École normale supérieure de Cachan

About: École normale supérieure de Cachan is a education organization based out in Cachan, Île-de-France, France. It is known for research contribution in the topics: Decidability & Nonlinear system. The organization has 2717 authors who have published 5585 publications receiving 175925 citations.

Electrical modeling of the influence of medium conductivity on electroporation

Abstract: Electroporation is the phenomenon in which cell membrane permeability is increased by exposing the cell to short high electric field pulses. Experimental data show that the amount of permeabilization depends on the conductivity of the extracellular medium. If medium conductivity decreases then it is necessary to deliver a pulse of larger field amplitude in order to achieve the same effect. Models that do not take into account the permeabilization effect on the membrane conductivity cannot reproduce qualitatively the experimental observations. Here we employ an exponential function for describing the strong dependence of membrane conductivity on transmembrane potential. Combining that model with numerical methods we demonstrate that the dependence on medium conductivity can be explained as being the result of increased membrane conductance due to electroporation. As experimentally observed, extracellular conductivities of about 1 and 0.1 S m−1 yield very similar results, however, for lower conductivities (<0.01 S m−1) the model predicts that significantly higher field magnitudes will be required to achieve the same amount of permeabilization.

The challenging life of wave energy devices at sea: A few points to consider

Abstract: Wave power devices offer great prospects for the marine renewable energy sector. But in comparison to wind energy, wave power is still in its infancy, mainly prototype-based, with technological gaps akin to those experienced in the wind sector some 15 years ago. Several aspects that did not seem significant at a first glance in the design phase, such as the interaction with the marine environment, turned out to be important when the first prototypes were put in the water. In fact, these devices have to face great challenges once at sea and several prototypes have not survived. Firstly, ocean waves are not such an innocuous, predictable flow of water and secondly, life thrives in the ocean. Wave power devices are perfect artificial reefs suitable for algal growth and colonization by many species. And they will have to sustain harsh conditions for over two decades while producing energy. For obvious reasons, there is a lack of existing literature on the subject. In this short review we address a simple question: how tough will the life of wave power devices at sea be? The answer is based on available evidence. We provide as well some ideas to take up the challenge.