1,721,056 research outputs found
Optical online oxygen monitoring of aerobic cultivations in shake flasks and microtiter plates
No full textTwo of the most important process parameters for aerobic cultivations of microorganisms and cells are the oxygen consumption and oxygen content within the cultivation broth. By means of the consumption, mass balances and stoichiometries can be calculated. On the basis of the oxygen content, an oxygen limitation can be identified doubtlessly. Additionally, the propagation of these parameters can be seen as a characteristic physiological fingerprint of an aerobic culture. Both parameters enable a sound and valid process monitoring and characterization. For these reasons, respective sensors and analytics are commonly applied in fermenter scale. However, the first steps of bioprocess development are generally performed in small scale experiments within shake flasks or microtiter plates. This is due to the ability to use smaller reaction volumes while performing a greater number of parallel experiments, which saves time, resources and consequently lowers the overall costs per experiment. Unfortunately, due to the small dimensions, respective sensors and analytics are not easily transferable from fermenter to small scale and the current solutions are not completely satisfying. To augment the process knowledge already in early process development, it is of general interest to develop new tools and improve existing technologies for small-scale bioreactors. Within this work, three different novel systems for online monitoring of aerobic cultures in small scale fermentations have been developed, introduced and characterized.Firstly, a novel shake flask based system for measuring the dissolved oxygen tension (DOT) is introduced. By using dispersed oxygen-sensitive nanoparticles, an easy to use, robust and reliable DOT measurement system was developed, which is applicable for almost all cultivation conditions in shake flasks and for both, soluble complex and synthetic media. Reliable DOT measurements were achieved using oxygen-sensitive nanoparticles added to the cultivation broth at a concentration of 0.1 g L 1. The biocompatibility of the dispersed oxygen-sensitive nanoparticles was demonstrated for H. polymorpha, X. campestris and E. coli by means of RAMOS cultivations. Furthermore, the importance of system calibration under cultivation conditions was demonstrated. Besides that, the ability of the dispersed oxygen-sensitive nanoparticles to withstand autoclaving is an additional advantage for sterile cultivations. This measurement system turned out to be a valuable alternative for existing DOT measurement systems in shake flask cultivations, especially at low filling volumes and high shaking frequencies. In combination with RAMOS data it was possible to determine kLa values online during cultivations of K. lactis, E. coli and H. polymorpha. The determined kLa values were investigated with respect to their corresponding uncertainties caused by systematic errors in OTR, DOT, L_(O_2 ) and p_(O_2)^gas estimations and sensor inertia. All kLa values were in good agreement with an empirical correlation based on the medium osmolality from the literature. Secondly, this oxygen-sensitive nanoparticle-based technique was transferred to the microtiter plate scale and combined with the established BioLector technology. The respective optical fiber of the oxygen analytic was integrated into the BioLector system and displaced via the BioLector movement axes underneath the microtiter plate. Since this system does not require the presence of optodes at the bottom of each well, the measurement system can be applied to various microtiter plates (MTPs). Finally, the cost constraints associated with MTPs possessing immobilized sensor spots (optodes) can be overcome using this technology. Additionally, the costs per cultivation are significantly reduced and the system provides a serious alternative to established devices. Furthermore, kLa values for the applied cultivation conditions were estimated and used to calculate the oxygen transfer rates (OTRs) in MTPs based on the DOT. OTRs calculated for the MTPs and OTRs determined in shake flasks via the RAMOS technology agreed very well with each other.Lastly, a microtiter plate-based µRAMOS system was developed to measuring the oxygen transfer rate (OTR) in every individual well of a 48-well microtiter plate. On the basis of a first four-well prototype a second enhanced prototype covering the whole 48-well microtiter plate was implemented. The necessary valve and sensor technology was thereby successfully integrated in a microfluidic microtiter plate cover. To compromise on sufficient measurement rates and an economically acceptable number of oxygen instruments an 8x48 optical multiplexer (MUX) was developed and utilized. By means of four exemplary RAMOS and µRAMOS cultivations, both systems delivered the same OTR signal quality. The cultivation throughput could be increased 6-fold compared to the established eight shake flask RAMOS system. Additionally, the media consumption was reduced 12.5-fold per cultivation from a typical filling volume of 10 mL in the shake flask to 800 µL in the microtiter plate. In summary, three novel measurement systems were successfully developed, built and characterized. These systems offer a sound determination of the dissolved oxygen tension and oxygen transfer rate respectively and turned out to be predestined small scale analytics for process development and characterization purposes
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
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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