1,866 research outputs found
Solution of polynomial Lyapunov and Sylvester equations
No full textA two-variable polynomial approach to solve the one-variable polynomial Lyapunov and Sylvester equations is proposed. Lifting the problem from the one-variable to the two-variable context gives rise to associated lifted equations which live on finite-dimensional vector spaces. This allows for the design of an iterative solution method which is inspired by the method of Faddeev for the computation of matrix resolvents. The resulting algorithms are especially suitable for applications requiring symbolic or exact computation
A two-variable approach to solve the polynomial Lyapunov equation
No full textA two-variable polynomial approach to solve the one-variable polynomial Lyapunov equation is proposed. Lifting the problem from the one-variable to the two-variable context allows to use Faddeev-type recursions in order to solve the polynomial Lyapunov equation in an iterative fashion. The method is especially suitable for applications requiring exact or symbolic computation
The Influence of Using a Static Diastolic Geometry in ECG Imaging
Get PDFOne of the common choices when performing electrocardiographic imaging (ECGI) is that the cardiac geometry is in a static, diastolic state. To test the influence of this approximation, we compared epicardial potential maps and isochrones during systolic and diastolic geometries in four patients. Zero-th order Tikhonov regularization was used to reconstruct ventricular epicardial potentials. A spatiotemporal estimation method was then used to determine the activation and recovery times from the reconstructed epicardial electrograms. Activation times (AT), recovery times (RT) and electrogram correlation coefficients (CC) were compared for both geometries. Furthermore, CC and differences in AT/ RT were correlated against the linear movement and a substitute for rotational movement. Poor correlation was found between linear/rotational movement and reconstruction differences. Overall, agreement between epicardial potential maps and isochrones of both geometries was high when assessed quantitatively, but regional differences might occur for qualitative interpretation. These differences mostly occurred in areas of flat T-waves. This novel, more accurate quantification of the influence of assuming a diastolic geometry in ECGI may further help in interpreting ECGI measurements.</p
Noninvasive assessment of dynamic cardiac electrophysiology in normal human subjects
No full textIntroduction
Electrocardiographic imaging (ECGI) has been used to investigate arrhythmia mechanisms in various conditions. Data on normal human subjects, especially in Europe, are scarce. Dynamic characteristics of ventricular activation and recovery during sinus rhythm have not been assessed before.
Purpose
To examine cardiac electrophysiology and its dynamic aspects in normal subjects using ECGI, in order to provide a range of normal patterns and values for activation (AT) and recovery times (RT), activation-recovery intervals (ARI, a surrogate for action potential duration) and their dynamicity.
Methods
11 Subjects (age 57±7 years, 27% male, all normal LVEF) with atypical chest pain who underwent a cardiac CT-scan as part of clinical care but who were negative for any pathology on full examination were included. A validated non-commercial potential-based formulation of ECGI was used to reconstruct unipolar electrograms (EGMs) on the epicardial surface for three sinus beats within minutes from each other, per individual. ATs and RTs were determined as the maximum negative upslope during QRS, and maximum positive upslope during T wave of the local EGMs. Additionally, we determined locations of first and last activation and recovery. Inter- and intra-individual differences were computed.
Results
Subjects had normal 12-lead characteristics without ST-deviations, and an average QTc interval of 415±18ms. Panel A shows ECGI during sinus rhythm for 3 representative subjects, and panel B summarizes all findings on the entire epicardium. The first epicardial activation breakthrough typically occurred on the right ventricle (RV), consistent with the concept that the thinner RV wall accounts for a faster transmural activation. Last activation was mostly on the base of the left ventricle (LV), on the inferior to lateral wall. Earliest recovery occurred predominantly on the anterior surface, while latest recovery occurred on the inferior surface. Complete activation of the epicardial surface (from earliest to latest AT) took 41±8ms, while recovery (earliest AT to latest RT) took 317±24ms and average ARI (local AT to local RT) took 232±23ms. Thus, inter-individual variation of recovery duration was higher than of activation. Intra-individual differences between beats in ATs, RTs and ARIs of distinct sinus beats were small (2.3±3.1ms, 9.7±8.8ms and 9.8±9.1ms, respectively) suggesting that ECGI enables stable reconstruction quality (panel C).
