Hz the digital signal will not accurately represent the actual signal. That is a rather incomplete description of aliasing. If you'd like to learn more, the University of California at Santa Cruz has a general discussion of converting a signal to digital form. Dewar A container used for cryogenic work, insulated by a vacuum space. As shown in the drawing, the thermal insulation is provided by a vacuum space.
Convection is when a section of hot liquid or gas moves from one place to another.
The third way for heat to travel is by radiation. This is what you feel when you stand in the sunlight or near a hot fire. In a Dewar, the insulating material is a vacuum space. That leaves only radiation, which is stopped by covering the insides of the vacuum space with reflective material, which reflects nearly all the radiation before it enters the Dewar. There is also a smaller Dewar with 25 liters of liquid helium at 1.3 Kelvin.