Fabrice Pellen

In this paper, we report a morphological study of the crystals and spores of different shapes synthesized by seven different strains of Bacillus thuringiensis. Crystals and spores were separated after 48 h of culture on T3 agar medium and imaged under a scanning electron microscope (SEM). Sizes of the crystals and spores were determined using Image J software. The results showed that crystal and spore sizes were normally distributed. In addition, the volumes and aspect ratios of the crystals and spores were calculated. The statistical analysis of the data showed the variability of the size distribution and morphological data of the crystals produced by the analyzed strains. Furthermore, variations in spore size and shape within the same serovar were observed, indicating that, perhaps, there are still some unexplored differences between strains of this serovar, making them less identical than what was believed so far.

Glass-ionomer cements (GIC) belong to the class of materials known as acid-base cements. The drying process of these materials and the evolution of their physical properties play an important role in the quality and durability of dental care. Since monitoring these processes contributes to the improvement of the knowledge on these materials, we aim in our work to monitor in real-time hardening of GIC using dynamic speckle. Speckle images are temporally analyzed by computing the temporal correlation coefficient. The temporal correlation curves present a Lorentzian profile, which characteristics vary during GIC hardening process.

In this paper, we report measurements of wine viscosity, correlated to polarized laser speckle results. Experiments were performed on white wine samples produced with a single grape variety. Effects of the wine making cellar, the grape variety, and the vintage on wine Brix degree, alcohol content, viscosity, and speckle parameters are considered. We show that speckle parameters, namely, spatial contrast and speckle decorrelation time, as well as the inertia moment extracted from the temporal history speckle pattern, are mainly affected by the alcohol and sugar content and hence the wine viscosity. Principal component analysis revealed a high correlation between laser speckle results on the one hand and viscosity and Brix degree values on the other. As speckle analysis proved to be an efficient method of measuring the variation of the viscosity of white mono-variety wine, one can therefore consider it as an alternative method to wine sensory analysis.

The hybrid lidar-radar technique is commonly used for shallow underwater target detection. This technique requires a powerful blue-green RF-modulated laser with stable microwave frequency. In this paper, a novel modulator design perfectly suited for this application is proposed. It consists of an extra-cavity modulator composed of two plane mirrors and a second-harmonic generator stage within the cavity to maximize the energy efficiency. This modulator is coupled with a picosecond Nd:YAG infrared laser source to insure the emission of a powerful pulse (up to 5 mJ). Results considering this architecture show stable modulation frequency and a powerful modulated beam. As the emitted signal lasts only a few nanoseconds, a range-gating method can be used for target localization. This emitted signal has experimentally proven to preserve input beam polarization, which also can be employed to enhance the target return.

The effectiveness of a pulsed radiofrequency modulated lidar and associated processing for underwater target detection at grazing incidence was experimentally assessed in a wave basin 50 m long and 20 m deep, under different conditions of swell produced within this facility to benefit from a controlled interface. This paper reports our experiments and offline data processing results, and describes significant improvements in the probability of detection that demonstrate the interest of using such a technique in this context.

Hyper-Rayleigh scattering is frequently used to determine all of the rotational invariants of the first hyperpolarizability tensor. It requires numerous polarization states of both incident and scattered light and thus justifies the use of a dual-rotating-retarder polarimeter. We optimized our experimental setup by reducing the condition number of the polarization processing matrix. Our numerical study showed that, on condition to make six measurements, the choice of the detector angle and of the angular steps of both retarders was paramount. Overspecifying the calculation through a much higher number of measurements allowed us to make broad optimal detector angles and retarder angular steps available. Numerical simulations are presented to optimize our experimental setup.