raul benitez - Academia.edu (original) (raw)

Papers by raul benitez

Research paper thumbnail of Identification of intracellular calcium dynamics in stimulated cardiomyocytes

We have developed an automatic method for the analysis and identification of dynamical regimes in... more We have developed an automatic method for the analysis and identification of dynamical regimes in intracellular calcium patterns from confocal calcium images. The method allows the identification of different dynamical patterns such as spatially concordant and discordant alternans, irregular behavior or phase-locking regimes such as period doubling or halving. The method can be applied to the analysis of different cardiac pathologies related to anomalies at the cellular level such as ventricular reentrant arrhythmias.

Research paper thumbnail of Characterization of the nonlinear content of the heart rate dynamics during myocardial ischemia

Medical Engineering & Physics, 2009

We develop a method to quantify the changes in heart rate dynamics during local myocardial ischem... more We develop a method to quantify the changes in heart rate dynamics during local myocardial ischemia induced by a percutaneous transluminal coronary angioplasty procedure (PTCA). The method introduces an index measuring the nonlinear content of the beat-to-beat (RR) time series by using nonlinear time series techniques such as surrogate data analysis and average mutual information.

Research paper thumbnail of Detection, Properties, and Frequency of Local Calcium Release from the Sarcoplasmic Reticulum in Teleost Cardiomyocytes

PLOS One, 2011

Calcium release from the sarcoplasmic reticulum (SR) plays a central role in the regulation of ca... more Calcium release from the sarcoplasmic reticulum (SR) plays a central role in the regulation of cardiac contraction and rhythm in mammals and humans but its role is controversial in teleosts. Since the zebrafish is an emerging model for studies of cardiovascular function and regeneration we here sought to determine if basic features of SR calcium release are phylogenetically conserved. Confocal calcium imaging was used to detect spontaneous calcium release (calcium sparks and waves) from the SR. Calcium sparks were detected in 16 of 38 trout atrial myocytes and 6 of 15 ventricular cells. The spark amplitude was 1.4560.03 times the baseline fluorescence and the time to half maximal decay of sparks was 2763 ms. Spark frequency was 0.88 sparks mm 21 min 21 while calcium waves were 8.5 times less frequent. Inhibition of SR calcium uptake reduced the calcium transient (F/F 0 ) from 1.7760.17 to 1.1260.18 (p = 0.002) and abolished calcium sparks and waves. Moreover, elevation of extracellular calcium from 2 to 10 mM promoted early and delayed afterdepolarizations (from 0.660.3 min 21 to 8.162.0 min 21 , p = 0.001), demonstrating the ability of SR calcium release to induce afterdepolarizations in the trout heart. Calcium sparks of similar width and duration were also observed in zebrafish ventricular myocytes. In conclusion, this is the first study to consistently report calcium sparks in teleosts and demonstrate that the basic features of calcium release through the ryanodine receptor are conserved, suggesting that teleost cardiac myocytes is a relevant model to study the functional impact of abnormal SR function.

Research paper thumbnail of Quantitative phase-field simulations of the wavelength selection during alloy redistribution transients

We study the initial stages of a directional solidification experiment of a mixture by means of a... more We study the initial stages of a directional solidification experiment of a mixture by means of a non-variational phase field model with fluctuations. This model does not invoke fluctuation-dissipation theorem to account for the fluctuations statistics. We devote our attention to the transient regime during which concentration gradients are building and fluctuations act to destabilize the interface. To this end we calculate both the temporally dependent growth rate of each mode and the power spectrum of the interface evolving under the effect of fluctuations. Theoretical predictions are compared to phase field simulations.

Research paper thumbnail of Identification of nonlinear cardiac cell dynamics using radial basis function regression

We present a novel method for the identification of the dynamics of physiological cardiac cell mo... more We present a novel method for the identification of the dynamics of physiological cardiac cell models. The main aim of the technique is to improve the computational efficiency of large-scale simulations of the electrical activity of the heart. The method identifies the dynamical attractor of a detailed physiological model using statistical learning techniques. In particular, a radial basis function regression method is used to capture the intrinsic dynamical features of the model, thus reducing the computational cost to quantitatively generate cardiac action potentials in a wide range of pacing conditions. The approach permits to recover key properties such as the action potential morphology and duration in a wide range of pacing frequencies.

Research paper thumbnail of DICA enhanced SVM classification approach to fault diagnosis for chemical processes

... Escudero,c Mois s Graellsa ac Chemical Engineering Department (DEQ), bAutomatic Control Depar... more ... Escudero,c Mois s Graellsa ac Chemical Engineering Department (DEQ), bAutomatic Control Department (ESAII), Software Department (LSI) EUETIB, Universitat Polit cnica de Catalunya (UPC), Comte d Urgell 187, Barcelona 08036, Spain, [isaac.monroy, raul ... [6] L Jiang and S ...

Research paper thumbnail of A semi-supervised approach to fault diagnosis for chemical processes

Computers & Chemical Engineering, 2010

... This scheme is tested by considering the 20 faults of the Tennessee Eastman Process (TEP) ben... more ... This scheme is tested by considering the 20 faults of the Tennessee Eastman Process (TEP) benchmark (Downs & Vogel ... information regarding the occurrence of this kind of faults may be inferred from the detection of an ... The fault diagnosis problem is presented in the next way. ...

