Existence and L∞ estimates for a class of singular ordinary differential equations

We prove the existence of a positive solution to an equation of the form (1/Φ(t)) (Φ(t)u′(t))′ = f(u(t)) with Dirichlet conditions where the friction term Φ′/Φ is increasing. Our method combines variational and topological arguments and provides an L∞ estimate of the solution.