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Organic micropollutant (OMP) biotransformation in aquatic systems and the role of dissolved organic matter (DOM) as auxiliary substrates
No full textFreshwater contamination by organic micropollutants (OMPs) represents a major threat for ecosystems and human health. A major source of this pollution is located in peri-urban catchments, as agricultural runoff and wastewater effluents can lead to significant inputs of OMPs into freshwater systems. Therefore, improving our understanding of OMP behaviour in both natural and engineered systems, and investigating their intersections is essential in order to protect freshwater resources. Biodegradation represents a key process for the removal of OMPs and for limiting their concentrations in aquatic systems. In wastewater treatment plants (WWTPs), autotrophic co-metabolic OMP transformation by ammonia oxidizing microorganisms has been suggested as an important process for OMP transformation. However, the exact mechanisms and the classes of OMPs susceptible to co-metabolic OMP transformation are not yet fully understood. Moreover, co-metabolic OMP transformation commonly does not result in OMP mineralization and hence in full OMP removal. Another process that may result in OMP mineralization is heterotrophic metabolic (i.e., growth-linked) OMP biodegradation. This process might thus play an essential role for full OMP removal in both WWTPs and natural systems. Considering the typically low concentrations of micropollutants in aquatic systems (ng-μg L-1), heterotrophic OMP degraders, in addition to OMPs, may depend on natural occurring carbon sources present in the pool of dissolved organic matter (DOM). Such auxiliary carbon sources might be vital for the survival of heterotrophic OMP degraders. However, the classes of DOM constituents that are biodegradable and available for OMP degraders under different conditions, and their effects on OMP biodegradation remain poorly investigated.The research performed in this PhD project aims at gaining a mechanistic understanding of co-metabolic and metabolic biodegradation of organic compounds (OMPs and DOM constituents) in aquatic systems. The main focus was on investigating links between the chemical structures of different organic compounds and their biodegradability. Furthermore, the role of different DOM constituents for heterotrophic OMP biodegradation was investigated in labscale experiments. Additionally, the quality and potential bioavailability of DOM from a peri-urban stream was characterized, in order to relate the results from lab-scale experiments to environmental conditions.The first part of this PhD thesis evaluates the role of ammonia oxidizing microorganisms for co-metabolic OMP transformation in WWTPs based on a literature review and the theoretical prediction of biodegradation pathways. A specific focus was on linking structural moieties of OMPs to reactions supported by the enzyme ammonia monooxygenase (AMO). The analysis showed that a high percentage of the investigated OMPs contains structural moieties that would be susceptible to AMO mediated transformations. Furthermore, AMO catalyzed transformations could explain the formation of various biotransformation products previously observed in pure culture studies with ammonia oxidizers or in microbial wastewater communities. Hence, our study suggests that in systems which are dominated by ammonia oxidizers, AMO mediated OMP transformation might significantly contribute to the overall OMP transformation. However, it remains important to additionally investigate metabolic heterotrophic OMP transformation, since this process might, in contrast to co-metabolic transformations, result in complete OMP removal.The main part of this thesis thus investigates metabolic heterotrophic OMP biodegradation. A specific focus was on elucidating the ability of a model OMP degrader (Novosphingobium sp. KN65.2) to biodegrade different DOM constituents and to elucidate its ability to compete for the uptake of these DOM constituents against a reference strain (Pseudomonas fluorescens sp. P17; generalist). Furthermore, the effect of four selected DOM constituents on OMP biodegradation was investigated. Theoretical pathway predictions were combined with laboratory experiments, fluorescence spectroscopy and parallel factor analysis (PARAFAC) to investigate growth-linked OMP-DOM biodegradation. This novel approach, combining different techniques, allowed us to gain a systematic understanding of OMP-DOM biodegradation mechanisms. All experiments were conducted with pure or binary cultures, chemically defined DOM constituents (aromatic amino acids and lignin derivatives), and the model OMP carbofuran (pesticide). Our results reveal a high specificity of the model OMP degrader for DOM constituents with parahydroxylated primary aromatic ring substituents and demonstrate that a range of naturally occurring substrates can support the strain’s growth, in addition to the OMP carbofuran. Competition experiments revealed a disadvantage of the OMP degrader to compete for the biodegradation of specific DOM constituents against the generalist. The disadvantage likely results from longer lag-phases observed for substrate degradation by the OMP degrader, indicating that experimental/environmental conditions which decrease these long lag-phases might significantly enhance the competitiveness of the model OMP degrader for the uptake of auxiliary substrates. Biodegradation kinetics of the OMP carbofuran were stable in the presence of all selected DOM constituents, indicating their suitability as auxiliary substrates for carbofuran biodegradation under the investigated conditions. However, the tested DOM constituents could be divided into two groups with distinct transformation mechanisms. This may, in the long-term, significantly influence their effect on OMP biodegradation. Our results thus highlight the importance of studying biodegradation mechanisms for an improved understanding of both the effect of DOM constituents on OMP biodegradation and the competiveness of OMP degraders for auxiliary substrate uptake.Finally, DOM samples taken from a peri-urban Danish stream were qualitatively characterized using fluorescence spectroscopy and PARAFAC analysis, a powerful tool to trace dynamics of environmental DOM in aquatic systems. The analysis revealed a seven component PARAFAC model, including two protein-like, and five humic-like components. The two protein-like components showed a significantly higher relative contribution to the total fluorescence signal compared to the five humic-like components for most sampling stations and field campaigns. Since fluorescence in the protein-like region is commonly associated with more labile DOM, this might indicate a potential source of auxiliary substrates for OMP degraders. However, a slight but steady increase of these two components in total fluorescence along downstream sampling stations might instead indicate that these components (partly) represent refractory substances (i.e. fluorescent micropollutants). This is reasonable, considering that three WWTP outlets feed into the studied stream and highlights the need to further investigate OMPs at the intersection of natural and engineered systems.In conclusion, this PhD thesis explored the co-metabolic and metabolic biodegradation of organic compounds (OMPs and DOM constituents) and contributed to an increased understanding of the relation between chemical structures and compound biodegradability by combining theoretical investigations and laboratory biodegradation experiments. In particular, experiments with pure cultures and chemically defined carbon sources demonstrated that subtle structural differences can significantly affect whether DOM constituents serve as growth substrate. These conceptualized studies should in the future be stepwise extended, for example, to additionally investigate the biodegradability of more complex DOM. This next step would provide detailed insights on biodegradation mechanisms together with an increased environmental representativeness.<br/
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
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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