Neighbors of knots in the Gordian graph

We show that every knot is one crossing change away from a knot of arbitrarily high bridge number and arbitrarily high bridge distance.Comment: Accepted by American Mathematical Monthly. New version incorporates referee comment

Bipolar ejection by the symbiotic binary system Z And during its 2006 outburst

High resolution data in the region of the line Halpha have been obtained at the time of the light maximum and after it of the 2006 optical outburst of the symbiotic binary Z And. A blue-shifted absorption component indicating outflow velocity of about 1400 km/s as well as additional emission components with similar velocities, situated on the two sides of the main peak of the line were observed during that time. It is suggested that all of them are spectral signature of bipolar outflow, observed for the first time in the optical spectrum of this binary. The emission measure and the mass of the nebular part of the streams were estimated approximately.Comment: 5 pages, 2 figures; to be published in MNRAS Letter