Spectral control over the interaction of ultrashort pulses in fiber lasers

The interaction of light pulses in passively mode-locked fiber lasers operating has been studied. The numerical simulation has been used to demonstrate that a narrow-band selector inserted in a laser cavity allows the character of the interaction to be changed: depending on the detuning of the selector passband from the center of the gain band, ultrashort pulses can both attract and repel one another. Peculiarities of the pulse interaction have been studied at different parameters of the laser system.     

A spectrally constrained dual-band normalization technique for protoporphyrin IX quantification in fluorescence-guided surgery

We report a dual-band normalization technique for in vivo quantification of the metabolic biomarker, protoporphyrin IX (PpIX), during brain tumor resection procedures. The accuracy of the approach was optimized in tissue simulating phantoms with varying absorption and scattering properties, validated with fluorimetric assessments on ex vivo brain tissue, and tested on human data acquired in vivo during fluorescence-guided surgery of brain tumors. The results demonstrate that the dual-band normalization technique allows PpIX concentrations to be accurately quantified by correction with reflectance data recorded and integrated within only two narrow wavelength intervals. The simplicity of the method lends itself to the enticing prospect that the method could be applicable to wide-field applications in quantitative fluorescence imaging and dosimetry in photodynamic therapy.     

Viscoplastic behaviour of steels during phase transformationsComportement viscoplastique des aciers en cours de transformation de phase

That contribution to transformation plasticity of steels arising from the so-called Greenwood–Johnson mechanism is often described using the model developed by Leblond and coworkers. This model made the assumption of purely plastic behaviour. It is extended here to incorporate viscous effects, which are present during some transformations, especially at high temperatures. The predictions of the original and extended models are compared to experimental results for a material for which the second contribution to transformation plasticity, due to the so-called Magee mechanism, is known to be negligible, and it is shown that the incorporation of viscous effects into the model significantly improves its predictions. To cite this article: Y. Vincent et al., C. R. Mecanique 331 (2003).