1,721,036 research outputs found
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
Der Selektionsdruck, in dynamischen Umweltbedingungen (von Sauerstoff und Stickstoff) auf das Konsortium von sulfatreduzierenden und fermentierenden Bakterien
No full textThe activity and diversity of prokaryotes is one of the keys to understand element cycling in our environment. Many microbes couple the oxidation of carbon compounds with the reduction of inorganic compounds such as oxygen, nitrogen,manganese, iron and sulfate. The sulfur cycle is one of the most important elements cycles, because of the high abundance of sulfate in the marine environment and the rich speciation of sulfur compounds at different redox states. The most stable and abundant form of sulfur is sulfate which is found in sea water at a high concentration of 28mM. About 50% of the remineralization of organic carbon substrates was suggested to be coupled to sulfate reduction. Sulfate reducers couple the oxidation of organic carbon compounds or hydrogen with the reduction of sulfate to sulfide. Their ability to oxidize organic carbon compounds is known to be mostly limited to those compounds that are produced by fermentative bacteria. However, only few studies directly address the ecological relationship between fermentative and sulfate reducing bacteria. This thesis addresses precisely this point. Consortia of sulfate reducing and fermentative bacteria were enriched in long term continuous culture incubations inoculated with biomass extracted form the top sediment layers of the intertidal flat Janssand in the German Wadden Sea. The cultures were provided with a marine medium that contained, in addition to sulfate, seven different amino acids, glucose and acetate in a ratio that mimicked the composition of decaying biomass (50% protein, 30% polymeric sugars, 20% lipids) in terms of its monomers. Chemical and metagenomic analysis were used to analyze the activity and community composition of the selected consortium. Most cultures were performed under stable, sulfate reducing conditions (Chapter 2). Chapter 3 addresses the effect of transient exposure to oxygen and nitrate on the enrichment of consortia of fermentative/sulfate reducing bacteria. Under all conditions investigated, the enriched sulfate reducers belonged to the Deltaproteobacteria, dominated by Desulfovibrio and Desulfotignum populations. The enriched fermentative bacteria were mainly affiliated with Firmicutes, followed by Spirochaetales. The enrichment and phylogenomic characterization of Candidatus Thammenomicrobium ektimisum , a fermentative representative of the candidate division Hyd24-12 is described in Chapter 4. The results presented in chapters 2 and 3 suggest that hydrogen and acetate were the main fermentation products. Metagenomic, transcriptomic and stoichiometric modeling of microbial metabolism suggested that the sulfate reducers displayed at least partially autotrophic growth by assimilating carbon dioxide, despite the supply of copious carbon sources to the cultures. Transient exposure to oxygen did not result in a strong selective effect, and neither the fermentative nor the sulfate reducing populations showed a strong transcriptional response to exposure to oxygen. Transient availability of nitrate led to the enrichment of a different population of Deltaproteobacteria, affiliated with Desulfuromonadales, in two replicate experiments. This population was apparently incapable of sulfate reduction but performed ammonification of nitrate to ammonia. Overall, the results presented in this thesis provide new insight in the selective pressure exerted by dynamic environmental conditions on sulfate reducing/fermentative consortia
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
Konkurrenz bei nitratreduzierenden mikrobiellen Gemeinschaften
No full textThe biogeochemical nitrogen cycle, including nitrate reduction processes, is highly affected by human activity such as fertilization and ammonia deposition caused by fossil fuel burning. Consequently, gaining a better understanding about the ecophysiology of nitrate-reducing microbial communities is crucial for inferring the impact of anthropogenic nitrogen input. Different nitrate-reducing pathways compete with each other for the electron acceptor nitrate: Denitrifiers reduce nitrate to dinitrogen and nitrous oxide while dissimilatory nitrate reducers reduce nitrate to ammonium. The outcome of this competition has important environmental consequences: denitrification removes fixed nitrogen from the ecosystem, while dissimilatory nitrite reduction to ammonium (DNRA) keeps fixed nitrogen bioavailable. Although a lot of studies have been performed on this topic, no conclusive factors responsible for the dominance of one or the other process could be identified so far. In this thesis, the competition between nitrate reduction pathways was addressed by combining continuous culture incubations of natural microbial communities with stable isotope labeling and metagenomics, complemented with metatranscriptomics and metaproteomics in order to gain insight into the identity, function and interaction of the enriched microbial populations. To be able to make the best use of the obtained metagenomic data a new metagenomic binning procedure was developed. Before the competition between two different nitrate reduction pathways was studied, the relationship between functional and compositional stability over time within one nitrate reduction pathway was investigated: In a heterotrophic denitrifying microbial community, enriched from a marine intertidal flat, strong community dynamics were occurring under constant conditions and during stable conversion of substrates. A stable metabolic interaction between the denitrifying populations and co-enriched fermenting microbes persisted throughout the experiment unaffected by the ongoing population dynamics. This indicated that functional stability was independent of the community composition. Apparently, only the persistence of the overall metabolic potential was important to maintain functional stability. This suggested that stochastic as well as deterministic processes are responsible for the observed community composition. Once the functional stability of denitrification was confirmed and interactions with other microbial guilds were known the competition between DNRA and denitrification was addressed. Several parallel continuous culture incubations that differed in one condition but were otherwise constant led to the identification of the generation time as most important control on the competition between DNRA and denitrification. The organic carbon to nitrate ratio and the kind of electron acceptor supplied (nitrate or nitrite) were identified as further controlling factors that together with the generation time discriminated between the two pathways. The metabolic interaction between nitrate- reducing and fermenting populations was stable under both pathways. One quarter of the nitrate reduction was coupled to the oxidation of sulfide, which was produced in the enrichment culture by microbial sulfate reduction, constituting a strong link between the nitrogen and sulfur cycle. All in all, this thesis provides new insights into the ecophysiology of microbial nitrate reducers by unraveling the driving forces of the competition between different nitrate reduction pathways and by revealing important metabolic interactions with other microbial guilds
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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