High-temperature superconductors are generally considered to be those that demonstrate superconductivity at or above the temperature of liquid nitrogen, or −196 °C (77 K), since this is the most easily attainable cryogenic temperature.
Of course, the T^4 dependence of black body radiation makes the radiated power damn small at low temperatures. It's about 460 W/m^2 around room temperature (300 K), but only 2 W/m^2 at the boiling point of nitrogen (77 K). Words and ideas I offer here may be used freely and without attribution.
I approach the arcane as Schumaker approaches a chicane - seeking a safe line through, but at the same time aware of the possibilities for mischief against my competitors. You can't be me, I'm taken
