Simonetta Filippi - Academia.edu (original) (raw)

Papers by Simonetta Filippi

2022 IEEE International Workshop on Metrology for Industry 4.0 & IoT (MetroInd4.0&IoT)

The electrophysiological modeling of excitable cells is a fundamental tool to understand their co... more The electrophysiological modeling of excitable cells is a fundamental tool to understand their collective behaviour, and to predict their response to endogenous or exogenous stimulation. Excitable cells constitute ideal biosensor models. They can be used to design inorganic sensors, reproduce the physiological circuitry, or build mixed inorganic-organic sensors, including cells in organic electronics. The most critical aspect in models, such as the Hodgkin-Huxley ones, is the determination of the values of the model parameters. Such values are, at present, mostly obtained from experimental electrophysiological data, and when those data lack for specific cells or channels, this can strongly impact the build of reliable models. Here we show how a proper usage of multiscale simulation tools, starting from molecular modeling, can provide reliable in silico estimation of ion channels conductance for cells modeling, discussed with respect to experimental data.

arXiv: Tissues and Organs, 2018

In this paper we introduce a new mathematical model for the active contraction of the cardiac mus... more In this paper we introduce a new mathematical model for the active contraction of the cardiac muscle under different thermo-electric and nonlinear conductivity properties. The passive hyperelastic response of the tissue is described by an orthotropic exponential model, whereas the ionic activity dictates active contraction incorporated through the concept of orthotropic active strain. We use a fully incompressible formulation, and the generated strain modifies directly the conductivity mechanisms in the medium through the pull-back transformation. We also investigate the influence of thermo-electric effects in the onset of multiphysics emergent spatiotemporal dynamics, using nonlinear diffusion. It turns out that these ingredients have a key role in reproducing pathological rhythms such as ventricular fibrillation, during inflammatory events, for instance. The specific structure of the governing equations (written in terms of Kirchhoff stress, displacements, solid pressure, electric...

Biosystems, 2020

Calcium controls a large number of cellular processes at different scales. Decades of studies hav... more Calcium controls a large number of cellular processes at different scales. Decades of studies have pointed out the importance of calcium signaling in regulating differentiation, apoptosis, mitosis and functions such as secretion, muscle contraction and memory. The space-time structure of calcium signaling is central to this complex regulation. In particular, cells within organisms behave as clocks beating their own biological time, although in several cases they can synchronize across long distances leading to an emergent space-time dynamics which is central for single cell and organ functioning. We use a mathematical model built on published experimental data of hepatic non-excitable cells, analyzing emerging calcium dynamics of cells clusters composed both of normally functioning cells and pathological aggregates. Calcium oscillations are investigated by varying the severity of dysfunction and size of pathological aggregate. We show how strong and localized heterogeneity in cellular properties can profoundly alter organized calcium dynamics leading to sub-populations of cells which create their own coordinated dynamical organization. Our simulations of Ca 2þ signals reveal how cell behaviors differ and are related to intrinsic time signals. Such different cells clusters dynamically influence each other so that non-physiological although organized calcium patterns are generated. This new reorganization of calcium activity may possibly be a precursor of cancer initiation.

Plastic & Reconstructive Surgery, 2018

Background: Brachioplasty is an increasingly performed procedure following massive weight loss. A... more Background: Brachioplasty is an increasingly performed procedure following massive weight loss. A visible scar is the main hindrance to this surgery. The aims of the study were to develop a physical model to investigate the ideal location of the surgical incision and to present the authors’ technical refinements with the posteromedial scar approach. Methods: Twenty-four postbariatric patients underwent brachioplasty with posteromedial scar placement, concomitant liposuction, fascial plication, and axillary Z-plasty. Skin specimens were tested and a physical model of the arm was set up to investigate the difference in mechanical stress on the posteromedial and medial scars. The validated Patient and Observer Scar Assessment Scale, the Vancouver Scar Scale, and a questionnaire assessing subjective improvements were administered to patients. Preoperative and postoperative photographs were assessed by three independent plastic surgeons. Results: The physical model showed that stress int...

