1,720,976 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
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
Biogenic volatile organic compound emissions from bioenergy plants and potential impacts on air chemistry
Get PDFBioenergy plant production is expected to rapidly expand in Europe in the near future. This might not only affect resource availability but will also influence the environment. Since many bioenergy plants do emit different amounts and different compositions of biogenic volatile organic compounds (BVOCs) compared to conventional agricultural crops, the new blend of highly reactive compounds might change the chemical composition of the atmosphere. BVOCs have a strong potential to enhance the photochemical O3 production, increase the formation of secondary organic aerosols (SOA), and prolong CH4 lifetime due to fast reactions with OH. These environmental impacts of bioenergy plants on air quality and the regional climate, however, are difficult to evaluate since accurate field observations of relevant crops are not available. Therefore, I studied a large range of BVOC fluxes from the most prominent bioenergy plants in Germany, which are maize, ryegrass, and oilseed rape, by applying field measurements and biogeochemical modeling. The plants were cultivated in Dedelow, Brandenburg, Germany and observed throughout the vegetative and reproductive development stages. Combining automatically moving large chambers and a proton transfer reaction–mass spectrometer (PTR-MS), I quantified the emission of numerous highly reactive terpenoids, together with several other BVOCs, including alcohols, aldehydes, ketones, benzenoids, and fatty acid derivatives. The characteristic seasonal BVOC flux pattern of each species, could be divided into groups and was associated to the different plant growth stages. The observations from the field campaigns were used to parameterize a biogeochemical ecosystem model coupled to a process-based BVOC emission model. The parameters for the BVOC model were fitted for each compound individually and comprise the standardized emission factor, an emission function curvature coefficient, and the fractionation into a light dependent (de novo emission) and light independent (pool emission) function. Therefore, I merged a mechanistic process-based de novo model with a pool emission approach into a joint BVOC emission model which was embedded in the biogeochemical framework LandscapeDNDC. Finally, total annual emissions were calculated in dependence on simulated plant growth and photosynthesis. Simulated BVOC emissions show that considerable differences between the investigated bioenergy plants exist with oilseed rape having 37-fold higher total annual emissions than maize (oilseed rape: 91.3 ± 8.0 mmol m-2 a-1; maize: 2.5 ± 0.1; and ryegrass: 15.7 ± 0.6). The differences in potential annual impacts on air chemistry are less pronounced between the plants, due to the large fraction of highly reactive terpenoids in the maize BVOC emissions. In particular, the difference is reduced to the 6-fold when the potential impact on OH-reactivity (a measure for O3 and SOA forming potential as well as indirect radiative forcing) is considered and to the 4.5-fold when the theoretically produced electricity yield is additionally taken as a reference. Thus, the results indicate that BVOC fluxes from large-scale bioenergy fields should be better differentiated, especially with regard to BVOC composition and reactivity. Additionally, the large impact of plant phenology on emission factors demands for elaborated models that should be based on measurements that cover the whole plant growth period.Es wird erwartet, dass der Anbau von Bioenergiepflanzen in Europa in naher Zukunft stark zunehmen wird. Dies hat nicht nur Einfluss auf die Ressourcenversorgung, sondern auch auf die Umwelt. Da viele Energiepflanzen andere Emissionsmengen und Gruppierungen von hochreaktiven biogenen flüchtigen organischen Verbindungen (BVOCs) aufweisen