A method and system for controlling access to an adapter, such as a graphics adapter, are disclosed. Each of these units is organized into independent segments having an I unit, multiple P units and R units interspersed among the P units. Also disclosed is a method of preparing such a membrane which involves spin coating a polymer solution containing the diblock copolymer to obtain a thin film, followed by annealing the thin film in a solvent vapor andor soaking in a solvent or mixture of solvents to form a nanoporous membrane.