We investigate the conditions for development of Kelvin-Helmoltz instabilities along a collimated wind flow from a low-mass star surrounded by a dense circumstellar disk, which could give rise to condensations with the characteristics of the chain of HH knots in the HH 7-11 system. The flow, using the observational parameters of the source, turns out to be clearly unstable. We give a simple estimate of the instability time scale, which turns out to be in good agreement with the characteristic time of development for outflows from low-mass young stellar objects.
The eclipsing binary SV Cam shows photometric features that suggest its membership to the RS CVn group. The existing light curves (covering the period 1947-1986) have been analyzed in order to isolate the contribution of the vave-like distortion; all the observations support the presence of an activity cycle, with a duration of about 10 years. By suppressing the contribution due to the stellar activity, we have derived an "average" light curve, cleaned from the effects due to the spots; this light curve has been analyzed by means of the Wood Computer code in order to get the physical parameters of the system.