1,720,953 research outputs found
Coupling Metabolic and Hydrodynamic Compartmental Models for Bioreactor Simulations
No full textLarge-scale bioreactors are widely employed across bioprocessing industries for the production of chemicals, pharmaceuticals, and biofuels. The increasing demand for specialized pharmaceuticals has motivated industries to optimize bioreactor operations. However, the complexity of multiphase interactions and the emergence of concentration gradients and intracellular heterogeneity in bioreactors pose significant challenges in accurately predicting and optimizing the performance of bioreactors. Simulations of numerical models have become invaluable for understanding these systems; however, the high computational cost of detailed models—particularly those involving multiphysics—limits their practicality. The computational cost of these models precludes them from being used for real-time applications or for extensive design optimizations.
To address this challenge, this thesis proposes computationally efficient methods to solve coupled metabolic and hydrodynamic compartmental models that describe key process dynamics.
The compartmental model (CM) approach is based on steady-state multiphase computational fluid dynamic simulations and is designed to accurately represent hydrodynamic properties such as turbulent dissipation energy, oxygen mass transfer, and flow topology. Conventional compartmentalization methods were found to introduce nonphysical ``short-cutting'' effects, leading to inaccuracies in mixing time predictions. To mitigate this, a refined compartmentalization approach was developed to better capture hydrodynamic mixing patterns. Then, a metabolic model was integrated with the compartmental model to explore the metabolic and hydrodynamic interactions.
In terms of the metabolic behavior, two key scenarios were considered: i) the intracellular concentrations were assumed to reach instantaneous equilibrium with their extracellular environments at all times and ii) the intracellular concentrations were not in equilibrium with their extracellular environments.
For the first case, where intracellular and extracellular equilibration was assumed, a binary search tree metabolic model (BSTMM) was developed from a dynamic flux balance analysis model and coupled with a CM describing the extracellular environment. This method significantly reduces computational complexity by substituting traditional linear optimization solvers with an online point-location approach. The coupled BSTMM-CM successfully captured diauxic growth dynamics and demonstrated substantial computational efficiency, enabling long-term bioprocess simulations on standard desktop hardware. However, kinetic parameters for metabolic models calibrated in small-scale bioreactors could not be directly applied to large-scale systems without recalibration. This finding suggested that intracellular heterogeneity may play a crucial role in metabolic regulation and must therefore be explicitly accounted for.
To address this, the second case considered a finite-rate adaptation mechanism governing equilibration between the extracellular and intracellular environments. A method of moments approach, assuming a truncated normal distribution, was implemented to reconstruct the number density function efficiently. This approach demonstrated that intracellular heterogeneity is most pronounced when the characteristic timescales of microbial adaptation and extracellular advection are comparable. The application of this approach to E. coli fermentation data reported in the literature resulted in improved fitting as compared to a model that ignores intracellular heterogeneity.
Furthermore, the impact of population heterogeneity on metabolic regulation was evaluated, revealing distinct variations in growth rate and substrate uptake across different regions of the bioreactor.
To further improve computational efficiency of the coupled PBM-CM, an adaptive population compartmental scheme is proposed, which dynamically adjusts the compartmentalization over the course of a simulation to balance accuracy and computational cost. This approach was found to be particularly effective for large-scale bioreactor simulations, especially when advection rates exceed microbial adaptation rates, leading to substantial reductions in simulation time with minimal loss of predictive accuracy.
This research significantly advances the modeling of large-scale bioreactors by integrating hydrodynamic and metabolic models into a computationally efficient framework. The developed methods provide more in-depth insights into the influence of concentration gradients and intracellular heterogeneity on microbial behavior, ultimately improving the predictive accuracy and scalability of bioprocess simulations
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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