1,721,007 research outputs found
Supplementary Dataset for "Most Earth-surface calcites precipitate out of isotopic equilibrium", by M. Daëron, R.N. Drysdale, M. Peral, D. Huyghe, D. Blamart, T.B. Coplen, F. Lartaud, and G. Zanchetta
No full textThis repository contains the raw data files and Python code used to generate all figures and equations included in the article "Most Earth-surface calcites precipitate out of isotopic equilibrium", by Daëron et al. (https://doi.org/10.1038/s41467-019-08336-5).</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
How I Learned to Stop Worrying and Embrace Isotopic Disequilibrium in Carbonate Minerals
No full textInternational audienc
Laser instrument for triple oxygen spectrometry dedicated to geochemistry
No full textLes techniques de spectroscopie d’absorption à haute précision sont désormais couramment utilisés en physique fondamentale et en métrologie. Plus récemment, elles ont gagné les faveurs des sciences de la terre, essentiellement en raison de leur compacité et de leur robustesse.Cependant, en particulier pour CO2 le potentiel de cette méthode n’a pas encore été pleinement exploité. Dans cette thèse, nous présentons un nouveau spectromètre exploitant le mécanisme de rétroaction optique pour verrouiller l’émission d’un laser DFB à une cavité optique de référence très stable à géométrie en V. De cette façon, nous obtenons une source dans le proche infra-rouge d’une largeur de raie inférieure au kHz dérivant de moins de 30Hz/s. Cette source très-fine et très-stable est alors couplée à un spectromètre à temps de déclin (Cavity Ring Down Spectrometer) de haute finesse et de grande stabilité dont la fréquence des modes optiques est gardée en résonance par un système de modulation. Nous démontrons que cet instrument atteint une sensibilité de 10-12cm-1 en 30 s, la durée d’un simple spectre, et nous montrons de plus, sur des spectres moins larges, que cette sensibilité atteint la valeur record de 3.8 x 10-14cm-1 lorsque on les moyenne pendant 10h.Nous avons utilisé cet instrument pour mesurer les rapports isotopiques du CO2 et nous avons démontré la faisabilité d’une mesure directe du Δ17O. Ce paramètre est un super-ratio qui nécessite la mesure précise de trois isotopologues du CO2 et qui apporte des informations sur l’environnement hydrologique du passé lorsqu’il est issu de roches carbonatées. Notre instrument atteint une précision de 10 ppm en un temps de mesure record de 10 minutes, démontrant que la spectroscopie laser offre des performances au niveau de l’état de l’art des spectromètres de masse dédiés à ce type de mesures et utilisés dans les études de géosciences. Nous faisons aussi la démonstration de la toute première mesure optique du ratio 16O13C18O/16O13C16O (« clumped isotope »), à un niveau de 20 ppm et qui conserve un large potentiel d’amélioration. Notre instrument pourrait mesurer en une fois tous les rapports isotopiques du CO2 utiles actuellement pour les géosciences.Nous avons par ailleurs utilisé le spectromètre pour une études sub-Doppler de transitions optiques saturées. Nous avons déterminé les fréquences de transition de la bande 30012<- 00001 du 13C16O2 en abondance naturelle avec une exactitude à l’échelle du kHz grâce au référencement de la source laser à un peigne optique auto référencé et asservi au GPS. En utilisant la méthode des combinaisons de différences nous avons pu redéterminer les constantes B, D et H des niveaux haut et bas, révélant des différences significatives avec les données de la littérature.De plus, nous avons étudié la transition S(2) de D2. Nous avons déterminé la fréquence de transition à pression nulle avec une exactitude record de 32 kHz, c’est-à-dire une précision relative de 1.7x10-10. Nous avons aussi investigué l’impact du choix du profil de raie sur la valeur des paramètres obtenus.L’instrument qui a été construit pendant cette thèse a satisfait à deux tâches majeures. Premièrement, il a permis de prouver la possibilité de mesurer le paramètre Δ17O dans le CO2 avec une précision remarquable et un temps record. Il a aussi permis de prouver que la mesure des « clumped isotopes » est possible. Bien qu’il faille encore investiguer précisément les effets de mémoire et de reproductibilité externe, le grand potentiel de cette technique pour les études de géosciences est clairement démontré.Deuxièmement, cet instrument est un outil précieux pour la spectroscopie en raison de sa très haute sensibilité et sa capacité à enregistrer très précisément les profils de raie. Enfin, le référencement à un peigne de fréquence permet une détermination précise des fréquences de transition et des déplacements de fréquence induits par la pression.High-precision molecular absorption spectroscopy has become a widely used tool in physics and metrology. More recently, such techniques have gained some favor in the earth sciences and industrial monitoring, mostly for their compactness and robustness. The determination of isotopic ratios of different isotopic systems is nowadays possible with commercially available laser spectrometers. However, in particular for CO2, the full potential of such techniques for highest precision measurements has yet to be exploited. In this thesis, we present a new spectrometer based on optical feedback frequency locking of a fibered distributed feedback laser (DFB) to a highly stable V-shaped reference cell. In such way, we obtain a near infra-red source reaching sub-kHz frequency resolution with a drift of 30 Hz/s. This ultra-narrow, ultra-stable laser source was then combined with a high-stability, high-finesse ring-down cell, using a robust dither lock scheme. We demonstrated a single-spectrum sensitivity of 1.2 x 10-12 cm-1, obtained in 30 seconds, and reported, for a narrow scan, a record-setting minimum detection level 3.8 x 10-14 cm-1, after less than 10 hours of measurement. We applied this instrument to the measurement of isotopic ratios in CO2 and demonstrated the feasibility of direct measurements of Δ17O in CO2. Δ17O is a super-ratio which requires precise measurements three isotopologues, offering information over the hydrological environment of the past, if measured from carbonate rocks. The instrument yielded a precision of 10 ppm in a record-setting measurement time of 10 minutes, demonstrating that laser spectrometers now perform on the same level as state-of-the-art isotopic ratio mass spectrometers currently used in geoscientific studies. We also demonstrated the first laser based measurements of the ratio 16O13C18O/13C16O2 ("clumped isotopes"), demonstrating a precision of 20 ppm with a strong potential to go further. The instrument shows the potential to measure all geoscientifically relevant isotopologue ratios in CO2 in one single measurement. Furthermore, we applied the instrument to Doppler-free saturated absorption spectroscopy. We determined transition frequencies of the 30012<--00001 band of 16O13C16O in natural abundance with kHz accuracy by referencing the laser source to a GPS-referenced optical frequency comb. Using combination differences, we were able to re-determine the B, D and H constant of the upper and lower state, providing evidence for differences between our experimental data and literature. Moreover, we investigated the S(2) transition of D2. The zero-pressure transition frequency was determined with a record-setting precision of 32 kHz, meaning an accuracy of 0.17 ppb. The impact of line profile choices on the retrieval of line specific parameters has been investigated. The instrumentation which was built during this thesis fulfills two major tasks: First, we have proven the capability of measuring Δ17O in CO2 with outstanding precision in record time. Moreover, we demonstrated a successful proof of concept for clumped isotope measurements. While a thorough investigation of memory effects and external reproducibility has yet to be done, it shows the great potential of this technique for use in the geosciences. Secondly, the instrument is a valuable tool for spectroscopy, exhibiting extremely high sensitivity and thus allowing the very precise determination of line-shape parameters and the validation of the most advanced line profiles. Moreover, comb-referencing allows for precise and accurate determination of transition frequencies and pressure induced shifts
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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