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  • Phospholamban knockout breaks arrhythmogenic Ca2+ waves and suppresses catecholaminergic polymorphic ventricular tachycardia in mice

     Bai, Yunlong; Jones, Peter; Guo, Jiqing; Zhong, Xiaowei; Clark, Robert; Zhou, Qiang; Wang, Ruiwu; Vallmitjana Lees, Alexander; Benitez Iglesias, Raul; Hove-Madsen, Leif; Semeniuk, Lisa; Guo, Ang; Song, Long-Sheng; Duff, Henry J.; Chen, S.R. Wayne
    Circulation research
    Date of publication: 2013-07-15
    Journal article

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    Rationale: Phospholamban (PLN) is an inhibitor of cardiac sarco(endo)plasmic reticulum Ca2+ ATPase. PLN knockout (PLN-KO) enhances sarcoplasmic reticulum Ca2+ load and Ca2+ leak. Conversely, PLN-KO accelerates Ca2+ sequestration and aborts arrhythmogenic spontaneous Ca2+ waves (SCWs). An important question is whether these seemingly paradoxical effects of PLN-KO exacerbate or protect against Ca2+-triggered arrhythmias. Objective: We investigate the impact of PLN-KO on SCWs, triggered activities, and stress-induced ventricular tachyarrhythmias (VTs) in a mouse model of cardiac ryanodine-receptor (RyR2)-linked catecholaminergic polymorphic VT. Methods and Results: We generated a PLN-deficient, RyR2-mutant mouse model (PLN-/-/RyR2-R4496C+/-) by crossbreeding PLN-KO mice with catecholaminergic polymorphic VT¿associated RyR2-R4496C mutant mice. Ca2+ imaging and patch-clamp recording revealed cell-wide propagating SCWs and triggered activities in RyR2- R4496C+/- ventricular myocytes during sarcoplasmic reticulum Ca2+ overload. PLN-KO fragmented these cell- wide SCWs into mini-waves and Ca2+ sparks and suppressed the triggered activities evoked by sarcoplasmic reticulum Ca2+ overload. Importantly, these effects of PLN-KO were reverted by partially inhibiting sarco(endo) plasmic reticulum Ca2+ ATPase with 2,5-di-tert-butylhydroquinone. However, Bay K, caffeine, or Li+ failed to convert mini-waves to cell-wide SCWs in PLN-/-/RyR2-R4496C+/- ventricular myocytes. Furthermore, ECG analysis showed that PLN-KO mice are not susceptible to stress-induced VTs. On the contrary, PLN-KO protected RyR2-R4496C mutant mice from stress-induced VTs. Conclusions: Our results demonstrate that despite severe sarcoplasmic reticulum Ca2+ leak, PLN-KO suppresses triggered activities and stress-induced VTs in a mouse model of catecholaminergic polymorphic VT. These data suggest that breaking up cell-wide propagating SCWs by enhancing Ca2+ sequestration represents an effective approach for suppressing Ca2+-triggered arrhythmias.

    Rationale: Phospholamban (PLN) is an inhibitor of cardiac sarco(endo)plasmic reticulum Ca2+ ATPase. PLN knockout (PLN-KO) enhances sarcoplasmic reticulum Ca2+ load and Ca2+ leak. Conversely, PLN-KO accelerates Ca2+ sequestration and aborts arrhythmogenic spontaneous Ca2+ waves (SCWs). An important question is whether these seemingly paradoxical effects of PLN-KO exacerbate or protect against Ca2+-triggered arrhythmias. Objective: We investigate the impact of PLN-KO on SCWs, triggered activities, and stress-induced ventricular tachyarrhythmias (VTs) in a mouse model of cardiac ryanodine-receptor (RyR2)-linked catecholaminergic polymorphic VT. Methods and Results: We generated a PLN-deficient, RyR2-mutant mouse model (PLN−/−/RyR2-R4496C+/−) by crossbreeding PLN-KO mice with catecholaminergic polymorphic VT–associated RyR2-R4496C mutant mice. Ca2+ imaging and patch-clamp recording revealed cell-wide propagating SCWs and triggered activities in RyR2-R4496C+/− ventricular myocytes during sarcoplasmic reticulum Ca2+ overload. PLN-KO fragmented these cell-wide SCWs into mini-waves and Ca2+ sparks and suppressed the triggered activities evoked by sarcoplasmic reticulum Ca2+ overload. Importantly, these effects of PLN-KO were reverted by partially inhibiting sarco(endo)plasmic reticulum Ca2+ ATPase with 2,5-di-tert-butylhydroquinone. However, Bay K, caffeine, or Li+ failed to convert mini-waves to cell-wide SCWs in PLN−/−/RyR2-R4496C+/− ventricular myocytes. Furthermore, ECG analysis showed that PLN-KO mice are not susceptible to stress-induced VTs. On the contrary, PLN-KO protected RyR2-R4496C mutant mice from stress-induced VTs. Conclusions: Our results demonstrate that despite severe sarcoplasmic reticulum Ca2+ leak, PLN-KO suppresses triggered activities and stress-induced VTs in a mouse model of catecholaminergic polymorphic VT. These data suggest that breaking up cell-wide propagating SCWs by enhancing Ca2+ sequestration represents an effective approach for suppressing Ca2+-triggered arrhythmias.

