1,721,058 research outputs found
Conductive Magnetite Nanoparticles Accelerate the Microbial Reductive Dechlorination of Trichloroethene by Promoting Interspecies Electron Transfer Processes
No full textPlaying your part: Conductive magnetite nanoparticles accelerate the microbial reductive dechlorination of trichloroethene (TCE), an ubiquitous and toxic subsurface contaminant. The stimulatory effect most likely results from the nanoparticles promoting the establishment of interspecies electron transfer (IET) processes between non-dechlorinating and dechlorinating microorganisms. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Microbial and kinetic characterization of pure and mixed cultures aerobically degrading 4-nitrophenol
No full textThe molecular and kinetic characterization of a microorganism able to aerobically degrade 4-nitrophenol (4NP) is presented. The microorganism was isolated from a mixed culture operating in a laboratory-scale sequencing batch reactor with an aerobic anoxic cycle. It was identified as a member of Ralstonia genus within Betaproteobacteria. It is a gram negative coccobacillum (cell length of 2-3 mu m) able to aerobically store lipid inclusions when grown aerobically on nitrophenol as the sole carbon source in the range of tested concentrations (80-320 mg l(-1)). Batch kinetic tests were performed with the pure culture, while the kinetics of the mixed biomass was directly investigated in the reactor. For pure cultures exponential growth was observed, with growth rate values in the range of 2-6 d(-1); in experiments with the mixed cultures 4NP concentrations were correlated with growth using the Haldane equation (k(max) = 0.30 mg 4NP mg(-1) VSS h(-1); K-s = 55 mg 4NP l(-1) and K-I = 15 mg 4NP l(-1)). Observed pure culture growth rates were higher than those of mixed cultures. This result can be explained by considering that in mixed culture the biomass is evaluated as volatile suspended solids, including both specialized biomass for 4NP removal and denitrifying bacteria. (c) 2005 Elsevier Ltd. All rights reserved
Effect of feeding regime and the sludge age on the fate of acetate and the microbial composition in sequencing batch reactor
No full textThe study investigated the effects of the feeding regime on the substrate metabolism under aerobic conditions. Throughout the study, two parallel sequencing batch reactors were operated using either short-term (pulse) or long-term (almost continuous) feeding of acetate at two different sludge ages of two days and eight days. The microbial characterization studies showed that the feeding regime did not change the microbial composition as determined by the fluorescent in situ hybridization (FISH) analysis, however did strongly affect the substrate utilization mechanism. Additionally, the same microbial culture was able to utilize acetate with or without poly - hydroxybutyrate (PHB) storage under pulse or continuous feeding, respectively. Conversely, the selected sludge ages induced significant changes in the microbial composition and floc structure, however, the well settling and bulking biomass selected at the sludge ages of eight days and two days, respectively, did not significantly affect the substrate utilization mechanism, where storage or growth prevailed as a result of either pulse or continuous feeding. © 2012 Copyright Taylor and Francis Group, LLC
Effect of feeding and sludge age on acclimated bacterial community and fate of slowly biodegradable substrate
No full textThe study investigated the effect of feeding regime and sludge age on starch utilization. For this purpose, parallel sequencing batch reactors were operated with pulse and continuous feeding of soluble starch at sludge ages of 8 and 2 days. Pulse feeding induced almost complete conversion of starch to glycogen, while storage was lowered and accompanied with direct growth under continuous feeding, regardless of sludge age. Low sludge age did not alter simultaneous storage and utilization for direct growth but it slightly favoured direct utilization due to faster growing biomass. Experimental results suggested adsorption of starch onto biomass as a preliminary removal mechanism prior to hydrolysis at sludge age of 8 days. Adsorption was not noticeable as substrate removal, glycogen generation and dissolved oxygen decrease were synchronous at sludge age of 2 days. Bacterial community always included fractions storing glycogen although sludge age only affected the relative magnitude of filamentous growth. (C) 2011 Elsevier Ltd. All rights reserved
Short-term and long-term effects on carbon storage of pulse feeding on acclimated or unacclimated activated sludge
No full textThis study was aimed to investigate the effect of different feeding patterns on the physiological state of the activated sludge and related microbial composition in an SBR (SRT of 2 days, acetate as the sole carbon source, aerobic conditions). The activated sludge was acclimated to two subsequent feeding patterns, namely to continuous feeding throughout the reaction phase and then to pulse feeding. FISH and microscopy staining procedure (Nile blue) were used to investigate the microbial composition, in combination with quantitative determination of storage. At steady state, storage was significant even under continuous feeding whereas pulse feeding brought a strong increase of both rate and yield of storage. Short-term and long-term effects were clearly distinguishable: the immediate adaptation of biomass coming from continuous feeding to a single spike accounted for a significant portion of the overall increase of both rate and yield of polymer storage that was obtained after long acclimation to pulse feeding. On the contrary, after either type of feeding, both cultures were mainly constituted from the members of Thauera/Azoarcus group. Thus, the same dominant group preferably consumed the acetate via storage or growth depending on acclimation conditions. Our study clearly showed that a progressive increase of storage capacity is not necessarily due to a shift of microbial composition. (C) 2011 Elsevier Ltd. All rights reserved
Extent of intracellular storage in single and dual substrate systems under pulse feeding
No full textThe study investigated the effect of acetate/starch mixture on the formation of storage biopolymers as compared with the storage mechanism in systems fed with these compounds as single substrates. Experiments involved two sequencing batch reactor sets operated at steady state, at sludge ages of 8 and 2 days, respectively. Each set included three different runs, one fed with acetate, the other with starch and the last one with the acetate/starch mixture. In single substrate systems with pulse feeding, starch was fully converted to glycogen, whereas 25 % of acetate was utilized for direct microbial growth at sludge age of 8 days, together with polyhydroxybutyric acid (PHB) storage. The lower sludge age slightly increased this fraction to 30 %. Feeding of acetate/starch mixture induced a significant increase in acetate utilization for direct microbial growth; acetate fraction converted to PHB dropped down to 58 and 50 % at sludge ages of 8 and 2 days respectively, while starch remained fully converted to glycogen for both operating conditions. Parallel microbiological analyses based on FISH methodology confirmed that the biomass acclimated to the substrate mixture sustained microbial fractions capable of performing both glycogen and PHB storage
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
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