Research paper thumbnail of Identification of intracellular calcium dynamics in stimulated cardiomyocytes

We have developed an automatic method for the analysis and identification of dynamical regimes in... more We have developed an automatic method for the analysis and identification of dynamical regimes in intracellular calcium patterns from confocal calcium images. The method allows the identification of different dynamical patterns such as spatially concordant and discordant alternans, irregular behavior or phase-locking regimes such as period doubling or halving. The method can be applied to the analysis of different cardiac pathologies related to anomalies at the cellular level such as ventricular reentrant arrhythmias.

Research paper thumbnail of Characterization of the nonlinear content of the heart rate dynamics during myocardial ischemia

Medical Engineering & Physics, 2009

We develop a method to quantify the changes in heart rate dynamics during local myocardial ischem... more We develop a method to quantify the changes in heart rate dynamics during local myocardial ischemia induced by a percutaneous transluminal coronary angioplasty procedure (PTCA). The method introduces an index measuring the nonlinear content of the beat-to-beat (RR) time series by using nonlinear time series techniques such as surrogate data analysis and average mutual information.

Research paper thumbnail of Detection, Properties, and Frequency of Local Calcium Release from the Sarcoplasmic Reticulum in Teleost Cardiomyocytes

PLOS One, 2011

Calcium release from the sarcoplasmic reticulum (SR) plays a central role in the regulation of ca... more Calcium release from the sarcoplasmic reticulum (SR) plays a central role in the regulation of cardiac contraction and rhythm in mammals and humans but its role is controversial in teleosts. Since the zebrafish is an emerging model for studies of cardiovascular function and regeneration we here sought to determine if basic features of SR calcium release are phylogenetically conserved. Confocal calcium imaging was used to detect spontaneous calcium release (calcium sparks and waves) from the SR. Calcium sparks were detected in 16 of 38 trout atrial myocytes and 6 of 15 ventricular cells. The spark amplitude was 1.4560.03 times the baseline fluorescence and the time to half maximal decay of sparks was 2763 ms. Spark frequency was 0.88 sparks mm 21 min 21 while calcium waves were 8.5 times less frequent. Inhibition of SR calcium uptake reduced the calcium transient (F/F 0 ) from 1.7760.17 to 1.1260.18 (p = 0.002) and abolished calcium sparks and waves. Moreover, elevation of extracellular calcium from 2 to 10 mM promoted early and delayed afterdepolarizations (from 0.660.3 min 21 to 8.162.0 min 21 , p = 0.001), demonstrating the ability of SR calcium release to induce afterdepolarizations in the trout heart. Calcium sparks of similar width and duration were also observed in zebrafish ventricular myocytes. In conclusion, this is the first study to consistently report calcium sparks in teleosts and demonstrate that the basic features of calcium release through the ryanodine receptor are conserved, suggesting that teleost cardiac myocytes is a relevant model to study the functional impact of abnormal SR function.

Research paper thumbnail of Quantitative phase-field simulations of the wavelength selection during alloy redistribution transients

We study the initial stages of a directional solidification experiment of a mixture by means of a... more We study the initial stages of a directional solidification experiment of a mixture by means of a non-variational phase field model with fluctuations. This model does not invoke fluctuation-dissipation theorem to account for the fluctuations statistics. We devote our attention to the transient regime during which concentration gradients are building and fluctuations act to destabilize the interface. To this end we calculate both the temporally dependent growth rate of each mode and the power spectrum of the interface evolving under the effect of fluctuations. Theoretical predictions are compared to phase field simulations.

Research paper thumbnail of Identification of nonlinear cardiac cell dynamics using radial basis function regression

We present a novel method for the identification of the dynamics of physiological cardiac cell mo... more We present a novel method for the identification of the dynamics of physiological cardiac cell models. The main aim of the technique is to improve the computational efficiency of large-scale simulations of the electrical activity of the heart. The method identifies the dynamical attractor of a detailed physiological model using statistical learning techniques. In particular, a radial basis function regression method is used to capture the intrinsic dynamical features of the model, thus reducing the computational cost to quantitatively generate cardiac action potentials in a wide range of pacing conditions. The approach permits to recover key properties such as the action potential morphology and duration in a wide range of pacing frequencies.

Research paper thumbnail of DICA enhanced SVM classification approach to fault diagnosis for chemical processes

... Escudero,c Mois s Graellsa ac Chemical Engineering Department (DEQ), bAutomatic Control Depar... more ... Escudero,c Mois s Graellsa ac Chemical Engineering Department (DEQ), bAutomatic Control Department (ESAII), Software Department (LSI) EUETIB, Universitat Polit cnica de Catalunya (UPC), Comte d Urgell 187, Barcelona 08036, Spain, [isaac.monroy, raul ... [6] L Jiang and S ...

Research paper thumbnail of A semi-supervised approach to fault diagnosis for chemical processes

Computers & Chemical Engineering, 2010

... This scheme is tested by considering the 20 faults of the Tennessee Eastman Process (TEP) ben... more ... This scheme is tested by considering the 20 faults of the Tennessee Eastman Process (TEP) benchmark (Downs & Vogel ... information regarding the occurrence of this kind of faults may be inferred from the detection of an ... The fault diagnosis problem is presented in the next way. ...