An apparatus comprises a writer, a near-field transducer, a channel waveguide proximate the NFT, a dielectric layer between the NFT and waveguide, and a plurality of heat sinks. A covering wall connects said first and second vanes, bypassing said actuator means and guiding means. The adaptive system includes modules that, when executed by the processing unit, cause the signal processing device to adaptively filter a desired signal using a correntropy cost function. Additional embodiments are disclosed. The bottom wall of the base modulates the magnetic field of the magnet, providing a modulated magnetic attachment force. A first outer diameter of a first portion, which is close to the hub, of the blade is different from a second outer diameter of a second portion, which is close to the shroud, of the blade.