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Microseismicity in subsurface geologic environments, such as sandstone gas reservoirs, is expected in the presence of liquid or gas injection. Although difficult to predict, the potential for microseismic events is important to field-scale projects, such as geologic storage of CO2, whereby the gas is injected into natural sandstone formations. We conjecture that a primary factor causing microseismicity is the existence of metastable states in a granular porous medium and provide experimental evidence for its validity. External perturbation triggers abrupt relaxation events which, with a certain probability, can grow into macroscopic microseismic events. Here, the triggering perturbation is produced by cooling to a cryogenic temperature. As the "sensor" for the abrupt relaxation events, we use thin Al films deposited on the sandstone surface. We show that as the temperature is varied, the films' resistance exhibits sharp jumps, which we attribute to mechanical restructuring or microfractures in the fabric of the sandstone. We checked the superconducting characteristics of the Al thin films on the sandstone and found microwave-induced Shapiro steps on the voltage–current diagrams. Such quantized steps provide indications that the film is made of a network of nanobridges, which makes it even more sensitive to abrupt relaxation events occurring in the substrate, i.e., in the underlying sandstone. [ABSTRACT FROM AUTHOR]

We report a superconducting kinetic inductance memory (SKIM) element, which can be controlled exclusively by the bias supercurrent, without involving magnetic fields and heating elements. The SKIM is nonvolatile memory. The device is made of two Nb Dayem bridges, and it can operate reliably up to 2.8 K. The achieved error rate is as low as one in 105 operations. [ABSTRACT FROM AUTHOR]

A highly focused electron beam can be used to shape nanodevices. We demonstrate electron beam etching of nanoholes through multiwalled carbon nanotubes (MWNTs) and niobium nanowires. Nanoholes, as small as ∼2.5 nm in diameter, can be reproducibly fabricated. This technique can also be used to fabricate constrictions and larger nanoholes in MWNTs. We argue that with some improvement, this technique might be used to pattern suspended graphene by the removal of targeted single atoms. [ABSTRACT FROM AUTHOR]

A thin-film Fabry-Perot superconducting resonator is used to reveal the Little and Parks (LP) effect [Phys. Rev. Lett. 9, 9 (1962)], even at temperatures much lower than the critical temperature. A pair of parallel nanowires is incorporated into the resonator at the point of the supercurrent antinode. As the magnetic field is ramped, Meissner currents develop, changing the resonance frequency of the resonator. The LP oscillation is revealed as a periodic set of distorted parabolas observed in the transmission of the resonator and corresponds to the states of the wire loop having different vorticities. We also report a direct observation of single and double phase slip events. [ABSTRACT FROM AUTHOR]

The effect of dielectric friction on the rate of charge separation in type II ZnSe/CdS semiconductor nanorods has been investigated using picosecond transient absorption spectroscopy. The spatial separation of an excited electron-hole pair was estimated from the redshift in band edge absorption corresponding to the decrease in the exciton binding energy. The present study identifies a considerable effect of the solvent polarity on the rate of charge separation in semiconductor heterostructures, which should be taken into account when selecting nanorod caging media, such as solvents or polymer matrices. [ABSTRACT FROM AUTHOR]