Devices, systems, and methods for measuring parallel tissue conductance, luminal cross-sectional areas, fluid velocity, andor determining plaque vulnerability using temperature. The printed circuit boards are stacked to increase the circuit density of the semiconductor structure. The prism may be configured to have an index of refraction that varies with changes in the applied electromagnetic field and that remains substantially constant with changes in wavelength of light over the predetermined wavelength range such that said light exiting from said prism deflects at a substantially controlled angle. A method for determining a bidirectional reflectance distribution function of a subject. The air flow is typically generated by a rotating disk of the disk drive.