Sergio Alonso old

Dr. Sergio Alonso Muñoz

Short CV

2014-2019: Ramón y Cajal research associate (Tenure track).Department of Applied Physics, Universitat Politècnica de Catalunya.

2011–2014: Postdoctoral research contract. Collective research project SFB 910: Control of self-organizing nonlinear systems, funded by the German Science Foundation. Department of Mathematical Modeling and Data Analysis, National institute of Science and Technology (Physikalisch-Technische Bundesanstalt), Berlin

2007–2010: Postdoctoral research contract. Collective research project SFB 555: Complex Nonlinear processes, funded by the German Science Foundation. Department of Mathematical Modeling and Data Analysis, National institute of Science and Technology (Physikalisch-Technische Bundesanstalt), Berlin

2005-2007: Postdoctoral research contract. Marie Curie Research training network: Unifying principles in non-equilibrium pattern formation, Department of Physical Chemistry, Fritz-Haber Institute of Max-Planck Society, Berlin.

2001-2004: PhD in the Advanced Physics program. PhD thesis title: Propagation of waves in excitable media under spatio-temporal forcing. Department Structure and Constituents of Matter, University of Barcelona.

1999-2001: Substitute assistant professor. Department Structure and Constituents of Matter, University of Barcelona.

1994-1998: Degree on Physics. University of Barcelona.

Research Interests

Modeling non-linear dynamics inside living cells

A spatial instability due to the difference on the diffusions at the membrane and in the cytosol or the viscoelastic properties of the cytoskeleton of the cell can produce a local increase of concentration inside the cell giving rise to the formation of domains of high concentration. The spatial organization of the molecules participating in a particular signaling pathway affects the global response of the cell. This spatial distribution of the molecules at the membrane is particularly relevant for processes of cell polarization and cell locomotion. the cell may produce the formation of domains of proteins/lipids at the membrane. The polarization of the cell precedes the activation of the cytoskeleton, which is responsible for division or locomotion. Cell motion is produced by the push at the membrane of the actin microfilament network, forming the cytoskeleton. The attachment of the filaments at the membrane is controlled by proteins which have certain affinity for the proteins involved in the polarization process.

Computational models of the micro-structure of cardiac tissue

Arrhythmias in cardiac tissue are related to irregular electrical wave propagation in the heart. Some types of arrhythmias have been frequently related with fibrosis and ischemia of the tissue. Cardiac tissue is typically model with the continuous cable equations. However, tissues are formed by a discrete network of cells, which, normally, are far to be homogeneous. The inclusion of non-conducting media among the cells, mimicking cardiac fibrosis, in models of cardiac tissue may lead to the formation of reentries and other dangerous arrhythmias. A localized region with a fraction of non-conducting media surrounded by homogeneous conducting tissue can become a source of reentry and ectopic beats. The fraction of non-conducting media in comparison with the fraction of healthy myocytes and the topological distribution of the cells determines the probability of ectopic beat generation.

Chemical reaction-diffusion equations

Spatially extended chemical reactions are systems where the observation of linear instabilities and different types of pattern formation in non-linear reaction-diffusion equations is well-controlled. The combination of reactions with different instabilities together with advection may produce new pattern formation mechanisms. It permits the study of multi-scale problems where two instabilities appear simultaneously in a co-dimensional point at different scales. On the other hand, chemical waves in extended chemical excitable media, e.g. the Belousov-Zhabotinsky reaction or catalytic oxidation in metal surfaces, can reproduce some of the particularities of electrical wave propagation in cardiac tissue.

Negative filament tension of scroll waves in excitable media

Scroll waves are vortices that occur in three-dimensional excitable media. Scroll waves have been observed in a variety of systems including cardiac tissue, where they are associated with cardiac arrhythmias. The disorganization of scroll waves into chaotic behavior is thought to be the mechanism of ventricular fibrillation. One possible mechanism for this process of scroll wave instability is negative filament tension. The resulting complex, often turbulent dynamics was studied in many generic models of excitable media as well as in physiologically realistic models of cardiac tissue. Negative filament tension is related to tissue excitability. We consider the application of the negative tension mechanism to computational cardiology, where it may be regarded as a fundamental mechanism that explains differences in the onset of arrhythmias in thin and thick tissue.

 

Stochastic reaction-diffusion equations

Active media are a suitable benchmark to study the constructive role of random fluctuations in pattern forming systems. The mathematical framework to model these pattern forming systems is by using Partial Differential Equations. The interaction between the non-linearities and the random perturbations can give rise to unexpected phenomena. Several types of non-linear systems are considered and in particular extended chemical reacions where the noise is externally controlled by a computer. White, globally temporal or spatio-temporal noises interact with spiral waves, Turing patterns, oscillations and traveling waves in a contra-intuitive way.