Experimental focusing shocklike dynamics in a nonlocal optical stochastic Kerr medium.

We experimentally study the propagating of an optical intensity jump discontinuity in a nonlocal stochastic Kerr focusing nematic liquid crystal cell. We show both theoretically and experimentally that nonlocality opens a route towards beam steering in our system. Indeed, the discontinuity trajectory follows a curve that bends with the injected power. Despite the stochastic nature of the medium and the constant presence of transverse instabilities, the development of a focusing shocklike dynamics is shown to survive. The distance Z_{s} for the focusing shock to occur follows a power law with the beam power P according to Z_{s}∝P^{χ}, with χ=-4/3, as for shock dynamics in self-defocusing media.

[Prescription, assay and interpretation of cardiac troponins tests: guidelines from SFBC-CNBC troponin working group]. / Recommandations sur la prescription, le dosage et l'interprétation des troponines cardiaques.

Troponin (I or T) has become the gold-standard marker in acute coronary syndromes during the last few years, as confirmed by a national survey realized within french clinical chemists, cardiologists and emergency practitioners. The importance of this marker and the heterogeneousness of circulating forms of troponin after myocardial necrosis fully justify international studies about standardization of this assay, which is a central bulk to reach a global market coherence. Checking analytical problems, although necessary, must be absolutely associated with an informed clinical interpretation. The knowledge of the crucial thresholds of each assay, the kinetic curves and the specificity limits of troponin assays allow the best use of their potential in diagnosis and prognosis together with an optimal patient care in very different clinical settings, in addition to others clinical and technical arguments. The quality improvement through successive generations of assay kits must nowadays persuade the physicians never to ignore a significant and valid troponin increase, which mainly reveals a cardiac injury, whatever its origin.

Demonstration of Long-Period-Grating Efficient Couplings with an External Medium of a Refractive Index Higher than that of Silica.

We discuss the behavior of the transmission spectra of a long-period grating (LPG) with an external medium of refractive index higher than that of silica. We studied the evolution of the features of LPG's surrounded by several liquid media for several kinds of fiber. The study demonstrated that the behavior depends strongly on the fiber type. Efficient couplings (efficiency greater than 50%) have been obtained with an external medium of a refractive index larger than that of silica. This result indicates that a LPG can operate with surrounding materials of a refractive index higher than that of silica, promising new applications for LPG's as active optical filters.

Non linearly induced self waveguiding structure in dye doped nematic liquid crystals confined in capillaries.

We report on experiments dealing with the propagation of a collimated laser beam in a dye doped nematic confined in a capillary of optical fiber size. The nematic is aligned in a such a way that the source beam is self focused. The behavior of the beam - focusing, multifocus regime, filamentation and undulation - already observed in larger cylindrical geometry and pure nematic is shown here to be reproduced in the dye doped medium, at much lower powers. Another feature is reported here: a stable regime looking like a waveguide appears in certain conditions, in which the beam to propagate in a narrow tube. This regime is simply modeled in terms of saturated reorientation of the nematic.

Design of a photowritten cavity neodymium-doped fiber laser tunable around an absorption molecular line.

Experiments have shown that it is possible to realize laser cavities photowritten within rare-earth-doped silicate fibers. Experimental results on a particular application, namely, the detection of gas traces by identification of one of the gas's absorption lines, are presented. Experiments on an absorption line of atmospheric water have been carried out to illustrate this purpose. Two lasers have been designed with particular characteristics (spectral linewidths, slope efficiencies, thresholds). Preliminary experimental results on the detection of an absorption line of atmospheric water have been obtained with fiber lasers and optoacoustic detection.