1,721,016 research outputs found
DGM : Directed-Graph Mapping as a novel tool to analyze cardiac arrhythmias
No full textCardiac arrhythmias and related diseases are the leading cause of death in the Western world. The management thereof currently accounts for about 9\% of the total health-care expenditure across the EU. Research on the mechanisms of arrhythmia and optimizations of diagnostic tools remain important.
The normal rhythm of the heart results in about 60 to 100 beats per minute, which accumulate roughly to about 3 billion beats in a lifetime. It is likely for this rhythm to get disturbed once in a while. Naturally, the heart rate increases with exercise or slows down during sleep. Drugs, alcohol, nicotine and the general health condition of a person may also affect the heart's condition. However, persistent abnormality of the heart rhythm can indicate cardiac arrhythmia and the associated complications will depend on the type of arrhythmia. In general, complications and symptoms of cardiac arrhythmias may include a racing or slow heartbeat, chest pain, shortness of breath or even anxiety and fatigue. In more severe cases cardiac arrhythmia can induce stroke, heart failure and sudden cardiac death.
Treatment of arrhythmia may include medication, specific therapies such as vagal maneuvers and cardioversion, surgery like ablation and maze procedures or the placement of implantable devices lika a pacemaker or defibrillator.
For this work, mainly ablation therapy is of interest. During ablation the electrophysiologist (EP) inserts a catheter (a measuring device with electrodes) into the heart and records the electrical activity. These electrical signals are presented on a color-coded map. Based on an educated interpretation of these color maps and corresponding signals the EP will gather knowledge about the mechanism maintaining the arrhythmia. Once the mechanism is understood and located, the EP will ablate or scar the heart tissue in order to stop electrical propagation in that specific region. This will stop the arrhythmia restoring the normal heart rhythm or convert the excitation pattern to a (usually) slower arrhythmia.
It can be very challenging to determine the mechanism of an arrhythmia and wrong ablation lines can make the heart prone to new arrhythmias and limits the myocardial contractility. Analysis of these electrical maps can be difficult and prone interpretation. Therefore, there is a need for automated and operator independent interpretations and strategies.
My dissertation is devoted to the development, applicability and accuracy of Directed-Graph Mapping or DGM on analysis of cardiac arrhythmia mechanisms. DGM is a mathematical approach based on concepts of network theory describing the properties of cardiac excitation waves. DGM takes as input the spatial coordinates of the electrodes and the Local Activation Time (LAT) of the signals. With this data, a directed graph is created. Based on validated algorithms of graph theory and new algorithms I designed, DGM automatically analyzes these graphs and presents the rotational circuit or focal sources of the arrhythmia under study
A study of the Gribov-Zwanziger framework: from propagators to glueballs
Get PDFThis thesis presents a study of the Gribov-Zwanziger framework: from propagators to glueballs. The chapters 2 and 3 are meant as an introduction and only require a basic knowledge of quantum field theory. Chapter 2 explains the techniques behind algebraic renormalization, which shall be widely used throughout this thesis, while chapter 3 tries to give a pedagogic overview of the Gribov-Zwanziger framework as this is not available yet in the literature. The subsequent chapters contain own research. First in chapter 4, we shall dig a bit deeper in the Gribov-Zwanziger framework, by exploring the BRST symmetry and the KO criterium. Next, in chapter 5 we shall elaborate on the ghost and the gluon propagator in the infrared and present a refined Gribov-Zwanziger action. Further, we present two chapters on the search for physical operators within the (refined) Gribov-Zwanziger framework, chapter 6 and 7. A small chapter 8 is devoted to some values for different glueballs. We end this thesis with the conclusions, chapter 9
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
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