als die meisten sonstigen Agrarpflanzen, könnte die chemische Zusammensetzung der Atmosphäre beeinflusst werden. BVOCs in der Atmosphäre können zu einer Zunahme der Konzentrationen von Ozon und sekundären organischen Aerosolen (SOA) führen, sowie die Lebensdauer des klimaschädlichen Gases Methan (CH4) durch Reaktionen mit dem Hydroxyl-Radikal (OH) verlängern. Diese negativen Einflüsse durch den vermehrten Anbau von Bioenergiepflanzen auf die Luftqualität und das regionale Klima sind jedoch schwer zu quantifizieren, da ausreichende Feldmessungen an diesen Pflanzen fehlen. Deshalb habe ich biogenic volatile organic compound (BVOC)-Flüsse aus den in Deutschland meistgenutzten Bioenergiepflanzen Mais, Weidelgras und Raps mittels Feldmessungen und biogeochemischer Modellierung genauer untersucht. Die Pflanzen wurden in Dedelow, Brandenburg, Deutschland angebaut und während der gesamten vegetativen und reproduktiven Entwicklungsstadien untersucht. Mit einer Kombination aus sich automatisch öffnenden und schließenden Großkammern und einem Protonentransferreaktionsmassenspektrometer (PTR-MS) konnte ich hohe Emissionsanteile von hochgradig reaktiven Terpenoiden sowie anderen BVOCs, darunter Alkohole, Aldehyde, Ketone, Benzonoide und Fettsäurederivate quantifizieren. Die Saisonalität der BVOC-Flüsse konnte in charakteristische Gruppen eingeteilt und den verschiedenen Entwicklungsstadien der Pflanze zugeordnet werden. Die Beobachtungen aus den Feldmessungen wurden unter anderem dafür verwendet, ein physiologisch-orientiertes BVOC Modell, das an ein biogeochemisches Ökosystem gekoppelt wurde, weiter zu entwickeln und zu parametrisieren. Die Parameter wurden für jeden einzelnen Stoff angepasst und beinhalten den Standardemissionsfaktor, den Krümmungskoeffizienten der Emissionsfunktion und den Anteil der lichtabhängigen und lichtunabhängigen Emissionsfunktion. Dazu wurde in dieser Arbeit ein Modell zusammengeführt, welches Emissionen von neu gebildeten Stoffen (lichtabhängige) und Emissionen aus dem Stoffspeicher (lichtunabhängig) simulieren kann. Das Modell wurde anschließend dazu verwendet, Jahresbilanzen der Emissionen zu erstellen, die nicht nur von der direkten meteorologischen Situation angetrieben werden, sondern auch vom Pflanzenwachstum und der Photosynthese abhängen. Simulierte jährliche BVOC-Gesamtemissionen weichen zwischen den Bioenergiepflanzen um den Faktor 37 zwischen der Art mit den niedrigsten und der mit den höchsten Emissionen ab (2.5 ± 0.1, 15.7 ± 0.6, and 91.3 ± 8.0 mmol m-2 a-1 aus Mais, Weidelgras und Raps). Aufgrund des hohen Anteils von hochreaktiven Terpenoiden an den emittierten BVOCs aus Mais, sind die Unterschiede von möglichen Auswirkungen auf die Luftchemie zwischen den Pflanzen weniger stark ausgeprägt. Bei Berücksichtigung der potentiellen OH-Reaktivität (ein Maß, das den Einfluss auf O3 und SOA Bildung, sowie den indirekten Klimaeinfluss wiedergibt) verringert sich dadurch der Unterschied zwischen den Arten in Bezug auf die Luftchemie auf den Faktor 6. Wenn zusätzlich auf die theoretische produzierbare Menge Strom skaliert wird, ergibt sich sogar nur ein Unterschied von dem Faktor 4.5. Die Ergebnisse zeigen, dass BVOC-Flüsse aus großflächigem Bioenergieanbau in Zukunft besser differenziert werden sollten. Dazu müssen eine Vielzahl unterschiedlicher Stoffe berücksichtigt werden. Da für den Einfluss auf die Luftchemie häufig eine zeitlich hoch aufgelöste Einschätzung der BVOC-Emission notwendig ist, muss zudem berücksichtigt werden, dass sich die Emissionsfaktoren mit dem Entwicklungsstadium ändern. Daher sollten auch Messungen verstärkt über längere Messzeiträume durchgeführt werden, die über mehrere Entwicklungsstufen hinweg gehen
Biogenic volatile organic compound emissions from bioenergy plants and potential impacts on air chemistry
No full textkoamabayili/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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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