Abstract: It is described herein an improved cryogenic storage unit (100). The improved cryogenic storage unit (100) may include an apparatus (1000) for thermal regulation in a cryogenic freezer (100). The improved cryogenic storage unit (100) may also include a cable gland (2000). The improved cryogenic storage unit (100) may also include a bearing assembly (3000). The improved cryogenic storage unit (100) may also include a system (4000) for charging a cryogen to a cryogenic freezer (100). The improved cryogenic storage unit (100) may also include a venting system (5000). The improved cryogenic storage unit (100) may also include an alignment of a lid (5300) and a handle (6000).

Abstract: A scanning probe microscope and methodology called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create images of nanoscale near-surface and subsurface features.