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On the use of selective environments in microalgal cultivation
No full textThis thesis deals with selective environments in microalgal cultivation. As explained in Chapter 1 microalgae have changed the course of life on Earth dramatically by performing oxygenic photosynthesis. In oxygenic photosynthesis electrons from water are used to reduce carbon dioxide to carbohydrates or lipids using solar energy. As a waste product oxygen is produced. The production of carbohydrates and particularly lipids by microalgae attracts currently considerable scientific interest as microalgal lipids can be converted to yield biodiesel. As the CO2 emitted upon combustion of this biodiesel has recently been withdrawn from the atmosphere by the microalgae, no net increase in atmospheric CO2 level takes place. Microalgae offer advantages over other lipid production platforms as microalgae are able to reach high intracellular lipid contents and need little freshwater and arable land. Chapter 2 describes the advantages and limitations of the application of a selective environment to obtain a certain functionality in a system. A selective environment aims to give a competitive advantage to a microorganism displaying the desired functionality. By rewarding microalgae for displaying a certain functionality it becomes in the interest of microalgae themselves to display this characteristic. The best reward in nature is an increased chance of survival. A selective environment therefore tries to couple the desired characteristic to an increased chance of survival. Microalgal cultivation based on selective environment fundamentally differs from cultivation of pure cultures. Maintaining the desired culture is the goal of the latter, whereas a microalgal cultivation process based on selective environments aims to maintain a functionality in a system. The species, or multiple species, displaying the desired functionality are expected to differ at different geographical places, with changing climate conditions and over time. Under any condition the species that thrives under these specific conditions by displaying the desired characteristic is enriched. Interesting microalgal functionalities from an industrial point of view include a high carbohydrate and lipid productivity. Both of these storage compounds are produced by microalgae to endure dynamic growth conditions. By limiting the presence of the essential microalgal nutrient nitrogen (in the form of NH4 + or NO3 –) to the dark phase solely an environment is created in which production of storage compounds in the light period is an advantageous strategy. Production of these compounds in the light period will allow microalgae to metabolise the available nitrogen in the dark period by supplying carbon skeletons and energy in the dark. Chapter 3 shows that such an environment enriches carbohydrate producing microalgae from a natural inoculum. Chapter 4 shows that both the moment of nitrogen addition as the amount of nitrogen dosed per microalgae had significant influence on the metabolic behaviour of marine microalgal cultures enriched using the procedure described in Chapter 3. Carbohydrate and lipid productivity proved maximal if ammonium was supplied at the start of the dark period rather than the light period, irrespective of the amount of nitrogen dosed per microalgae. Increasing the amount of nitrogen dosed per microalgae, by increasing the volume exchange ratio from 33 to 50 percent per cycle, induced a decrease in storage compound production if ammonium was supplied in the light period whereas the storage compound productivity was comparable when ammonium was supplied in the dark period. Chapter 5 shows that the enriched microalgal community was highly dependent on an environmental parameters as the presence of silicate. If silicate was present at non-limiting concentrations the enriched culture was dominated by diatoms, whereas green algae were dominant if silicate was absent. Both cultures showed however the same functionality of producing large amounts of carbohydrates in the light period to be able to consume the supplied nitrogen source in the dark period. These results, together with the data obtained under marine conditions, showed that carbohydrate production can be achieved under various conditions, as long as a carbon fixation in the light period is uncoupled from nitrogen uptake in the dark. Diatoms have interesting characteristics for large-scale microalgal cultivation. These include a relative easy solid-liquid separation after cultivation, increased resistance to predators and the possibility to synthesize lipids under silicate limitation. Supplying NH4 + in a pulse, either at the start of the light or the dark period under non-limiting silicate levels, enriched a culture fully dominated by the diatom Nitzschia palea from a natural inoculum, as described in Chapter 6. The metabolic behaviour of the enriched culture was highly influenced by the moment of nitrogen addition. Biomass was the main photosynthetic product in the light period if nitrogen was dosed at the start of the light period, whereas carbohydrates were the main photosynthetic product if nitrogen was dosed at the start of the dark period. Subjecting the enriched cultures to prolonged periods of nitrogen or silicate limitation induced different metabolic responses. Cell numbers increased four times and carbohydrates were the main storage compounds under nitrogen limitation, while cell division abruptly ceased and lipids were the preferred storage compound under silicate limitation. In all experiments carried out in this thesis carbohydrates were the preferred microalgal storage compounds. Uncoupling of carbon fixation in the light from nitrogen uptake in the dark enriched under variable conditions (freshwater, marine, under high silicate concentrations) carbohydrate producing microalgae from a natural inoculum. Intracellular carbohydrate levels typically increased from10 to 50 % of organic dry weight in the light period. Although no liquid and gas flows leaving and entering the systems were sterilised and despite regular cleaning of the systems the enriched cultures were highly stable in time. This shows that if carbohydrate productivity is aimed for a proper selective environment has been identified and tested. A better understanding of the ecological role of lipids and carbohydrates in microalgae will help creating selective environment for lipid production. Besides drawing general conclusions, Chapter 7 elaborates more on possible strategies to enrich lipid producing microalgae. The strategy advocated in this thesis, rewarding a microalga for displaying a functionality by coupling it to an increased chance of survival by imposing a selective environment, will prove a valuable tool if the ecological role of lipids is better understood.BiotechnologyApplied Science
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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