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    Low density lipoproteins promote unstable calcium handling accompanied by reduced SERCA2 and connexin-40 expression in cardiomyocytes  Open access

     Barriga, Montserrat; Cal, Roi; Cabello, Núria; Llach, Anna; Vallmitjana Lees, Alexander; Benitez Iglesias, Raul; Badimon, Lina; Llorente Cortés, Vicenta; Cinca Cosculluela, Juan; Hove-Madsen, Leif
    PLoS one
    Date of publication: 2013-03-13
    Journal article

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    The damaging effects of high plasma levels of cholesterol in the cardiovascular system are widely known, but little attention has been paid to direct effects on cardiomyocyte function. We therefore aimed at testing the hypothesis that Low Density Lipoprotein (LDL) cholesterol affects calcium dynamics and signal propagation in cultured atrial myocytes. For this purpose, mRNA and protein expression levels were determined by real time PCR and western blot analysis, respectively, and intracellular calcium was visualized in fluo-4 loaded atrial HL-1 myocyte cultures subjected to field stimulation. At low stimulation frequencies all cultures had uniform calcium transients at all tested LDL concentrations. However, 500 µg LDL/mL maximally reduced the calcium transient amplitude by 43% from 0.30±0.04 to 0.17±0.02 (p<0.05). Moreover, LDL-cholesterol dose-dependently increased the fraction of alternating and irregular beat-to-beat responses observed when the stimulation interval was shortened. This effect was linked to a concurrent reduction in SERCA2, RyR2, IP3RI and IP3RII mRNA levels. SERCA2 protein levels were also reduced by 43% at 200 µg LDL/mL (p<0.05) and SR calcium loading was reduced by 38±6% (p<0.001). By contrast, HDL-cholesterol had no significant effect on SERCA expression or SR calcium loading. LDL-cholesterol also slowed the conduction velocity of the calcium signal from 3.2+0.2 mm/s without LDL to 1.7±0.1 mm/s with 500 µg LDL/mL (p<0.05). This coincided with a reduction in Cx40 expression (by 44±3%; p<0.05 for mRNA and by 79±2%; p<0.05 for Cx40 protein at 200 µg/ml LDL) whereas the Cx-43 expression did not significantly change. In conclusion, LDL-cholesterol destabilizes calcium handling in cultured atrial myocytes subjected to rapid pacing by reducing SERCA2 and Cx40 expression and by slowing the conduction velocity of the calcium signal.

    The damaging effects of high plasma levels of cholesterol in the cardiovascular system are widely known, but little attention has been paid to direct effects on cardiomyocyte function. We therefore aimed at testing the hypothesis that Low Density Lipoprotein (LDL) cholesterol affects calcium dynamics and signal propagation in cultured atrial myocytes. For this purpose, mRNA and protein expression levels were determined by real time PCR and western blot analysis, respectively, and intracellular calcium was visualized in fluo-4 loaded atrial HL-1 myocyte cultures subjected to field stimulation. At low stimulation frequencies all cultures had uniform calcium transients at all tested LDL concentrations. However, 500 mg LDL/mL maximally reduced the calcium transient amplitude by 43% from 0.3060.04 to 0.1760.02 (p,0.05). Moreover, LDLcholesterol dose-dependently increased the fraction of alternating and irregular beat-to-beat responses observed when the stimulation interval was shortened. This effect was linked to a concurrent reduction in SERCA2, RyR2, IP3RI and IP3RII mRNA levels. SERCA2 protein levels were also reduced by 43% at 200 mg LDL/mL (p,0.05) and SR calcium loading was reduced by 3866% (p,0.001). By contrast, HDL-cholesterol had no significant effect on SERCA expression or SR calcium loading. LDLcholesterol also slowed the conduction velocity of the calcium signal from 3.2+0.2 mm/s without LDL to 1.760.1 mm/s with 500 mg LDL/mL (p,0.05). This coincided with a reduction in Cx40 expression (by 4463%; p,0.05 for mRNA and by 7962%; p,0.05 for Cx40 protein at 200 mg/ml LDL) whereas the Cx-43 expression did not significantly change. In conclusion, LDLcholesterol destabilizes calcium handling in cultured atrial myocytes subjected to rapid pacing by reducing SERCA2 and Cx40 expression and by slowing the conduction velocity of the calcium signal.

