Lever-assisted two-noise stochastic resonance.

A critical interplay of two correlated noises in a nonlinear symmetrical two-well potential system is experimentally demonstrated. One state can become completely noise free, leading to an infinite Kramers time. If an independent lever breaks the potential symmetry, stochastic resonance is recovered. In this new regime, we obtain a plateau, i.e., a high signal-to-noise ratio even for vanishing forcing signals.

Stochastic resonances in an optical two-order parameter vectorial system.

We show experimentally that optical two-dimensional systems such as vectorial lasers can exhibit novel stochastic resonances. All optical noise and modulation of this system allows the isolation of so-called inhibitional and rotational stochastic resonances. In particular, incoherent rotational tunneling is shown to be sensitive enough to be also induced by Faraday noise and by quantum noise, i.e., external spontaneous emission.

Frequency fluctuations of stabilized lasers with anisotropic feedbacks.

A random phase method is proposed to determine the perturbation of the Allan variance of frequency stabilized lasers submitted to optical feedbacks. The role of different feedbacks is quantitatively described for both one-oscillating-eigenstate stabilized lasers and two-oscillating-eigenstate stabilized lasers. The importance of the feedback polarization is isolated in each system. In both cases, the experimental measurements of the Allan variance and of the peak-to-peak frequency variations due to a periodic modulation of the feedback phase are found to be in agreement with the theoretical predictions.

[Comparison of 2 groups of patients hospitalized at 10 years' interval for recent myocardial infarction]. / Comparaison de deux groupes de patients hospitalisés à 10 ans d'intervalle pour un infarctus du myocarde récent.

The aim of this study was to compare two groups of patients admitted consecutively to the Coronary Care Unit in 1972-73 (223 cases) and in 1982-83 (243 cases) for recent myocardial infarction, and followed up for at least 15 days, to try and appreciate the influence of changes in treatment which had taken place during this interval on outcome and mortality. The two groups were comparable with regards to age, sex, time of admission with respect to onset of symptoms, previous vascular disease, and principal coronary risk factors. The clinical presentation of myocardial infarction and its common complications (cardiac failure, arrhythmias) were unchanged at 10 years' interval. The only statistically significant but unexplained difference was the lower proportion of posterior infarctions in 1982-1983 compared to 1972-1973. This decrease was partly due to the increased detection of rudimentary infarcts by more specific enzyme methods. The decrease in the proportion of posterior infarcts probably also explained the lower numbers of atrioventricular blocks. Other differences between the two groups were not statistically significant (slight increase in age, fewer women, lower incidence of cardiac failure). The mortality rate was exactly the same at 20.6%, and the causes of death were identical. The results support those of other rare studies of the same subject showing the lack of effect of recent therapeutic innovations on the majority of patients with myocardial infarction.

Twofold critical geometry for lasers.

Use of a twofold critical cavity is proposed to obtain a symmetrical saturated absorption peak on a symmetrical background. The experimental verification is performed on the CH(4)3.39-microm system. This geometry is expected to provide optical frequency standards with better reproducibility.