Chaos, Solitons & Fractals, 2018

Recent findings based on calcium fluorescence imaging of pancreatic islets, also combined with op... more Recent findings based on calcium fluorescence imaging of pancreatic islets, also combined with optogenetic techniques, showed that β-cells synchronization underlie a small-world and scale-free functional organization, where specified hubs are responsible of the emergent coordination in electrical activity. Despite these features were suggested to be linked to an efficient spreading of information and calcium waves, it is still unclear from what they emerge, if they can still be observed when different dynamical variables are used to build functional networks, and how they vary upon changes in control parameters. In this work we investigate this aspect with a novel hybrid discrete-continuum mathematical model, coupling the stochastic electrical dynamics of β-cell clusters to nonlinear reaction-diffusion of glucose. By analyzing cells activity with the use of dynamical functional networks computed on the correlations between cells membrane voltage signals, we recover functional features in accordance to experimental observations. We further show that such properties are observed during specific phases of the complex electrical bursting oscillation, and are affected by glucose diffusion. These results suggest that functional properties derived from experimental calcium signals, on a time scale on the order of tens of seconds, are also recovered at a much faster time scale, i.e., on the order of hundreds of milliseconds. We finally describe how such functional features are strongly linked to synchronization patterns, in which coordinated sub-clusters of cells naturally emerge from the underlying dynamics.

International Journal of Modern Physics D, 2017

Short and long-duration gamma-ray bursts (GRBs) have been recently sub-classified into seven fami... more Short and long-duration gamma-ray bursts (GRBs) have been recently sub-classified into seven families according to the binary nature of their progenitors. For short GRBs, mergers of neutron star binaries (NS–NS) or neutron star-black hole binaries (NS-BH) are proposed. For long GRBs, the induced gravitational collapse (IGC) paradigm proposes a tight binary system composed of a carbon–oxygen core (CO[Formula: see text]) and a NS companion. The explosion of the CO[Formula: see text] as supernova (SN) triggers a hypercritical accretion process onto the NS companion which might reach the critical mass for the gravitational collapse to a BH. Thus, this process can lead either to a NS-BH or to NS–NS depending on whether or not the accretion is sufficient to induce the collapse of the NS into a BH. We shall discuss for the above compact object binaries: (1) the role of the NS structure and the equation-of-state on their final fate; (2) their occurrence rates as inferred from the X and gamm...

Mpf2010 Iv International Symposium on Modeling of Physiological Flows, Jun 2, 2010

Rotating spiral waves of electrical activity, experimentally observed in excitable biological tis... more Rotating spiral waves of electrical activity, experimentally observed in excitable biological tissues, play a central role in heart dynamics in reason of their connection with arrhythmias and fibrillation. Many mathematical models fine tuned on experiments have been developed in order to quantitatively understand and control these life threatening events. Usually these models neglected the role of heat transfer and temperature changes, which are relevant to the cardiac electrical system [1,2]. In particular experiments were devoted also to understand the cardiac heat production possibly associated with its mechanical work [3]. Moreover, during heart surgery, thermal cooling can influence cardiac activity in a marked way: notably arrhythmias and fibrillations can occur during the re-thermalization from hypothermia although the use of a controlled hypothermic protocols for the right atrium have been recently shown to reduce postoperative atrial fibrillation [4]. It appears mandatory then to include thermal effects in existing mathematical models. In this paper, adopting a scheme already presented in recent publications on neural and intestinal excitable tissues [5,6,7], we present a thermo-electric ionic model of miocardial tissue accounting for heat transfer effects. More in detail we analyze the problem using Fenton-Karma electrophysiological cardiac model with temperature dependent gradients and coupled with Pennes' bio-heat equation stressing the role of thermal inhomogeneities in promoting arrhythmogenic events. References [1] E. S. D. Brown, “Temperature and the Responsive Mechanism of Cardiac Muscle: I. Temperature and the Duration of Contraction”, J. Exp. Biol. vol.7: 373-384 (1930). [2] E. S. D. Brown, “Temperature and the Responsive Mechanism of Cardiac Muscle: II. Temperature and The Rate of the Rhythm of the Isolated Sinus”, J. Exp. Biol. vol.7:385-389 (1930). [3] C. L. Gibbs, J B Chapman, “Cardiac Heat Production”, Annual Review of Physiology, October, Vol. 41: 507-519 (1979). [4] M. A. J. M. Huybregts R. de Vroege and W. van Oeveren, A New System for Right Atrial Cooling, Ann Thorac Surg ;vol. 85:1421-1424 (2008). [5] D. Bini, C. Cherubini and S. Filippi, “Heat Transfer in FitzHugh-Nagumo model”, Phys Rev.E vol.74: 041905 (2006). [6] D. Bini, C. Cherubini and S. Filippi, “On vortices heating biological excitable media ”, Chaos, Solitons & Fractals, ,vol.42: 2057-2066 (2009). [7] A. Gizzi, C. Cherubini, S. Migliori, R. Alloni, R. Portuesi and S. Filippi, “On the electrical intestine turbulence induced by temperature changes”, Physical Biology , in press (2010).