  • Multilevel analysis of calcium dynamics in stimulated cultures of cardiomyocytes

     Vallmitjana Lees, Alexander; Hove-Madsen, Leif; Barriga, Montserrat; Benitez Iglesias, Raul
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2013-07-05
    Presentation of work at congresses

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    We present an automatic method to characterize calcium activity in a culture of cardiac cells from a sequence of microscopy fluorescence images. The approach quantifies both the response of each individual cell in the culture to external field stimulation and the propagation properties of calcium wave-fronts, thus providing complementary informa- tion at different physiological levels. The technique classifies the response of each cell as regular or irregular based on a set of dynamical and morphological features of the calcium transients. Isochronal maps were constructed from the local activation times across the culture, and the front propagation was classified as planar or non-planar. The method has been applied to a set of 35 experiments, and the results indicate a significative connection between irregular behavior at the single-cell level and irregular front propagation.

    We present an automatic method to characterize calcium activity in a culture of cardiac cells from a sequence of microscopy fluorescence images. The approach quantifies both the response of each individual cell in the culture to external field stimulation and the propagation properties of calcium wave-fronts, thus providing complementary information at different physiological levels. The technique classifies the response of each cell as regular or irregular based on a set of dynamical and morphological features of the calcium transients. Isochronal maps were constructed from the local activation times across the culture, and the front propagation was classified as planar or non-planar. The method has been applied to a set of 35 experiments, and the results indicate a significative connection between irregular behavior at the single-cell level and irregular front propagation

  • A method to characterize calcium activity in stimulated cultures of cardiac myocytes

     Benitez Iglesias, Raul; Vallmitjana Lees, Alexander; Hove-Madsen, Leif
    Annual Meeting of Biophysical Society
    Presentation's date: 2013-02-06
    Presentation of work at congresses

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  • Inteligencia artificial avanzada

     Benitez Iglesias, Raul; Escudero Bakx, Gerard; Kanaan Izquierdo, Samir; Masip Rodó, David
    Date of publication: 2013-07-08
    Book

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    En este libro se introducen los conceptos fundamentales de la Inteligencia Artificial, desde una visión muy orientada al reconocimiento de patrones. El lector podrá encontrar una revisión completa de las técnicas avanzadas más usadas en el campo del aprendizaje automático. El texto se ha enfocado desde un punto de vista eminentemente práctico. Las explicaciones teóricas de las diferentes técnicas se basan en la resolución de problemas concretos. Los algoritmos están acompañados de ejemplos, escritos en Python, con aplicaciones directas en ámbitos como el procesado de imágenes o el análisis de textos. Los diferentes capítulos comprenden las técnicas de aprendizaje no supervisado, los métodos de reducción de la dimensionalidad y extracción de características (PCA, NMF, ICA, LDA, MDS), los principales algoritmos de clasificación de patrones (probabilísticos, kNN, SVM y Boosting) y diferentes métodos de optimización.

  • Adenosine A2A receptor activation decreases beat-to-beat stability of intracellular calcium transients and their propagation in atrial myocytes

     Barriga, Montserrat; Molina, Cristina E.; Llach, Anna; Cabello, Núria; Vallmitjana Lees, Alexander; Benitez Iglesias, Raul; Padró, Josep; Cinca Cosculluela, Juan; Hove-Madsen, Leif
    Annual Meeting of Biophysical Society
    Presentation's date: 2012-02-28
    Presentation of work at congresses

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  • Detection and classification of spontaneous calcium release events in cardiac myocytes

     Benitez Iglesias, Raul; Vallmitjana Lees, Alexander; Hove-Madsen, Leif; Jones, Peter P.
    Annual Meeting of Biophysical Society
    Presentation's date: 2012-02-27
    Presentation of work at congresses

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  • Automatic method for the detection and characterization of Calcium activity in cardiac cells

     Vallmitjana Lees, Alexander; Alvarez Lacalle, Enrique; Hove-Madsen, Leif; Benitez Iglesias, Raul
    IEEE International Symposium on Biomedical Imaging
    Presentation's date: 2012-05-05
    Presentation of work at congresses

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  • Disrupting Ca2+ waves, but not Ca2+ leak, protects against cardiac arrhythmia

     Jones, Peter; Bai, Yunlong; Vallmitjana Lees, Alexander; Wang, Ruiwu; Clark, Robert; Zhou, Qiang; Benitez Iglesias, Raul; Hove-Madsen, Leif; Chen, S.
    International Society for Heart Research Australasian Section Annual Scientific Meeting
    Presentation's date: 2012-08-16
    Presentation of work at congresses

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  • Spatial channel interactions in cochlear implants

     Tang, Qing; Benitez Iglesias, Raul; Zeng, Fan-Gang
    Journal of neural engineering
    Date of publication: 2011-07-13
    Journal article

