1,720,977 research outputs found
Enrichment of a PHA producing microbial community in a continuous bioreactor setup
Get PDFPolyhydroxyalkanoates (PHAs) are biosynthetic polyesters, biodegradable and biocompatible making them of great interest for industrial purposes. The use of low value substrates with mixed microbial communities (MMC) is a strategy currently used to decrease the elevated PHA production costs. PHA production process requires an important step for selection and enrichment of PHA-storing microorganisms which is usually carried out in a Sequencing Batch Reactor (SBR).
The aim of this study was to optimize the PHA accumulating culture selection stage using a 2-stage Continuous Stirrer Tank Reactor (CSTR) system. The system was composed by two separate feast and famine bioreactors operated continuously, mimicking the feast and famine phases in a SBR system. Acetate was used as carbon source and biomass seed was highly enriched in Plasticicumulans acidivorans obtained from activated sludge. The system was operated under two different sets of conditions (setup 1 and 2), maintaining a system total retention time of 12 hours and an OLR of 2.25 Cmmol/L.h-1. An average PHB-content of 3.3 % wt was obtained in setup 1 and 4.8% wt in setup 2. Several other experiments were performed in order to better understand the continuous system behaviour, using biomass from the continuous system. With the fed-batch experiment a maximum of 8.1% PHB was stored and the maximum substrate uptake and specific growth rates obtained in the growth experiment (1.15 Cmol Cmol-1.h-1 and 0.53 Cmol Cmol-1.h-1) were close to the ones from continuous system (1.12 Cmol Cmol-1.h-1 and 0.59 Cmol Cmol-1.h-1). The microbial community was characterized trough microscopic visualization, Denaturing Gradient Gel Electrophoresis (DGGE) analysis and Fluorescent in situ hybridization (FISH). The last studied performed mimicked the continuous system by building up a SBR system with all the same operational conditions while adding an extra acetate dosage during the 12 h cycle, simulating the substrate passing from the feast to the famine reactors under continuous operation. It was shown that possibly the continuous system was not able to efficiently select for PHB storing organisms under the operational conditions imposed, although the selected culture was capable of consuming the substrate and grow fast. This main conclusion might have resulted from two major factors affecting the system performance: the ammonium concentration in the Feast reactor and the amount of substrate leaching from the Feast to the Famine reactor
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
Impact of increased phenol loading rate on the phenol removal of an anaerobic membrane bioreactor operated at high sodium concentration
No full textCertain industrial wastewaters have posed a big challenge to biological water treatment systems because of their high toxic organic compounds concentration (e.g. phenol) and high salinity. The maximum biomass specific phenol bioconversion rate (PhCR) of a mesophilic (35 °C) anaerobic membrane bioreactor (AnMBR) under high sodium concentration [18.6 g Na+/L] condition was studied by an increase in the biomass specific phenol loading rate (PhLR) through hydraulic retention time (HRT) decrease. The maximum PhCR achieved in our research was 73 mg Ph-COD/gVSS-COD.d, with acetate as co-substrate [2g AC-COD/L]. This result was lower than that reported by the previous study of Bioxtreme (193 mg Ph-COD/gVSS-COD.d) at lower sodium concentration [8.0 g Na+/L]. On the other hand, a simplified ADM1 model was used to model the conversion of acetate to methane in batch experiments, among which, the inhibition of substrate (acetate or phenol) on microbial growth rate was described by Haldane equation. The kinetic parameters for acetate degradation were Ks,AC=300 mg COD/L, KI,AC=821mg COD/L, km,AC I =0.246 mg COD/mg COD.h without phenol addition and Ks,AC=300 mg COD/L, KI,AC=806 mg COD/L, km,AC I=0.236 mg COD/mgCOD.h with the addition of 714 mg Ph-COD/L (300 mg Ph/L) at sodium concentration of 18.6 g Na+/L, while it was Ks,AC=6.7 10-9 mg COD/L, KI,AC=5670 mg COD/L, km,AC I=0.043 mg COD/mgCOD.h at lower sodium concentration [8.0 g Na+/L] without phenol addition.The kinetic parameters estimated for the batch experiments were applied in a mathematical model describing a dynamic experiment carried out in the AnMBR1 and validated with different HRTs. In the model, the conversion from phenol to acetate was considered and the kinetic parameters estimated for phenol degradation were Ks,Ph=20 mg COD/L, KI,Ph=300 mg COD/L, km,Ph I=0.008 mg COD/mgCOD.h. It was proved that the simplified ADM1 model could well predict the phenol and acetate concentrations in the reactor at different PhLRs. This research has provided an experimental and modeling approach for the maximum PhCR determination and could contribute to the understanding of the inhibition effect of sodium and phenol on PhCR in the treatment process of saline phenolic wastewater.Bioxtrem
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
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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