1,720,958 research outputs found
Anaerobic sludge granulation at high salinity
No full textIndustries, such as leather tanning, agro-food, fisheries, petroleum, petrochemical and textile dyeing produce saline wastewater. As a result approximately 5% of the globally generated wastewater is hypersaline (salinity above 3.5%). Because salts have a negative effect on microbial activity, biological treatment processes are usually not considered for such wastewaters and they are treated with more expensive physical-chemical processes. Hence, there is a need to broaden the application of more sustainable biological treatment methods. In particular, anaerobic biological treatment should be considered due to possibility of converting organics into biogas, low energy requirements for operation, and production of small amounts of bio-solids. Amongst the anaerobic biological treatment technologies those based on formation of granular sludge are of special interest. This is due to superb settling velocities and a high methanogenic activity of the granules, which allows for a compact reactor design capable of handling high volumetric organic loading rates. Before this research, anaerobic granular sludge was reported to be unsuitable for treatment of highly saline wastewater because methanogens are inhibited by the salinity and sludge granules disintegrate/do not form. The main objective of this thesis was to accomplish anaerobic granulation at high salinity from dispersed biomass and to investigate strategies of overcoming salt toxicity to microorganisms. In Chapter 2 we investigated the possibility to form granules from dispersed biomass at low (5 g Na+/L) and high salinity (20 g Na+/L) in upflow anaerobic sludge blanket (UASB) reactors under other conditions known to improve fresh water granulation. The wastewater contained a complex, energy rich and proteinaceous substrate – a mixture of glucose, acetate and tryptone. This allowed a surprisingly fast development of anaerobic granules (within 45 days), even at 20 g Na+/L (~ 50 g/L NaCl). Although the COD (chemical oxygen demand, a measurement for organic pollution) removal efficiency was slightly better at 5 g Na+/L compared to 20 g Na+/L, at both salinities the removal efficiency exceeded 98% at organic loading rates as high as 16 g COD/L/d. To remain viable at high salinity, most prokaryotes synthesize or take up from bulk liquid small organic molecules called osmolytes. Uptake of osmolytes from bulk liquid is energetically more favourable compered to synthesis. Furthermore, it is known that methanogens mainly use nitrogen containing molecules, such as amino acids or their derivatives for osmoprotection. Also, extracellular polymeric substances (EPS) – the structural gluing material of granules - in anaerobic granular sludge consist of a large weight fraction of proteins (up to 90%). Thus, we hypothesized, that proteinaceous substrate in Chapter 2 potentially provided bioenergetically favourable synthesis precursors of osmolytes and EPS. This hypothesis was investigated in Chapters 3-5. In Chapter 3 proteins and amino acids were inspected for their potential to alleviate osmotic shock stress of acetoclastic methanogens in granular sludge. Aspartate, glutamate, gelatine and tryptone could all alleviate the negative effects of high salinity on methanogens. Furthermore, analysis of nitrogen containing osmolytes accumulated by salt adapted granular sludge revealed glutamate and N-acetyl-β-lysine as the major osmolytes. This could in part explain the positive effect of amino acids on methanogenic activity: glutamate could be taken up directly from the bulk liquid, while N-acetyl-β-lysine could be synthesized from aspartate after uptake in the cell. Hydrolysis of a protein (gelatine) and a peptide (tryptone) potentially could also provide both of these amino acids, thereby explaining their positive effect on methanogenic activity. In Chapter 4 the (positive) effect of proteinaceous substrates on the rate of anaerobic sludge granulation was investigated. In UASB reactor experiments, glucose and acetate were present in the wastewater, together with a third co-substrate that was different for each reactor. If proteinaceous compounds (tryptone or gelatine) were added as the third substrate, granulation at 20 g Na+/L already was observed after 40-50 days. With starch as the third substrate well settling granule-alike aggregates formed. However, this was only possible after a much longer period (~180 days) than with the proteinaceous substrate. Still, apparently methanogenic adaptation and sludge granulation can be achieved at high salinity even without addition of proteins implying that a broader spectrum of saline wastewater is amenable for anaerobic granular treatment without the need of protein dosing. In Chapter 5, the possibility to estimate the amount of proteinaceous substrate for enhanced granulation based on osmotic pressure calculations was studied. The experimental results agreed with calculations, which allowed for a nine fold decrease of protein concentration compared to the arbitrary chosen amounts in Chapter 2 and Chapter 4. In Chapter 6 microbial molecular and microscopy analyses revealed that in sludge granules of reactors supplied with proteinaceous substrate the dominant methanogenic archaea at two different salinities (5 and 20 g Na+/L) belonged to Methanosaeta in its filamentous form. Interestingly, also the dominant bacteria were present as filaments (Streptococcus at 5 g Na+/L and bacterium belonging to Defluvitaleaceae at 20 g Na+/L). An experiment was also performed in which the granulation at 20 g Na+/L from dispersed biomass was studied without a proteinaceous substrate, but with amino acids leucine and proline instead. In this reactor, the bacteria belonging to Defluvitaleaceae disappeared and the granulation was not achieved. In Chapter 7, ion exchange membranes were prepared with EPS extracted from high salinity adapted granules and shown to selectively transport cations and partially repel anions. Interestingly, EPS exhibited a higher selectivity for potassium transport compared to sodium, even though potassium and sodium have the same valence and similar physical-chemical properties. As potassium selectivity has commercial relevance, future studies focusing on the reason for this selectivity perhaps can result in the development of commercial potassium selective membranes. For microbial cells such improved transport of ions through EPS seems to have a negative effect. In methanogenic activity assays potassium was much more toxic compared to sodium suggesting that cation toxicity may be influenced by properties of EPS, i.e. the better the ion can diffuse through the EPS, the more toxic it is (Chapter 7). Finally, in Chapter 8 the results of this research are discussed in a broader context and future research directions are proposed
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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