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  • Enhanced plant fault diagnosis based on the characterization of transient stages

     Monroy Chora, Isaac; Benitez Iglesias, Raul; Escudero Bakx, Gerard; Graells Sobre, Moises
    Computers & chemical engineering
    Date of publication: 2011-12-05
    Journal article

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    This paper introduces a data-based fault diagnosis system that includes an enhanced characterization of faults during transient stages. First, data under abnormal operating conditions (AOC) is projected onto a reference PCA model constructed with data under normal operating conditions (NOC). T2 and Q-statistic measures of this first PCA model are both used to detect the fault and to estimate the duration and delay of its transient evolution. After a dimensionality reduction, a second NOC PCA model is used to process data before diagnosing the faults by standard classification methods such as Artificial Neural Networks (ANN) or Support Vector Machines (SVM). A quantitative validation of the procedure has been carried out using simulated on-line data sets of the Tennessee Eastman Process (TEP). Results indicate that the incorporation of transient data in models improves the overall diagnosis performance, regardless of the particular choice between the statistical methods or the classification methods.

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    Detection, properties, and frequency of local calcium release from the sarcoplasmic reticulum in teleost cardiomyocytes  Open access

     Llach, Anna; Molina, Cristina E.; Alvarez Lacalle, Enrique; Tort, Lluis; Hove-Madsen, Leif; Benitez Iglesias, Raul
    PLoS one
    Date of publication: 2011-08-29
    Journal article

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    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 mm21 min21 while calcium waves were 8.5 times less frequent. Inhibition of SR calcium uptake reduced the calcium transient (F/F0) 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 min21 to 8.162.0 min21, 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.

  • Smart calibration for video game play by people with a movement impairment

     Perez, Sergi; Benitez Iglesias, Raul; Reinkensmeyer, David J.
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2011-09-03
    Presentation of work at congresses

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  • Effects of atrial fibrillation on the distribution, dimensions, and frequency of calcium sparks in human atrial myocytes

     Barriga, Montserrat; Llach, Anna; Alvarez Lacalle, Enrique; Cabello, N.; Ballester, B.; Vallmitjana Lees, Alexander; Muñoz, C.; Benitez Iglesias, Raul; Cinca Cosculluela, Juan; Hove-Madsen, Leif
    European Society of Cardiology Congress
    Presentation's date: 2011-08-27
    Presentation of work at congresses

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  • Identification of Nonlinear Cardiac Cell Dynamics Using Radial Basis Function Regression

     Kanaan Izquierdo, Samir; Velazquez Lerma, Susana Adriana; Benitez Iglesias, Raul
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2011-09-03
    Presentation of work at congresses

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  • A semi-supervised approach to fault diagnosis for chemical processes

     Monroy Chora, Isaac; Benitez Iglesias, Raul; Escudero Bakx, Gerard; Graells Sobre, Moises
    Computers & chemical engineering
    Date of publication: 2010-01-04
    Journal article

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  • Effect of the resting membrane potential on the distribution, dimensions, and frequency of calcium sparks in human atrial myocytes

     Barriga, Montserrat; Alvarez Lacalle, Enrique; Llach, Anna; Vallmitjana Lees, Alexander; Muñoz, C.E.; Cinca Cosculluela, Juan; Benitez Iglesias, Raul; Hove-Madsen, Leif
    European heart journal
    Date of publication: 2010-09
    Journal article

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  • Effect of the resting membrane potential on the distribution, dimensions, and frequency of calcium sparks in human atrial myocytes

     Barriga, Montserrat; Alvarez Lacalle, Enrique; Llach, Anna; Vallmitjana Lees, Alexander; Muñoz, C.E.; Cinca Cosculluela, Juan; Benitez Iglesias, Raul; Hove-Madsen, Leif
    European Society of Cardiology Congress
    Presentation's date: 2010-09-01
    Presentation of work at congresses

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    Identification of intracellular calcium dynamics in stimulated cardiomyocytes  Open access

     Vallmitjana Lees, Alexander; Barriga, Montserrat; Nenadic, Zoran; Llach, Anna; Alvarez Lacalle, Enrique; Hove-Madsen, Leif; Benitez Iglesias, Raul
    IEEE Engineering in Medicine and Biology Society
    Presentation's date: 2010-09-01
    Presentation of work at congresses

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    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.

