A verification criterion with three significant applications

International audienc

Resonant photo-thermal conversion for sub-terahertz imaging

An original design of generic interest is proposed for fast imaging, in the field of sub-terahertz frequencies, by means of resonant coupling between an ultra-thin photo-thermal converter and a metallic grid upstream an infrared camera. The material is a sheet of polyimide material with a high content of absorptive carbon inclusions. We make use of the large difference between the IR and THz wavelengths in a quarter-wave planar geometry, to ensure a highly efficient and stable conversion process. A complete setup has been implemented for demonstration purposes, using the beam from a Gunn diode at 110 GHz. Experimental results are in good agreement with the predictions from the numerical model, which helps to validate the concept and the requirements for geometrical adjustment

Enabling a sarcomere to run and breath

An extremely simple model of a compass gait biped consisting of three points is considered. Two of them are for the legs and the third one is for the hips, with additional kinematic conditions (three joints). It is a model capable in its passive form of descending a slope by simple gravity. We consider it here on level ground in an active form, i. e. with bio-actuators at the joints. Each bio-actuator develops a force torsor obtained from two Hill-type muscles (two serie and parallel elastic elements, one contracting element) acting on either side of the joint. The contractile element is a zero dimensional sarcomere of Huxley type whose attachment and detachment coefficients rates are linked to Ca2+ and ATP concentrations by empirical relationships [Bestel 2000]. Assuming that the ATP “consumed” in the vicinity of the myosin fiber is identical to that “produced” in the vicinity of an associated mitochondria, a kinetic model of the oxidative phosphorylation chain [Korzeniewski 2007] links the ATP to the oxygen and NADH concentrations in mitochondria. Several other internal variables are included as cytochrome c and cytochrome oxidase concentrations. The Ca2+ concentrations are the control variable of the whole complex. We then determine a temporal profile of Ca2+ which, included in a Keller dynamic process, produces a run cycle associated with O2 and NADH consumptions. This rudimentary model establishes a connection between consumed matter (O2, NADH) and produced movement. It is capable of raising the numerical difficulties linked to the multiple constraints taken into account. The future and ultimate objective is to solve a race time minimization problem constrained by the energy / matter consumption as done by [Aftalion & al 2014] heuristically, while in addition bringing furthermore a crucial biological basis to these constraints