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Here we report successful interferometric coupling of two large telescopes with single-mode fibers. Interference fringes were obtained in the 2- to 2.3-micrometer wavelength range on the star 107 Herculis by using the two Keck 10-meter telescopes, each feeding their common interferometric focus with 300 meters of single-mode fibers. This experiment demonstrates the potential of fibers for future kilometric arrays of telescopes and is the first step toward the 'OHANA (Optical Hawaiian Array for Nanoradian Astronomy) interferometer at the Mauna Kea observatory in Hawaii. It opens the way to sensitive optical imagers with resolutions below 1 milli‐arc second. Our experimental setup can be directly extended to large telescopes separated by many hundreds of meters.

The intrinsic response time τi of semiconductor avalanches has been determined from microwave measurements on Si, Ge, and GaAs IMPATT diodes of various structures (n+‐p, p+‐n, Schottky barrier). A theory has been developed to calculate τi for these diodes. It was found that the effect of carrier diffusion has to be taken into account to remove a systematic discrepancy between experimental and theoretical values of τi. For Si the value of the average high‐field diffusion constant D=80 cm2/sec for E=400 kV/cm, taken from the literature, could be used satisfactorily. For Ge and GaAs, where no information on D is available, D=100 cm2/sec for E=200 kV/cm and D=250 cm2/sec for E=400 kV/cm, respectively, had to be chosen to explain the experimental values of τi.

The authors report the case of a 16 year-old girl with the following features: clinically, a progressive bulbar paralysis, a weakness and wasting of muscles predominantly in the upper limbs; pathologically, a severe neuronal loss in the motor nuclei of the VIIth, IXth, XIIth cranial nerves and in the anterior horns of the cervical and thoracic spinal cord, a demyelinisation of the corticospinal tracts. A classification of progressive bulbar paralysies in infants and children is proposed. In the first group, the peripheral motoneuron is the only involved. Such cases are often called Fazio-Londe disease and can be related to those cases of infantile spinal amyotrophy either of the Werdnig-Hoffmann type or, most often, of the Wolfhardt-Kugelberg type. In the second group, the corticospinal tract is also involved. Some of these cases can be included in the spinocerebellar degenerations but others, such as the case reported here, are strongly reminiscent of the adult amyotrophic lateral sclerosis.

A parallel resonant circuit representing the small-signal behaviour of the avalanche region of IMPATT diodes is given. The components are calculated in a nonquasistatic manner for different ionisation rates and drift velocities of electrons and holes. With the results, the avalanche frequencies of Si, Ge and GaAs as functions of the avalanche zone width are compared.