  We study the equilibrium properties of a quantum dot connected to a bulk lead
by a single-mode quantum point contact. The ground state energy and other
thermodynamic characteristics of the grain show periodic dependence on the gate
voltage (Coulomb blockade). We consider the case of almost perfect
transmission, and show that the oscillations exist as long as the transmission
coefficient of the contact is less than unity. Near the points where the dot
charge is half-integer the thermodynamic characteristics show a non-analytic
behavior identical to that of the two-channel spin-1/2 Kondo model. In
particular, at any transmission coefficient the capacitance measured between
the gate and the lead shows periodic logarithmic singularities as a function of
the gate voltage.
