We present the results of infrared observations of the BL Lacertae object Markarian 501 obtained with the Telescopio Carlos Sanchez of El Observatorio del Teide, Tenerife, Spain. We report the detection of rapid infrared variations. On two nights the K (2.2 micron) magnitude shows variations which a Chi-Squared test establishes have a probability

We describe an experiment aimed at diffraction-limited imaging of astronomical sources in the 2-5/micron range. It is based on a rotation shearing interferometer that extracts the complex degree of coherence of the wavefront directly in the pupil plane. Interference fringes are produced by a Michelson interferometer in the image of the telescope

For a curve C, viewed as a cycle in its Jacobian, we study its image n_*C under multiplication by n on JC. We prove that the subgroup generated by these cycles, in the Chow group modulo algebraic equivalence, has rank at most d-1, where d is the gonality of C. We also discuss some general facts on the action of n_* on the Chow groups.

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We present here the results of the second multisite campaign of the STEPHI (STEllar PHotometry International) network. This three weeks rapid photometry campaign is devoted to the Delta Scuti star GX Peg. Observations, data reduction and analysis are described. Multiperiodicity is shown and five frequencies are unambiguously detected.