most abundant fraction of grains comes from high metallicity AGB stars of approximately solar mass. A minor fraction of the grains exhibit large excesses in 16O and formed in core collapse supernova ejecta. Grains with extreme 17O excesses are the latest addition to the presolar grain inventory. These grains may come from binary star systems where one star goes nova. Numerous presolar SiC and N-anomalous carbonaceous grains were identified in the matrix of ALHA77307. The SiC grains are predominantly mainstream grains and may have condensed in 1-3Mï AGB stars. The carbonaceous grains may have formed by ionmolecule reactions in the protosolar nebula or interstellar medium. A few carbonaceous grains exhibit 13C-rich compositions; grains with such compositions are rare, which implies that either the fractionation effects that produce C anomalies in opposite directions cancel them out or secondary processing destroyed grains with C anomalies. The elemental compositions of the silicate grains are predominantly nonstoichiometric: 61%), with some grains exhibiting olivine- or pyroxene-like compositions. About 25% of the silicate grains contain Ca and/or Al. Furthermore, most of the presolar silicates are Fe-rich with Fe contents reaching up to about 45 at.% in contrast to equilibrium condensation models, which predict Mg-rich phases such as forsterite and enstatite to form. Although secondary alteration processes have probably modified the compositions of some presolar silicate grains in Acfer 094, the source of the Fe enrichments in most silicate grains is arguably primary. This work has led to the identification of presolar Si-oxide and Mg-oxide grains that had not been observed before. The formation of SiO2 grains requires non-equilibrium conditions in the outflows of stars. The abundance of SiC and silicate grains in ALHA77307 is high indicating its pristine characteristics, similar to the CR chondrites QUE 99177 and MET 00426. Although, the number of stardust grains identified in the enstatite chondrite SAH 97096 is low, their identification indicates that such grains were not all destroyed during the high temperature phase experienced by enstatite chondrites. Finally, silicate grain abundances are much higher than oxide grain abundances in all the three meteorites
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
- …
