We present a model of exo-prosthesis of knee in which the function of the anterior and posterior crossed ligaments (PCL) is made possible thanks to four bars fixed on the femoral and tibia parts of the prosthesis. The evolution of the projection of the rotation center of the real knee on the tibia plateau in the course of the flexion, strongly depends in the condyles shapes. Conversely, if we know the projection of the rotation center of the prosthesis (the meeting point of the four bars) we can associate a fictive shape of the condyles that a real knee would have when generating the same motion as done by the prosthesis. We optimize the motion of the prosthesis in order that fictive and real anatomical condyles are as near as possible. The flexion is enabled by a ‘universal joint’ of four bars whose anchorage points and dimensions are optimized in such a way that the difference between the shape of condyles associated to the prosthesis and the real condyles, got from anatomical measures, was a little as possible. This model of prosthesis leads to a kinematics much closer to the one of the real knee than any other types of exo-prosthesis. Moreover this model lowers the center of rotation of the whole and enables a good stability when you are standing. Though, the beginning of the flexion, the stability has to be still improved to have a commercial purpose.

The effects of continuous thermal annealing on the performances in terms of reflectivity of Mo/Si, Mo/C, Ni/C multilayer mirrors are studied. The measurements of reflectivity around 100eV are performed by using the synchrotron radiation supplied by Super-AGO at the LURE. Variations of reflectivity versus the temperature are recorded. We observe that the period of the Mo/Si mirror decreases, the one of the Mo/C mirror remains constant and the one of the Ni/C increases as the annealing temperature increases. These behaviours are discuted in the framework of material science.

We present experimental and theoretical studies of the diffraction by an x-ray lamellar multilayer amplitude grating. The main diffraction properties of such a device are given. Experimental efficiency curves are obtained at 800 eV photon energy using synchrotron radiation. The features observed in these curves are identified and interpreted by means of two theoretical methods. Particular emphasis is given to structures observed for the first time which had been theoretically predicted.

The specular attenuation factor S of a scalar wave reflected by a random rough surface is given for an oblique incidence. The dependence of the S factor upon various models of surface autocovariance function, the glancing angle and the radiation energy is shown in the X-UV range.

The spectral distribution of continuous X radiation, specularly reflected in the vicinity of the La LIII edge, is determined for various glancing angles. An anomalous behaviour of reflectivity is revealed, associated with a maximum in the photoabsorption spectrum. A simple theoretical model accounts for the phenomenon.