  • On-Line Fault Diagnosis Based on the Identification of Transient Stages

     Monroy Chora, Isaac; Benitez Iglesias, Raul; Escudero Bakx, Gerard; Graells Sobre, Moises
    European Symposium on Computer Aided Process Engineering
    Presentation's date: 2010-06-07
    Presentation of work at congresses

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  • Non-ideal behavior in the electronic implementation of chaotic dynamical systems

     Benitez Iglesias, Raul; Cosp Vilella, Jordi
    Emerging Topics in Dynamical Systems and Partial Differential Equations
    Presentation's date: 2010-06-01
    Presentation of work at congresses

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  • DESARROLLO DE TÉCNICAS DE ANÁLISIS DE SITEMAS COMPLEJOS PARA EL ESTUDIO DE PROBLEMAS EN FISIOLOGÍA CARDÍACA

     Kanaan Izquierdo, Samir; Vallmitjana Lees, Alexander; Escudero Bakx, Gerard; Velazquez Lerma, Susana Adriana; Benitez Iglesias, Raul
    Participation in a competitive project

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  • Characterization of the nonlinear content of the heart rate dynamics during myocardial ischemia

     Benitez Iglesias, Raul; Alvarez Lacalle, Enrique; Echebarria Dominguez, Blas; Gomis Román, Pedro; Vallverdú Ferrer, Montserrat; Caminal Magrans, Pedro
    Medical engineering and physics
    Date of publication: 2009-07
    Journal article

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  • Metodo de detección de eventos locales de Iiberación de calcio intracelular

     Benitez Iglesias, Raul; Alvarez Lacalle, Enrique; Alvarez-Lacalle, Enric; Hove-Madsen, Leif
    Date of request: 2009-03-13
    Invention patent

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    Método de detección de eventos locales de liberación de calcio intracelular.

    La presente invención trata de un método de detección de eventos locales de liberación de calcio intracelular comprendiendo las siguientes etapas:

    - adquirir una secuencia de imágenes bidimensionales de una sección determinada de una o más células, incluyendo información relativa a actividad de calcio intracelular;

    - normalizar dichas imágenes;

    - realizar un análisis estadístico de la distribución espacio-temporal de píxeles en dicha secuencia de imágenes normalizadas, para determinar unas regiones de interés, y determinar que dichas regiones de interés son candidatas a contener un evento local de liberación de calcio intracelular de interés; y.

    - realizar las siguientes etapas, automáticamente y de manera previa a dicho análisis estadístico:

    - detectar eventos globales de liberación de calcio en una o más de las imágenes de dicha sucesión de imágenes; y

    - realizar dicho análisis estadístico solamente sobre las imágenes en las cuales no se han detectado eventos globales de liberación de calcio.

  • DICA enhanced SVM classification approach to fault diagnosis for chemical processes

     Monroy Chora, Isaac; Benitez Iglesias, Raul; Escudero Bakx, Gerard; Graells Sobre, Moises
    European Symposium on Computer Aided Process Engineering
    Presentation's date: 2009-06-04
    Presentation of work at congresses

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  • Efecto del potencial de membrana sobre las dimensiones, la cinética y la frecuencia de la liberación local de calcio en miocitos auriculares humanos

     Barriga, Montserrat; Alvarez Lacalle, Enrique; Llach, Anna; Vallmitjana Lees, Alexander; Muñoz Guijosa, Cristian; Cinca Cosculluela, Juan; Benitez Iglesias, Raul; Hove-Madsen, Leif
    Congreso de la Sociedad Española de Cardiología
    Presentation's date: 2009-10-21
    Presentation of work at congresses

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  • MÉTODO DE DETECCIÓN DE EVENTOS LOCALES DE LIBERACIÓN DE CALCIO INTRACELULAR

     Benitez Iglesias, Raul; Alvarez Lacalle, Enrique; Hove-Madsen, Leif
    Date of request: 2009-03-13
    Invention patent

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    Método de detección de eventos locales de liberación de calcio intracelular.

    La presente invención trata de un método de detección de eventos locales de liberación de calcio intracelular comprendiendo las siguientes etapas:

    - adquirir una secuencia de imágenes bidimensionales de una sección determinada de una o más células, incluyendo información relativa a actividad de calcio intracelular;

    - normalizar dichas imágenes;

    - realizar un análisis estadístico de la distribución espacio-temporal de píxeles en dicha secuencia de imágenes normalizadas, para determinar unas regiones de interés, y determinar que dichas regiones de interés son candidatas a contener un evento local de liberación de calcio intracelular de interés; y.

    - realizar las siguientes etapas, automáticamente y de manera previa a dicho análisis estadístico:

    - detectar eventos globales de liberación de calcio en una o más de las imágenes de dicha sucesión de imágenes; y

    - realizar dicho análisis estadístico solamente sobre las imágenes en las cuales no se han detectado eventos globales de liberación de calcio.