Physical Biology, 2015

Coordinated insulin secretion is controlled by electrical coupling of pancreatic β-cells due to c... more Coordinated insulin secretion is controlled by electrical coupling of pancreatic β-cells due to connexin-36 gap junctions. Gap junction coupling not only synchronizes the heterogeneous β-cell population, but can also modify the electrical behavior of the cells. These phenomena have been widely studied with mathematical models based on data from mouse β-cells. However, it is now known that human β-cell electrophysiology shows important differences to its rodent counterpart, and although human pancreatic islets express connexin-36 and show evidence of β-cell coupling, these aspects have been little investigated in human β-cells. Here we investigate theoretically, the gap junction coupling strength required for synchronizing electrical activity in a small cluster of cells simulated with a recent mathematical model of human β-cell electrophysiology. We find a lower limit for the coupling strength of approximately 20 pS (i.e., normalized to cell size, ∼2 pS pF(-1)) below which spiking electrical activity is asynchronous. To confront this theoretical lower bound with data, we use our model to estimate from an experimental patch clamp recording that the coupling strength is approximately 100-200 pS (10-20 pS pF(-1)), similar to previous estimates in mouse β-cells. We then investigate the role of gap junction coupling in synchronizing and modifying other forms of electrical activity in human β-cell clusters. We find that electrical coupling can prolong the period of rapid bursting electrical activity, and synchronize metabolically driven slow bursting, in particular when the metabolic oscillators are in phase. Our results show that realistic coupling conductances are sufficient to promote synchrony in small clusters of human β-cells as observed experimentally, and provide motivation for further detailed studies of electrical coupling in human pancreatic islets.

Journal of the Mechanics and Physics of Solids

Lettere al Nuovo Cimento, 1984

A Newtonian approach to the problem of the capture of particles by a gravitational condensation i... more A Newtonian approach to the problem of the capture of particles by a gravitational condensation in a Friedmann universe is considered. Explicit formulae are given for the value of the momenta and injection angles leading to the capture, and a comparison is made with analogous fully relativistic results.

ABSTRACT Postoperative or paralytic ileus (PI) is a temporary aftermath of major ab-dominal surge... more ABSTRACT Postoperative or paralytic ileus (PI) is a temporary aftermath of major ab-dominal surgeries. PI prevents the passage of food throughout the lumen leading to bloat-ing, distension, emesis and pain. A plausi-ble mathematical model for this phenomenol-ogy physiologically fine tuned including ther-mal variations, is presented here. Using COMSOL Multiphysics the existing intestinal ionic model have been implemented in three-dimensions.

Frontiers in Genetics, 2014

This work deals with the particular nature of network-based approach in biology. We will comment ... more This work deals with the particular nature of network-based approach in biology. We will comment about the shift from the consideration of the molecular layer as the definitive place where causative process start to the elucidation of the among elements (at any level of biological organization they are located) interaction network as the main goal of scientific explanation. This shift comes from the intrinsic nature of networks where the properties of a specific node are determined by its position in the entire network (top-down explanation) while the global network characteristics emerge from the nodes wiring pattern (bottom-up explanation). This promotes a "middle-out" paradigm formally identical to the time honored chemical thought holding big promises in the study of biological regulation.

