Biomedical subjects

Alberto P Muñuzuri

Publications and source records attributed to Alberto P Muñuzuri.

9 recordsLinked to original sources

PubMed2006

Experimental evidence of localized oscillations in the photosensitive chlorine dioxide-iodine-malonic acid reaction.

The interaction between Hopf and Turing modes has been the subject of active research in recent years. We present here experimental evidence of the existence of mixed Turing-Hopf modes in a two-dimensional system. Using the photosensitive chlorine dioxide-iodine-malonic acid reaction (CDIMA) and external constant background illumination as a control parameter, standing spots oscillating in amplitude and with hexagonal ordering were observed. Numerical simulations in the Lengyel-Epstein model for the CDIMA reaction confirmed the results.

Biological Clocks↗

PubMed2006

Active media under rotational forcing.

The bubble-free Belousov-Zhabotinsky reaction has been used to study the effects of centrifugal forces on autowave propagation. The reaction parameters were chosen such that the system oscillates naturally creating target waves. In the present study, the system was forced to rotate with a constant velocity around a central axis. In studying the effects of such a forcing on the system, we focused on target dynamics. The system reacts to this forcing in different ways, the most spectacular being a dramatic increase in the period of the target, the effect growing stronger as we move away from the center of rotation. A numerical study was carried out using the two-variable Oregonator model, modified to include convective effects through the diffusion coefficient. The numerical results showed a good qualitative agreement with those of the experiments.

Journal Article↗

PubMed2006

Waving patterns: a general transition from stationary to moving forced Turing structures.

We perform experiments on the chlorine dioxide-iodine-malonic acid (CDIMA) reaction forced with light with a pattern of moving stripes in which the spatiotemporal behavior is the oscillating movement of stripes (waving). This behavior is seen for different relative wavelengths between stationary and moving patterns. Different velocities of forcing may produce different modes of relaxation of the pattern in order to get to the natural Turing wavelength. Zigzag or Eckhaus instabilities may affect the symmetry of the pattern but do not influence the waving movement of stripes.

Journal Article↗

PubMed2006

On the orientation of stripes in fish skin patterning.

This paper is focused on the study of the stripes orientation in the fish skin patterns. Based on microscopic observations of the pigment cells behavior at the embryonic stage, the key aspects of the pigmentation process are implemented in an experimental reaction-diffusion system. The experiment consists of a photosensitive Turing pattern of stripes growing directionally in one direction with controlled velocity. Different growth velocities of the system rearrange the stripes in the same three possible orientations observed in the skin of the colored fishes: parallel, oblique, and perpendicular. Our results suggest that the spreading velocity of the pigment cells in the fish dermis selects the orientation in the patterning processes.

Animals↗

PubMed2006

Experimental steady pattern formation in reaction-diffusion-advection systems.

We present here experimental evidence of a mechanism of a steady-chemical pattern formation called "flow-and-diffusion structures" (FDS). Experiments were performed using the photosensitive chlorine dioxide-iodine-malonic acid reaction, where the differential diffusion can be chemically controlled. Using the analogy between an advection boundary and a moving boundary, we obtain the formation of spatially periodic steady patterns, which matches all the previously theoretical predictions for FDS patterns. Numerical simulations are also reported in agreement with the experimental results.

Journal Article↗

PubMed2006

Effect of axial growth on Turing pattern formation.

We have performed one-dimensional and two-dimensional experiments and simulations to study the formation of patterns in a system that grows continuously in one direction. Depending on the growth velocity, three basic spatial configurations can be obtained: stripes that are parallel, oblique, or perpendicular to the growth direction. The dependence of the wavelength on the growth velocity has also been observed. Our results illustrate the importance of these growth mechanisms in determining the final configuration of chemical and biological pattern-forming processes.

Chlorine Compounds↗

PubMed2006

Robustness and stability of flow-and-diffusion structures.

Reaction-diffusion-advection systems have revealed an interesting variety of pattern formation mechanism during the last years. Inside this field, flow-and-diffusion structures (FDSs) appear as a generalization of the mechanism of spatial symmetry breaking for different diffusion coefficients and flow rates of activator and inhibitor. The recent experimental validation of FDSs situates these structures in the focus of the actual research. We will report here an experimental and numerical analysis of the theoretically predicted robustness of these flow-and-diffusion structures by using different boundary profiles of illumination used to obtain FDSs. The results here shown reveal important characteristics related with the coexistence and interaction between these structures.

Journal Article↗

PubMed2005

Turing instability controlled by spatiotemporal imposed dynamics.

The study of the spatiotemporal response of pattern forming systems to spatially resonant external forcing has unveiled striking new phenomena which challenge the understanding of self-organization in nonlinear, nonequilibrium systems. Here we show that a simple spatiotemporal two-dimensional forcing of a system supporting an intrinsic wavelength but no intrinsic frequency, under conditions of spatial resonance, may induce complex and entirely new spatiotemporal behaviors which do not reflect in any simple way the structure of the imposed forcing. We demonstrate this phenomenon in the Turing regime of the (photosensitive) CDIMA reaction by projecting a traveling stripe light pattern onto the reactor. By controlling the velocity of the forcing we induce distinct dynamical regimes that express the externally imposed frequency in new and intriguing ways. A detailed analysis of the experimental relevant parameters is presented.

Journal Article↗

PubMed2004

Control of chemical pattern formation by a clock-and-wavefront type mechanism.

The segmentation of many animals ranging from insects to mammals involves the sequential formation of stationary stripes of gene expression that are perpendicular to the growth axis of the developing embryo. This process has been accounted for by a variety of theoretical "clock-and-wavefront" type models that involve the arrest of an oscillation (the clock) at a moving boundary (the wavefront). Here, we demonstrate experimentally that progressive arrest of a homogeneous oscillation can control the symmetry as well as the wavelength of spatial structures in a chemical system. We show how a spontaneously formed, labyrinthine pattern can be converted into a pattern composed of ordered, parallel stripes and confirm a previously predicted proportionality between the wavelength and the period of the homogeneous oscillation. Our experiments provide the first experimental demonstration of a general mechanism for the control of pattern formation that has been hypothesized to operate in the context of biological morphogenesis.

Animals↗