Biomedical subjects

Patrick De Kepper

Publications and source records attributed to Patrick De Kepper.

4 recordsLinked to original sources

PubMed2006

Spatiotemporal dynamics of the Landolt reaction in an open spatial reactor with conical geometry.

In a previous study, the iodate-sulfite proton autoactivated reaction (Landolt reaction) was shown to exhibit spatial bistability and spatiotemporal oscillations when operated in an open spatial reactor with fixed "thickness", i.e., feed boundary to core distance. Here, we show that the spatial reactors with conical geometry enable one to rapidly probe the sensitivity of the above phenomena over a large range of the "thickness" parameter. This often-neglected parameter in chemical pattern studies plays an important role on the selection and stability of states. We reveal that the quenching capacity of slow diffusing polyacrylate ions on the spatiotemporal oscillations depends on this "thickness". The presented results should be useful for further research on reaction diffusion patterns and chemomechanical structures.

Journal Article↗

PubMed2005

Wave patterns driven by chemomechanical instabilities in responsive gels.

The first experimental evidence of a chemomechanical mechanism leading to morphogenetic instabilities is demonstrated experimentally. The system consists of a pH-responsive gel that swells at high pH and shrinks at low pH, and a bistable reaction system exhibiting an acid steady state (pH approximately 2) and an alkaline steady state (pH approximately 10). Within the gel, the steady state selection depends on the gel size. We show that in a constant and uniform nonequilibrium chemical environment, the responsive gel undergoes large amplitude dynamical deformations under the form of travelling contraction waves and complex spatio-temporal volume oscillations. These deformations are coupled to concentration patterns of protons. We present different sequences of dynamical behaviors observed under various controlled chemical conditions. A simple heuristic model is proposed to account for the observations. These experiments open a new route for pattern formation driven by chemical energy, in soft matter systems.

Electrodes↗

PubMed2005

Glycolytic oscillations and waves in an open spatial reactor: Impact of feedback regulation of phosphofructokinase.

An open spatial reactor has been designed for the investigation of spatio-temporal dynamics of glycolysis. The reactor consists of a diffusive layer made of gel-fixed yeast extract which is in contact with a continuously stirred reservoir to supply this layer with substrates. The coupling between reaction and diffusion in the gel layer enables the formation of spatio-temporal patterns. Temporal oscillations of glycolysis are simply induced by feeding the yeast extract with sugar. Under properly chosen conditions, these oscillations sustain for more than 12 h. A necessary prerequisite for the generation of oscillations is that the ATP concentration in the feeding solution must be high enough to allow for negative feedback of phosphofructokinase. Otherwise, the interplay between ATP-consuming and ATP-producing reactions leads to an unfavorable low ATP/AMP ratio. The generation of travelling NADH-waves is observed in the diffusive layer, when feeding the yeast extract with substrates. Break-up of circular-shaped waves is repeatedly observed, resulting in the formation of rotating NADH-spirals.

Adenosine Monophosphate↗

PubMed2005

Turing patterns, spatial bistability, and front interactions in the [ClO2, I2, I-, CH2(COOH)2] reaction.

Recent experiments by Szalai and De Kepper performed in open spatial reactors have shown that the rich variety of dynamic properties of the chlorine dioxide-iodide-chlorite-iodine-malonic acid family of reactions is far from being exhausted: stable inhomogeneous patterns due to front interactions and transient labyrinthine structures are now added to the spatial bistability and Turing patterns as possible spatial behavior. The two latter phenomena, already observed in the chlorine dioxide-iodide (CDI) and the chlorine dioxide-iodide-malonic acid (CDIMA) reactions, respectively, were kept as limiting cases in the new setup. In this paper, we numerically analyze an extension of the most detailed available model of the CDI system (Lengyel et al.) including a reaction between I2 and MA that comes from the presence of the latter into the flow. The resulting nine-variable model is simulated in one and two dimensions, taking into account the proper constraints of the boundary-fed system. The nonequilibrium phase diagram closely follows the results of the experiments of ref 1. In particular, the model reproduces observations on spatial bistability, stationary front interactions, and Turing patterns. In addition, it predicts a new region of spatial bistability.

Journal Article↗