  • RED TRANSFRONTERIZA PARA LA DETERMINACION Y GESTION DE FLUJOS DE AGUA, CARBONO Y ENERGIA

     Meca Alvarez, Esteban; Pino Gonzalez, David; Mazon Bueso, Jordi; Benitez Iglesias, Raul
    Participation in a competitive project

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  • Robust unsupervised detection of action potentials with probabilistic models

     Benitez Iglesias, Raul; Nenadic, Zoran
    IEEE transactions on biomedical engineering
    Date of publication: 2008-04
    Journal article

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  • Denoising de señales mediante técnicas probabilísticas

     Benitez Iglesias, Raul
    Congreso de Física Estadística
    Presentation of work at congresses

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  • Human-robot cooperative movement training: Learning a novel sensory motor transformation during walking with robotic assistance-as-needed

     Jeremy, L Emken; Benitez Iglesias, Raul; Reinkensmeyer, David J
    Journal of neuroengineering and rehabilitation
    Date of publication: 2007-03
    Journal article

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  • Motor Adaptation as a Greedy Optimization of Error and Effort

     Jeremy, L Emken; Benitez Iglesias, Raul; Athanasios, Sideris; Reinkensmeyer, James E Bobrow And David J
    Journal of neurophysiology
    Date of publication: 2007-03
    Journal article

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  • Detección y clasificación de potenciales de acción en señales neurofisiológicas mediante técnicas bayesianas

     Benitez Iglesias, Raul
    Nolineal 2007 : Nuevos retos y perspectivas de la dinámica no lineal y sus aplicaciones
    Presentation's date: 2007-06-06
    Presentation of work at congresses

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  • Detección y clasificación de potenciales de acción en señales neurofisiológicas mediante técnicas bayesianas

     Benitez Iglesias, Raul
    Nolineal 2007 : Nuevos retos y perspectivas de la dinámica no lineal y sus aplicaciones
    Presentation of work at congresses

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  • ORDEN, RUIDO Y DINÁMICAS EMERGENTES BAJO NOLINEALIDADES

     Ramirez de La Piscina Millan, Laureano; Peñaranda Ayllon, Angelina; Haurie Ibarra, Laia; Meca Alvarez, Esteban; Rodriguez Cantalapiedra, Inmaculada; Lacasta Palacio, Ana Maria; Benitez Iglesias, Raul; Formosa Mitjans, Joan; Gonzalez Cinca, Ricardo; Suñol Galofre, Francesc Xavier; Arias Calderón, Santiago
    Participation in a competitive project

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  • 9è Premi a la Qualitat en la Docència Universitària

     Domingo Peña, Joan; Valero Garcia, Miguel; Calviño Tavares, Francisco; Armengol Cebrian, Jesús; Bara Temes, Francisco Javier; Almajano Pablos, Maria Pilar; Robert i Sanxis, Francesc Josep; Pretel Sanchez, M. del Carmen; Usandizaga Calparsoro, Miguel M.; Giraldo Giraldo, Beatriz F.; Gomez Urgelles, Joan Vicenç; Gorchs Altarriba, Roser; Perez Poch, Antoni; Cadenato Matia, Ana Maria; Benitez Iglesias, Raul; Guerrero Zapata, Josep Maria; Navarro Moldes, Leandro; Jordana Barnils, Josep; Martínez García, Herminio
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  • III Premios de la UEM a la Calidad en la Docencia Universitaria

     Domingo Peña, Joan; Valero Garcia, Miguel; Calviño Tavares, Francisco; Armengol Cebrian, Jesús; Bara Temes, Francisco Javier; Almajano Pablos, Maria Pilar; Robert i Sanxis, Francesc Josep; Pretel Sanchez, M. del Carmen; Usandizaga Calparsoro, Miguel M.; Giraldo Giraldo, Beatriz F.; Gomez Urgelles, Joan Vicenç; Gorchs Altarriba, Roser; Perez Poch, Antoni; Cadenato Matia, Ana Maria; Benitez Iglesias, Raul; Guerrero Zapata, Josep Maria; Navarro Moldes, Leandro; Jordana Barnils, Josep; Martínez García, Herminio
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  • Premi Jaume Vicens Vives a la Qualitat en la Docència 2006

     Domingo Peña, Joan; Calviño Tavares, Francisco; Armengol Cebrian, Jesús; Almajano Pablos, Maria Pilar; Robert i Sanxis, Francesc Josep; Bara Temes, Francisco Javier; Pretel Sanchez, M. del Carmen; Jordana Barnils, Josep; Martínez García, Herminio; Valero Garcia, Miguel; Usandizaga Calparsoro, Miguel M.; Giraldo Giraldo, Beatriz F.; Gomez Urgelles, Joan Vicenç; Gorchs Altarriba, Roser; Perez Poch, Antoni; Cadenato Matia, Ana Maria; Guerrero Zapata, Josep Maria; Navarro Moldes, Leandro; Benitez Iglesias, Raul
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  • Sharp-interface projection of a fluctuating phase-field model