Astronomy & Astrophysics - ASTRON ASTROPHYS, 1991

Generalization of the velocity field in an anisotropic and inhomogeneous ellipsoid to the nonline... more Generalization of the velocity field in an anisotropic and inhomogeneous ellipsoid to the nonlinear case proposed by Filippi et al. (1990) is extended to cover the most general directions of the vorticity and angular velocity. A Roberts form for density is used instead of the restricted Ferrers density. Equilibrium sequences are determined, and their stability against odd and even modes of oscillation is discussed. Dedekind's and Riemann's theorems are extended. The dynamical case and the angular momentum, precession, vorticity, and energy of the sequences are also examined.

Physical Review E, 2005

An extended Fitzhugh-Nagumo model including linear viscoelasticity is derived in general and stud... more An extended Fitzhugh-Nagumo model including linear viscoelasticity is derived in general and studied in detail in the one-dimensional case. The equations of the theory are numerically integrated in two situations: ͑i͒ a free insulated fiber activated by an initial Gaussian distribution of action potential, and ͑ii͒ a clamped fiber stimulated by two counter phased currents, located at both ends of the space domain. The former case accounts for a description of the physiological experiments on biological samples in which a fiber contracts because of the spread of action potential, and then relaxes. The latter case, instead, is introduced to extend recent models discussing a strongly electrically stimulated fiber so that nodal structures associated on quasistanding waves are produced. Results are qualitatively in agreement with physiological behavior of cardiac fibers. Modifications induced on the action potential of a standard Fitzhugh-Nagumo model appear to be very small even when strong external electric stimulations are activated. On the other hand, elastic backreaction is evident in the model.

Physical Review E, 2009

It is commonly accepted that reaction-diffusion equations cannot be obtained by a Lagrangian fiel... more It is commonly accepted that reaction-diffusion equations cannot be obtained by a Lagrangian field theory. Guided by the well known connection between quantum and diffusion equations, we implement here a Lagrangian approach valid for totally general nonlinear reacting-diffusing systems which allows the definition of global conserved observables derived using Nöther's theorem.

Physical Review D, 2011

ABSTRACT

Europhysics Letters (EPL), 1990

ABSTRACT

2022 IEEE International Workshop on Metrology for Industry 4.0 & IoT (MetroInd4.0&IoT)

The electrophysiological modeling of excitable cells is a fundamental tool to understand their co... more The electrophysiological modeling of excitable cells is a fundamental tool to understand their collective behaviour, and to predict their response to endogenous or exogenous stimulation. Excitable cells constitute ideal biosensor models. They can be used to design inorganic sensors, reproduce the physiological circuitry, or build mixed inorganic-organic sensors, including cells in organic electronics. The most critical aspect in models, such as the Hodgkin-Huxley ones, is the determination of the values of the model parameters. Such values are, at present, mostly obtained from experimental electrophysiological data, and when those data lack for specific cells or channels, this can strongly impact the build of reliable models. Here we show how a proper usage of multiscale simulation tools, starting from molecular modeling, can provide reliable in silico estimation of ion channels conductance for cells modeling, discussed with respect to experimental data.

arXiv: Tissues and Organs, 2018

In this paper we introduce a new mathematical model for the active contraction of the cardiac mus... more In this paper we introduce a new mathematical model for the active contraction of the cardiac muscle under different thermo-electric and nonlinear conductivity properties. The passive hyperelastic response of the tissue is described by an orthotropic exponential model, whereas the ionic activity dictates active contraction incorporated through the concept of orthotropic active strain. We use a fully incompressible formulation, and the generated strain modifies directly the conductivity mechanisms in the medium through the pull-back transformation. We also investigate the influence of thermo-electric effects in the onset of multiphysics emergent spatiotemporal dynamics, using nonlinear diffusion. It turns out that these ingredients have a key role in reproducing pathological rhythms such as ventricular fibrillation, during inflammatory events, for instance. The specific structure of the governing equations (written in terms of Kirchhoff stress, displacements, solid pressure, electric...

