1,720,997 research outputs found
Climate change effects on planktonic bacterial communities in the ocean: from structure and function to long-term and large scale observations.
No full textPlanktonic bacterial communities of marine environments can be considered to be affected by climate change through a set of direct and indirect effects. As direct effects of climate change, elevated temperature and ambient CO2 levels have to be taken into account. As indirect effects a large spectrum of impacts ranging from increased stratification of surface water, deoxygenation of subsurface water, increased occurrence of extreme weather events, and a changed food chain and nutrient regime resulting in a changed top down and bottom up control for bacterioplankton. All these direct and indirect effects will affect bacterial communities in a multifaceted way. Changes in the bacterial communities due to climate change impacts can be expected on all different taxonomic levels, i.e. from the clonal intraspecies level to the phylum level. The focus of the article will be on the evaluation of bacterioplankton observations over time and space and along climate gradients in the frame of environmental parameters allowing modelling with respect to climate change scenarios. A specific emphasis will be on bacterioplankton analysis based on analysis of samples of the Continuous Plankton Recorder Archive. This sample archive allowed insights into particle associated bacteria of coastal environments over more than the last 60 years. Beside effects of climate change effectors on bacterial growth and community composition, effects of climate change on bacteria-mediated marine biogeochemical cycling and potential hazards by increased abundance of pathogenic bacteria such as Vibrio cholerae will be considered
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
Denitrifikation in der Wassersäule der Zentralen Ostsee : Regulationsfaktoren und mikrobiologische Aspekte = Denitrification in the water column of the Central Baltic : Regulatory Factors and Microbiological Aspects
No full textIm Sommer 1986 und 1987 wurden Untersuchungen zur Denitrifikation in der Wassersäule der zentralen Ostsee durchgeführt Schwerpunkt der Untersuchungen war, die regulierenden Mechanismen der Denitrifikation zu erforschen. Als Untersuchungsgebiete dienten das zentral gelegene Gotlandtief und die im Norden gelegene Station T.
- Denitrifikationsraten wurden mit Hilfe der Azetylenblockmethode erfaßt. Die ermittelten Raten lagen zwischen 13,8 und 110 nmol N/l x d.
- Vor dem Hintergrund der gängigen bakteriologischen Rahmenparameter wurde die Anzahl von Denitrifikanten und Nitratreduzierern erfaßt. Die Anzahl der heterotrophen Denitrifikanten in der Wassersäule bewegte sich zwischen ungefähr 50 und 2400 Bakterien pro ml.
- Es zeigte sich, daß die Denitrifikation in der Wassersäule der zentralen Ostsee, sowohl in Bezug auf die Umsatzraten, als auch die räumliche Ausdehnung durch den verfügbaren organischen Kohlenstoff limitiert war. Die geringe Verfügbarkeit schien die Denitrifikation im wesentlichen auf "energiereiche" Grenzschichten wie oxisch-anoxische und Sediment-Wasser-Grenzschichten zu beschränken.
- Für die Denitrifikation an der oxisch-anoxischen Grenzfläche konnte gezeigt weiden, daß autotrophe Denitrifikation unter Nutzung von reduzierten Schwefelverbindungen aus dem anoxischen Bereich als Elektronendonatoren einen bedeutenden Beitrag zu leisten vermag ("H2S-Denitrifikation")..
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
Whole-genome enrichment provides deep insights into Vibrio cholerae metagenome from an African river
No full textThe detection and typing of Vibrio cholerae in natural aquatic environments encounter major methodological challenges related to the fact that the bacterium is often present in environmental matrices at very low abundance in nonculturable state. This study applied, for the first time to our knowledge, a whole-genome enrichment (WGE) and next generation sequencing (NGS) approach for direct genotyping and metagenomic analysis of low abundant V. cholerae DNA (<50 genome unit/L) from natural water collected in the Morogoro river (Tanzania). The protocol is based on the use of biotinylated RNA baits for target enrichment of V. cholerae metagenomic DNA via hybridization.
An enriched V. cholerae metagenome library was generated and sequenced on a Illumina MiSeq platform. Up to 1.8X107 bp (4.5x mean read depth) were found to map against V. cholerae reference genome sequences representing an increase of about 2500 times in target DNA coverage compared to theoretical calculations of performance for shotgun metagenomics. Analysis of metagenomic data revealed the presence of several V. cholerae virulence and virulence associated genes in river water including major virulence regions (e.g. CTX prophage and Vibrio pathogenicity island-1) and genetic markers of epidemic strains (e.g. O1-antigen biosynthesis gene cluster) that were not detectable by standard culture and molecular techniques. Overall, besides providing a powerful tool for direct genotyping of V. cholerae in complex environmental matrices this study provides a “proof of concept” on the methodological gap that might currently preclude a more comprehensive understanding of toxigenic V. cholerae emergence from natural aquatic environments
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
Climate influence on Vibrio and associated human diseases during the past half-century in the coastal North Atlantic
No full textClimate change is having a dramatic impact on marine animal and plant communities but little is known of its influence on marine prokaryotes, which represent the largest living biomass in the world oceans and play a fundamental role in maintaining life on our planet.
In this study, for the first time to our knowledge, experimental evidence is provided on the link between multidecadal climatic variability in the temperate North Atlantic and the presence and spread of an important group of marine prokaryotes, the vibrios, which are responsible for several infections in both humans and animals. Using archived formalin-preserved plankton samples collected by the Continuous Plankton Recorder survey over the past half-century (1958–2011), we assessed retrospectively the relative abundance of vibrios, including human pathogens, in nine areas of the North Atlantic and North Sea and showed correlation with climate and plankton changes. Generalized additive models revealed that long-term increase in Vibrio abundance is promoted by increasing sea surface temperatures (up to ∼1.5 °C over the past 54 y) and is positively correlated with the Northern Hemisphere Temperature (NHT) and Atlantic Multidecadal Oscillation (AMO) climatic indices (P < 0.001). Such increases are associated with an unprecedented occurrence of environmentally acquired Vibrio infections in the human population of Northern Europe and the Atlantic coast of the United States in recent years
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
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