     Benitez Iglesias, Raul; Ramirez de La Piscina Millan, Laureano
    Physical review E: statistical, nonlinear, and soft matter physics
    Date of publication: 2005-06
    Journal article

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  • Phase-field study of transient stages and fluctuations in solidification  Open access

     Benitez Iglesias, Raul
    Defense's date: 2005-01-27
    Department of Applied Physics, Universitat Politècnica de Catalunya
    Theses

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    L'estudi de la formació de microstructures en processos de solidificació té importants aplicacions científiques i tecnològiques. L'aparició d'aquestes estructures determina les propietats elèctriques i mecàniques del material solidificat, i té per tant un important interès tecnològic. La majoria d'aquestes estructures tenen el seu origen en una desestabilització morfològica de la interfase sòlid-líquid que es produeix a mesura que el front avança. Per aquest motiu, l'estudi del comportament dinàmic de la interfase resulta essencial per entendre els mecanismes que intervenen en la creació d'aquests patrons. Els processos de solidificació solen descriure's mitjançant problemes de contorn mòbil. Aquestes formulacions consten d'equacions per a la difusió del calor i de massa en les fases sòlida i líquida, que s'han de resoldre imposant l'acompliment de diverses condicions de contorn mòbils a la interfase. Els problemes de contorn mòbil, malgrat contenir tots els elements que intervenen en la dinàmica i ser de molta utilitat en l'àmbit de l'enginyeria, requereixen un cost computacional que no permet simular sistemes reals en règims interfacials complexos. Els mètodes de camp de fase (phase-field methods), van aparèixer a principis dels anys vuitanta com una eina computacional que permetia l'estudi de fenòmens interfacials de caire general. Aquests mètodes descriuen la forma de la interfase mitjançant un camp continu que pren valors diferents i constants en les dues fases. La dinàmica d'aquest camp és llavors acoblada al camp de difusió de calor o massa que determina l'avanç del front de solidificació. Un dels avantatges d'aquests mètodes és que la seva simulació no requereix d'algorismes de seguiment de la interfase (front tracking algorithsms). És ben conegut que les característiques principals de les microestructures en solidificació, es determinen durant els transitoris inicials en els que els corrents de massa i calor s'adapten a la evolució dinàmica del front. Un dels objectius en aquesta tesi és el de fer servir mètodes de camp de fase per descriure de forma quantitativa aquests transitoris. Per comprovar la validesa del nostre procediment, es realitza una comparació quantitativa entre els resultats numèrics obtinguts i diferents prediccions analítiques derivades del problema de contorn mòbil. Per un altra banda, la desestabilització del front es veu afectada per la presència de fluctuacions al sistema. Aquestes pertorbacions microscòpiques poden tenir el seu origen a les fluctuacions termodinàmiques internes, o bé ser conseqüència de imperfeccions experimentals que actuen com a font externa de soroll. El segon objectiu d'aquesta tesi és la introducció de fluctuacions en mètodes de camp de fase, de forma que es pugui estudiar l'amplificació dinàmica de les pertorbacions microscòpiques que acaben donant lloc a estructures macroscòpiques. Per finalitzar, analitzem el problema de la selecció en solidificació direccional. Estudiem els règims lineal i no-lineal, tot determinant les condicions, el moment i la forma en que apareixen les estructures dendrítiques i cel·lulars.