Biosystems, 2020

Calcium controls a large number of cellular processes at different scales. Decades of studies hav... more Calcium controls a large number of cellular processes at different scales. Decades of studies have pointed out the importance of calcium signaling in regulating differentiation, apoptosis, mitosis and functions such as secretion, muscle contraction and memory. The space-time structure of calcium signaling is central to this complex regulation. In particular, cells within organisms behave as clocks beating their own biological time, although in several cases they can synchronize across long distances leading to an emergent space-time dynamics which is central for single cell and organ functioning. We use a mathematical model built on published experimental data of hepatic non-excitable cells, analyzing emerging calcium dynamics of cells clusters composed both of normally functioning cells and pathological aggregates. Calcium oscillations are investigated by varying the severity of dysfunction and size of pathological aggregate. We show how strong and localized heterogeneity in cellular properties can profoundly alter organized calcium dynamics leading to sub-populations of cells which create their own coordinated dynamical organization. Our simulations of Ca 2þ signals reveal how cell behaviors differ and are related to intrinsic time signals. Such different cells clusters dynamically influence each other so that non-physiological although organized calcium patterns are generated. This new reorganization of calcium activity may possibly be a precursor of cancer initiation.

Plastic & Reconstructive Surgery, 2018

Background: Brachioplasty is an increasingly performed procedure following massive weight loss. A... more Background: Brachioplasty is an increasingly performed procedure following massive weight loss. A visible scar is the main hindrance to this surgery. The aims of the study were to develop a physical model to investigate the ideal location of the surgical incision and to present the authors’ technical refinements with the posteromedial scar approach. Methods: Twenty-four postbariatric patients underwent brachioplasty with posteromedial scar placement, concomitant liposuction, fascial plication, and axillary Z-plasty. Skin specimens were tested and a physical model of the arm was set up to investigate the difference in mechanical stress on the posteromedial and medial scars. The validated Patient and Observer Scar Assessment Scale, the Vancouver Scar Scale, and a questionnaire assessing subjective improvements were administered to patients. Preoperative and postoperative photographs were assessed by three independent plastic surgeons. Results: The physical model showed that stress int...

Chaos, Solitons & Fractals, 2018

Recent findings based on calcium fluorescence imaging of pancreatic islets, also combined with op... more Recent findings based on calcium fluorescence imaging of pancreatic islets, also combined with optogenetic techniques, showed that β-cells synchronization underlie a small-world and scale-free functional organization, where specified hubs are responsible of the emergent coordination in electrical activity. Despite these features were suggested to be linked to an efficient spreading of information and calcium waves, it is still unclear from what they emerge, if they can still be observed when different dynamical variables are used to build functional networks, and how they vary upon changes in control parameters. In this work we investigate this aspect with a novel hybrid discrete-continuum mathematical model, coupling the stochastic electrical dynamics of β-cell clusters to nonlinear reaction-diffusion of glucose. By analyzing cells activity with the use of dynamical functional networks computed on the correlations between cells membrane voltage signals, we recover functional features in accordance to experimental observations. We further show that such properties are observed during specific phases of the complex electrical bursting oscillation, and are affected by glucose diffusion. These results suggest that functional properties derived from experimental calcium signals, on a time scale on the order of tens of seconds, are also recovered at a much faster time scale, i.e., on the order of hundreds of milliseconds. We finally describe how such functional features are strongly linked to synchronization patterns, in which coordinated sub-clusters of cells naturally emerge from the underlying dynamics.

International Journal of Modern Physics D, 2017

Short and long-duration gamma-ray bursts (GRBs) have been recently sub-classified into seven fami... more Short and long-duration gamma-ray bursts (GRBs) have been recently sub-classified into seven families according to the binary nature of their progenitors. For short GRBs, mergers of neutron star binaries (NS–NS) or neutron star-black hole binaries (NS-BH) are proposed. For long GRBs, the induced gravitational collapse (IGC) paradigm proposes a tight binary system composed of a carbon–oxygen core (CO[Formula: see text]) and a NS companion. The explosion of the CO[Formula: see text] as supernova (SN) triggers a hypercritical accretion process onto the NS companion which might reach the critical mass for the gravitational collapse to a BH. Thus, this process can lead either to a NS-BH or to NS–NS depending on whether or not the accretion is sufficient to induce the collapse of the NS into a BH. We shall discuss for the above compact object binaries: (1) the role of the NS structure and the equation-of-state on their final fate; (2) their occurrence rates as inferred from the X and gamm...

