1,721,410 research outputs found
Comparison of Prototype and Laboratory Experiments on MOMA GCMS: Results from the AMASE11 Campaign
No full textThe characterization of any organic molecules on Mars is a top-priority objective for the ExoMars European Space Agency-Russian Federal Space Agency joint mission. The main instrument for organic analysis on the ExoMars rover is the Mars Organic Molecule Analyzer (MOMA). In preparation for the upcoming mission in 2018, different Mars analog samples are studied with MOMA and include samples collected during the Arctic Mars Analog Svalbard Expedition (AMASE) to Svalbard, Norway. In this paper, we present results obtained from two different Mars analog sites visited during AMASE11, Colletthøgda and Botniahalvøya. Measurements were performed on the samples during AMASE11 with a MOMA gas chromatograph (GC) prototype connected to a commercial mass spectrometer (MS) and later in home institutions with commercial pyrolysis-GCMS instruments. In addition, derivatization experiments were performed on the samples during AMASE11 and in the laboratory. Three different samples were studied from the Colletthøgda that included one evaporite and two carbonate-bearing samples. Only a single sample was studied from the Botniahalvøya site, a weathered basalt covered by a shiny surface consisting of manganese and iron oxides. Organic molecules were detected in all four samples and included aromatics, long-chained hydrocarbons, amino acids, nucleobases, sugars, and carboxylic acids. Both pyrolysis and derivatization indicated the presence of extinct biota by the detection of carboxylic acids in the samples from Colletthøgda, while the presence of amino acids, nucleobases, carboxylic acids, and sugars indicated an active biota in the sample from Botniahalvøya. The results obtained with the prototype flight model in the field coupled with repeat measurements with commercial instruments within the laboratory were reassuringly similar. This demonstrates the performance of the MOMA instrument and validates that the instrument will aid researchers in their efforts to answer fundamental questions regarding the speciation and possible source of organic content on Mars
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
Search for prebiotic chemistry and clues of life on the ocean worlds through in situ chemical analyses of organic matter
No full textLa présence d'océans sous la surface de certains des satellites glacés de Jupiter (e.g. Europe) et de Saturne (e.g. Titan, Encelade) couplée à l'existence de geysers permettant l'échantillonnage de leurs profondeurs a fait émerger le fort potentiel exobiologique de ces corps planétaires du système solaire. De telles découvertes ont suscité le développement de futures missions spatiales (Dragonfly pour Titan et concepts de missions pour Europe et Encelade) pour comprendre la chimie de surface de ces mondes-océan, et par extension de rechercher des traces de chimie prébiotique ou de vie passée ou actuelle. La quête de telles signatures nécessite un analyseur chimique à bord des sondes qui seront envoyées dans le système solaire externe. De nombreuses techniques analytiques peuvent être mises en œuvre mais la chromatographie en phase gazeuse couplée à la spectrométrie de masse (CPG-SM) apparaît comme une technique de premier choix pour tenter de répondre à ces questions, de par son héritage dans l'exploration spatiale, sa capacité à analyser une large gamme de composés organiques et son potentiel pour détecter des biosignatures notamment par l'étude de l'énantiomérie des espèces chirales.L'objectif de ce travail de thèse est de préparer la future analyse chimique in situ de ces lunes glacées, d'une part par l'amélioration des connaissances scientifiques et d'autre part par l'optimisation technique des instruments. Il s'agit d'évaluer et d'optimiser les capacités analytiques de la CPG-SM et des méthodes de préparation d'échantillon associées, afin de détecter des molécules organiques et biosignatures avec les contraintes analytiques connues et/ou attendues sur ces corps planétaires (richesse en matière organique des échantillons prélevés pour Titan et présence d'eau de sels pour les échantillons à la surface d'Europe et d'Encelade). Dans le cas d'Europe et Encelade, l'étude d'échantillons hypersalins terrestres a permis de mettre en avant les capacités de la CPG-SM et des méthodes de prétraitements associées pour la recherche de molécules organiques d'intérêt pour l'exobiologie malgré la présence de sels. Pour évaluer l'impact du sel sur ces méthodes, le développement d'un protocole de dessalement a été entrepris et mis en place. Outre l'aspect analytique, mon travail a permis la sélection et la caractérisation des performances des colonnes chromatographiques (générale et chirale) qui seront intégrées à l'instrument DraMS à bord de la sonde Dragonfly (e.g. Dragonfly Mass Spectrometer, DraMS). Pour ces différents aspects, ce travail s'est appuyé sur l'étude d'échantillon analogues synthétiques (tholins pour Titan) mais aussi naturels (lac hypersalin pour Europe et Encelade).The presence of oceans beneath the surface of some of Jupiter's (e.g. Europa) and Saturn's (e.g. Titan, Enceladus) icy satellites, coupled with the existence of geysers that allow their depths to be sampled, has highlighted the strong exobiological potential of these planetary bodies in the solar system. Such discoveries have motivated the development of future space missions (Dragonfly for Titan and mission concepts for Europa and Enceladus) to understand the surface chemistry of these ocean worlds, and by extension to search for traces of prebiotic chemistry or past or present life. The search for such signatures requires a chemical analyzer on board the probes that will be sent into the outer solar system. Many analytical techniques can be used, but gas chromatography-mass spectrometry (GC-MS) appears to be one of the best techniques for answering these questions, thanks to its heritage in space exploration, its ability to analyze a wide range of organic compounds, and its potential for detecting biosignatures, especially by studying the enantiomery of chiral species.The aim of this thesis is to prepare for future in situ chemical analysis of these icy moons, both by improving our scientific knowledge and by technically optimizing our instruments. The main purpose is to evaluate and optimize the analytical capabilities of GC-MS and associated sample preparation methods, in order to detect organic molecules and biosignatures within the analytical constraints known and/or expected on these planetary bodies (richness in organic matter in samples from Titan, and presence of water and salts in samples from the surface of Europa and Enceladus, etc.). In the case of Europa and Enceladus, the study of hypersaline terrestrial samples has highlighted the ability of GC-MS and associated pretreatment methods to find organic molecules of interest for exobiology, despite the presence of salts. In order to assess the impact of salt on these methods, a desalination protocol was developed and implemented. In addition to the analytical aspect, my work has enabled the selection and characterization of the performance of the chromatographic columns (general and chiral) that will be integrated into the DraMS instrument on board the Dragonfly probe (e.g. Dragonfly Mass Spectrometer, DraMS). For these different aspects, this work was based on the study of synthetic analogous samples (tholins for Titan) as well as natural ones (hypersaline lake for Europa and Enceladus)
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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