1,720,967 research outputs found
Syntrophic hydrocarbon metabolism under methanogenic conditions
No full textMethanogenic metabolism of organic matter is a key process in both natural and engineered systems. Methanogenic hydrocarbon degradation is an important biogeochemical process in the deep subsurface, and subsurface hydrocarbon contamination is frequently remediated by methanogenic processes. Despite the importance of methanogenic processes in hydrocarbon-impacted systems, we currently have an incomplete understanding of the hydrocarbon activation and degradation pathways used by the syntrophic bacteria, the roles of the non-hydrocarbon degrading syntrophs, which are often present in high abundance, and the ways in which syntrophic bacteria and methanogenic archaea establish and maintain relationships that allow them to coordinate their metabolism. By studying methanogenic hydrocarbon degrading enrichment cultures, we remove many complicating features of natural systems and can gain a basic understanding of the primary factors governing hydrocarbon metabolism under methanogenic conditions. In this dissertation, we describe several methanogenic hydrocarbon degrading enrichment cultures with a major focus on a toluene degrading methanogenic enrichment culture. Methanogenic hydrocarbon degrading communities consist of a diverse assemblage of Archaea and Bacteria dominated by members of the Methanomicrobia, Firmicutes, Deltaproteobacteria, Chloroflexi, Spirochaetes and other bacterial phyla in smaller proportions. Using stable isotope probing, key organisms involved in the degradation of toluene were identified, including Desulfosporosinus sp., which is associated with toluene activation as well as Syntrophus- like organisms and Desulfovibrio sp. Metabolite and metagenomic analysis indicate that fumarate addition is involved in toluene activation in this culture and results from this and other cultures suggest that fumarate addition is a key mechanism involved in the activation of alkanes, monoaromatic and polyaromatic hydrocarbons under methanogenic conditions. Comparative metagenomic analysis suggests that key functional features that distinguish methanogenic hydrocarbon degrading cultures include enrichment of archaeal and bacterial hydrogenases, as well as functions related to the regulation of redox conditions, energy conservation and methanogenesis. Hydrogen and/or formate transfer appears to play a major role in metabolite and electron transfer in these cultures. A better understanding of the processes involved in methanogenic hydrocarbon metabolism may provide us with the knowledge to develop new tools to monitor, control and harness these technologies to the benefit of ourselves and our environment
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
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
Spectrometric analysis of the metabolism and adsorption of naphthenic acid fraction compounds in a phytoremediation treatment system
No full textBitumen mining in northern Alberta produces large volumes of oil sands process-affected water (OSPW) that require treatment before being released into the environment. Naphthenic acid fraction compounds (NAFCs) are considered primary contributors to OSPW toxicity; therefore, remediation efforts often target these compounds. Phytoremediation is proposed as a feasible treatment for OSPW using a constructed wetland treatment system (CWTS) strategy due to the cost-effective and low-maintenance nature of this technology. A CWTS uses plants and their associated microorganisms to take advantage of natural metabolic processes for the uptake and biotransformation of environmental contaminants. While CWTSs for OSPW treatment have demonstrated success in attenuating NAFCs and reducing toxicity in mesocosm and pilot-scale studies, the fate of NAFCs in a CWTS is not well understood. This thesis research aimed to gain insight into NAFC fate in CWTSs by exploring NAFC biotransformation processes in plant tissues and the adsorption characteristics of NAFCs onto sediment substrates. A method for extracting NAFCs and their metabolites from plant tissues was developed and used to extract the isotopically labelled model compound 1-adamantanecarboxylic acid (¹³C-AdCA) and NAFCs from OSPW. This method, in combination with high-resolution Orbitrap mass spectrometry, was used to track the uptake, translocation, and biotransformation within plant roots and shoots. These experiments showed a general decrease in compound abundance over time, indicative of transformation events. The OSPW treatments further demonstrated that the majority of NAFCs were completely transformed in root and shoot tissues. Additionally, incubation studies were conducted to test parameters associated with NAFC adsorption onto various sediments. The adsorption of NAFCs from OSPW onto a sediment substrate from the oil sands region appeared to be impacted by the properties of the OSPW itself, including NAFC concentration, class differences, or shifts in carbon number and double bond equivalents. Other factors, such as water quality characteristics, may also impact adsorption. Overall, the results of this research provide insight into the fate of NAFCs in phytoremediation systems, guiding future metabolomics studies and considerations for the large-scale implementation of plant-based technologies in OSPW treatment strategies
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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