Mpf2010 Iv International Symposium on Modeling of Physiological Flows, Jun 2, 2010

Rotating spiral waves of electrical activity, experimentally observed in excitable biological tis... more Rotating spiral waves of electrical activity, experimentally observed in excitable biological tissues, play a central role in heart dynamics in reason of their connection with arrhythmias and fibrillation. Many mathematical models fine tuned on experiments have been developed in order to quantitatively understand and control these life threatening events. Usually these models neglected the role of heat transfer and temperature changes, which are relevant to the cardiac electrical system [1,2]. In particular experiments were devoted also to understand the cardiac heat production possibly associated with its mechanical work [3]. Moreover, during heart surgery, thermal cooling can influence cardiac activity in a marked way: notably arrhythmias and fibrillations can occur during the re-thermalization from hypothermia although the use of a controlled hypothermic protocols for the right atrium have been recently shown to reduce postoperative atrial fibrillation [4]. It appears mandatory then to include thermal effects in existing mathematical models. In this paper, adopting a scheme already presented in recent publications on neural and intestinal excitable tissues [5,6,7], we present a thermo-electric ionic model of miocardial tissue accounting for heat transfer effects. More in detail we analyze the problem using Fenton-Karma electrophysiological cardiac model with temperature dependent gradients and coupled with Pennes' bio-heat equation stressing the role of thermal inhomogeneities in promoting arrhythmogenic events. References [1] E. S. D. Brown, “Temperature and the Responsive Mechanism of Cardiac Muscle: I. Temperature and the Duration of Contraction”, J. Exp. Biol. vol.7: 373-384 (1930). [2] E. S. D. Brown, “Temperature and the Responsive Mechanism of Cardiac Muscle: II. Temperature and The Rate of the Rhythm of the Isolated Sinus”, J. Exp. Biol. vol.7:385-389 (1930). [3] C. L. Gibbs, J B Chapman, “Cardiac Heat Production”, Annual Review of Physiology, October, Vol. 41: 507-519 (1979). [4] M. A. J. M. Huybregts R. de Vroege and W. van Oeveren, A New System for Right Atrial Cooling, Ann Thorac Surg ;vol. 85:1421-1424 (2008). [5] D. Bini, C. Cherubini and S. Filippi, “Heat Transfer in FitzHugh-Nagumo model”, Phys Rev.E vol.74: 041905 (2006). [6] D. Bini, C. Cherubini and S. Filippi, “On vortices heating biological excitable media ”, Chaos, Solitons & Fractals, ,vol.42: 2057-2066 (2009). [7] A. Gizzi, C. Cherubini, S. Migliori, R. Alloni, R. Portuesi and S. Filippi, “On the electrical intestine turbulence induced by temperature changes”, Physical Biology , in press (2010).

Physical Biology, 2015

Coordinated insulin secretion is controlled by electrical coupling of pancreatic β-cells due to c... more Coordinated insulin secretion is controlled by electrical coupling of pancreatic β-cells due to connexin-36 gap junctions. Gap junction coupling not only synchronizes the heterogeneous β-cell population, but can also modify the electrical behavior of the cells. These phenomena have been widely studied with mathematical models based on data from mouse β-cells. However, it is now known that human β-cell electrophysiology shows important differences to its rodent counterpart, and although human pancreatic islets express connexin-36 and show evidence of β-cell coupling, these aspects have been little investigated in human β-cells. Here we investigate theoretically, the gap junction coupling strength required for synchronizing electrical activity in a small cluster of cells simulated with a recent mathematical model of human β-cell electrophysiology. We find a lower limit for the coupling strength of approximately 20 pS (i.e., normalized to cell size, ∼2 pS pF(-1)) below which spiking electrical activity is asynchronous. To confront this theoretical lower bound with data, we use our model to estimate from an experimental patch clamp recording that the coupling strength is approximately 100-200 pS (10-20 pS pF(-1)), similar to previous estimates in mouse β-cells. We then investigate the role of gap junction coupling in synchronizing and modifying other forms of electrical activity in human β-cell clusters. We find that electrical coupling can prolong the period of rapid bursting electrical activity, and synchronize metabolically driven slow bursting, in particular when the metabolic oscillators are in phase. Our results show that realistic coupling conductances are sufficient to promote synchrony in small clusters of human β-cells as observed experimentally, and provide motivation for further detailed studies of electrical coupling in human pancreatic islets.