    Crystal growth is a non-equilibrium process which involves physical mechanisms at very different scales. When a solidification front advances, mass and heat diffusion processes are combined with interfacial phenomena like capillarity or kinetic attachment. A complex interplay between these mechanisms gives rise to complex interfacial structures like snowflakes or cellular patterns. The formation of microstructures in solidification has both a scientific and a technological interest. On one hand, the study of the different interfacial structures constitutes a fundamental problem in the field of non-equilibrium pattern-forming systems. On the other side, from a technological point of view, the presence of microstructures determines the final mechanical and electrical properties of the processed material. Directional solidification is a controlled solidification technique which reproduces the conditions occurring in some important metallurgical processes like material casting or zone melting refining procedures. In a directional solidification experiment, the alloy sample is pulled at a constant velocity towards the cold region of an externally-imposed temperature gradient. Depending on the growth conditions, a morphological destabilization of the solid-liquid interface occurs during early transient stages. These initial transients are associated to a solute redistribution process due to the adaptation of the concentration field to the forced motion of the sample. The main objective of this thesis is to study the dynamical evolution of the morphological deformations of the front from these initial transients to the final stages where the properties of the interfacial pattern are determined. An important point in this process is that the internal fluctuations of the system play the role of an initiation mechanism for the morphological deformations of the front. During the initial transients, some of these microscopic perturbations are amplified by several orders of magnitude, and a range of wavelengths becomes morphologically unstable. The interfacial deformations of the front can be then characterized by means of power spectrum techniques. In order to study the dynamical evolution of the solidification front in directional solidification, we have used both theoretical and computational approaches: The main computational technique used in this thesis is the phase-field approach, which is a powerful method to simulate complex interfacial phenomena. The model equations describe the evolution of a continuous field , which takes different constant values at the solid and liquid bulks of the system. This field is then coupled with equations for the mass diffusion, and allows performing numerical studies without simulating the standard Stefan-like moving boundary problem. The phase-field method provides a diffuse interface description in which the transition from solid to liquid happens in a region of a certain thickness. The interface thickness introduces a new length in the simulations which must be taken into account to recover quantitative results. One major point in this thesis concerns with the introduction of fluctuations in phase-field methods. In the particular case of variational phase-field formulations -in which the model equations can be derived from a single free energy functional for the whole system-, the introduction of fluctuations can be done by applying the Fluctuation-Dissipation theorem. Variational formulations, however, although their appealing structure, present a poor computational efficiency and cannot be used to obtain quantitative results. To this extent, we have derived a general approach which does not relay in the Fluctuation-Dissipation assumption and permits to introduce fluctuations in both variational and non-variational phase-field formulations. Well-established analytical techniques like boundary integral methods for the transient front position and linear stability analysis of the interface during the transient have been used as theoretical predictions for the computational results. The dynamical evolution of the solidification front can be divided in two stages: A linear regime where the initial noise is amplified, and a non-linear coarsening process where the final properties of the interfacial pattern are selected. We have studied these different stages of the solidification process by using the phase-field approach, and good agreement is obtained when comparing with well-established theoretical and experimental predictions.

  • Grup de Turbulencia, Fluctuacions i Difusió (Ayuda para grupos de investigación consolidados)

     Ramirez de La Piscina Millan, Laureano; Platonov, Alexei; Carrillo Cortes, Jose Alejandro; Sekula, Emil; Peñaranda Ayllon, Angelina; Echebarria Dominguez, Blas; Auguet Sangra, Carlota Eugenia; Meca Alvarez, Esteban; Cami Babra, Enrique; Castilla Lopez, Roberto; Rodriguez Cantalapiedra, Inmaculada; Grau Barcelo, Joan; Lacasta Palacio, Ana Maria; Redondo Apraiz, Jose Manuel; Sanchez Ariz, Miguel A.; Benitez Iglesias, Raul; Gonzalez Cinca, Ricardo
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  • IEEE transactions on biomedical engineering

     Benitez Iglesias, Raul
    Collaboration in journals

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  • Interpretació dels resultats d'una activitat d'AC en l'àmbit de l'automàtica

     Benitez Iglesias, Raul
    Jornada d'anàlisi d'experiències d'aprenentatge cooperatiu
    Presentation's date: 2005-06-01
    Presentation of work at congresses

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  • Stochastic sharp-interface projection of a phase-field model

     Benitez Iglesias, Raul; Ramirez de La Piscina Millan, Laureano
    Congreso de Física Estadística
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  • Stochastic sharp-interface projection of a phase-field model

     Benitez Iglesias, Raul
    Congreso de Física Estadística
    Presentation's date: 2005-06-27
    Presentation of work at congresses

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    Stochastic Phase-Field simulations of symmetric alloy solidification  Open access

     Benitez Iglesias, Raul; Ramirez de La Piscina Millan, Laureano
    Fluctuation and noise letters
    Date of publication: 2004-09
    Journal article

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    We study initial transient stages in directional solidification by means of a non-variational phase field model with fluctuations. This model applies for the symmetric solidification of dilute binary solutions and does not invoke fluctuation-dissipation theorem to account for the fluctuation statistics. We devote our attention to the transient regime during which concentration gradients are building up 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. Quantitative agreement is found when comparing the phase-field simulations with theoretical predictions.

  • Noise in Complex Systems and Stochastic Dynamics II

     Benitez Iglesias, Raul; Ramirez de La Piscina Millan, Laureano
    Proceedings - SPIE
    Date of publication: 2004-01
    Journal article

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    Phase-field models in interfacial pattern formation out of equilibrium  Open access

     Gonzalez Cinca, Ricardo; Folch, R; Benitez Iglesias, Raul; Ramirez de La Piscina Millan, Laureano; Casademunt Viader, Jaume; Hrndez-Machado, A
    Date of publication: 2004-06
    Book chapter

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  • Autoorganización en sistemas complejos bajo fluctuaciones

     Ramirez de La Piscina Millan, Laureano; Peñaranda Ayllon, Angelina; Auguet Sangra, Carlota Eugenia; Meca Alvarez, Esteban; Cami Babra, Enrique; Rodriguez Cantalapiedra, Inmaculada; Lacasta Palacio, Ana Maria; Benitez Iglesias, Raul; Gonzalez Cinca, Ricardo
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