1,721,225 research outputs found
Estimating functional networks in dynamical biological systems through convex optimization theory
Full text linkComplex systems abound in the natural and social world, e.g across systems as apparently diverse such as the human brain, the immune system, economics, and the worldwide web. Yet despite three decades of intense research activity in studying complexity, many big issues remain only partially resolved, including a good quantitative definition for a complex system. Many approaches, from time series analysis and stochastic modeling, have been proposed to model the behavior of complex systems based on observed time series by separating the systems’ behavior between observed macroscopic and hidden microscopic scales. One of the most flexible and easy to implement, in the context of linear signal processing, is the Vector Autoregressive Model (VAR) whose identification process is at the basis of the most used estimators for analyzing the statistical dependencies between different time series representing the activity of the entire dynamical system. However, the identification procedure for specific combinations of the number of processes-number of observations in the time series could lead to a severe correlation between the regressors resulting in high bias and variance in the used estimator, which can be counteracted with the use of penalized regression techniques. The first part of this thesis work has been focused on introducing and testing multivariate convex regression methodologies, as a tool for estimating the statistical dependencies among different dynamical systems. Since that there are no extensive studies available that assess the performance of different penalized regression techniques in different experimental conditions, in Chapter 1 I report a comparative analysis among different penalized regression techniques in the context of convex optimization which guarantees the existence of a solution to the VAR identification problem. Another important tool for investigating and quantifying information processing is represented by the Information theory that has already been proved to be a useful framework for the design and analysis of complex self-organized systems. In this context, it has been recently introduced a tool able to compute any measure of information dynamics from the parameters of a VAR model used to characterizes an observed multivariate Gaussian process even in combination with state-space modeling. Motivated by the fact that penalized regression techniques were not yet introduced and tested for the decomposition of information processing, Chapter 2 it is investigated the possibility to integrate the so-called LASSO regression, in a framework for the computation of these measures. The results of Chapters 1 and 2 clearly demonstrated that could be computationally very onerous, especially if combined with state-space modeling and in conditions of very long time series and dynamical systems with a very high number of processes. For this reason, in Chapter 3 we tried to overcome this computational limitation by introducing an Artificial Neural Network equivalent to a VAR model. In particular, thanks to a new training algorithm based on Stochastic gradient descent it has been possible to induce sparsity in the weights matrix of the network during the training phase, but with a less computational cost if compared with traditional LASSO implementation. This new tool was then combined with a state-space model and using for Granger causality (GC) estimation and tested on different real complex systems. Given the results of Chapters 1, 2, and 3 in Chapter 4 an extensive analysis of the performance of different methods in estimating GC, was performed. In particular, due to the high dimension of the observed data, the “curse of dimensionality” may arise leading to unreliable estimation of direct causality. With the aim of carrying out an extensive comparative study, the performance of different methodologies, available in the current literature and explored in this thesis work, for the estimation of GC have been compared. Furthermore, we provided an implementation in combination with space state models for the methods that were not previously tested with this strategy. The performance of all the methods for GC estimation combined or not with state-space models have been tested in two different simulation studies. A conclusion summarizing the main contributions of this Ph.D. project, together with their impact and limitations, closes this dissertation
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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