Journal of the Mechanics and Physics of Solids

Lettere al Nuovo Cimento, 1984

A Newtonian approach to the problem of the capture of particles by a gravitational condensation i... more A Newtonian approach to the problem of the capture of particles by a gravitational condensation in a Friedmann universe is considered. Explicit formulae are given for the value of the momenta and injection angles leading to the capture, and a comparison is made with analogous fully relativistic results.

ABSTRACT Postoperative or paralytic ileus (PI) is a temporary aftermath of major ab-dominal surge... more ABSTRACT Postoperative or paralytic ileus (PI) is a temporary aftermath of major ab-dominal surgeries. PI prevents the passage of food throughout the lumen leading to bloat-ing, distension, emesis and pain. A plausi-ble mathematical model for this phenomenol-ogy physiologically fine tuned including ther-mal variations, is presented here. Using COMSOL Multiphysics the existing intestinal ionic model have been implemented in three-dimensions.

Frontiers in Genetics, 2014

This work deals with the particular nature of network-based approach in biology. We will comment ... more This work deals with the particular nature of network-based approach in biology. We will comment about the shift from the consideration of the molecular layer as the definitive place where causative process start to the elucidation of the among elements (at any level of biological organization they are located) interaction network as the main goal of scientific explanation. This shift comes from the intrinsic nature of networks where the properties of a specific node are determined by its position in the entire network (top-down explanation) while the global network characteristics emerge from the nodes wiring pattern (bottom-up explanation). This promotes a "middle-out" paradigm formally identical to the time honored chemical thought holding big promises in the study of biological regulation.

Astronomy & Astrophysics - ASTRON ASTROPHYS, 1991

Generalization of the velocity field in an anisotropic and inhomogeneous ellipsoid to the nonline... more Generalization of the velocity field in an anisotropic and inhomogeneous ellipsoid to the nonlinear case proposed by Filippi et al. (1990) is extended to cover the most general directions of the vorticity and angular velocity. A Roberts form for density is used instead of the restricted Ferrers density. Equilibrium sequences are determined, and their stability against odd and even modes of oscillation is discussed. Dedekind's and Riemann's theorems are extended. The dynamical case and the angular momentum, precession, vorticity, and energy of the sequences are also examined.

Physical Review E, 2005

An extended Fitzhugh-Nagumo model including linear viscoelasticity is derived in general and stud... more An extended Fitzhugh-Nagumo model including linear viscoelasticity is derived in general and studied in detail in the one-dimensional case. The equations of the theory are numerically integrated in two situations: ͑i͒ a free insulated fiber activated by an initial Gaussian distribution of action potential, and ͑ii͒ a clamped fiber stimulated by two counter phased currents, located at both ends of the space domain. The former case accounts for a description of the physiological experiments on biological samples in which a fiber contracts because of the spread of action potential, and then relaxes. The latter case, instead, is introduced to extend recent models discussing a strongly electrically stimulated fiber so that nodal structures associated on quasistanding waves are produced. Results are qualitatively in agreement with physiological behavior of cardiac fibers. Modifications induced on the action potential of a standard Fitzhugh-Nagumo model appear to be very small even when strong external electric stimulations are activated. On the other hand, elastic backreaction is evident in the model.

Physical Review E, 2009

It is commonly accepted that reaction-diffusion equations cannot be obtained by a Lagrangian fiel... more It is commonly accepted that reaction-diffusion equations cannot be obtained by a Lagrangian field theory. Guided by the well known connection between quantum and diffusion equations, we implement here a Lagrangian approach valid for totally general nonlinear reacting-diffusing systems which allows the definition of global conserved observables derived using Nöther's theorem.

Physical Review D, 2011

ABSTRACT

Europhysics Letters (EPL), 1990

ABSTRACT