Conclusion
In this cohort, noninvasive ECGI provides novel insights in ventricular electrophysiology. Electrical recovery is more variable than activation, both intra-individually and inter-individually. Overall, AT, RT and ARI differences between sinus beats were low. ECGI appears suitable to assess dynamic electrical patterns during cardiac pathology
Noninvasive assessment of dynamic cardiac electrophysiology in normal human subjects
No full textIntroduction
Electrocardiographic imaging (ECGI) has been used to investigate arrhythmia mechanisms in various conditions. Data on normal human subjects, especially in Europe, are scarce. Dynamic characteristics of ventricular activation and recovery during sinus rhythm have not been assessed before.
Purpose
To examine cardiac electrophysiology and its dynamic aspects in normal subjects using ECGI, in order to provide a range of normal patterns and values for activation (AT) and recovery times (RT), activation-recovery intervals (ARI, a surrogate for action potential duration) and their dynamicity.
Methods
11 Subjects (age 57±7 years, 27% male, all normal LVEF) with atypical chest pain who underwent a cardiac CT-scan as part of clinical care but who were negative for any pathology on full examination were included. A validated non-commercial potential-based formulation of ECGI was used to reconstruct unipolar electrograms (EGMs) on the epicardial surface for three sinus beats within minutes from each other, per individual. ATs and RTs were determined as the maximum negative upslope during QRS, and maximum positive upslope during T wave of the local EGMs. Additionally, we determined locations of first and last activation and recovery. Inter- and intra-individual differences were computed.
Results
Subjects had normal 12-lead characteristics without ST-deviations, and an average QTc interval of 415±18ms. Panel A shows ECGI during sinus rhythm for 3 representative subjects, and panel B summarizes all findings on the entire epicardium. The first epicardial activation breakthrough typically occurred on the right ventricle (RV), consistent with the concept that the thinner RV wall accounts for a faster transmural activation. Last activation was mostly on the base of the left ventricle (LV), on the inferior to lateral wall. Earliest recovery occurred predominantly on the anterior surface, while latest recovery occurred on the inferior surface. Complete activation of the epicardial surface (from earliest to latest AT) took 41±8ms, while recovery (earliest AT to latest RT) took 317±24ms and average ARI (local AT to local RT) took 232±23ms. Thus, inter-individual variation of recovery duration was higher than of activation. Intra-individual differences between beats in ATs, RTs and ARIs of distinct sinus beats were small (2.3±3.1ms, 9.7±8.8ms and 9.8±9.1ms, respectively) suggesting that ECGI enables stable reconstruction quality (panel C).
Conclusion
In this cohort, noninvasive ECGI provides novel insights in ventricular electrophysiology. Electrical recovery is more variable than activation, both intra-individually and inter-individually. Overall, AT, RT and ARI differences between sinus beats were low. ECGI appears suitable to assess dynamic electrical patterns during cardiac pathology
Cultural representation of sexual dissent in comics: the "desired men" of Ralf König in Der bewegte Mann
Get PDFEn este artículo se abordará la representación de la sexualidad disidente en una de las obras inaugurales de Ralf König, el ciclo Der bewegte Mann, constituido por dos partes publicadas en los años ochenta y que nos permiten apreciar la emergencia del autor en el mercado editorial alemán, así como sus operaciones de resistencia ante los intentos de normalización y represión por parte de la heteronormatividad.In this article, the representation of sexual dissent in German author Ralf König will be adressed. The work analize the cycle Der bewegte Mann, consisting of two parts published in the eighties and that allows us to appreciate the emergence of the author in the german publishing, as well as its operations of resistance to the attempts of normalization and repression by heteronormativity.Fil: Saxe, Facundo. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación. Instituto de Investigaciones en Humanidades y Ciencias Sociales (UNLP-CONICET); Argentina
Representación cultural de la disidencia sexual en el cómic: los «hombres deseados» de Ralf König en Der bewegte Mann
Get PDFEn este artículo se abordará la representación de la sexualidad disidente en una de las obras inaugurales de Ralf König, el ciclo Der bewegte Mann, constituido por dos partes publicadas en los años ochenta y que nos permiten apreciar la emergencia del autor en el mercado editorial alemán, así como sus operaciones de resistencia ante los intentos de normalización y represión por parte de la heteronormatividad.In this article, the representation of sexual dissent in German author Ralf König will be adressed. The work analize the cycle Der bewegte Mann, consisting of two parts published in the eighties and that allows us to appreciate the emergence of the author in the german publishing, as well as its operations of resistance to the attempts of normalization and repression by heteronormativity.Facultad de Humanidades y Ciencias de la Educació
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