1,720,974 research outputs found
Estudio de la dinámica eléctrica cardíaca: análisis y modelado de índices temporales y espectrales basados en el procesado del electrocardiograma de superficie
No full textGrado obtenido: Doctor de la Universidad de Buenos AiresDisciplina: IngenieríaFil: Valverde, Esteban Raúl. Universidad de Buenos Aires. Facultad de Ingenierí
Análisis electrocardiográfico latido-a-latido de la variabilidad de la repolarización ventricular en pacientes posinfarto de miocardio.
No full textResumen: Se evalua el índice TSV durante los estadios healing y healed del infarto de miocardio utilizando las doce derivaciones estandarizadas del ECG, encontrándose que el tiempo transcurrido luego del infarto influye en la modulación de la variabilidad de la repolarización ventricular latido-a-latido utilizando el criterio ML, y que la mejor detección de dicha variabilidad en los grupos anterior e inferior se obtuvo en las derivaciones V4 y aVF respectivamente.Fil: Arini, Pedro. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; Argentina.Fil: Valverde, Esteban. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica. Buenos Aires, Argentina.\n2.-Fil: Valverde, Esteban. CONICET. Instituto Argentino de Matemática 'Alberto P. Calderón'; Argentina
Assessment of delayed ventricular activation after myocardial infarction
No full textExperimental and clinical studies have shown that after myocardial infarction (MI), increases the risk to develop cardiac arrhythmias. We have evaluated the ventricular activation during healing (MI7) and healed (MI60) stages after MI. We carried out a comparative study between the QRS spectral variance (QRSSV) index and late potentials (LPs) obtained by the Signal-averaged (SaECG) technique. The electrocardiograms of 48 healthy subjects (CTRL); 84 patients in MI7 and 41 in MI60 without VT/VF; and also 7 patients in MI7 and 6 in MI60 with VT/VF, were analysed utilizing the Frank leads. The QRSSV has increased (p < 0.05) in patients without VT/VF for all leads during MI7 and MI60 with respect to CTRL, and just in a few leads in patients with VT/VF. Conversely, we have only found significant proportion of LPs in MI7 with respect to CTRL in patients with VT/VF and none without VT/VF. This investigation might help to comprehend the influence of time in patients with and without VT/VF. We conclude that SaECG could be restricted to locate stable and delayed depolarization, while the QRSSV index could detect both stable and unstable activation disorders in whole depolarization.Fil: Valverde, Esteban Raul. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; ArgentinaFil: Arini, Pedro David. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; Argentin
Study of T-wave spectral variance during acute myocardial ischemia
No full textSeveral studies have shown that beat-to-beat variability of ventricular repolarization morphology, which can be measured by T-wave spectral variance (TSV) index based on the 2D-FFT, is asociated with an increased risk for developing ventricular arrhythmias. In the present study we tested TSV index during percutaneous coronary intervention (PCI) procedure in the orthogonal X, Y and Z leads for both non-filtered T-waves (T N ) and filtered T-waves (T F , which was obtained by reducing the ST-segment modification due to acute ischemia). Also, we analyzed the intraindividual and interindividual variations of TSV index, in order to determine reliable limits of significant repolarization variability due to an ischemic cardiac process. The study group consisted of 62 patients, in which two ECG control and one ECG recording during PCI-procedure were obtained. Results indicate that TSV index showed significant differences during PCI-procedure respect to control situation in all ECG leads for both T N (p <; 10 -8 ) and T F (p <; 0.05). Moreover, TSV index presented a high stability in each patient and a significant larger variability between patients. We conclude that TSV index offers a robust tool for evaluating beat-to-beat repolarization variability during acute ischemia.Fil: Valverde, Esteban R.. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Arini, Pedro David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; ArgentinaXXIX International Conference on Computing in CardiologyCracoviaPoloniaAGH University of Science and TechnologyInstitute of Electrical and Electronics Engineer
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
Spatio-temporal features of variability repolarization during acute myocardial ischemia
No full textSeveral studies have shown that dynamic variability of ventricular repolarization morphology is associated with an increased risk for developing ventricular arrhythmias. We evaluated beat-to bea ventricular repolarization variability using the T-wave spectral variance (TSV) index during acute myocardial ischemia from the spatial electrocardiogram ECG planes. The study group consisted of 71 patients in which the three orthogonal XYZ leads were obtained during both control (5 min.) and percutaneous coronary intervention (4 min. 36 sec. ± 80 sec.) of different arteries. Three spatial ECG planes were determined: the frontal plane (FP) defined by XY-leads, the horizontal plane (HP) defined by XZ-leads and the sagittal plane (SP) defined by YZ-leads. Results indicated that the TSV index has shown the most important significant differences with respect to control in: FP to the left anterior descending coronary artery occlusion (p < 0.001 in X-lead; p < 0.0001 in Ylead), HP to the right coronary artery occlusion (p < 0.001 in Y-lead; p < 0.0001 in Z-lead) and SP to the left circumflex coronary artery occlusion (p < 0.01 in Xlead; p < 0.01 in Z-lead). We conclude that TSV index offers a robust tool for evaluating beat-to-beat repolarization variability during acute ischemia, which depends on the link between the occluded artery and the analyzed ECG plane.Fil: Valverde, Esteban Raul. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; ArgentinaFil: Arini, Pedro David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; ArgentinaReunión de Trabajo en Procesamiento de la Información y ControlArgentinaUniversidad Nacional de Río Negr
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
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